Melatonin Pulse Treatment Optimization: Boosting Vase Life and Postharvest Quality in Cut Roses (Rosa hybrida cv. Samurai)

Melatonin Pulse Treatment Optimization: Boosting Vase Life and Postharvest Quality in Cut Roses (Rosa hybrida cv. 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Samurai) sara Shamsinejad, Safoora Saadati, Vahid Reza Saffari, Zahra Pakkish This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8762944/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 15 You are reading this latest preprint version Abstract Cut roses ( Rosa hybrida L. cv. Samurai) undergo rapid postharvest senescence, limiting vase life and quality. While the preservative effect of melatonin is established, a critical barrier to its commercial adoption is the lack of standardized, cost-effective application protocols. This study evaluated melatonin's efficacy as a biostimulant, applied via pulse (30-min immersion) or continuous (vase solution) methods at 0.1 mM and 1 mM concentrations, testing the hypothesis that a brief pulse treatment acts as a priming stimulus for a more efficient defense response. Assessed parameters included vase life, flower quality, diameter, chlorophyll and anthocyanin contents, electrolyte leakage, relative water content, solution uptake, and antioxidant enzyme activities. The 0.1 mM pulse treatment extended vase life by 61% (9.67 vs. 6.00 days), improved flower quality (5.00 vs. 3.33), increased diameter by 18% (51.00 vs. 43.33 mm), enhanced chlorophyll by 22% and anthocyanin by 36%, and reduced electrolyte leakage by 43%, with strong correlations to vase life (r = 0.71–0.94, P < 0.001). The 0.1 mM continuous treatment was less effective, and 1 mM concentrations showed minimal benefits. These results suggest that a brief pulse treatment effectively primes the rose's endogenous defense systems, offering a highly efficient strategy. Melatonin's antioxidant and anti-senescence properties provide a sustainable, cost-effective strategy for extending rose vase life, with 0.1 mM pulse application as the most effective method for commercial floriculture. Cut roses ( Rosa hybrida L. cv. Samurai) undergo rapid postharvest senescence, limiting vase life and quality. This study evaluated melatonin's efficacy as a biostimulant, applied via pulse (30-min immersion) or continuous (vase solution) methods at 0.1 mM and 1 mM concentrations, in a completely randomized design with three replicates of 10 stems per treatment. Assessed parameters included vase life, flower quality, diameter, chlorophyll and anthocyanin contents, electrolyte leakage, relative water content, solution uptake, and antioxidant enzyme activities. The 0.1 mM pulse treatment extended vase life by 61% (9.67 vs. 6.00 days), improved flower quality (5.00 vs. 3.33), increased diameter by 18% (51.00 vs. 43.33 mm), enhanced chlorophyll by 22% and anthocyanin by 36%, and reduced electrolyte leakage by 43%, with correlations to vase life (r = 0.71–0.94, P < 0.001). The 0.1 mM continuous treatment was less effective, and 1 mM concentrations showed minimal benefits. Melatonin's antioxidant and anti-senescence properties provide a sustainable, cost-effective strategy for extending rose vase life, with 0.1 mM pulse application as the most effective method for commercial floriculture. Melatonin Postharvest Roses Vase life Quality Figures Figure 1 Figure 2 1. Introduction Roses ( Rosa spp.), known as the "queen of flowers", are central to the global floriculture industry, valued for their aesthetic appeal, color diversity, and cultural significance [ 1 ]. The cut flower market exceeded $ 40 billion in 2024, with roses dominating due to their use in arrangements and gifting [ 2 ]. However, postharvest longevity is limited by rapid senescence, causing economic losses and reduced consumer satisfaction [ 3 – 5 ]. This complex deterioration process is driven by an interplay of physiological and biochemical stressors, including: (1) oxidative damage from reactive oxygen species (ROS), which compromises membrane integrity, lipids, and proteins [ 6 , 7 ]; (2) ethylene-induced petal abscission and senescence via upregulation of biosynthetic genes [ 8 , 9 ]; (3) vascular occlusions from microbial proliferation and physiological plugging, impeding water uptake [ 10 ]; and (4) loss of hydraulic conductivity and turgor pressure, resulting in wilting [ 6 , 9 , 11 , 12 ]. Conventional