Phytohormones methyl jasmonate (MeJA) and gamma-aminobutyric acid (GABA) up-regulates growth and PS II photochemistry in brinjal and tomato seedlings exposed to cadmium toxicity

Phytohormones methyl jasmonate (MeJA) and gamma-aminobutyric acid (GABA) up-regulates growth and PS II photochemistry in brinjal and tomato seedlings exposed to cadmium toxicity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Phytohormones methyl jasmonate (MeJA) and gamma-aminobutyric acid (GABA) up-regulates growth and PS II photochemistry in brinjal and tomato seedlings exposed to cadmium toxicity Varunendra Kumar Singh, Shobhit Raj Vimal, Sheo Mohan Prasad This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4340560/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Aug, 2024 Read the published version in Plant Growth Regulation → Version 1 posted 6 You are reading this latest preprint version Abstract Cadmium (cd) toxicity has become a major threat to the crop productivity and vegetables appeared to be on major risk. In present study, the potential of methyl jasmonate (MeJA, 0.015 µM) and gamma-aminobutyric acid (GABA 15 µM) was explored to alleviate the cd toxicity (12 µM) in tomato and brinjal seedlings. Cd declined fresh dry mass by 21% and 18% in tomato seedlings and 27% and 25% in brinjal seedlings. Cd significantly damage pigments contents (Chl a , Chl b and Car), PS II photochemistry (Chl a fluorescence kinetics) and photosynthetic gas exchange parameters in both seedlings. Furthermore, Cd exacerbated oxidative biomarkers and antioxidant enzymes CAT, SOD, POD and GST in both the seedlings. Phytohormones MeJA and GABA application to seedlings led to significant declined Cd uptake, oxidative biomarkers, antioxidative enzymes activity and up-regulation in leaves gas exchange parameters, photosynthetic performance and seedlings growth parameters. Additionally, biosynthetic inhibitors diethyldithiocarbamic acid (DIECA) of MeJA and 3-Mercaptopropionic acid (MPA) of GABA further raised Cd uptake, thereby excessive increase in oxidative biomarkers worsened Cd toxicity on photosynthesis, hence growth was greatly reduced. Thus, the study concludes that as compared to brinjal seedlings, tomato showed greater tolerance to Cd toxicity, and GABA plays a crucial role in mitigating the Cd toxicity, however, GABA and MeJA together more efficiently alleviated the toxicity. Antioxidants Oxidative biomarkers Photosynthesis Signalling molecules Sustainable agriculture Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Brinjal ( Solanum melongena L.) and tomato ( S. lycopersicum L.) are the important vegetables that are widely cultivated in Indian subcontinent and world as well. Vegetables are rich in vitamins, minerals, and antioxidants; hence they are important components of human food. The production and quality of vegetables are being compromised due to biotic and abiotic stresses. In recent years, heavy metal contamination is increased due to enhanced anthropogenic activities. Cadmium (Cd) is of particular concern as it is one of the most toxic metals, and due to mining, painting, industrial waste, excessive use of agricultural fertilizers and pesticides, irrigation practices with contaminated water, application in nickel-cadmium batteries as electrodes and in semiconducting solar panels (Wang et al. 2021 ; Genchi et al. 2020 ; Mir et al. 2022 ), its concentration rises above threshold limit. Cd pollution of soil and water is a major global threat to human health, agri-food systems and ecosystems. It is found in nature in the form of divalent metallic element and when present in excess amounts; it generates reactive oxygen species in excess which affect plant growth, metabolism, productivity, and vigour (Haider et al. 2021 ). Its concentrations in agricultural soil above 3 mg g –1 is considered dangerous for crop cultivation (Lux et al. 2011 ). Although it is not essential for plant growth and development but plants absorb it by involving Ca 2+ channels. Its excessive accumulation in plants may have major adverse effects on human health through the food chain (Haider et al. 2021 ). Cadmium toxicity caused serious threats to plants and disturbed normal physiological and biochemical activity and as a result shunted growth, decreased chlorophyll contents and efficiency of photosystem II in plants were observed (Piacentini et al. 2021 ). Furthermore, cadmium toxicity results into excessive production of reactive oxygen species (ROS) which harm plant membranes and destroys cell organelles and macromolecules (Unsal et al. 2020 ). Nowadays numerous studies suggest that various plant growth regulators (PGRs) and signalling molecules that are exogenously applied to plants significantly reduce the effects of abiotic and biotic stresses by modifying several biochemical pathways (Shah et al. 2021 ). Methyl jasmonate (MeJA) is one the key signalling molecules with a variety of roles in plants, including activating defence mechanisms, controlling growth and development, and interacting with other phytohormones (Mir et al. 2018 ). MeJA plays a critical role in the mitigation of environmental stresses under various conditions through various mechanisms like, improving the antioxidant mechanism and increasing the production of osmoregulators in plants (Raza et al. 2022 ; Mousavi et al. 2020 ). Previous studies showed that exogenous application of MeJA mitigates the chromium toxicity in calendula oficinalis (Barzin et al. 2022 ), enhanced cold tolerance in watermelon (Li et al. 2021 ), enhances the salinity tolerance in lemon seeds (Asadi and Jalilian 2021 ), drought tolerance in cowpea plant (Sadeghipour 2018 ), induced heat tolerance in the wheat plant (Fatima et al. 2021). However, there is currently limited information about the MeJA function in controlling Cd toxicity in vegetable crops. Likewise, another plant growth regulator gamma-aminobutyric acid (GABA) is a four-carbon non-proteinogenic amino acid. Under various types of biotic and abiotic stresses, GABA quickly accumulates in plant tissues and works like an endogenous signaling molecule in plant growth and development (Li et al., 2021 ; Suhel et al., 2022 ). Exposure of a variety of stressful conditions: osmotic pressure, high temperatures, salinity stress, cold shock, and heavy metal toxicity have been linked to the accumulation of GABA (Seifikalhor et al. 2020 ; Sheteiwy et al. 2019 ). In recent years, it has been demonstrated that exogenously applied GABA enhanced the cold tolerance in tomato (Liu et al. 2020 ), improved heat tolerance in tea (Ren et al. 2021 ), enhanced salt stress tolerance in the mulberry (Zhang et al. 2022), drought stress reduction in Phaseolus vulgaris (Abd El-Gawad et al. 2021 ) and alleviated arsenic toxicity in tomato and brinjal seedlings (Suhel et al. 2022 ). The protective effects of GABA against stress-related oxidative damage in a variety of plant species have been exhibited (Choe et al. 2021 ). Since GABA and MeJA alone has a distinct role in reducing abiotic stress in plants, however, the relationship between GABA and MeJA signalling under Cd stress has not yet been investigated in crops in general and vegetables in particular. Therefore, in present study an attempt has been made to investigate the crosstalk between GABA and MeJA in alleviating cadmium toxicity in two vegetable crops tomato and brinjal by examining growth, light harvesting pigments, PS II photochemistry, photosynthetic gas exchange, accumulation of intracellular Cd, oxidative biomarkers and antioxidant system. 2. Materials and Methods 2.1 Experimental plants and growth condition The healthy seeds of two vegetables, brinjal ( Solanum melongena L. var. KSP-1307 ARUN) and tomato ( Solanum lycopersicum L. var. BSS-791) were procured from the certified supplier of Prayagraj district, UP, India. Uniform-sized seeds of both vegetables were selected and surface sterilization was done with a 10% (sodium hypochlorite) solution for 20 min and rinsed with sterilized distilled water several times. Thereafter, seeds were wrapped with muslin cloth and kept in darkness at 25 ± 2°C for 24 hrs under sterilized conditions. Sprouted seeds were sown in a plastic tray containing sterilized sand and kept in the dark until seedlings emerged. The tray containing seedlings was transferred into the growth chamber (CDR model GRW-300Ge, Athens) under a light intensity of 240 ± 30 mol photons m − 2 s − 1 , 16:8 hrs of day and night period and relative humidity maintained at 65–70% at 25 ± 2°C for 21 days. During the growth period, seedlings were irrigated with water and half-strength Hoagland's nutrition solution alternatively. On the emergence of the secondary leaf, the seedlings were uprooted carefully and washed under running water and thereafter they z were placed in half-strength Hoagland solution for 24 h for acclimatization. Finally, seedlings were grown hydroponically in growth medium containing different combinations. 2.2 Treatment of seedlings with GABA, MeJA, and Cd The seedlings of both the experimental plants were treated with 12 µM Cd (CdCl 2 ), 15 µM GABA and 0.015 µM MeJA (Sigma-Aldrich) separately and in combination as required. The concentrations of Cd, GABA, and MeJA were selected after a series of screening experiments for a details study. Furthermore, to understand the role of the signalling molecules GABA and MeJA, 20µM MPA (3-mercaptopropionic acid; biosynthetic inhibitors of GABA) and 5 µM DIECA (diethyledithiocarbamic acid; biosynthetic inhibitors of MeJA) were applied. With different combinations, the treatments were given for five days under hydroponics conditions and the experimental setups consisted of: CK (control), Cd, Cd + GABA, Cd + MeJA, Cd + GABA + MeJA, Cd + GABA + DIECA, Cd + MeJA + MPA. After 5 days of treatments various growth, physiological and biochemical attributes in both seedlings were analysed. 2.3 Determination of growth attributes Growth was measured as fresh and dry mass of both plant seedlings by digital electronic balance (Mettler Toledo, Switzerland, min. accuracy 0.1 mg). The seedlings of each setup were harvested and after determining fresh mass, seedlings were dried in a hot oven at 80°C for 48 h before the measurement of dry mass. 2.4 Estimation of Cd content Samples from each set were digested in a tri acid mixture (5:1:1 ratio, v/v) (HNO 3 , H 2 SO 4, and HClO 4 in 5:1:1 ratio, v/v) at 80°C until a transparent solution was formed to determine the amount of Cd present in the roots and shoots (Allen et al. 1986 ). Following cooling, Whatman No. 42 was used to filter the digested material, and double distilled water was used to maintain the filtrate up to 15 milliliters. Using a suitable drift blank and an atomic absorption spectrometer (iCE 3000 Series, Thermo Scientific, UK) equipped with a specific metal lamp, the amount of Cd in the digested samples was determined. 2.5 Determination of photosynthetic pigments The 50 mg leaf from each sample was crushed and the pigments were extracted in 80% acetone. The absorbance of transparent suspension was recorded at 663, 646, and 470 nm spectrophotometrically (Shimadzu double beam UV–Visible spectrophotometer-1700, Japan) and the amount of chlorophyll a (Chl a ) and b (Chl b ) and carotenoids (Car) was calculated by the equation given by Lichtenthaler ( 1987 ). 2.6 Determination of chlorophyll a fluorescence kinetics (JIP test) Chlorophyll a fluorescence transient was assayed in intact leaves of treated and untreated seedlings with the help of a handheld leaf fluorometer (FluorPen FP 100, Photon System Instruments, Czech Republic). Prior to the measurement, the seedlings were preincubated for half an hour dark. The performance of photochemistry of photosystem II was determined according to the method given by Strasser et al. ( 2000 ) by analysing the status of quantum yield of primary photochemistry (F V /Fm or ϕP 0 ), maximum quantum efficiency of PS II photochemistry (Ψ 0 ), yield of electron transport per trapped exciton (ϕE 0 ), performance index of PS II (PI ABS ) and also the energy fluxes per active reaction centre (ABS/RC, TR 0 /RC, ET 0 /RC and DI 0 /RC). 2.7 Estimation of photosynthetic gas exchange parameters The LCiSD portable photosynthesis system (L. MAN-LCI-SD, biosynthetic Ltd, EN11 0NT, UK) was applied to analyse the net photosynthetic rate (A), stomatal conductance (Gs), gas exchange indices including intercellular CO 2 concentration (Ci), and transpiration rate (E) of a fully exposed secondary leaves in seedlings. Throughout the measurements, the ambient CO 2 (380 ± 10 µmol mol − 1 ) concentration, leaf temperature (25 ± 2°C), photosynthetic photon flux density (1200 ± 250 µmol m − 2 s − 1 ) and relative humidity (70%) were maintained. 2.8 Estimation of oxidative stress indices 2.8.1 Biochemical estimation of oxidative stress biomarkers Superoxide radical (SOR; O 2 •‾) and hydrogen peroxide (H 2 O 2 ) contents in treated and untreated leaf samples were estimated by adopting the methods of Elstner and Heupel ( 1976 ) and Velikova et al. ( 2000 ), respectively. The assay of superoxide radical (SOR) was performed in in each sample based on the formation of NO 2 − from hydroxylamine in the presence of O 2 ·− . The content of O 2 ·− was quantified with the help of a standard curve prepared by the graded solution of NaNO 2 . Likewise, for H 2 O 2 content the absorbance in each reaction mixture was recorded at 390 nm and the amount was calculated by using a standard curve prepared with graded solution of H 2 O 2 . The lipid peroxidation as malondialdehyde (MDA) contents was estimated according to method of Heath and Packer ( 1968 ). The absorbance of the supernatant was read at 532 and 600 nm and the value for non-specific absorbance of each sample at 600 nm was subtracted from absorbance recorded at 532 nm, and malondialdehyde equivalents content was calculated by using an extinction coefficient of 155 mM − 1 cm − 1 . 2.8.2 Determination of membrane stability index Membrane stability index (MSI) of leaf samples of both seedlings was measured according to the method of Gong et al. (1998). Fresh leaf (200 mg) was cut into equal size pieces and placed in a test containing 20 ml of deionized water and incubated at 30°C for 2h. The test tubes containing each sample were placed on a rotary shaker and at the end electric conductivity of the solution was recorded (C 1 ) using an electric conductivity meter. Likewise, an equal amount of leaf discs from untreated seedlings were placed in another test tube and placed in a boiling water bath at 100°C for 15 min. After cooling, the electric conductive of samples was determined (C 2 ) as earlier. The membrane stability index was calculated using the following equation. MSI = [1- (C 1 /C 2 )] x100 2.8.3 In-vivo analysis of oxidative stress biomarkers In-vivo visualization of reactive oxygen species (ROS: O 2 • ‾ and H 2 O 2 ) was performed using nitroblue tetrazolium (NBT) and 3,3ʹ-Diaminobenzidine (DAB) as per the methods of Frahry and Schopfer ( 2001 ) and Thordal-Christensen et al. ( 1997 ), respectively. For visualizing O 2 •‾and H 2 O 2 , leaves, and root tips were incubated in nitro blue tetrazolium (NBT, prepared in potassium phosphate buffer pH 6.4) containing 10 mM Na-azide (Sigma Aldrich), and 1% solution of 3, 3′-diaminobenzidine (DAB) (Sigma Aldrich) in the light and dark until blue and brown spots respectively appeared. After this, leaves and root tips were bleached by immersing in boiling ethanol to visualize blue and brown spots, respectively, and photographed. Lipid peroxidation and membrane damage were visualized using Schiff’s reagent and Evans's blue according to the methods of Pompella et al. ( 1987 ) and Yamamoto et al. ( 2001 ), respectively. To localize lipid peroxidation products and plasma membrane integrity, leaves and root tips were stained with Schiff’s reagent and Evans blue (0.025%, w/v prepared in 100 µM of CaCl 2 , pH 5.6), respectively for 20 min. Thereafter, leaves and root tips were bleached by immersing in boiling ethanol to clearly visualize pink and blue spots, respectively, and photographed. 2.9 Estimation of enzymatic antioxidants activities The activity of superoxide dismutase (SOD; EC 1.15.1.1) in leaf samples was measured using the method ascribed by Giannopolitis and Ries ( 1977 ), and one unit of SOD activity was defined as the quantity of enzyme required to prevent 50% of NBT reduction by O 2 •‾. The activity of peroxidase (POD; EC 1.11.1.7) was determined using the method described by Zhang ( 1992 ) and 1 nmol guaiacol oxidized min − 1 is considered as one unit of POD activity. Catalase (EC 1.11.3.6) activity was measured by monitoring the dissociation of H 2 O 2 at 240 nm for 1 min with a UV-visible spectrophotometer (Shimadzu, Japan) and CAT activity was calculated by using an extinction coefficient of 39.4 mM − 1 cm − 1 (Aebi 1984 ). Further, 1 nmol H 2 O 2 dissociated min − 1 is defined as one unit (U) of enzyme activity. The activity of glutathione-S-transferase (GST, EC 2.5.1.18) was measured using the Habig et al. ( 1974 ) method. One unit (U) of enzyme activity denotes as one nmol of CDNB-conjugates produced min − 1 . 2.10 Statistical analysis For the analysis of the data, a one-way analysis of variance (one-way ANOVA) was used. As a post hoc test to examine significant differences across several treatments at p˂0.05 significance level, Duncan's multiple range test (DMRT) was used. For each treatment, three separate biological duplicates for each treatment were performed. 3. Results 3.1 GABA and MeJA alleviate Cd toxicity on growth Results about growth attributes of fresh and dry mass of tomato and brinjal seedlings were displayed in Fig. (1,2). Cd treatment (12 µM) caused diminished growth as the reduction in fresh and dry mass was 21% and 18% in tomato and 27% and 25% in brinjal seedlings, respectively over the values of the control. Under similar stress, the exogenous supplementation of GABA (15 µM) induced significant alleviatory effects on growth attributes as the decrease in fresh and dry biomass remained to be 5% and 2% in tomato and 8% and 3% in brinjal seedlings, respectively (Fig. 1 , 2 ). Likewise, MeJA (0.015 µM) when applied alleviated the Cd toxicity as the suppression in fresh was only 8% and 10%) and in dry mass, it was only 4% and 6% in tomato and brinjal seedlings, respectively. Combined application of GABA and MeJA completely restored the damaging effect of Cd on tested growth attributes, besides there was a marginal increase in growth as compared to the values recorded for control plants. To understand the ameliorative role of endogenous GABA and MeJA against Cd toxicity on growth attributes the biosynthetic inhibitors of MeJA (DIECA, 5 µM) and GABA (MPA, 20 µM) were applied in Cd-stressed seedlings (Fig. 1 , 2 ). The results revealed that with DIECA (Cd + GABA + DIECA) and MPA (Cd + MeJA + MPA) the alleviation of inhibitory effects due to Cd on fresh mass was reversed showing the reduction of 25% and 35% in tomato and 30% and 38% in brinjal seedlings, respectively. Similar trends were also observed in the reduction of dry mass in both the seedlings under similar treatments with inhibitors (DIECA and MPA) (Fig. 1 , 2 ). 3.2 Gamma-aminobutyric acid and methyl jasmonate down regulate intracellular cadmium Cd treatment resulted in a substantial accumulation of Cd in both the seedlings and the content was greater in brinjal (72%) than that of tomato (58%) compared to nontreated control. The seedlings exogenously treated with GABA exhibited a considerable decrease in 22% and 20% and MeJA declined 14% and 6%, in brinjal and tomato compared to Cd treated seedlings. Combined treatment (Cd + MeJA + GABA) caused further reduction in the accumulation of Cd and it was found to be 33% and 18% in brinjal and tomato compared to Cd treated seedlings. Contrary to this, when tested plants were exposed to Cd + MeJA + MPA then the Cd content enhanced 16% and 8% in brinjal and tomato compared to Cd treated seedlings. In Cd + GABA + DIECA treatments the intracellular accumulation of Cd was increased further 8% and 3% in brinjal and tomato compared to Cd treated seedlings (Fig. 4 ). 3.3 Gamma-aminobutyric acid and methyl jasmonate protect photosynthetic pigments against Cd stress One of the most important factors for determining how plants respond to metal stress is the analysis of photosynthetic pigments which play an important role in the photosynthetic processes of the plants. Photosynthetic pigments (Chl a , Chl b , and Car) were reduced by 14%, 23% and 11% in tomato and 18%, 26%, and 14% in brinjal seedlings, respectively under Cd toxicity in comparison to the respective control values (Table 1 ). Unlike to this, on exogenous application of GABA the negative impact of Cd was alleviated, and the reduction in values of Chl a , Chl b , and Car were decreased by only 3%, 5%, and 2% in tomato and 5, 7, and 3% in brinjal seedlings (Table 1 ). Similar ameliorative results were also obtained with MeJA treatments on Chl a , Chl b , and Car under Cd stress in both seedlings, however, the recovery against Cd toxicity on pigment contents (Chl a , Chl b , and Car) was slightly lower than that observed with GABA (Table 1 ). The GABA and MeJA together alleviated more effectively as the negative effect of Cd was completely restored and the values were even greater than that of respective controls. Furthermore, to analyze the alleviatory effects caused by GABA and MeJA on Cd induced toxicity their specific biosynthetic inhibitors were used (Table 1 ). With the combinations of Cd + GABA + DIECA and Cd + MeJA + MPA the alleviation in the levels of pigment contents (Chl a , Chl b , and Car) was further reversed depicting the decline 16%, 26%, 14% and 20%, 34%, 19% in tomato and 21%, 30%, 17% and 24%, 36%, 23% in brinjal seedlings respectively over the values of control. Table 1 Regulation of photosynthetic pigments Chl a , Chl b , and Cars by GABA and MeJA in tomato and brinjal seedlings growing under Cd stress. Treatment Tomato Brinjal Chl a (µg g − 1 FM) Chl b (µg g − 1 FM) Car (µg g − 1 FM) Chl a (µg g − 1 FM) Chl b (µg g − 1 FM) Car (µg g − 1 FM) Ck 1380 ± 22b 576 ± 9ab 480 ± 7ab 1272 ± 20b 535 ± 8ab 440 ± 7ab Cd 1182 ± 19d 440 ± 7c 425 ± 6d 1040 ± 17d 396 ± 6 c 375 ± 6d Cd + GABA 1338 ± 21bc 546 ± 8b 470 ± 7b 1250 ± 19bc 496 ± 8 b 425 ± 7b Cd + MeJA 1324 ± 20c 535 ± 8bc 465 ± 7bc 1180 ± 19c 478 ± 7bc 417 ± 6bc Cd + GABA + MeJA 1420 ± 22a 585 ± 9a 485 ± 8a 1298 ± 21a 541 ± 9a 448 ± 7a Cd + GABA + DIECA 1155 ± 18de 423 ± 6cd 412 ± 6c 1005 ± 16de 380 ± 6cd 365 ± 6c Cd + MeJA + MPA 1102 ± 17e 378 ± 5d 385 ± 6e 965 ± 15e 341 ± 5d 335 ± 5e Data are means ± standard error of three independent biological replicates (n = 3). Values within the same column followed by different letters are statistically different at p˂0.05 significance level according to the Duncan’s multiple range test (DMRT) 3.4 Gamma-aminobutyric acid and methyl jasmonate alleviate the negative effect of Cd stress on PS II Photochemistry To understand the impact of Cd and its regulation by GABA and MeJA on photosynthesis PS II photochemistry was analyzed by JIP test and results are depicted in Table 2 . The results indicate that Cd toxicity exerted a negative impact on the values of chlorophyll a fluorescence kinetics parameters such as quantum yield of primary photochemistry (Phi_P 0 ), yield of electron transport per trapped exciton (Phi_E 0) , the maximum quantum efficiency of PS П photochemistry (Psi_0), the performance index of PS II (PI ABS ) while the energy flux parameters [the energy for absorption of photon per active reaction center (ABS/RC), trapped energy per active reaction center (TR 0 /RC), electron transport per active reaction center (ET 0 /RC) and energy dissipation per active reaction center (DI 0 /RC) ] were increased significantly under Cd toxicity. Exogenous usage of signalling molecules GABA and MeJA individually and both together alleviate the negative impact of Cd toxicity on these parameters (Table 2 ). Contrary to this, the MeJA inhibitor DIECA intensified the Cd toxicity on energy flux parameters (Table 2 ). Furthermore, the application of biosynthetic inhibitor (MPA) of GABA showed a greater increase in energy flux parameters even in the presence of MeJA. Table 2 Regulation of chlorophyll a fluorescence characteristic by GABA and MeJA in tomato and brinjal seedlings exposed to Cd stress. Treatments Tomato Phi_P0 Phi_E0 Psi_0 PI ABS ABS/RC ET0/RC TR0/RC DI0/RC Ck 0.790 ± 0.013a 0.530 ± 0.011c 0.588 ± 0.008c 3.532 ± 0.050a 2.240 ± 0.042f 0.966 ± 0.018f 1.894 ± 0.029f 0.774 ± 0.011c Cd 0.711 ± 0.011d 0.429 ± 0.013d 0.478 ± 0.006d 2.659 ± 0.031cd 2.783 ± 0.035c 1.212 ± 0.013c 2.436 ± 0.024c 0.885 ± 0.013bc Cd + GABA 0.776 ± 0.013b 0.576 ± 0.009b 0.623 ± 0.008ab 3.101 ± 0.044b 2.538 ± 0.044d 1.056 ± 0.017d 2.198 ± 0.030e 0.731 ± 0.011d Cd + MeJA 0.758 ± 0.013bc 0.588 ± 0.012ab 0.618 ± 0.009b 2.840 ± 0.040c 2.657 ± 0.045cd 1.140 ± 0.018cd 2.225 ± 0.028d 0.756 ± 0.011 d Cd + GABA + MeJA 0.728 ± 0.011c 0.601 ± 0.008a 0.635 ± 0.012a 3.475 ± 0.050ab 2.496 ± 0.046e 0.994 ± 0.018 e 1.927 ± 0.031ef 0.720 ± 0.010e Cd + GABA + DIECA 0.698 ± 0.013e 0.427 ± 0.014d 0.460 ± 0.013de 2.551 ± 0.036d 3.214 ± 0.031b 1.289 ± 0.013b 2.642 ± 0.020b 0.898 ± 0.009b Cd + MeJA + MPA 0.647 ± 0.013f 0.412 ± 0.011e 0.431 ± 0.006e 2.296 ± 0.033e 3.782 ± 0.028a 1.332 ± 0.012a 2.886 ± 0.027a 0.935 ± 0.012a Brinjal Ck 0.775 ± 0.011a 0.527 ± 0.010c 0.626 ± 0.009c 2.431 ± 0.035a 2.198 ± 0.03f 0.845 ± 0.018f 1.745 ± 0.033f 0.671 ± 0.009c Cd 0.671 ± 0.009d 0.435 ± 0.009d 0.425 ± 0.006d 1.661 ± 0.023cd 2.556 ± 0.049c 1.225 ± 0.010c 2.085 ± 0.028c 0.740 ± 0.010bc Cd + GABA 0.731 ± 0.010b 0.496 ± 0.011b 0.675 ± 0.009ab 2.201 ± 0.031b 2.118 ± 0.049d 0.892 ± 0.019d 1.782 ± 0.037e 0.601 ± 0.008de Cd + MeJA 0.742 ± 0.010bc 0.488 ± 0.009ab 0.655 ± 0.014b 2.284 ± 0.032c 2.322 ± 0.047cd 0.921 ± 0.018cd 1.811 ± 0.036d 0.635 ± 0.009d Cd + GABA + MeJA 0.720 ± 0.010c 0.510 ± 0.014a 0.687 ± 0.115 a 2.675 ± 0.038ab 2.074 ± 0.048e 0.858 ± 0.021e 1.758 ± 0.038ef 0.598 ±. 0009e Cd + GABA + DIECA 0.679 ± 0.009e 0.391 ± 0.009d 0.410 ± 0.009de 1.355 ± 0.019d 3.015 ± 0.041b 1.306 ± 0.008b 2.225 ± 0.026b 0.781 ± 0.011b Cd + MeJA + MPA 0.626 ± 0.009f 0.422 ± 0.012e 0.391 ± 0.008e 1.296 ± 0.018e 3.315 ± 0.042a 1.328 ± 0.006a 2.554 ± 0.023a 0.795 ± 0.012a Data are means ± standard error of three independent biological replicates (n = 3). The quantum yield of primary photochemistry (Phi_P0), yield of electron transport per trapped exciton (Psi_0), quantum yield of electron transport (Phi_E0), performance index of PS II (PI ABS ), the energy fluxes for absorption of photon per active reaction center (ABS/RC), trapped energy flux per active RC (TR0/RC), electron transport flux per active RC (ET0/RC) and energy dissipation flux per active RC (DI0/RC). 3.5 Gamma-aminobutyric acid and methyl jasmonate ameliorate Cd toxicity on photosynthetic gas exchange parameters Photosynthetic gas exchange parameters were also adversely affected by Cd toxicity in tomato and brinjal seedlings. (Table 3 ,4). Upon Cd exposure, leaves gas exchange parameters A, Ci, gs, E, were inhibited by 23%, 18%, 28% and 20% in tomato and by 25%, 21%, 31% and 22% in brinjal, compared to control. However, the application of exogenous GABA significantly alleviated the toxicity of Cd on A, Ci, gs, and E values as it was decreased by only 8%, 2%, 7%, and 3% in tomato and 11%, 4%, 9% and 5% in brinjal, respectively over the values of respective controls. Under similar stress conditions when the seedlings were treated with MeJA significant amelioration (11%, 5%, 10%, and 8% in tomato and 13%, 7%, 12%, and 9% in brinjal seedlings) was noticed in A, Ci, gs, and E respectively. Furthermore, when seedlings were subjected to GABA and MeJA treatments damaging effects of Cd on these parameters were overcome in both the seedlings completely (Table 3 ,4). Table 3 Regulation of photosynthetic characteristics: A, Ci, gs, and E in tomato seedlings by GABA and MeJA growing under Cd toxicity. Treatments Tomato A (µmol CO 2 m − 2 s − 1 ) Ci (µmol CO 2 mol − 1 ) Gs (mol H 2 O m − 2 s − 1 ) E (m mol H 2 O m − 2 s − 1 ) Ck 10.49 ± 0.16b 280.66 ± 4.05b 0.14 ± 0.002a 3.11 ± 0.050ab Cd 8.04 ± 0.12 e 232.67 ± 3.36e 0.10 ± 0.001d 2.49 ± 0.040d Cd + GABA 9.60 ± 0.15c 274.37 ± 4.59c 0.13 ± 0.002b 3.01 ± 0.048b Cd + MeJA 9.35 ± 0.15d 266.00 ± 4.47d 0.12 ± 0.002c 2.85 ± 0.046c Cd + GABA + MeJA 10.91 ± 0.17a 292.67 ± 4.74a 0.14 ± 0.002a 3.15 ± 0.050a Cd + GABA + DIECA 7.75 ± 0.12f 218.33 ± 3.15f 0.09 ± 0.001e 2.38 ± 0.038e Cd + MeJA + MPA 7.12 ± 0.11g 191.33 ± 2.76g 0.75 ± 0.001f 2.25 ± 0.037f Brinjal Ck 9.54 ± 0.15ab 237.00 ± 3.83b 0.13 ± 0.002b 3.11 ± 0.063b Cd 7.15 ± 0.11d 185.33 ± 2.99d 0.08 ± 0.001e 2.57 ± 0.049e Cd + GABA 8.40 ± 0.13b 228.00 ± 3.68c 0.12 ± 0.001c 3.07 ± 0.060c Cd + MeJA 8.25 ± 0.13c 220.33 ± 3.55cd 0.11 ± 0.001d 2.98 ± 0.057d Cd + GABA + MeJA 9.79 ± 0.15a 252.67 ± 4.07a 0.14 ± 0.002a 3.32 ± 0.065a Cd + GABA + DIECA 6.88 ± 0.11e 168.33 ± 2.72e 0.07 ± 0.001f 1.90 ± 0.047f Cd + MeJA + MPA 6.18 ± 0.10f 139.67 ± 2.41f 0.06 ± 0.001g 1.35 ± 0.044g Data are means ± standard error of six replicates (n = 6). Bars followed by different letters are significantly different at p < 0.05 according to the Duncan’s multiple range test. Data are means ± standard error of three independent biological replicates (n = 3). Values within the same column followed by letters are statistically different at p˂0.05 significance level according to the Duncan’s multiple range test. To explore the relationship between GABA and MeJA regarding the alleviatory role, the biosynthetic inhibitors of GABA (MPA) and MeJA (DIECA) [in combinations (Cd + GABA + DIECA; Cd + MeJA + MPA)] were applied and the inhibitory effect of Cd became more prominent, however, this effect appeared to be more prominent with the inhibitor (MPA) of GABA. 3.6 Gamma-aminobutyric acid and methyl jasmonate down-regulate oxidative biomarkers and protect against damage under Cd stress To pinpoint the damaging effect of Cd on growth and related parameters such as photosynthetic pigments, PS II photochemistry, and gas exchange parameters, and the role of GABA and MeJA on the oxidative stress biomarkers were analysed (Fig. 3 , 4 ). The oxidative biomarkers SOR, H 2 O 2, and MDA equivalents were found to increase by 20%, 33%, and 38% in tomato, respectively, while the corresponding rise in the values was 24%, 39%, and 46% in brinjal seedlings under Cd stress. A considerable decrease in SOR, H 2 O 2 , MDA was noticed in Cd-stressed tomato seedlings in the presence of GABA as 3%, 11% and 13% and MeJA i.e. 6%, 19% and 16%, respectively. Further, as on the application of both the signalling molecules, the negative effects of Cd were completely overcome in both the seedlings, thereby the levels of oxidative biomarkers were decreased to the extent even less than that of control (untreated samples) (Fig. 5 ). Together with the biosynthetic inhibitor (MPA) of GABA the levels of oxidative biomarkers were excessively risen, while with inhibitor (DIECA) of MeJA the rise in these markers were also increased but the levels were found to be comparatively low than those observed with MPA, an inhibitor of GABA (Fig. 5 ). Further, the formation/accumulation of oxidative biomarkers in leaves under Cd stress and with different combinations were visualized by histochemical staining by blue formazan due to a reaction between NBT and SOR, by brown spots as s results of the reaction of hydrogen peroxide and DAB and by pink colour developed between the reaction of lipid peroxidation product and Shiff reagent (Fig. 7 ). The intensity of the blue colour was noticeable during Cd toxicity. With the biosynthetic inhibitors of GABA and MeJA the blue colour became more intense. The exogenously applied GABA and MeJA exhibited decreased colour intensity, hence showing the appreciable decrease in ROS content. Under Cd stress the biosynthesis inhibitors of MeJA and GABA exhibited more intense brown colour, and the increasing order is as Cd˂ MeJA˂ GABA as seen in Fig. 7 . Under GABA and MeJA treatment, the formation of brown colour in cells was quite less. The results revealed that histochemical analysis supports the biochemical data regarding H 2 O 2 generation under Cd toxicity and the subsequent effects of GABA and MeJA with and without their biosynthetic inhibitors. The lipid peroxidation as studied by histochemical staining with the Schiff reagent exhibited with the greater intensity of pink colour was noticed under Cd toxicity alone and also with inhibitors of GABA and MeJA. The exogenously used GABA / MeJA appreciably lowered the colour intensity, and this result indicates the ameliorative effect of GABA and MeJA under Cd toxicity. 3.7 Gamma-aminobutyric acid and methyl jasmonate ameliorate Cd toxicity on membrane stability index The data related to oxidative damage indices such as membrane stability index (MSI) are depicted in Fig. 3 . Cd declined MSI by 15 and 20% in tomato and brinjal, respectively in comparison to their control values. After the supplementation of GABA under Cd toxicity, MSI is declined by 2% and 5% in tomato and brinjal, respectively to their control values, similarly on the addition of MeJA the decrement of MSI is 4% and 8% in tomato and brinjal seedlings, respectively. When we applied both together GABA + MeJA under Cd stress, the MSI is enhanced by 2% and 3% in tomato and brinjal seedlings, respectively to their respective control values. The addition of MPA and DIECA caused further decline in MSI in both vegetables. On the application of MPA the MSI was greatly decreased by 31% and 34% in tomato and brinjal seedlings, respectively with their respective control values (Fig. 3 ). 3.7 Gamma-aminobutyric acid and methyl jasmonate up-regulate enzymatic antioxidant system under stress To keep the oxidants under control in the biological system, the plant possesses an array of antioxidant systems which include enzymatic and non-enzymatic antioxidants. The status of enzymatic antioxidants in test plants is displayed in Fig. 6 . Cadmium treatment resulted in enhanced activity of SOD, POD, CAT, and GST by 15, 30, 16, and 11% in tomato and 19, 36, 25, 14% in brinjal seedlings, respectively with their respective control values. The increment of SOD, POD, CAT, and GST was further enhanced in the presence of exogenous GABA (activity raised by 5, 11, 3, and 2% in tomato and 7, 13, 5, and 5% in brinjal seedlings, respectively), and the corresponding increase in the enzyme activity with exogenous MeJA (activity enhanced by 8, 14, 6, and 5% in tomato and 11, 16, 7, and 7% in brinjal seedlings, respectively) was noticed (Fig. 6 ). In the combined treatments Cd + GABA + MeJA the activity of SOD, POD, CAT, and GST showed further decreasing trend in both the seedlings, however, it was still greater than that of respective controls. To understand the interaction between GABA and MeJA the specific inhibitors of GABA (Cd + MeJA + MPA) and MeJA (Cd + GABA + DIECA) were applied, the results revealed that the activity of SOD, POD, CAT, and GST was increased by 31, 43, 25, 22% in tomato and 34, 46, 35, 25% in brinjal seedlings exposed with Cd + MeJA + MPA. Under similar treatments the corresponding increase with Cd + GABA + DIECA combination was 20, 35, 19, 16% in tomato and 24, 40, 29, 20% in brinjal seedlings, respectively (Fig. 6 ). 