postharvest interventions, such as chemical preservatives (e.g., silver thiosulfate, 8-hydroxyquinoline) and cold storage, mitigate these issues to varying degrees but are limited by inconsistent efficacy, high costs, and environmental concerns from chemical residues [ 13 – 16 ]. This necessitates innovative, sustainable strategies to enhance vase life while aligning with eco-friendly floriculture practices [ 17 , 18 ]. Melatonin (N-acetyl-5-methoxytryptamine), a pleiotropic indoleamine, has emerged as a promising biostimulant in postharvest horticulture, extending beyond its established role in circadian regulation to exhibit potent antioxidant and regulatory functions in plants [ 19 , 20 ]. Its efficacy in delaying senescence is well-documented across cut flowers, including roses [ 21 ], anthurium [ 22 ], carnations [ 23 , 24 ], gerberas [ 25 ], Chrysanthemum [ 26 ], and peonies [ 27 ], as well as fruits like sweet cherries [ 28 ], and pears [ 29 ]. Melatonin's multifaceted mechanisms include: (1) direct scavenging of ROS (e.g., superoxide, hydrogen peroxide) and upregulation of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), mitigating oxidative stress [ 20 , 28 , 30 ].; (2) suppression of ethylene biosynthesis through downregulation of ACC synthase (ACS) and ACC oxidase (ACO) genes, reducing petal abscission [ 29 , 31 ]; (3) enhancement of hydraulic conductivity via upregulation of aquaporin genes (PIP, TIP), improving water relations and turgor maintenance [ 32 – 34 ]; and (4) antimicrobial activity that curbs bacterial growth in vase solutions, preventing vascular blockages [ 25 , 35 , 36 ]. Additionally, melatonin modulates phytohormone crosstalk, elevating indole-3-acetic acid (IAA) to counteract abscisic acid (ABA)-mediated stress and sustaining carbohydrate reserves to support energy demands [ 37 – 39 ]. These actions collectively preserve chlorophyll content, delay petal senescence, and enhance visual quality [ 40 , 41 ]. However, for widespread commercial adoption, understanding how to apply melatonin is as critical as knowing that it works. Previous studies have demonstrated its efficacy but often using a single application method, leaving a significant gap in our knowledge of optimized protocols. Specifically, the comparative efficacy of a brief, resource-saving pulse treatment versus a continuous vase solution application, and the interaction of these methods with concentration, remains unexplored. This study was therefore designed not merely to reconfirm the benefits of melatonin, but to directly address this applied knowledge gap. We hypothesize that a short pulse treatment acts as a priming stimulus, triggering a more robust and sustained endogenous defense response compared to continuous exposure. This study systematically compares pulse versus continuous methods at two concentrations to identify an optimized protocol for commercial scalability. Despite these advances, the optimal application strategy for melatonin in cut roses remains underexplored. Pulse treatments (short-term immersion) may prime defense and antioxidant systems, offering a rapid, cost-effective intervention, while continuous exposure in vase solutions could provide sustained protection against oxidative and microbial stress. The comparative efficacy of these methods, particularly at varying physiological concentrations (e.g., 0.1 and 1 mM), is a critical knowledge gap [ 21 , 23 ]. This study investigates the effects of pulse versus continuous melatonin treatments at 0.1 and 1 mM on the postharvest vase life of cut roses, hypothesizing that application method and concentration interactively modulate senescence pathways. By elucidating an optimized melatonin application protocol, this research aims to deliver a sustainable, cost-effective strategy to enhance the postharvest quality and commercial value of cut roses, contributing to greener floriculture practices. 2. Materials and Methods 2.1. Plant material Cut roses ( Rosa hybrida L. cv. Samurai) were harvested at the commercial maturity stage (tight bud, outer petals unfurling) from a commercial greenhouse in Zarand, Kerman province, Iran. Stems were uniformly selected for length (approximately 50 cm), free from defects or diseases, and immediately transported to the laboratory under hydrated conditions (wrapped in moist paper and placed in buckets with distilled water). Upon arrival, stems were re-cut underwater to a uniform length of 40 cm to remove air emboli, basal leaves were removed to prevent microbial contamination in vase solutions, and 4 leaves were retained per stem to standardize foliage load and minimize variability in physiological measurements. Each treatment was replicated three times, with each replicate consisting of 10 cut stems (one stem per vase), resulting in a total of 150 stems (5 treatments × 3 replicates × 10 stems). 