4. Discussion The two vegetables tomato and brinjal are important crops, widely grown in Indian continent, facing serious threats due to rise in heavy metal contamination. In current study, the seedlings of tomato and brinjal exposed to Cd showed a significant reduction in growth (Fig. 1 , 2 ) and such an adverse effect was more prominent in brinjal seedlings. Similar observations were also recorded in Trigonella (Bashri et al. 2021 ), rice (Huang et al. 2021 ) and wheat seedlings (Zeshan et al. 2022 ) under Cd stress. In both the seedlings Cd diminished the growth which could occur due to (i) damage caused to the light harvesting pigments Chl a, b and Cars (Bashri et sl. 2021) (ii) negative impact on PS II photochemistry (Liu et al. 2020 ), and (iii) excess accumulation of SOR and hydrogen peroxide that led to oxidation of nucleic acids (Sanghai et al. 2021) and proteins (Alamri et al. 2021 ) and peroxidation of lipids (Fig. 5 ). The exogenously applied signalling molecules GABA or MeJA significantly alleviated the Cd toxicity in both the seedlings as reduction in growth attributes was recovered to the greater extent (Fig. 1 , 2 ). Many studies were earlier reported similar results (Zaid and Mohammad, 2018 ; Kaya et al. 2021 ; Wei et al. 2021 ). Combined application of GABA and MeJA was found to be more effective in recovering the loss of growth of tested vegetables due to Cd stress. Our results are in congruence with earlier findings where GABA has been shown to efficiently ameliorated the negative effect of arsenic on growth in tomato and brinjal seedlings (Suhel et al. 2024) and Cd on apples (Li et al. 2022). Likewise, exogenously applied MeJA mitigated the damaging effect of Cd stress on growth of Brassica oleracea L (Srihindi et al. 2020). Tomato and brinjal seedlings (Suhel et al. 2022 ), Cd toxicity in maize plant (Seifikalhor et al. 2020 ) and tobacco (He et al. 2021 ) and phenanthrene phytotoxicity in cucumber (Guo et al. 2021 ). To study the impact of MeJA, its inhibitor DIECA in the presence of GABA exhibited significant decrease in the fresh/ dry mass of tomato and brinjal seedlings over the values to Cd stress. While with the inhibitor (MPA) of GABA a greater decrease was noticed in fresh mass/dry mass. These results reveal that GABA appears to be the main signalling molecule for alleviation of Cd toxicity, while MeJA regulates the GABA mediated toxicity amelioration in both the tested seedlings. In this study, it was noticed that accumulation of Cd in seedlings of tomato and brinjal (Fig. 3 ) exhibited severe oxidative burst as evidenced by enhanced levels of SOR (O 2 •− ), H 2 O 2 and MDA. Moreover, Cd can block ETC (electron transport chain) or displace the iron (Fe) molecule with other protein molecules that cause the abundant production of ROS inside the cell (Genchi et al. 2020 ). The growth of seedlings is mainly regulated by photosynthesis and status of light harvesting pigments. A significant decrease in photosynthetic pigment contents under Cd stress was observed and these results are in consistent with the earlier findings where Cd induces senescence in the leaf of pea plants and inhibited the biosynthesis of chlorophyll (Bashri et al. 2021 ; Hayat et al. 2021 ). Conversely, the exogenous application of GABA and MeJA alone or together significantly up-regulated Chl and Car contents under Cd stress. The considerable rise in Chl and Car contents by the application of GABA and MeJA alone and together might have direct correlation with an alleviating effect on the growth performance of seedlings under Cd toxicity. In consonance with our results, Suhel et al. ( 2022 ) have shown the involvement of GABA in protecting Chl and Car in plants grown under As stress. Furthermore, MeJA exposure increased 5-aminolevulinic acid production, thereby up-regulation of gene expression which is linked with chlorophyll biosynthesis (Ueda and Saniewski 2006 ). Therefore, MJA positively modulated the efficiency of the photosynthetic apparatus; hence induces the level of tolerance against Cd toxicity tolerance in tested plants. Besides this, Salavati et al. ( 2021 ) has suggested that down-regulation in the degrading process of Chl and Car by exogenous MeJA treatment significantly contributed to the improvement of pigment contents in Oryza sativa seedlings under Pb stress. The gas exchange parameters viz. A, Ci, Gs, and E were used to determine the photosynthetic activities, and in tomato and brinjal seedlings these parameters were negatively affected under Cd toxicity (Table 3 ,4). Similar trends were also reported by Huarancca et al. ( 2018 ) in Chenopodium quinoa under UV stress. According to Mosadegh et al. ( 2019 ), the reduction in photosynthetic rate might be caused by the degradation of pigments. In current study Cd could restrain the stomatal apertures, hence negatively affected the A, Ci, Gs, and E parameters because of the photosynthetic interruption as noticed in other study (Zhao et al. 2021 ). Stomatal and non-stomatal factors are the two categories of factors that influence the rate of photosynthetic activity in plants. Papadakis et al. ( 2023 ) suggested that variations in stomatal conductance and intercellular carbon dioxide concentration should be examined concurrently in order to assess the factors that influence the rate of photosynthetic activity of plants. It is a well-known fact that Cd decreases Gs and causes a real decrease in Ci, which in turn makes the plant more susceptible to photoinhibition (Zhao et al. 2021 ). In fact, under restricting states of CO 2 fixation, the rate of reducing power production could decrease the rate of its utilization in the photosynthetic electron transport chain, accordingly harming the photosynthetic mechanical apparatus. The significant decrease in net photosynthesis rate suggests that Cd toxicity can influence photosynthesis by influencing primary photochemistry, electron transport, enzyme activity, biochemical reactions of the Calvin cycle, and changes in chloroplast structure, as previously discovered in a few studies (Nwugo and Huerta 2008 ). Cao et al. ( 2020 ) reported that E is important for the transport of inorganic nutrients over long distances via xylem tissues. In present study, under Cd toxicity the transpiration rate was decreased (Table 2 ), however, after applying GABA and MeJA the photosynthesis was improved because of an increment in CO 2 fixation by increasing the value of Ci, Gs, E and A. In another study, GABA enhanced these activities under heat and drought stress in the Helianthus annuus plant (Abdel Razik et al. 2021 ). Similarly, MeJA also enhanced the values of these attributes of photosynthesis which are reported in rice plant which was exposed to heat stress (Tang et al. 2022 ). When Gs values were found to increase, the mesophyll cell's capacity to take up CO 2 may increase and this would enhance the Calvin cycle’s capacity to take up CO 2 (Messinger et al. 2006 ). A quick and non-destructive method to evaluate the photosynthetic efficiency of stressed plants is chlorophyll a fluorescence. Previous researches have demonstrated that Cd impacted photosynthetic pigments and net photosynthesis in tomato seedlings (Song et al. 2024 ; Yadav et al. 2022 ). Cd is known to inhibit PS II activity by interfering with electron flow at the oxidation side and harming the PS II reaction centre (Bashri and Prasad 2015 ), hence in the present study, a marked decrease in oxygen yield might have occurred due to a direct effect of Cd on light reactions including oxygen evolving complex. In current study, different fluorescence parameters were detected to observe the change in the photochemistry of photosystem PS II (Table 2 ). The values of Phi_E 0 , Phi_0, Phi_P 0 and PI ABS were decreased significantly, and the values of energy flux parameters ET 0 /RC, TR 0 /RC and DI 0 /RC were increased under Cd toxicity (Table 2 ). Khan et al. ( 2019 ) also reported that decreased values of Phi_E 0 , Phi_0, and Phi_P 0 under Cd stress suggested disturbed electron flow between the photosystems which ultimately reduced the performance index (PI ABS ) of tested tomato seedlings. An increase in the values of specific energy flux parameters such as ABS/RC, ET 0 /RC, TR 0 /RC, DI 0 /RC suggested the dissipation of excess light energy under Cd stress. The application of exogenous GABA and MeJA alone and together exhibited alleviating effects on Phi_E 0 , Phi_0, Phi_P 0 , PI ABS in both tested seedlings. These improved values may be correlated with the result of decreased Cd uptake. Specific energy flux parameters were reduced in response to the exogenous GABA and MeJA while inhibitors MPA and DIECA with Cd worsened the damage to the PS II. ROS generation in living cells under aerobic condition is the results of metabolic reactions, and under stress ROS are produced at several sites of respiratory electron transport, photosynthetic electron transport, peroxisome, several sites of cytosol l and the apoplast in huge amount. Further, imbalance between ROS production and safe detoxification generates oxidative stress and its accumulation in high amount in cells becomes harmful to vital part of cells (Zulfiqar and Ashraf 2021 ). In current study, under Cd accelerated production/accumulation of ROS disturbed the metabolism of test plants thereby damaging impact on photosynthetic apparatus and growth of test seedlings was noticed (Fig. 5 ). Exogenous application of GABA and MeJA alone/together in both Cd stressed plants caused significant lowering in the level of ROS in tissues, and this effect was more pronounced GABA treated seedlings. As a result, significant alleviation in oxidative damage (lipid peroxidation and membrane damage) was observed. Contrary to this, when seedlings were treated with the inhibitors (MPA and DIECA) of GABA and MeJA the excess accumulation of ROS was seen, hence aggravated the damaging effects in both the seedlings (Fig. 5 ). Earlier findings have also demonstrated that GABA down regulates oxidative biomarkers hence significant improvement in the functioning of photosynthetic apparatus in tomato and brinjal seedlings under arsenic stress (Suhel et al. 2022 ) and in tobacco (He et al. 2021 ) under Cd stress by substantial reduction in oxidative stress. Likewise, MeJA also plays an important role in Cd toxicity alleviation on structure and function chloroplast in Pisum sativus L. (Manzoor et al. 2022 ) and Mentha arvensis (Zaid et al. 2018) exposed to Cd stress by decreasing oxidative damage. The biosynthetic inhibitor of GABA (MPA) and MeJA (DIECA) also induced O 2 • − and H 2 O 2 production and together with Cd it further enhanced the production of ROS in the tomato and brinjal seedlings in comparison to Cd stress (Fig. 5 ). Histochemical analysis also revealed that excess accumulation of H 2 O and O 2 •‾ was also visualized in leaves of both the seedlings exposed Cd stress (Fig. 4 ), and the intensity of colours developed due to SOR and H 2 O 2 was considerably decreased by the application of GABA and MeJA. Further, the intensity of colours became more intense when inhibitors (MPA and DIECA) of GABA and MeJA were applied in Cd stressed both the seedlings (Fig. 7 ). Furthermore, excessive rise in oxidative stress radicals due to Cd exposure to test plants enhanced the lipid peroxidation and membrane damage as shown by in vivo analysis where intensity of colour developed between the reaction of MDA equivalents and Schiff ‘reagent and also due to the staining with Evans’ blue reagent became more intense. However, GABA and MeJA application exhibited less intense colour in both the seedlings grown under Cd stress and again colour became more intense when treated with biosynthetic inhibitors and this effect was more prominent with the inhibitor of GABA. Enhanced level of H 2 O 2 may be assigned due to the altered photosynthetic process that resulted into leakage of electrons to oxygen. As a consequence of this increased lipid and protein degradation and damage to the plasma membranes and its stability are observed. Decrease in membrane stability, in turn might be associated with an increased accumulation of Cd in tissues (Emamverdian et al. 2023). However, exogenous application of GABA and MeJA significantly lowered Cd-mediated rise in oxidative stress (Fig. 4 ) and thus membrane stability must have been improved. Every cell is empowered with antioxidant system; enzymatic and non-enzymatic. The antioxidants efficiently neutralize the oxidants, hence proved to be beneficial components of defense system as they limit the ROS under control. In current study under Cd stress considerable increase the activity of SOD, POD and CAT could not keep the ROS levels under control as a result of this increased damage to lipids and membrane caused substantial damage to photosynthesis (Tables 3 and 4), thus Cd toxicity significantly affected the growth of both the seedlings. When Cd stressed seedlings of both vegetables were treated with GABA and MeJA either alone or in combinations exhibited significant lowering in SOD, CAT and POD activity, however the enzymatic antioxidants kept the ROS levels under control and this could also be supported by improved activity of photosynthesis (Fig. 6 , Table 3 , 4). Notwithstanding to this, the treatment with Cd + GABA + DIECA and Cd + MeJA + MPA raised the activity of SOD, POD and CAT, however ROS contents were enhanced significantly high (Fig. 6 ) thereby inhibiting the photosynthetic activity of both the seedlings. Under similar experimental conditions GST activity exhibited similar trend as noticed with other studied enzymatic antioxidants this could support the plants by sequestering the xenobiotic and finally channelized these radicals into vacuoles. Various studies have also demonstrated that under metal toxicity, GST enzyme plays a major role in removing the reactive lipid derivatives and harmful carbonyl groups (Sharapov et al. 2021 ; Singh et al. 2013 ). Exogenously application of GABA and MeJA minimizes the build-up of ROS and reduces the negative effect on lipids and membranes. Several studies have found that SOD, POD, CAT, and GST activity increase under metal stress. (Suhel et al. 2022 , Singh et al. 2020 ; Singh and Prasad 2019 ; Ahmad et al. 2018 ). In this study, the greater rise of SOD, POD, CAT, and GST activities greatly increased under Cd toxicity which reflected in the form of decreased growth characteristics. Exogenous application of GABA and MeJA lowered SOD, POD, CAT, and GST activities (Fig. 6 ). The improved growth of both the seedlings after exogenous application of GABA and MeJA suggested that the activity of SOD and POD was balanced and it sufficient to control the level of O 2 •− and H 2 O 2 (Fig. 6 ). The activation of GST is required GABA and MeJA-mediated mitigation of Cd toxicity in both the seedlings. 5. Conclusion The results conclude that the growth of tomato and brinjal seedlings were diminished by Cd, which could occur due to inhibitory effect on PSII photochemistry, light harvesting pigments and gas exchange parameters. Under Cd stress, despite of accelerated activity of SOD, CAT, POD and GST the oxidative biomarkers (O 2 •‾, H 2 O 2 , and MDA) were greatly higher. Exogenous application of MeJA and GABA individually or in combinations alleviated Cd toxicity by significantly lowering the oxidative biomarkers, hence improved the photosynthetic efficiency and growth. The biosynthetic inhibitors of GABA and MeJA application suggested that GABA and MeJA alleviated the toxicity of Cd, however GABA appears to play greater role in minimizing Cd toxicity in both the seedlings. The study further demonstrated that tomato seedlings were found to show more tolerance to Cd as compare to brinjal which could be due to strong antioxidant system and GABA/MeJA alleviation that negatively affects plant growth. According to these findings, brinjal is more vulnerable to Cd toxicity than tomato. This study can be helpful for minimizing the effect of Cd toxicity in the food chain using the justified amount of MeJA and GABA. Abbreviations Chl a Chlorophyll a Chl b Chlorophyll b Car Carotenoids A Respiration rates Ci Intracellular CO 2 concentration Gs Stomatal conductance E Transpiration rate Phi_P 0 The quantum yield of primary photochemistry Psi_0 Yield of electron transport per trapped exciton Phi_E 0 Quantum yield of electron transport PI ABS Performance index of PS II ABS/RC The energy fluxes for absorption of photon per active reaction center TR 0 /RC Trapped energy flux per active RC ET 0 /RC Electron transport flux per active RC DI 0 /RC Energy dissipation flux per active RC SOR; O 2 •‾ Superoxide radical H 2 O 2 Hydrogen peroxide MDA Malondialdehyde equivalent content SOD Superoxide dismutase POD Peroxidase CAT Catalase GST Glutathione-S-transferase MeJA Methyl jasmonate GABA Gamma-aminobutyric acid MPA 3-mercaptopropionic acid DIECA Diethyledithiocarbamic acid Declarations Acknowledgment The authors are very thankful to Head, Department of Botany, University of Allahabad, for providing laboratory facilities. 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Environ Sci Pollut Res 28(37):51854-51864. https://doi.org/10.1007/s11356-021-14252-3 Yadav M, Gupta P, Seth CS (2022). Foliar application of α-lipoic acid attenuates cadmium toxicity on photosynthetic pigments and nitrogen metabolism in Solanum lycopersicum L. Acta Physiol Plant 44(11): 112. https://doi.org/10.1007/s11738-022-03445-z Yamamoto Y, Kobayashi Y, Matsumoto H (2001) Lipid peroxidation is an early symptom triggered by aluminum, but not the primary cause of elongation inhibition in pea roots. Plant physiol 125(1): 199-208. https://doi.org/10.1104/pp.125.1.199 Zaid A, Mohammad F (2018) Methyl jasmonate and nitrogen interact to alleviate cadmium stress in Mentha arvensis by regulating physio-biochemical damages and ROS detoxification. J Plant Growth Regul 37(4):1331-1348. https://doi.org/10.1007/s00344-018-9854-3 Zhao H, Guan J, Liang Q, Zhang X, Hu H, Zhang J (2021). Effects of cadmium stress on growth and physiological characteristics of sassafras seedlings. Sci rep 11(1):9913. https://doi.org/10.1038/s41598-021-89322-0 Zeshan A, Abdullah M, Adil MF, Wei D, Noman M, Ahmed T, Shamsi IH (2022) Improvement of morpho-physiological, ultrastructural and nutritional profiles in wheat seedlings through astaxanthin nanoparticles alleviating the cadmium toxicity. J Hazard Mater 424: 126511. https://doi.org/10.1016/j.jhazmat.2021.126511 Zhang HH, Wang Y, Li X, Guoqiang H, Yanhuib C, Zhiyuan T, Jieyu S, Nan X, Guangyu S (2020) Chlorophyll synthesis and the photoprotective mechanism in leaves of mulberry ( Morus alba L.) seedlings under NaCl and NaHCO 3 stress revealed by TMT-based proteomics analyses. Ecotoxicol Environ Saf 190: 110164. https://doi.org/10.1016/j.ecoenv.2020.110164 Zhang XZ (1992) The measurement and mechanism of lipid peroxidation and SOD, POD and CAT activities in biological system. Res Method Crop Physiol pp 208-211 Zhang M, Liu Z, FanY, Liu C, Wang H, Li Y, Ji X (20220 Characterization of GABA-transaminase gene from mulberry ( Morus multicaulis ) and its role in salt stress tolerance. Genes 13(3): 501. https://doi.org/10.3390/genes13030501 Zhao H, Guan J, Liang Q, Zhang X, HuH, Zhang J (2021) Effects of cadmium stress on growth and physiological characteristics of sassafras seedlings. Sci Rep 11(1):1-11. https://doi.org/10.1038/s41598-021-89322-0 Zulfiqar F, Ashraf M (2021) Bioregulators: unlocking their potential role in regulation of the plant oxidative defense system. Plant Mol Biol 105(1):11-41. https://doi.org/10.1007/s11103-020-01077-w Cite Share Download PDF Status: Published Journal Publication published 10 Aug, 2024 Read the published version in Plant Growth Regulation → Version 1 posted Editorial decision: Minor revisions 20 Jun, 2024 Reviewers agreed at journal 28 May, 2024 Reviewers invited by journal 26 May, 2024 Editor invited by journal 02 May, 2024 Editor assigned by journal 29 Apr, 2024 First submitted to journal 28 Apr, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4340560","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":306811200,"identity":"b5956153-f8d6-4517-ac3f-4750bbff9b13","order_by":0,"name":"Varunendra Kumar Singh","email":"","orcid":"","institution":"University of Allahabad Faculty of Science","correspondingAuthor":false,"prefix":"","firstName":"Varunendra","middleName":"Kumar","lastName":"Singh","suffix":""},{"id":306811201,"identity":"318f5b49-b00b-4892-bb0c-bfaf2392f943","order_by":1,"name":"Shobhit Raj Vimal","email":"","orcid":"","institution":"University of Allahabad Faculty of Science","correspondingAuthor":false,"prefix":"","firstName":"Shobhit","middleName":"Raj","lastName":"Vimal","suffix":""},{"id":306811202,"identity":"05ec70b5-0aed-471c-8ca8-10dcb05238a2","order_by":2,"name":"Sheo Mohan Prasad","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIiWNgGAWjYJCCDzCGBIjFxk5YB+MMGEsSxGJjJkWLNA+IJKTFXPrwwcafOXfy+fsPP7xt82ubPB8zA+OHjzm4tVj2pSU28257ZjnjRpqxdW7fbcM2ZgZmyZnbcGsxOMNj/phx22EDhhsMZtK5PbcZgVrYmHnxazFs/AnUIn/++Ddpy57b9kRpaeAFajE4kGMmzfDjdiJBLZY9bGC/GBjeyCm27G24ndzGzNiM1y/mPMzAENt2x0Du/PGNN378uW07v7354IeP+BwGoQ5AKMY2MNmAWz2GFoY/eBWPglEwCkbBCAUAL8lT0Js1gwAAAAAASUVORK5CYII=","orcid":"","institution":"Allahabad University: University of Allahabad","correspondingAuthor":true,"prefix":"","firstName":"Sheo","middleName":"Mohan","lastName":"Prasad","suffix":""}],"badges":[],"createdAt":"2024-04-29 06:10:51","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4340560/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4340560/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10725-024-01202-5","type":"published","date":"2024-08-10T15:58:14+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":57894999,"identity":"4ec18a2e-59a5-488e-9902-98ea86f4c994","added_by":"auto","created_at":"2024-06-07 07:22:57","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":114185,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of exogenous applied GABA and MeJA treatment on the fresh mass of tomato and brinjal seedlings exposed to Cd toxicity. Each pot contains two seedlings. Data are means ± standard error of three independent biological replicates (n=3). Bars followed by different letters are statistically different at p˂0.05 significance level according to the DMRT. Small letters were used for brinjal and capital letters for tomato.