2.2. Preparation of melatonin solutions Melatonin (N-acetyl-5-methoxytryptamine, purity ≥ 98%, Sigma-Aldrich, USA) was dissolved in absolute ethanol (0.1% v/v) as a co-solvent to enhance solubility, then diluted to the desired concentrations (0.1 mM and 1 mM) using distilled water. Control solutions consisted of distilled water with 0.1% ethanol to account for any solvent effects. All solutions were freshly prepared on the day of treatment and adjusted to pH 5.5–6.0 using 0.1 M HCl or NaOH to mimic typical vase water conditions [ 12 ]. 2.3. Treatment applications The experiment followed a completely randomized design (CRD) with a 2 × 2 factorial arrangement (method: pulse/continuous; concentration: 0.1/1 mM) plus a control, resulting in five treatments: (1) control (distilled water with 0.1% ethanol), (2) 0.1 mM melatonin pulse, (3) 1 mM melatonin pulse, (4) 0.1 mM melatonin continuous, and (5) 1 mM melatonin continuous. All treatments were applied immediately after stem preparation. For pulse treatments, stems were immersed up to 10 cm from the base in melatonin solutions (0.1 or 1 mM) for 30 minutes at 20°C in the dark, then rinsed with distilled water and transferred to vases with fresh distilled water, refreshed every 48 hours. For continuous treatments, stems were placed in vases with melatonin-infused solutions (0.1 or 1 mM), replaced every 48 hours to maintain concentration. To prevent melatonin degradation under light, all vases were covered with opaque material [ 19 ]. Vases were maintained at 20 ± 2°C, 60–70% relative humidity, and a 12-hour photoperiod (15–20 µmol m⁻² s⁻¹ PPFD). Each treatment had three replicates of 10 stems (one per vase). 2.4. Measurement of postharvest parameters Postharvest parameters were assessed primarily at the conclusion of the vase life period, with the exception of vase life, flower quality, and solution uptake, which were evaluated dynamically throughout the experiment. Physiological and biochemical parameters were measured on leaf tissues, while anthocyanin content was quantified specifically in petals. 2.5. Vase life Vase life was determined as the number of days from the start of the experiment until flowers exhibited senescence, defined as wilting of > 50% of petals, petal discoloration, or bent neck (peduncle bending > 45°). Daily visual assessments were conducted by two independent observers, and the average was recorded [ 42 , 43 ]. 2.6. Flower quality Flower quality was evaluated daily on a subjective scale from 1 to 5, where: 5 = excellent (fully turgid, vibrant color, no wilting); 4 = good (minor petal edge curling, slight color fading); 3 = moderate (noticeable wilting on 25–50% petals); 2 = poor (severe wilting, significant discoloration); and 1 = unacceptable (complete wilting or abscission). Scores were averaged across replicates [ 44 ]. 2.7. Flower diameter Flower diameter was measured using a digital caliper (accuracy ± 0.01 mm) at the end of the vase life period. The maximum diameter of the flower head was recorded as the distance across the outermost petals at their widest point. Measurements were taken in two perpendicular directions, and the average was calculated for each flower [ 45 ]. 2.8. Chlorophyll content index Chlorophyll content index was indirectly assessed as the chlorophyll index using a SPAD-502 chlorophyll meter (Konica Minolta, Japan) at the end of the vase life period. Measurements were taken on the middle portion of three leaves per stem, and the average SPAD value was recorded [ 46 ]. 2.9. Pigment content (chlorophyll, carotenoids, and anthocyanins) Fresh leaf tissue was pulverized in 70% acetone and centrifuged at 350 × g for 15 min at ambient temperature to produce a clarified supernatant. The absorbance of this extract was recorded spectrophotometrically at 663.2 nm, 646.8 nm, and 470 nm. Pigment levels were determined using equations derived from Lichtenthaler, (1987) and expressed as mg g⁻¹ fresh weight (FW). Anthocyanin content was measured in petal samples collected at the end of the vase life period. A 0.5 g sample of fresh petal tissue was extracted in 10 mL of acidified methanol (1% HCl v/v) overnight at 4°C in the dark. After centrifugation (10,000 × g, 10 min), absorbance was measured at 530 nm and 657 nm using a spectrophotometer [ 48 ]. 