\u003c/p\u003e","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/e6f2d774fd5cedade435b28a.jpg"},{"id":57894343,"identity":"9bb2984b-07c0-4829-ad70-1b133ccf7049","added_by":"auto","created_at":"2024-06-07 07:14:57","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":121899,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of exogenous applied GABA and MeJA treatment on the dry mass of tomato and brinjal seedlings exposed to Cd toxicity. Each pot contains two seedlings. Data are means ± standard error of three independent biological replicates (n=3). Bars followed by different letters are statistically different at p˂0.05 significance level according to the DMRT. Small letters were used for brinjal and capital letters for tomato.\u003c/p\u003e","description":"","filename":"Fig.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/44b33e494fe527d98a0fb28e.jpg"},{"id":57894344,"identity":"8d81dcb7-aea3-4ec1-a0b7-255aeb87861a","added_by":"auto","created_at":"2024-06-07 07:14:57","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":118875,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of exogenous supplementation of gamma-aminobutyric acid (GABA), methyl jasmonate (MeJA) treatment on MSI% s in leaf of tomato and brinjal seedlings exposed to Cd toxicity. The results presented are means ± standard error of three replicates (n = 3). Different letters assigned to the bar testimony significant P \u0026lt; 0.05 difference as per DMRT analysis of one-way ANOVA. Small letters were used for brinjal and capital letters for tomato.\u003c/p\u003e","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/19b133742548dcc805d0c5ee.jpg"},{"id":57894342,"identity":"107fa3a2-45fb-428a-bf88-fdafb3352c09","added_by":"auto","created_at":"2024-06-07 07:14:57","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":103874,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of exogenous supplementation of gamma-aminobutyric acid (GABA), methyl jasmonate (MeJA) treatment on Cadmium accumulation in leaf of tomato and brinjal seedlings exposed to Cd toxicity. The results presented are means ± standard error of three replicates (n = 3). Different letters assigned to the bar testimony significant P \u0026lt; 0.05 difference as per DMRT analysis of one-way ANOVA. Small letters were used for brinjal and capital letters for tomato.\u003c/p\u003e","description":"","filename":"Fig.4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/f7d5a6039a44700b4c82ec3d.jpg"},{"id":57895000,"identity":"61d1eb38-4ca8-4160-819e-392ac0b96172","added_by":"auto","created_at":"2024-06-07 07:22:57","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":269557,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of exogenous supplementation of gamma-aminobutyric acid (GABA), methyl jasmonate (MeJA) treatment on oxidative stress biomarkers: superoxide radical (SOR) (A), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) (B), and malondialdehyde (MDA) equivalents (C) contents in leaf of tomato and brinjal seedlings exposed to Cd toxicity. Results presented are means ± standard error of three replicates (n = 3). Different letters assigned to the bar testimony significant P\u0026lt;0.05 difference as per DMRT analysis of one-way ANOVA. Small letters were used for brinjal and capital letters for tomato.\u003c/p\u003e","description":"","filename":"Fig.5..jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/565683ee9c18eba557971f2f.jpg"},{"id":57894345,"identity":"b2a91fb5-bae2-45a7-a79f-e51a33a52a16","added_by":"auto","created_at":"2024-06-07 07:14:57","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":356930,"visible":true,"origin":"","legend":"\u003cp\u003eImpact of exogenous GABA and MeJA treatment on activity of enzymatic antioxidants: superoxide dismutase (SOD) (a), peroxidase (POD) (b), catalase (CAT) (c) and glutathione-S-transferase (GST) (d) in leaf of tomato and brinjal seedlings exposed to Cd toxicity. Results presented are means ± standard error of three replicates (n = 3). Different letters assigned to the bar’s testimony significant P \u0026lt; 0.05 difference as per DMRT analysis of one-way ANOVA. Small letters were used for brinjal and capital letters for tomato.\u003c/p\u003e","description":"","filename":"Fig.6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/ea9601567b969929cd8cd300.jpg"},{"id":57894348,"identity":"5bd43975-9ca6-48fa-a260-1e31c381bab5","added_by":"auto","created_at":"2024-06-07 07:14:58","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":285022,"visible":true,"origin":"","legend":"\u003cp\u003eHistochemical analysis of superoxide radical (O\u003csub\u003e2\u003c/sub\u003e•‾), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e), lipid peroxidation and membrane damage (MD) in leaves of tomato and brinjal seedlings exposed to Cd toxicity. I, Ck; II, Cd; III, Cd+GABA; IV, Cd+MeJA; V, Cd+MeJA+GABA; VI, Cd+GABA+DIECA and VII, Cd+MeJA+MPA.\u003c/p\u003e","description":"","filename":"Fig.7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/a517b00c2130a709c664e111.jpg"},{"id":62298705,"identity":"3556d39b-cbba-4f91-80ac-72c9065d2015","added_by":"auto","created_at":"2024-08-12 16:16:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2562819,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4340560/v1/24036290-f24b-41f5-a0f1-f83ca30944f5.pdf"}],"financialInterests":"","formattedTitle":"Phytohormones methyl jasmonate (MeJA) and gamma-aminobutyric acid (GABA) up-regulates growth and PS II photochemistry in brinjal and tomato seedlings exposed to cadmium toxicity","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eBrinjal (\u003cem\u003eSolanum melongena\u003c/em\u003e L.) and tomato (\u003cem\u003eS. lycopersicum\u003c/em\u003e L.) are the important vegetables that are widely cultivated in Indian subcontinent and world as well. Vegetables are rich in vitamins, minerals, and antioxidants; hence they are important components of human food. The production and quality of vegetables are being compromised due to biotic and abiotic stresses. In recent years, heavy metal contamination is increased due to enhanced anthropogenic activities. Cadmium (Cd) is of particular concern as it is one of the most toxic metals, and due to mining, painting, industrial waste, excessive use of agricultural fertilizers and pesticides, irrigation practices with contaminated water, application in nickel-cadmium batteries as electrodes and in semiconducting solar panels (Wang et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Genchi et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Mir et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), its concentration rises above threshold limit. Cd pollution of soil and water is a major global threat to human health, agri-food systems and ecosystems. It is found in nature in the form of divalent metallic element and when present in excess amounts; it generates reactive oxygen species in excess which affect plant growth, metabolism, productivity, and vigour (Haider et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Its concentrations in agricultural soil above 3 mg g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e is considered dangerous for crop cultivation (Lux et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Although it is not essential for plant growth and development but plants absorb it by involving Ca\u003csup\u003e2+\u003c/sup\u003e channels. Its excessive accumulation in plants may have major adverse effects on human health through the food chain (Haider et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Cadmium toxicity caused serious threats to plants and disturbed normal physiological and biochemical activity and as a result shunted growth, decreased chlorophyll contents and efficiency of photosystem II in plants were observed (Piacentini et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Furthermore, cadmium toxicity results into excessive production of reactive oxygen species (ROS) which harm plant membranes and destroys cell organelles and macromolecules (Unsal et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Nowadays numerous studies suggest that various plant growth regulators (PGRs) and signalling molecules that are exogenously applied to plants significantly reduce the effects of abiotic and biotic stresses by modifying several biochemical pathways (Shah et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Methyl jasmonate (MeJA) is one the key signalling molecules with a variety of roles in plants, including activating defence mechanisms, controlling growth and development, and interacting with other phytohormones (Mir et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). MeJA plays a critical role in the mitigation of environmental stresses under various conditions through various mechanisms like, improving the antioxidant mechanism and increasing the production of osmoregulators in plants (Raza et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Mousavi et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Previous studies showed that exogenous application of MeJA mitigates the chromium toxicity in \u003cem\u003ecalendula oficinalis\u003c/em\u003e (Barzin et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), enhanced cold tolerance in watermelon (Li et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), enhances the salinity tolerance in lemon seeds (Asadi and Jalilian \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), drought tolerance in cowpea plant (Sadeghipour \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), induced heat tolerance in the wheat plant (Fatima et al. 2021). However, there is currently limited information about the MeJA function in controlling Cd toxicity in vegetable crops.\u003c/p\u003e \u003cp\u003eLikewise, another plant growth regulator gamma-aminobutyric acid (GABA) is a four-carbon non-proteinogenic amino acid. Under various types of biotic and abiotic stresses, GABA quickly accumulates in plant tissues and works like an endogenous signaling molecule in plant growth and development (Li et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Suhel et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Exposure of a variety of stressful conditions: osmotic pressure, high temperatures, salinity stress, cold shock, and heavy metal toxicity have been linked to the accumulation of GABA (Seifikalhor et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Sheteiwy et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In recent years, it has been demonstrated that exogenously applied GABA enhanced the cold tolerance in tomato (Liu et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), improved heat tolerance in tea (Ren et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), enhanced salt stress tolerance in the mulberry (Zhang et al. 2022), drought stress reduction in \u003cem\u003ePhaseolus vulgaris\u003c/em\u003e (Abd El-Gawad et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and alleviated arsenic toxicity in tomato and brinjal seedlings (Suhel et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The protective effects of GABA against stress-related oxidative damage in a variety of plant species have been exhibited (Choe et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSince GABA and MeJA alone has a distinct role in reducing abiotic stress in plants, however, the relationship between GABA and MeJA signalling under Cd stress has not yet been investigated in crops in general and vegetables in particular. Therefore, in present study an attempt has been made to investigate the crosstalk between GABA and MeJA in alleviating cadmium toxicity in two vegetable crops tomato and brinjal by examining growth, light harvesting pigments, PS II photochemistry, photosynthetic gas exchange, accumulation of intracellular Cd, oxidative biomarkers and antioxidant system.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Experimental plants and growth condition\u003c/h2\u003e \u003cp\u003eThe healthy seeds of two vegetables, brinjal (\u003cem\u003eSolanum melongena\u003c/em\u003e L. var. KSP-1307 ARUN) and tomato (\u003cem\u003eSolanum lycopersicum\u003c/em\u003e L. var. BSS-791) were procured from the certified supplier of Prayagraj district, UP, India. Uniform-sized seeds of both vegetables were selected and surface sterilization was done with a 10% (sodium hypochlorite) solution for 20 min and rinsed with sterilized distilled water several times. Thereafter, seeds were wrapped with muslin cloth and kept in darkness at 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C for 24 hrs under sterilized conditions. Sprouted seeds were sown in a plastic tray containing sterilized sand and kept in the dark until seedlings emerged. The tray containing seedlings was transferred into the growth chamber (CDR model GRW-300Ge, Athens) under a light intensity of 240\u0026thinsp;\u0026plusmn;\u0026thinsp;30 mol photons m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 16:8 hrs of day and night period and relative humidity maintained at 65\u0026ndash;70% at 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C for 21 days. During the growth period, seedlings were irrigated with water and half-strength Hoagland's nutrition solution alternatively. On the emergence of the secondary leaf, the seedlings were uprooted carefully and washed under running water and thereafter they z were placed in half-strength Hoagland solution for 24 h for acclimatization. Finally, seedlings were grown hydroponically in growth medium containing different combinations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Treatment of seedlings with GABA, MeJA, and Cd\u003c/h2\u003e \u003cp\u003eThe seedlings of both the experimental plants were treated with 12 \u0026micro;M Cd (CdCl\u003csub\u003e2\u003c/sub\u003e), 15 \u0026micro;M GABA and 0.015 \u0026micro;M MeJA (Sigma-Aldrich) separately and in combination as required. The concentrations of Cd, GABA, and MeJA were selected after a series of screening experiments for a details study. Furthermore, to understand the role of the signalling molecules GABA and MeJA, 20\u0026micro;M MPA (3-mercaptopropionic acid; biosynthetic inhibitors of GABA) and 5 \u0026micro;M DIECA (diethyledithiocarbamic acid; biosynthetic inhibitors of MeJA) were applied. With different combinations, the treatments were given for five days under hydroponics conditions and the experimental setups consisted of: CK (control), Cd, Cd\u0026thinsp;+\u0026thinsp;GABA, Cd\u0026thinsp;+\u0026thinsp;MeJA, Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA, Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA, Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA. After 5 days of treatments various growth, physiological and biochemical attributes in both seedlings were analysed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Determination of growth attributes\u003c/h2\u003e \u003cp\u003eGrowth was measured as fresh and dry mass of both plant seedlings by digital electronic balance (Mettler Toledo, Switzerland, min. accuracy 0.1 mg). The seedlings of each setup were harvested and after determining fresh mass, seedlings were dried in a hot oven at 80\u0026deg;C for 48 h before the measurement of dry mass.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e2.4 Estimation of Cd content\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eSamples from each set were digested in a tri acid mixture (5:1:1 ratio, v/v) (HNO\u003csub\u003e3\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4,\u003c/sub\u003e and HClO\u003csub\u003e4\u003c/sub\u003e in 5:1:1 ratio, v/v) at 80\u0026deg;C until a transparent solution was formed to determine the amount of Cd present in the roots and shoots (Allen et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1986\u003c/span\u003e). Following cooling, Whatman No. 42 was used to filter the digested material, and double distilled water was used to maintain the filtrate up to 15 milliliters. Using a suitable drift blank and an atomic absorption spectrometer (iCE 3000 Series, Thermo Scientific, UK) equipped with a specific metal lamp, the amount of Cd in the digested samples was determined.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Determination of photosynthetic pigments\u003c/h2\u003e \u003cp\u003eThe 50 mg leaf from each sample was crushed and the pigments were extracted in 80% acetone. The absorbance of transparent suspension was recorded at 663, 646, and 470 nm spectrophotometrically (Shimadzu double beam UV\u0026ndash;Visible spectrophotometer-1700, Japan) and the amount of chlorophyll a (Chl \u003cem\u003ea\u003c/em\u003e) and b (Chl \u003cem\u003eb\u003c/em\u003e) and carotenoids (Car) was calculated by the equation given by Lichtenthaler (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1987\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Determination of chlorophyll a fluorescence kinetics (JIP test)\u003c/h2\u003e \u003cp\u003eChlorophyll \u003cem\u003ea\u003c/em\u003e fluorescence transient was assayed in intact leaves of treated and untreated seedlings with the help of a handheld leaf fluorometer (FluorPen FP 100, Photon System Instruments, Czech Republic). Prior to the measurement, the seedlings were preincubated for half an hour dark. The performance of photochemistry of photosystem II was determined according to the method given by Strasser et al. (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2000\u003c/span\u003e) by analysing the status of quantum yield of primary photochemistry (F\u003csub\u003eV\u003c/sub\u003e/Fm or ϕP\u003csub\u003e0\u003c/sub\u003e), maximum quantum efficiency of PS II photochemistry (Ψ\u003csub\u003e0\u003c/sub\u003e), yield of electron transport per trapped exciton (ϕE\u003csub\u003e0\u003c/sub\u003e), performance index of PS II (PI\u003csub\u003eABS\u003c/sub\u003e) and also the energy fluxes per active reaction centre (ABS/RC, TR\u003csub\u003e0\u003c/sub\u003e/RC, ET\u003csub\u003e0\u003c/sub\u003e/RC and DI\u003csub\u003e0\u003c/sub\u003e/RC).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Estimation of photosynthetic gas exchange parameters\u003c/h2\u003e \u003cp\u003eThe LCiSD portable photosynthesis system (L. MAN-LCI-SD, biosynthetic Ltd, EN11 0NT, UK) was applied to analyse the net photosynthetic rate (A), stomatal conductance (Gs), gas exchange indices including intercellular CO\u003csub\u003e2\u003c/sub\u003e concentration (Ci), and transpiration rate (E) of a fully exposed secondary leaves in seedlings. Throughout the measurements, the ambient CO\u003csub\u003e2\u003c/sub\u003e (380\u0026thinsp;\u0026plusmn;\u0026thinsp;10 \u0026micro;mol mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) concentration, leaf temperature (25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C), photosynthetic photon flux density (1200\u0026thinsp;\u0026plusmn;\u0026thinsp;250 \u0026micro;mol m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and relative humidity (70%) were maintained.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8 Estimation of oxidative stress indices\u003c/h2\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e2.8.1 Biochemical estimation of oxidative stress biomarkers\u003c/h2\u003e \u003cp\u003eSuperoxide radical (SOR; O\u003csub\u003e2\u003c/sub\u003e\u0026bull;\u0026oline;) and hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) contents in treated and untreated leaf samples were estimated by adopting the methods of Elstner and Heupel (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1976\u003c/span\u003e) and Velikova et al. (\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2000\u003c/span\u003e), respectively. The assay of superoxide radical (SOR) was performed in in each sample based on the formation of NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e from hydroxylamine in the presence of O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u003cb\u003e\u0026middot;\u0026minus;\u003c/b\u003e\u003c/sup\u003e. The content of O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u003cb\u003e\u0026middot;\u0026minus;\u003c/b\u003e\u003c/sup\u003e was quantified with the help of a standard curve prepared by the graded solution of NaNO\u003csub\u003e2\u003c/sub\u003e. Likewise, for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content the absorbance in each reaction mixture was recorded at 390 nm and the amount was calculated by using a standard curve prepared with graded solution of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. The lipid peroxidation as malondialdehyde (MDA) contents was estimated according to method of Heath and Packer (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1968\u003c/span\u003e). The absorbance of the supernatant was read at 532 and 600 nm and the value for non-specific absorbance of each sample at 600 nm was subtracted from absorbance recorded at 532 nm, and malondialdehyde equivalents content was calculated by using an extinction coefficient of 155 mM\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003ecm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e2.8.2 Determination of membrane stability index\u003c/h2\u003e \u003cp\u003e Membrane stability index (MSI) of leaf samples of both seedlings was measured according to the method of Gong et al. (1998). Fresh leaf (200 mg) was cut into equal size pieces and placed in a test containing 20 ml of deionized water and incubated at 30\u0026deg;C for 2h. The test tubes containing each sample were placed on a rotary shaker and at the end electric conductivity of the solution was recorded (C\u003csub\u003e1\u003c/sub\u003e) using an electric conductivity meter. Likewise, an equal amount of leaf discs from untreated seedlings were placed in another test tube and placed in a boiling water bath at 100\u0026deg;C for 15 min. After cooling, the electric conductive of samples was determined (C\u003csub\u003e2\u003c/sub\u003e) as earlier. The membrane stability index was calculated using the following equation.\u003c/p\u003e \u003cp\u003eMSI = [1- (C\u003csub\u003e1\u003c/sub\u003e/C\u003csub\u003e2\u003c/sub\u003e)] x100\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e2.8.3 In-vivo analysis of oxidative stress biomarkers\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003e \u003cem\u003eIn-vivo\u003c/em\u003e visualization of reactive oxygen species (ROS: O\u003csub\u003e2\u003c/sub\u003e\u0026bull; \u0026oline; and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) was performed using nitroblue tetrazolium (NBT) and 3,3ʹ-Diaminobenzidine (DAB) as per the methods of Frahry and Schopfer (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) and Thordal-Christensen et al. (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e1997\u003c/span\u003e), respectively. For visualizing O\u003csub\u003e2\u003c/sub\u003e\u0026bull;\u0026oline;and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, leaves, and root tips were incubated in nitro blue tetrazolium (NBT, prepared in potassium phosphate buffer pH 6.4) containing 10 mM Na-azide (Sigma Aldrich), and 1% solution of 3, 3\u0026prime;-diaminobenzidine (DAB) (Sigma Aldrich) in the light and dark until blue and brown spots respectively appeared. After this, leaves and root tips were bleached by immersing in boiling ethanol to visualize blue and brown spots, respectively, and photographed. Lipid peroxidation and membrane damage were visualized using Schiff\u0026rsquo;s reagent and Evans's blue according to the methods of Pompella et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1987\u003c/span\u003e) and Yamamoto et al. (\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2001\u003c/span\u003e), respectively. To localize lipid peroxidation products and plasma membrane integrity, leaves and root tips were stained with Schiff\u0026rsquo;s reagent and Evans blue (0.025%, w/v prepared in 100 \u0026micro;M of CaCl\u003csub\u003e2\u003c/sub\u003e, pH 5.6), respectively for 20 min. Thereafter, leaves and root tips were bleached by immersing in boiling ethanol to clearly visualize pink and blue spots, respectively, and photographed.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e2.9 Estimation of enzymatic antioxidants activities\u003c/h2\u003e \u003cp\u003eThe activity of superoxide dismutase (SOD; EC 1.15.1.1) in leaf samples was measured using the method ascribed by Giannopolitis and Ries (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1977\u003c/span\u003e), and one unit of SOD activity was defined as the quantity of enzyme required to prevent 50% of NBT reduction by O\u003csub\u003e2\u003c/sub\u003e\u0026bull;\u0026oline;. The activity of peroxidase (POD; EC 1.11.1.7) was determined using the method described by Zhang (\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e1992\u003c/span\u003e) and 1 nmol guaiacol oxidized min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is considered as one unit of POD activity. Catalase (EC 1.11.3.6) activity was measured by monitoring the dissociation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e at 240 nm for 1 min with a UV-visible spectrophotometer (Shimadzu, Japan) and CAT activity was calculated by using an extinction coefficient of 39.4 mM\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Aebi \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Further, 1 nmol H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e dissociated min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is defined as one unit (U) of enzyme activity. The activity of glutathione-S-transferase (GST, EC 2.5.1.18) was measured using the Habig et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1974\u003c/span\u003e) method. One unit (U) of enzyme activity denotes as one nmol of CDNB-conjugates produced min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e2.10 \u003cem\u003eStatistical analysis\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eFor the analysis of the data, a one-way analysis of variance (one-way ANOVA) was used. As a post hoc test to examine significant differences across several treatments at \u003cem\u003ep˂0.05\u003c/em\u003e significance level, Duncan's multiple range test (DMRT) was used. For each treatment, three separate biological duplicates for each treatment were performed.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.1 GABA and MeJA alleviate Cd toxicity on growth\u003c/h2\u003e \u003cp\u003eResults about growth attributes of fresh and dry mass of tomato and brinjal seedlings were displayed in Fig.\u0026nbsp;(1,2). Cd treatment (12 \u0026micro;M) caused diminished growth as the reduction in fresh and dry mass was 21% and 18% in tomato and 27% and 25% in brinjal seedlings, respectively over the values of the control. Under similar stress, the exogenous supplementation of GABA (15 \u0026micro;M) induced significant alleviatory effects on growth attributes as the decrease in fresh and dry biomass remained to be 5% and 2% in tomato and 8% and 3% in brinjal seedlings, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e,\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Likewise, MeJA (0.015 \u0026micro;M) when applied alleviated the Cd toxicity as the suppression in fresh was only 8% and 10%) and in dry mass, it was only 4% and 6% in tomato and brinjal seedlings, respectively. Combined application of GABA and MeJA completely restored the damaging effect of Cd on tested growth attributes, besides there was a marginal increase in growth as compared to the values recorded for control plants.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo understand the ameliorative role of endogenous GABA and MeJA against Cd toxicity on growth attributes the biosynthetic inhibitors of MeJA (DIECA, 5 \u0026micro;M) and GABA (MPA, 20 \u0026micro;M) were applied in Cd-stressed seedlings (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e,\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The results revealed that with DIECA (Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA) and MPA (Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA) the alleviation of inhibitory effects due to Cd on fresh mass was reversed showing the reduction of 25% and 35% in tomato and 30% and 38% in brinjal seedlings, respectively. Similar trends were also observed in the reduction of dry mass in both the seedlings under similar treatments with inhibitors (DIECA and MPA) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e3.2\u003c/b\u003e \u003cb\u003eGamma-aminobutyric acid and methyl jasmonate down regulate intracellular cadmium\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eCd treatment resulted in a substantial accumulation of Cd in both the seedlings and the content was greater in brinjal (72%) than that of tomato (58%) compared to nontreated control. The seedlings exogenously treated with GABA exhibited a considerable decrease in 22% and 20% and MeJA declined 14% and 6%, in brinjal and tomato compared to Cd treated seedlings. Combined treatment (Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;GABA) caused further reduction in the accumulation of Cd and it was found to be 33% and 18% in brinjal and tomato compared to Cd treated seedlings. Contrary to this, when tested plants were exposed to Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA then the Cd content enhanced 16% and 8% in brinjal and tomato compared to Cd treated seedlings. In Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA treatments the intracellular accumulation of Cd was increased further 8% and 3% in brinjal and tomato compared to Cd treated seedlings (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.3 \u003cem\u003eGamma-aminobutyric acid and methyl jasmonate protect photosynthetic pigments against Cd stress\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eOne of the most important factors for determining how plants respond to metal stress is the analysis of photosynthetic pigments which play an important role in the photosynthetic processes of the plants. Photosynthetic pigments (Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e, and Car) were reduced by 14%, 23% and 11% in tomato and 18%, 26%, and 14% in brinjal seedlings, respectively under Cd toxicity in comparison to the respective control values (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Unlike to this, on exogenous application of GABA the negative impact of Cd was alleviated, and the reduction in values of Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e, and Car were decreased by only 3%, 5%, and 2% in tomato and 5, 7, and 3% in brinjal seedlings (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Similar ameliorative results were also obtained with MeJA treatments on Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e, and Car under Cd stress in both seedlings, however, the recovery against Cd toxicity on pigment contents (Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e, and Car) was slightly lower than that observed with GABA (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The GABA and MeJA together alleviated more effectively as the negative effect of Cd was completely restored and the values were even greater than that of respective controls. Furthermore, to analyze the alleviatory effects caused by GABA and MeJA on Cd induced toxicity their specific biosynthetic inhibitors were used (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). With the combinations of Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA and Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA the alleviation in the levels of pigment contents (Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e, and Car) was further reversed depicting the decline 16%, 26%, 14% and 20%, 34%, 19% in tomato and 21%, 30%, 17% and 24%, 36%, 23% in brinjal seedlings respectively over the values of control.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRegulation of photosynthetic pigments Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e, and Cars by GABA and MeJA in tomato and brinjal seedlings growing under Cd stress.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTreatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eTomato\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eBrinjal\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChl \u003cem\u003ea\u003c/em\u003e (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e FM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChl \u003cem\u003eb\u003c/em\u003e (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e FM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCar (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e FM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eChl \u003cem\u003ea\u003c/em\u003e (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e FM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eChl \u003cem\u003eb\u003c/em\u003e (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e FM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCar (\u0026micro;g g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e FM)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1380\u0026thinsp;\u0026plusmn;\u0026thinsp;22b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e576\u0026thinsp;\u0026plusmn;\u0026thinsp;9ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e480\u0026thinsp;\u0026plusmn;\u0026thinsp;7ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1272\u0026thinsp;\u0026plusmn;\u0026thinsp;20b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e535\u0026thinsp;\u0026plusmn;\u0026thinsp;8ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e440\u0026thinsp;\u0026plusmn;\u0026thinsp;7ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1182\u0026thinsp;\u0026plusmn;\u0026thinsp;19d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e440\u0026thinsp;\u0026plusmn;\u0026thinsp;7c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e425\u0026thinsp;\u0026plusmn;\u0026thinsp;6d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1040\u0026thinsp;\u0026plusmn;\u0026thinsp;17d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e396\u0026thinsp;\u0026plusmn;\u0026thinsp;6 c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e375\u0026thinsp;\u0026plusmn;\u0026thinsp;6d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1338\u0026thinsp;\u0026plusmn;\u0026thinsp;21bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e546\u0026thinsp;\u0026plusmn;\u0026thinsp;8b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e470\u0026thinsp;\u0026plusmn;\u0026thinsp;7b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1250\u0026thinsp;\u0026plusmn;\u0026thinsp;19bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e496\u0026thinsp;\u0026plusmn;\u0026thinsp;8 