2.10. Electrolyte leakage Electrolyte leakage, an indicator of membrane integrity, was measured using leaf discs (1 cm diameter, 10 discs per replicate) excised at the end of the vase life period. Discs were washed with distilled water, immersed in 20 mL distilled water, and shaken at 100 rpm for 24 hours at 25°C. Initial conductivity (EC 1 ) was measured using a conductivity meter (Apera EC20, Apera Instruments, China). Samples were then autoclaved at 121°C for 20 min to release total electrolytes, cooled, and final conductivity (EC 2 ) was measured. Ion leakage (%) was calculated as: (EC 1 / EC 2 ) × 100 [ 49 ]. 2.11. Relative water content (RWC) Relative water content was assessed on leaf samples collected at the end of the vase life period. Fresh weight (F W ) was recorded immediately after sampling. Leaves were floated in distilled water for 24 hours at 4°C to achieve turgid weight (T W ), then oven-dried at 70°C for 48 hours to obtain dry weight (D W ). RWC (%) was calculated as: [(F W – D W ) / (T W – D W )] × 100 [ 50 ]. 2.12. Solution uptake Solution uptake was measured daily by recording the volume of solution consumed per stem. Vases were initially filled with 500 mL of treatment solution or distilled water (control). Each day, the volume of solution remaining in each vase was measured, and the consumed volume was replenished to maintain 500 mL. The total volume consumed per stem was calculated as the sum of daily consumption over the vase life period, adjusted for evaporative losses using control vases without stems. Solution uptake was expressed as mL stem⁻¹ and averaged across replicates [ 51 ]. 2.13. Fresh-to-dry weight ratio The fresh-to-dry weight ratio was determined to assess the plant's hydration status at the end of the vase life period. Leaf samples were collected and immediately weighed to obtain the fresh weight (F W ). The samples were then oven-dried at 70°C for 48 hours until a constant dry weight (D W ) was achieved. The fresh-to-dry weight ratio was calculated using the formula F W / D W [ 52 ]. 2.14. Antioxidant enzyme activities Peroxidase (POD) and catalase (CAT) activities were measured using leaf samples collected at the end of the vase life period. For both enzymes, 0.5 g of fresh leaf tissue was homogenized in 5 mL of 50 mM phosphate buffer (pH 7.0) containing 1% polyvinylpyrrolidone (PVP) at 4°C, centrifuged at 12,000 × g for 15 min at 4°C, and the supernatant used as the enzyme extract. POD activity was determined by measuring guaiacol oxidation at 470 nm (UV-1800, Shimadzu, Japan) in a reaction mixture containing 50 mM phosphate buffer (pH 7.0), 20 mM guaiacol, 10 mM H₂O₂, and 0.1 mL enzyme extract. Activity was expressed as U g⁻¹ FW, where one unit (U) represents the amount of enzyme causing a 0.01 increase in absorbance per minute [ 53 ]. CAT activity was measured by monitoring H₂O₂ decomposition at 240 nm in a reaction mixture containing 50 mM phosphate buffer (pH 7.0), 15 mM H₂O₂, and 0.1 mL enzyme extract. Activity was expressed as U g⁻¹ FW, where one unit (U) represents the amount of enzyme causing a 0.01 increase in absorbance per minute, calculated using the extinction coefficient of 39.4 mM⁻¹ cm⁻¹ [ 54 ]. 2.15. Statistical analysis Data were analyzed using analysis of variance (ANOVA) in SAS software (version 9.4, SAS Institute, USA). The factorial arrangement included two factors: application method (pulse vs. continuous) and concentration (0.1 mM vs. 1 mM), with a control treatment. Means were separated using Duncan’s multiple range test at P ≤ 0.05. 3. Results The effects of melatonin applied via pulsed or continuous methods at 0.1 mM and 1 mM concentrations on postharvest characteristics of cut rose flowers were evaluated against an untreated control. All measured parameters, except carotenoid content, exhibited statistically significant differences (p < 0.05). 