b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e425\u0026thinsp;\u0026plusmn;\u0026thinsp;7b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1324\u0026thinsp;\u0026plusmn;\u0026thinsp;20c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e535\u0026thinsp;\u0026plusmn;\u0026thinsp;8bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e465\u0026thinsp;\u0026plusmn;\u0026thinsp;7bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1180\u0026thinsp;\u0026plusmn;\u0026thinsp;19c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e478\u0026thinsp;\u0026plusmn;\u0026thinsp;7bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e417\u0026thinsp;\u0026plusmn;\u0026thinsp;6bc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1420\u0026thinsp;\u0026plusmn;\u0026thinsp;22a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e585\u0026thinsp;\u0026plusmn;\u0026thinsp;9a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e485\u0026thinsp;\u0026plusmn;\u0026thinsp;8a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1298\u0026thinsp;\u0026plusmn;\u0026thinsp;21a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e541\u0026thinsp;\u0026plusmn;\u0026thinsp;9a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e448\u0026thinsp;\u0026plusmn;\u0026thinsp;7a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1155\u0026thinsp;\u0026plusmn;\u0026thinsp;18de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e423\u0026thinsp;\u0026plusmn;\u0026thinsp;6cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e412\u0026thinsp;\u0026plusmn;\u0026thinsp;6c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1005\u0026thinsp;\u0026plusmn;\u0026thinsp;16de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e380\u0026thinsp;\u0026plusmn;\u0026thinsp;6cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e365\u0026thinsp;\u0026plusmn;\u0026thinsp;6c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1102\u0026thinsp;\u0026plusmn;\u0026thinsp;17e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e378\u0026thinsp;\u0026plusmn;\u0026thinsp;5d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e385\u0026thinsp;\u0026plusmn;\u0026thinsp;6e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e965\u0026thinsp;\u0026plusmn;\u0026thinsp;15e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e341\u0026thinsp;\u0026plusmn;\u0026thinsp;5d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e335\u0026thinsp;\u0026plusmn;\u0026thinsp;5e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003eData are means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of three independent biological replicates (n\u0026thinsp;=\u0026thinsp;3). Values within the same column followed by different letters are statistically different at p˂0.05 significance level according to the Duncan\u0026rsquo;s multiple range test (DMRT)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003e3.4\u003c/b\u003e \u003cb\u003eGamma-aminobutyric acid and methyl jasmonate alleviate the negative effect of Cd stress on PS II Photochemistry\u003c/b\u003e\u003c/p\u003e \u003cp\u003eTo understand the impact of Cd and its regulation by GABA and MeJA on photosynthesis PS II photochemistry was analyzed by JIP test and results are depicted in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The results indicate that Cd toxicity exerted a negative impact on the values of chlorophyll \u003cem\u003ea\u003c/em\u003e fluorescence kinetics parameters such as quantum yield of primary photochemistry (Phi_P\u003csub\u003e0\u003c/sub\u003e), yield of electron transport per trapped exciton (Phi_E\u003csub\u003e0)\u003c/sub\u003e, the maximum quantum efficiency of PS П photochemistry (Psi_0), the performance index of PS II (PI\u003csub\u003eABS\u003c/sub\u003e) while the energy flux parameters [the energy for absorption of photon per active reaction center (ABS/RC), trapped energy per active reaction center (TR\u003csub\u003e0\u003c/sub\u003e/RC), electron transport per active reaction center (ET\u003csub\u003e0\u003c/sub\u003e/RC) and energy dissipation per active reaction center (DI\u003csub\u003e0\u003c/sub\u003e/RC) ] were increased significantly under Cd toxicity. Exogenous usage of signalling molecules GABA and MeJA individually and both together alleviate the negative impact of Cd toxicity on these parameters (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Contrary to this, the MeJA inhibitor DIECA intensified the Cd toxicity on energy flux parameters (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Furthermore, the application of biosynthetic inhibitor (MPA) of GABA showed a greater increase in energy flux parameters even in the presence of MeJA.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRegulation of chlorophyll \u003cem\u003ea\u003c/em\u003e fluorescence characteristic by GABA and MeJA in tomato and brinjal seedlings exposed to Cd stress.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTreatments\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003eTomato\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePhi_P0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePhi_E0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePsi_0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePI\u003csub\u003eABS\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eABS/RC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eET0/RC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eTR0/RC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eDI0/RC\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.790\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.530\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.588\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.532\u0026thinsp;\u0026plusmn;\u0026thinsp;0.050a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.240\u0026thinsp;\u0026plusmn;\u0026thinsp;0.042f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.966\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.894\u0026thinsp;\u0026plusmn;\u0026thinsp;0.029f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.774\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.711\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.429\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.478\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.659\u0026thinsp;\u0026plusmn;\u0026thinsp;0.031cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.783\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.212\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.436\u0026thinsp;\u0026plusmn;\u0026thinsp;0.024c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.885\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013bc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.776\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.576\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.623\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.101\u0026thinsp;\u0026plusmn;\u0026thinsp;0.044b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.538\u0026thinsp;\u0026plusmn;\u0026thinsp;0.044d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.056\u0026thinsp;\u0026plusmn;\u0026thinsp;0.017d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.198\u0026thinsp;\u0026plusmn;\u0026thinsp;0.030e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.731\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.758\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.588\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.618\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.840\u0026thinsp;\u0026plusmn;\u0026thinsp;0.040c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.657\u0026thinsp;\u0026plusmn;\u0026thinsp;0.045cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.140\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.225\u0026thinsp;\u0026plusmn;\u0026thinsp;0.028d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.756\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011 d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.728\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.601\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.635\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.475\u0026thinsp;\u0026plusmn;\u0026thinsp;0.050ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.496\u0026thinsp;\u0026plusmn;\u0026thinsp;0.046e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.994\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018 e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.927\u0026thinsp;\u0026plusmn;\u0026thinsp;0.031ef\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.720\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.698\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.427\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.460\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.551\u0026thinsp;\u0026plusmn;\u0026thinsp;0.036d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.214\u0026thinsp;\u0026plusmn;\u0026thinsp;0.031b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.289\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.642\u0026thinsp;\u0026plusmn;\u0026thinsp;0.020b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.898\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.647\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.412\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.431\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.296\u0026thinsp;\u0026plusmn;\u0026thinsp;0.033e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.782\u0026thinsp;\u0026plusmn;\u0026thinsp;0.028a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.332\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.886\u0026thinsp;\u0026plusmn;\u0026thinsp;0.027a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.935\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBrinjal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.775\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.527\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.626\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.431\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.198\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.845\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.745\u0026thinsp;\u0026plusmn;\u0026thinsp;0.033f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.671\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.671\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.435\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.425\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.661\u0026thinsp;\u0026plusmn;\u0026thinsp;0.023cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.556\u0026thinsp;\u0026plusmn;\u0026thinsp;0.049c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.225\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.085\u0026thinsp;\u0026plusmn;\u0026thinsp;0.028c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.740\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010bc\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.731\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.496\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.675\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.201\u0026thinsp;\u0026plusmn;\u0026thinsp;0.031b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.118\u0026thinsp;\u0026plusmn;\u0026thinsp;0.049d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.892\u0026thinsp;\u0026plusmn;\u0026thinsp;0.019d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.782\u0026thinsp;\u0026plusmn;\u0026thinsp;0.037e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.601\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008de\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.742\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.488\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.655\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.284\u0026thinsp;\u0026plusmn;\u0026thinsp;0.032c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.322\u0026thinsp;\u0026plusmn;\u0026thinsp;0.047cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.921\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.811\u0026thinsp;\u0026plusmn;\u0026thinsp;0.036d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.635\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.720\u0026thinsp;\u0026plusmn;\u0026thinsp;0.010c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.510\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.687\u0026thinsp;\u0026plusmn;\u0026thinsp;0.115 a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.675\u0026thinsp;\u0026plusmn;\u0026thinsp;0.038ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.074\u0026thinsp;\u0026plusmn;\u0026thinsp;0.048e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.858\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.758\u0026thinsp;\u0026plusmn;\u0026thinsp;0.038ef\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.598 \u0026plusmn;. 0009e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.679\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.391\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.410\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009de\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.355\u0026thinsp;\u0026plusmn;\u0026thinsp;0.019d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.015\u0026thinsp;\u0026plusmn;\u0026thinsp;0.041b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.306\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.225\u0026thinsp;\u0026plusmn;\u0026thinsp;0.026b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.781\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.626\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.422\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.391\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.296\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.315\u0026thinsp;\u0026plusmn;\u0026thinsp;0.042a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.328\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.554\u0026thinsp;\u0026plusmn;\u0026thinsp;0.023a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.795\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003eData are means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of three independent biological replicates (n\u0026thinsp;=\u0026thinsp;3). The quantum yield of primary photochemistry (Phi_P0), yield of electron transport per trapped exciton (Psi_0), quantum yield of electron transport (Phi_E0), performance index of PS II (PI\u003csub\u003eABS\u003c/sub\u003e), the energy fluxes for absorption of photon per active reaction center (ABS/RC), trapped energy flux per active RC (TR0/RC), electron transport flux per active RC (ET0/RC) and energy dissipation flux per active RC (DI0/RC).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.5 \u003cem\u003eGamma-aminobutyric acid and methyl jasmonate ameliorate Cd toxicity on photosynthetic gas exchange parameters\u003c/em\u003e\u003c/h2\u003e \u003cp\u003ePhotosynthetic gas exchange parameters were also adversely affected by Cd toxicity in tomato and brinjal seedlings. (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e,4). Upon Cd exposure, leaves gas exchange parameters A, Ci, gs, E, were inhibited by 23%, 18%, 28% and 20% in tomato and by 25%, 21%, 31% and 22% in brinjal, compared to control. However, the application of exogenous GABA significantly alleviated the toxicity of Cd on A, Ci, gs, and E values as it was decreased by only 8%, 2%, 7%, and 3% in tomato and 11%, 4%, 9% and 5% in brinjal, respectively over the values of respective controls. Under similar stress conditions when the seedlings were treated with MeJA significant amelioration (11%, 5%, 10%, and 8% in tomato and 13%, 7%, 12%, and 9% in brinjal seedlings) was noticed in A, Ci, gs, and E respectively. Furthermore, when seedlings were subjected to GABA and MeJA treatments damaging effects of Cd on these parameters were overcome in both the seedlings completely (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e,4).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRegulation of photosynthetic characteristics: A, Ci, gs, and E in tomato seedlings by GABA and MeJA growing under Cd toxicity.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTreatments\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eTomato\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (\u0026micro;mol CO\u003csub\u003e2\u003c/sub\u003e m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e s \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCi (\u0026micro;mol CO\u003csub\u003e2\u003c/sub\u003e mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGs (mol H\u003csub\u003e2\u003c/sub\u003eO m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e s \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eE (m mol H\u003csub\u003e2\u003c/sub\u003eO m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e s \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e280.66\u0026thinsp;\u0026plusmn;\u0026thinsp;4.05b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.050ab\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e232.67\u0026thinsp;\u0026plusmn;\u0026thinsp;3.36e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.040d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e274.37\u0026thinsp;\u0026plusmn;\u0026thinsp;4.59c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.048b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e266.00\u0026thinsp;\u0026plusmn;\u0026thinsp;4.47d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.85\u0026thinsp;\u0026plusmn;\u0026thinsp;0.046c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e292.67\u0026thinsp;\u0026plusmn;\u0026thinsp;4.74a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.050a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e218.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.15f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.038e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e191.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.76g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.037f\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBrinjal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCk\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15ab\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e237.00\u0026thinsp;\u0026plusmn;\u0026thinsp;3.83b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.063b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e185.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.99d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.049e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e228.00\u0026thinsp;\u0026plusmn;\u0026thinsp;3.68c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.060c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e220.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.55cd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.057d\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e252.67\u0026thinsp;\u0026plusmn;\u0026thinsp;4.07a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.065a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e168.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.72e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.047f\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e139.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.41f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.044g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eData are means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of six replicates (n\u0026thinsp;=\u0026thinsp;6). Bars followed by different letters are significantly different at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 according to the Duncan\u0026rsquo;s multiple range test. Data are means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of three independent biological replicates (n\u0026thinsp;=\u0026thinsp;3). Values within the same column followed by letters are statistically different at p˂0.05 significance level according to the Duncan\u0026rsquo;s multiple range test.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTo explore the relationship between GABA and MeJA regarding the alleviatory role, the biosynthetic inhibitors of GABA (MPA) and MeJA (DIECA) [in combinations (Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA; Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA)] were applied and the inhibitory effect of Cd became more prominent, however, this effect appeared to be more prominent with the inhibitor (MPA) of GABA.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.6 \u003cem\u003eGamma-aminobutyric acid and methyl jasmonate down-regulate oxidative biomarkers and protect against damage under Cd stress\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo pinpoint the damaging effect of Cd on growth and related parameters such as photosynthetic pigments, PS II photochemistry, and gas exchange parameters, and the role of GABA and MeJA on the oxidative stress biomarkers were analysed (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The oxidative biomarkers SOR, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2,\u003c/sub\u003e and MDA equivalents were found to increase by 20%, 33%, and 38% in tomato, respectively, while the corresponding rise in the values was 24%, 39%, and 46% in brinjal seedlings under Cd stress. A considerable decrease in SOR, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, MDA was noticed in Cd-stressed tomato seedlings in the presence of GABA as 3%, 11% and 13% and MeJA i.e. 6%, 19% and 16%, respectively. Further, as on the application of both the signalling molecules, the negative effects of Cd were completely overcome in both the seedlings, thereby the levels of oxidative biomarkers were decreased to the extent even less than that of control (untreated samples) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Together with the biosynthetic inhibitor (MPA) of GABA the levels of oxidative biomarkers were excessively risen, while with inhibitor (DIECA) of MeJA the rise in these markers were also increased but the levels were found to be comparatively low than those observed with MPA, an inhibitor of GABA (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFurther, the formation/accumulation of oxidative biomarkers in leaves under Cd stress and with different combinations were visualized by histochemical staining by blue formazan due to a reaction between NBT and SOR, by brown spots as s results of the reaction of hydrogen peroxide and DAB and by pink colour developed between the reaction of lipid peroxidation product and Shiff reagent (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The intensity of the blue colour was noticeable during Cd toxicity. With the biosynthetic inhibitors of GABA and MeJA the blue colour became more intense. The exogenously applied GABA and MeJA exhibited decreased colour intensity, hence showing the appreciable decrease in ROS content. Under Cd stress the biosynthesis inhibitors of MeJA and GABA exhibited more intense brown colour, and the increasing order is as Cd˂ MeJA˂ GABA as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Under GABA and MeJA treatment, the formation of brown colour in cells was quite less. The results revealed that histochemical analysis supports the biochemical data regarding H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation under Cd toxicity and the subsequent effects of GABA and MeJA with and without their biosynthetic inhibitors. The lipid peroxidation as studied by histochemical staining with the Schiff reagent exhibited with the greater intensity of pink colour was noticed under Cd toxicity alone and also with inhibitors of GABA and MeJA. The exogenously used GABA / MeJA appreciably lowered the colour intensity, and this result indicates the ameliorative effect of GABA and MeJA under Cd toxicity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e3.7 Gamma-aminobutyric acid and methyl jasmonate ameliorate Cd toxicity on membrane stability index\u003c/h2\u003e \u003cp\u003eThe data related to oxidative damage indices such as membrane stability index (MSI) are depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Cd declined MSI by 15 and 20% in tomato and brinjal, respectively in comparison to their control values. After the supplementation of GABA under Cd toxicity, MSI is declined by 2% and 5% in tomato and brinjal, respectively to their control values, similarly on the addition of MeJA the decrement of MSI is 4% and 8% in tomato and brinjal seedlings, respectively. When we applied both together GABA\u0026thinsp;+\u0026thinsp;MeJA under Cd stress, the MSI is enhanced by 2% and 3% in tomato and brinjal seedlings, respectively to their respective control values. The addition of MPA and DIECA caused further decline in MSI in both vegetables. On the application of MPA the MSI was greatly decreased by 31% and 34% in tomato and brinjal seedlings, respectively with their respective control values (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e3.7 \u003cem\u003eGamma-aminobutyric acid and methyl jasmonate up-regulate enzymatic antioxidant system under stress\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo keep the oxidants under control in the biological system, the plant possesses an array of antioxidant systems which include enzymatic and non-enzymatic antioxidants. The status of enzymatic antioxidants in test plants is displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Cadmium treatment resulted in enhanced activity of SOD, POD, CAT, and GST by 15, 30, 16, and 11% in tomato and 19, 36, 25, 14% in brinjal seedlings, respectively with their respective control values. The increment of SOD, POD, CAT, and GST was further enhanced in the presence of exogenous GABA (activity raised by 5, 11, 3, and 2% in tomato and 7, 13, 5, and 5% in brinjal seedlings, respectively), and the corresponding increase in the enzyme activity with exogenous MeJA (activity enhanced by 8, 14, 6, and 5% in tomato and 11, 16, 7, and 7% in brinjal seedlings, respectively) was noticed (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e). In the combined treatments Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;MeJA the activity of SOD, POD, CAT, and GST showed further decreasing trend in both the seedlings, however, it was still greater than that of respective controls. To understand the interaction between GABA and MeJA the specific inhibitors of GABA (Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA) and MeJA (Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA) were applied, the results revealed that the activity of SOD, POD, CAT, and GST was increased by 31, 43, 25, 22% in tomato and 34, 46, 35, 25% in brinjal seedlings exposed with Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA. Under similar treatments the corresponding increase with Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA combination was 20, 35, 19, 16% in tomato and 24, 40, 29, 20% in brinjal seedlings, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe two vegetables tomato and brinjal are important crops, widely grown in Indian continent, facing serious threats due to rise in heavy metal contamination. In current study, the seedlings of tomato and brinjal exposed to Cd showed a significant reduction in growth (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and such an adverse effect was more prominent in brinjal seedlings. Similar observations were also recorded in \u003cem\u003eTrigonella\u003c/em\u003e (Bashri et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), rice (Huang et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and wheat seedlings (Zeshan et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) under Cd stress. In both the seedlings Cd diminished the growth which could occur due to (i) damage caused to the light harvesting pigments Chl \u003cem\u003ea, b\u003c/em\u003e and Cars (Bashri et sl. 2021) (ii) negative impact on PS II photochemistry (Liu et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and (iii) excess accumulation of SOR and hydrogen peroxide that led to oxidation of nucleic acids (Sanghai et al. 2021) and proteins (Alamri et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and peroxidation of lipids (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The exogenously applied signalling molecules GABA or MeJA significantly alleviated the Cd toxicity in both the seedlings as reduction in growth attributes was recovered to the greater extent (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Many studies were earlier reported similar results (Zaid and Mohammad, \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kaya et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wei et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Combined application of GABA and MeJA was found to be more effective in recovering the loss of growth of tested vegetables due to Cd stress. Our results are in congruence with earlier findings where GABA has been shown to efficiently ameliorated the negative effect of arsenic on growth in tomato and brinjal seedlings (Suhel et al. 2024) and Cd on apples (Li et al. 2022). Likewise, exogenously applied MeJA mitigated the damaging effect of Cd stress on growth of \u003cem\u003eBrassica oleracea\u003c/em\u003e L (Srihindi et al. 2020).\u003c/p\u003e \u003cp\u003eTomato and brinjal seedlings (Suhel et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), Cd toxicity in maize plant (Seifikalhor et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and tobacco (He et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and phenanthrene phytotoxicity in cucumber (Guo et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). To study the impact of MeJA, its inhibitor DIECA in the presence of GABA exhibited significant decrease in the fresh/ dry mass of tomato and brinjal seedlings over the values to Cd stress. While with the inhibitor (MPA) of GABA a greater decrease was noticed in fresh mass/dry mass. These results reveal that GABA appears to be the main signalling molecule for alleviation of Cd toxicity, while MeJA regulates the GABA mediated toxicity amelioration in both the tested seedlings. In this study, it was noticed that accumulation of Cd in seedlings of tomato and brinjal (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e) exhibited severe oxidative burst as evidenced by enhanced levels of SOR (O\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e\u0026bull;\u0026minus;\u003c/sup\u003e), H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and MDA. Moreover, Cd can block ETC (electron transport chain) or displace the iron (Fe) molecule with other protein molecules that cause the abundant production of ROS inside the cell (Genchi et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The growth of seedlings is mainly regulated by photosynthesis and status of light harvesting pigments. A significant decrease in photosynthetic pigment contents under Cd stress was observed and these results are in consistent with the earlier findings where Cd induces senescence in the leaf of pea plants and inhibited the biosynthesis of chlorophyll (Bashri et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Hayat et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Conversely, the exogenous application of GABA and MeJA alone or together significantly up-regulated Chl and Car contents under Cd stress. The considerable rise in Chl and Car contents by the application of GABA and MeJA alone and together might have direct correlation with an alleviating effect on the growth performance of seedlings under Cd toxicity. In consonance with our results, Suhel et al. (\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) have shown the involvement of GABA in protecting Chl and Car in plants grown under As stress. Furthermore, MeJA exposure increased 5-aminolevulinic acid production, thereby up-regulation of gene expression which is linked with chlorophyll biosynthesis (Ueda and Saniewski \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Therefore, MJA positively modulated the efficiency of the photosynthetic apparatus; hence induces the level of tolerance against Cd toxicity tolerance in tested plants. Besides this, Salavati et al. (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) has suggested that down-regulation in the degrading process of Chl and Car by exogenous MeJA treatment significantly contributed to the improvement of pigment contents in \u003cem\u003eOryza sativa\u003c/em\u003e seedlings under Pb stress.\u003c/p\u003e \u003cp\u003eThe gas exchange parameters viz. A, Ci, Gs, and E were used to determine the photosynthetic activities, and in tomato and brinjal seedlings these parameters were negatively affected under Cd toxicity (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e,4). Similar trends were also reported by Huarancca et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) in \u003cem\u003eChenopodium quinoa\u003c/em\u003e under UV stress. According to Mosadegh et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), the reduction in photosynthetic rate might be caused by the degradation of pigments. In current study Cd could restrain the stomatal apertures, hence negatively affected the A, Ci, Gs, and E parameters because of the photosynthetic interruption as noticed in other study (Zhao et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Stomatal and non-stomatal factors are the two categories of factors that influence the rate of photosynthetic activity in plants. Papadakis et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) suggested that variations in stomatal conductance and intercellular carbon dioxide concentration should be examined concurrently in order to assess the factors that influence the rate of photosynthetic activity of plants.\u003c/p\u003e \u003cp\u003eIt is a well-known fact that Cd decreases Gs and causes a real decrease in Ci, which in turn makes the plant more susceptible to photoinhibition (Zhao et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In fact, under restricting states of CO\u003csub\u003e2\u003c/sub\u003e fixation, the rate of reducing power production could decrease the rate of its utilization in the photosynthetic electron transport chain, accordingly harming the photosynthetic mechanical apparatus. The significant decrease in net photosynthesis rate suggests that Cd toxicity can influence photosynthesis by influencing primary photochemistry, electron transport, enzyme activity, biochemical reactions of the Calvin cycle, and changes in chloroplast structure, as previously discovered in a few studies (Nwugo and Huerta \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCao et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) reported that E is important for the transport of inorganic nutrients over long distances via xylem tissues. In present study, under Cd toxicity the transpiration rate was decreased (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), however, after applying GABA and MeJA the photosynthesis was improved because of an increment in CO\u003csub\u003e2\u003c/sub\u003e fixation by increasing the value of Ci, Gs, E and A. In another study, GABA enhanced these activities under heat and drought stress in the \u003cem\u003eHelianthus annuus\u003c/em\u003e plant (Abdel Razik et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Similarly, MeJA also enhanced the values of these attributes of photosynthesis which are reported in rice plant which was exposed to heat stress (Tang et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). When Gs values were found to increase, the mesophyll cell's capacity to take up CO\u003csub\u003e2\u003c/sub\u003e may increase and this would enhance the Calvin cycle\u0026rsquo;s capacity to take up CO\u003csub\u003e2\u003c/sub\u003e (Messinger et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA quick and non-destructive method to evaluate the photosynthetic efficiency of stressed plants is chlorophyll \u003cem\u003ea\u003c/em\u003e fluorescence. Previous researches have demonstrated that Cd impacted photosynthetic pigments and net photosynthesis in tomato seedlings (Song et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Yadav et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Cd is known to inhibit PS II activity by interfering with electron flow at the oxidation side and harming the PS II reaction centre (Bashri and Prasad \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), hence in the present study, a marked decrease in oxygen yield might have occurred due to a direct effect of Cd on light reactions including oxygen evolving complex. In current study, different fluorescence parameters were detected to observe the change in the photochemistry of photosystem PS II (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The values of Phi_E\u003csub\u003e0\u003c/sub\u003e, Phi_0, Phi_P\u003csub\u003e0\u003c/sub\u003e and PI\u003csub\u003eABS\u003c/sub\u003e were decreased significantly, and the values of energy flux parameters ET\u003csub\u003e0\u003c/sub\u003e/RC, TR\u003csub\u003e0\u003c/sub\u003e/RC and DI\u003csub\u003e0\u003c/sub\u003e/RC were increased under Cd toxicity (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Khan et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) also reported that decreased values of Phi_E\u003csub\u003e0\u003c/sub\u003e, Phi_0, and Phi_P\u003csub\u003e0\u003c/sub\u003e under Cd stress suggested disturbed electron flow between the photosystems which ultimately reduced the performance index (PI\u003csub\u003eABS\u003c/sub\u003e) of tested tomato seedlings. An increase in the values of specific energy flux parameters such as ABS/RC, ET\u003csub\u003e0\u003c/sub\u003e/RC, TR\u003csub\u003e0\u003c/sub\u003e/RC, DI\u003csub\u003e0\u003c/sub\u003e/RC suggested the dissipation of excess light energy under Cd stress. The application of exogenous GABA and MeJA alone and together exhibited alleviating effects on Phi_E\u003csub\u003e0\u003c/sub\u003e, Phi_0, Phi_P\u003csub\u003e0\u003c/sub\u003e, PI\u003csub\u003eABS\u003c/sub\u003e in both tested seedlings. These improved values may be correlated with the result of decreased Cd uptake. Specific energy flux parameters were reduced in response to the exogenous GABA and MeJA while inhibitors MPA and DIECA with Cd worsened the damage to the PS II.\u003c/p\u003e \u003cp\u003eROS generation in living cells under aerobic condition is the results of metabolic reactions, and under stress ROS are produced at several sites of respiratory electron transport, photosynthetic electron transport, peroxisome, several sites of cytosol l and the apoplast in huge amount. Further, imbalance between ROS production and safe detoxification generates oxidative stress and its accumulation in high amount in cells becomes harmful to vital part of cells (Zulfiqar and Ashraf \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In current study, under Cd accelerated production/accumulation of ROS disturbed the metabolism of test plants thereby damaging impact on photosynthetic apparatus and growth of test seedlings was noticed (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Exogenous application of GABA and MeJA alone/together in both Cd stressed plants caused significant lowering in the level of ROS in tissues, and this effect was more pronounced GABA treated seedlings. As a result, significant alleviation in oxidative damage (lipid peroxidation and membrane damage) was observed. Contrary to this, when seedlings were treated with the inhibitors (MPA and DIECA) of GABA and MeJA the excess accumulation of ROS was seen, hence aggravated the damaging effects in both the seedlings (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Earlier findings have also demonstrated that GABA down regulates oxidative biomarkers hence significant improvement in the functioning of photosynthetic apparatus in tomato and brinjal seedlings under arsenic stress (Suhel et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and in tobacco (He et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) under Cd stress by substantial reduction in oxidative stress. Likewise, MeJA also plays an important role in Cd toxicity alleviation on structure and function chloroplast in \u003cem\u003ePisum sativus\u003c/em\u003e L. (Manzoor et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and \u003cem\u003eMentha arvensis\u003c/em\u003e (Zaid et al. 2018) exposed to Cd stress by decreasing oxidative damage. The biosynthetic inhibitor of GABA (MPA) and MeJA (DIECA) also induced O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026bull;\u003cb\u003e\u0026minus;\u003c/b\u003e\u003c/sup\u003e and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production and together with Cd it further enhanced the production of ROS in the tomato and brinjal seedlings in comparison to Cd stress (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Histochemical analysis also revealed that excess accumulation of H\u003csub\u003e2\u003c/sub\u003eO and O\u003csub\u003e2\u003c/sub\u003e\u0026bull;\u0026oline; was also visualized in leaves of both the seedlings exposed Cd stress (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e), and the intensity of colours developed due to SOR and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was considerably decreased by the application of GABA and MeJA. Further, the intensity of colours became more intense when inhibitors (MPA and DIECA) of GABA and MeJA were applied in Cd stressed both the seedlings (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Furthermore, excessive rise in oxidative stress radicals due to Cd exposure to test plants enhanced the lipid peroxidation and membrane damage as shown by in vivo analysis where intensity of colour developed between the reaction of MDA equivalents and Schiff \u0026lsquo;reagent and also due to the staining with Evans\u0026rsquo; blue reagent became more intense. However, GABA and MeJA application exhibited less intense colour in both the seedlings grown under Cd stress and again colour became more intense when treated with biosynthetic inhibitors and this effect was more prominent with the inhibitor of GABA. Enhanced level of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e may be assigned due to the altered photosynthetic process that resulted into leakage of electrons to oxygen. As a consequence of this increased lipid and protein degradation and damage to the plasma membranes and its stability are observed. Decrease in membrane stability, in turn might be associated with an increased accumulation of Cd in tissues (Emamverdian et al. 2023). However, exogenous application of GABA and MeJA significantly lowered Cd-mediated rise in oxidative stress (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e) and thus membrane stability must have been improved.\u003c/p\u003e \u003cp\u003eEvery cell is empowered with antioxidant system; enzymatic and non-enzymatic. The antioxidants efficiently neutralize the oxidants, hence proved to be beneficial components of defense system as they limit the ROS under control. In current study under Cd stress considerable increase the activity of SOD, POD and CAT could not keep the ROS levels under control as a result of this increased damage to lipids and membrane caused substantial damage to photosynthesis (Tables\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and 4), thus Cd toxicity significantly affected the growth of both the seedlings. When Cd stressed seedlings of both vegetables were treated with GABA and MeJA either alone or in combinations exhibited significant lowering in SOD, CAT and POD activity, however the enzymatic antioxidants kept the ROS levels under control and this could also be supported by improved activity of photosynthesis (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, 4). Notwithstanding to this, the treatment with Cd\u0026thinsp;+\u0026thinsp;GABA\u0026thinsp;+\u0026thinsp;DIECA and Cd\u0026thinsp;+\u0026thinsp;MeJA\u0026thinsp;+\u0026thinsp;MPA raised the activity of SOD, POD and CAT, however ROS contents were enhanced significantly high (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e) thereby inhibiting the photosynthetic activity of both the seedlings. Under similar experimental conditions GST activity exhibited similar trend as noticed with other studied enzymatic antioxidants this could support the plants by sequestering the xenobiotic and finally channelized these radicals into vacuoles. Various studies have also demonstrated that under metal toxicity, GST enzyme plays a major role in removing the reactive lipid derivatives and harmful carbonyl groups (Sharapov et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Singh et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Exogenously application of GABA and MeJA minimizes the build-up of ROS and reduces the negative effect on lipids and membranes. Several studies have found that SOD, POD, CAT, and GST activity increase under metal stress. (Suhel et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, Singh et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Singh and Prasad \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ahmad et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In this study, the greater rise of SOD, POD, CAT, and GST activities greatly increased under Cd toxicity which reflected in the form of decreased growth characteristics. Exogenous application of GABA and MeJA lowered SOD, POD, CAT, and GST activities (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The improved growth of both the seedlings after exogenous application of GABA and MeJA suggested that the activity of SOD and POD was balanced and it sufficient to control the level of O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026bull;\u0026minus;\u003c/sup\u003e and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The activation of GST is required GABA and MeJA-mediated mitigation of Cd toxicity in both the seedlings.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe results conclude that the growth of tomato and brinjal seedlings were diminished by Cd, which could occur due to inhibitory effect on PSII photochemistry, light harvesting pigments and gas exchange parameters. Under Cd stress, despite of accelerated activity of SOD, CAT, POD and GST the oxidative biomarkers (O\u003csub\u003e2\u003c/sub\u003e\u0026bull;\u0026oline;, H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, and MDA) were greatly higher. Exogenous application of MeJA and GABA individually or in combinations alleviated Cd toxicity by significantly lowering the oxidative biomarkers, hence improved the photosynthetic efficiency and growth. The biosynthetic inhibitors of GABA and MeJA application suggested that GABA and MeJA alleviated the toxicity of Cd, however GABA appears to play greater role in minimizing Cd toxicity in both the seedlings. The study further demonstrated that tomato seedlings were found to show more tolerance to Cd as compare to brinjal which could be due to strong antioxidant system and GABA/MeJA alleviation that negatively affects plant growth. According to these findings, brinjal is more vulnerable to Cd toxicity than tomato. This study can be helpful for minimizing the effect of Cd toxicity in the food chain using the justified amount of MeJA and GABA.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eChl \u003cem\u003ea\u0026nbsp;\u003c/em\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Chlorophyll a\u003c/p\u003e\n\u003cp\u003eChl \u003cem\u003eb\u003c/em\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Chlorophyll b\u003c/p\u003e\n\u003cp\u003eCar \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Carotenoids\u003c/p\u003e\n\u003cp\u003eA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Respiration rates\u003c/p\u003e\n\u003cp\u003eCi \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Intracellular CO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003econcentration\u003c/p\u003e\n\u003cp\u003eGs \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Stomatal conductance\u003c/p\u003e\n\u003cp\u003eE \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Transpiration rate\u003c/p\u003e\n\u003cp\u003ePhi_P\u003csub\u003e0 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/sub\u003eThe quantum yield of primary photochemistry\u003c/p\u003e\n\u003cp\u003ePsi_0 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Yield of electron transport per trapped exciton\u003c/p\u003e\n\u003cp\u003ePhi_E\u003csub\u003e0\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Quantum yield of electron transport\u003c/p\u003e\n\u003cp\u003ePI\u003csub\u003eABS\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Performance index of PS II\u003c/p\u003e\n\u003cp\u003eABS/RC \u0026nbsp; \u0026nbsp;The energy fluxes for absorption of photon per active reaction center\u003c/p\u003e\n\u003cp\u003eTR\u003csub\u003e0\u003c/sub\u003e/RC \u0026nbsp; \u0026nbsp; Trapped energy flux per active RC\u003c/p\u003e\n\u003cp\u003eET\u003csub\u003e0\u003c/sub\u003e/RC \u0026nbsp; \u0026nbsp; \u0026nbsp; Electron transport flux per active RC\u003c/p\u003e\n\u003cp\u003eDI\u003csub\u003e0\u003c/sub\u003e/RC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Energy dissipation flux per active RC\u003c/p\u003e\n\u003cp\u003eSOR; O\u003csub\u003e2\u003c/sub\u003e•‾ \u0026nbsp; \u0026nbsp;Superoxide radical\u003c/p\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Hydrogen peroxide\u003c/p\u003e\n\u003cp\u003eMDA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Malondialdehyde equivalent content\u003c/p\u003e\n\u003cp\u003eSOD \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Superoxide dismutase\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePOD \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Peroxidase\u003c/p\u003e\n\u003cp\u003eCAT \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Catalase\u003c/p\u003e\n\u003cp\u003eGST \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Glutathione-S-transferase\u003c/p\u003e\n\u003cp\u003eMeJA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Methyl jasmonate\u003c/p\u003e\n\u003cp\u003eGABA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Gamma-aminobutyric acid\u003c/p\u003e\n\u003cp\u003eMPA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;3-mercaptopropionic acid\u003c/p\u003e\n\u003cp\u003eDIECA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Diethyledithiocarbamic acid\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are very thankful to Head, Department of Botany, University of Allahabad, for providing laboratory facilities. University Grant Commission, New Delhi, India is acknowledged for providing financial support to Varunendra Kumar Singh as UGC-AU research scholarship to carry out the present work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e SMP designed experiments. VKS performed experiments. SMP and VKS analysed data. VKS and SRV wrote the manuscript. SMP, SRV and VKS corrected the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting intrests:\u003c/strong\u003e \u0026nbsp;Authors have no competing intrests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAbd El-Gawad HG, Mukherjee S, FaraR, Abd Elbar OH, Hikal M, Abou El-Yazied A, Ibrahim MF (2021) Exogenous \u0026gamma;-aminobutyric acid (GABA)-induced signaling events and field performance associated with mitigation of drought stress in \u003cem\u003ePhaseolus vulgaris\u003c/em\u003eL. 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Plant Mol Biol 105(1):11-41. https://doi.org/10.1007/s11103-020-01077-w\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"plant-growth-regulation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"grow","sideBox":"Learn more about [Plant Growth Regulation](https://www.springer.com/journal/10725)","snPcode":"10725","submissionUrl":"https://submission.nature.com/new-submission/10725/3","title":"Plant Growth Regulation","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Antioxidants, Oxidative biomarkers, Photosynthesis, Signalling molecules, Sustainable agriculture","lastPublishedDoi":"10.21203/rs.3.rs-4340560/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4340560/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCadmium (cd) toxicity has become a major threat to the crop productivity and vegetables appeared to be on major risk. In present study, the potential of methyl jasmonate (MeJA, 0.015 \u0026micro;M) and gamma-aminobutyric acid (GABA 15 \u0026micro;M) was explored to alleviate the cd toxicity (12 \u0026micro;M) in tomato and brinjal seedlings. Cd declined fresh dry mass by 21% and 18% in tomato seedlings and 27% and 25% in brinjal seedlings. Cd significantly damage pigments contents (Chl \u003cem\u003ea\u003c/em\u003e, Chl \u003cem\u003eb\u003c/em\u003e and Car), PS II photochemistry (Chl \u003cem\u003ea\u003c/em\u003e fluorescence kinetics) and photosynthetic gas exchange parameters in both seedlings. Furthermore, Cd exacerbated oxidative biomarkers and antioxidant enzymes CAT, SOD, POD and GST in both the seedlings. Phytohormones MeJA and GABA application to seedlings led to significant declined Cd uptake, oxidative biomarkers, antioxidative enzymes activity and up-regulation in leaves gas exchange parameters, photosynthetic performance and seedlings growth parameters. Additionally, biosynthetic inhibitors diethyldithiocarbamic acid (DIECA) of MeJA and 3-Mercaptopropionic acid (MPA) of GABA further raised Cd uptake, thereby excessive increase in oxidative biomarkers worsened Cd toxicity on photosynthesis, hence growth was greatly reduced. Thus, the study concludes that as compared to brinjal seedlings, tomato showed greater tolerance to Cd toxicity, and GABA plays a crucial role in mitigating the Cd toxicity, however, GABA and MeJA together more efficiently alleviated the toxicity.\u003c/p\u003e","manuscriptTitle":"Phytohormones methyl jasmonate (MeJA) and gamma-aminobutyric acid (GABA) up-regulates growth and PS II photochemistry in brinjal and tomato seedlings exposed to cadmium toxicity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-07 07:14:52","doi":"10.21203/rs.3.rs-4340560/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Minor revisions","date":"2024-06-21T03:06:25+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-05-28T06:17:50+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-26T06:38:46+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Plant Growth Regulation","date":"2024-05-03T03:29:21+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-29T18:56:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Plant Growth Regulation","date":"2024-04-29T02:10:39+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"plant-growth-regulation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"grow","sideBox":"Learn more about [Plant Growth Regulation](https://www.springer.com/journal/10725)","snPcode":"10725","submissionUrl":"https://submission.nature.com/new-submission/10725/3","title":"Plant Growth Regulation","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4811726c-89be-4fa8-b0be-7a5ec4a7352f","owner":[],"postedDate":"June 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-08-12T16:07:11+00:00","versionOfRecord":{"articleIdentity":"rs-4340560","link":"https://doi.org/10.1007/s10725-024-01202-5","journal":{"identity":"plant-growth-regulation","isVorOnly":false,"title":"Plant Growth Regulation"},"publishedOn":"2024-08-10 15:58:14","publishedOnDateReadable":"August 10th, 2024"},"versionCreatedAt":"2024-06-07 07:14:52","video":"","vorDoi":"10.1007/s10725-024-01202-5","vorDoiUrl":"https://doi.org/10.1007/s10725-024-01202-5","workflowStages":[]},"version":"v1","identity":"rs-4340560","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4340560","identity":"rs-4340560","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}