3.1. Vase life and overall quality The control group had an average vase life of 6.00 days. Melatonin treatments extended vase life, with pulsed 0.1 mM melatonin achieving the longest duration at 9.67 days (a 61% increase), followed by continuous 0.1 mM melatonin at 9.00 days (a 50% increase). The 1 mM treatments were less effective, with vase lives of 8.67 days for pulsed and 8.00 days for continuous applications (Fig. 1 a). Flower quality, rated on a 1–5 scale, averaged 3.33 in the control. Both pulsed and continuous 0.1 mM melatonin treatments achieved the maximum score of 5.00, while 1 mM treatments yielded lower scores of 3.67 for pulsed and 3.33 for continuous applications (Fig. 1 b). Correlation analysis revealed a strong positive association between vase life and flower quality (r = 0.71, p < 0.01), indicating that enhanced quality contributes significantly to prolonged longevity (Table 1 ). Table 1. Pearson correlation coefficients among postharvest parameters of cut roses ( Rosa hybrida L. cv. Samurai) treated with melatonin. VF FQ FD CI Chl a Chl b Chl T Car Ant EL RWC SU FW/FD POD CAT VF 1 FQ 0.71 ** 1 FD 0.84 *** 0.82 *** 1 CI 0.90 *** 0.75 ** 0.77 ** 1 Chl a 0.76 *** 0.84 *** 0.88 *** 0.74 ** 1 Chl b 0.81 *** 0.82 *** 0.91 *** 0.78 *** 0.98 *** 1 Chl T 0.78 *** 0.84 *** 0.87 *** 0.76 ** 0.99 *** 0.99 *** 1 Car 0.58 * 0.48 ns 0.68 ** 0.60 * 0.62 * 0.66 ** 0.64 ** 1 Ant 0.81 *** 0.67 ** 0.84 *** 0.74 ** 0.65 ** 0.70 ** 0.67 ** 0.64 ** 1 EL -0.71 ** -0.61 * -0.88 *** -0.59 * -0.65 ** -0.74 ** -0.68 ** -0.50 * -0.70 ** 1 RWC 0.83 *** 0.87 *** 0.93 *** 0.87 *** 0.88 *** 0.92 *** 0.89 *** 0.60 * 0.81 *** -0.79 *** 1 SU 0.80 *** 0.71 ** 0.84 *** 0.80 *** 0.74 ** 0.78 *** 0.75 ** 0.72 ** 0.85 *** -0.777 *** 0.85 *** 1 FW/FD 0.86 *** 0.76 *** 0.86 *** 0.91 *** 0.78 ** 0.83 *** 0.80 *** 0.74 ** 0.85 *** -0.75 ** 0.92 *** 0.93 *** 1 POD 0.94 *** 0.70 ** 0.89 *** 0.86 *** 0.78 *** 0.83 *** 0.80 *** 0.69 ** 0.93 *** -0.75 ** 0.87 *** 0.88 *** 0.91 *** 1 CAT 0.92 *** 0.74 ** 0.88 *** 0.89 *** 0.82 *** 0.86 *** 0.83 *** 0.66 ** 0.76 *** -0.77 ** 0.87 *** 0.88 *** 0.91 *** 0.90 *** 1 Significance levels are denoted as: * (P < 0.05), ** (P < 0.01), *** (P 0.05). VF: Vase life; FQ: Flower quality; FD: flower diameter; CI: Chlorophyll index; Chl a: Chlorophyll a; Chl b: Chlorophyll b; Chl T: Chlorophyll T; Car: Carotenoids; Ant: Anthocyanins; EL: Electrolyte leakage; RWC: Relative water content; SU: Solution uptake; FW/FD: Fresh-to-dry weight ratio; c: Peroxidase activity; CAT: Catalase activity. 3.2. Morphological and pigment-related parameters The control group exhibited an average flower diameter of 43.33 mm. Melatonin treatments increased flower diameter, with continuous 0.1 mM melatonin yielding the highest value at 51.00 mm (an 18% increase), followed by pulsed 0.1 mM melatonin at 49.67 mm. The 1 mM treatments resulted in intermediate diameters of 46.67 mm for pulsed and 45.67 mm for continuous applications (Fig. 1 c). Flower diameter showed a strong positive correlation with vase life (r = 0.84, p < 0.001), highlighting its role in extending postharvest longevity (Table 1 ). The chlorophyll index in the control group was 45.50, with pulsed 0.1 mM melatonin showing the highest increase of 22%, followed by continuous 0.1 mM melatonin at approximately 14%. The 1 mM treatments exhibited smaller gains: about 13% for pulsed and 7% for continuous applications (Fig. 1 d). Similarly, chlorophyll contents in the control were Chl a: 1.22 mg g⁻¹ FW, Chl b: 0.47 mg g⁻¹ FW, and total: 1.69 mg g⁻¹ FW. Pulsed 0.1 mM melatonin yielded the greatest enhancements—Chl a by roughly 27%, Chl b by 32%, and total by 28%—while continuous 0.1 mM melatonin followed closely with increases of about 25% for Chl a, 30% for Chl b, and 26% for total. The 1 mM treatments showed more modest improvements: pulsed with around 11% for Chl a, 15% for Chl b, and 12% for total; and continuous with minimal rises of 1% for Chl a, 4% for Chl b, and 2% for total (Fig. 1 e-g). Overall, chlorophyll content displayed a strong positive correlation with vase life(r > 0.75, p < 0.01), highlighting its role in extending flower longevity (Table 1 ). Carotenoid content in the control was 0.29 mg g⁻¹ FW, with slight increases for pulsed and continuous 0.1 mM melatonin treatments, and even smaller changes for 1 mM treatments. These differences were not statistically significant (Fig. 1 h). Anthocyanin content in the control group was measured at 267.41 mg/100 g fresh weight (FW). Application of 0.1 mM melatonin, both pulsed and continuous, significantly elevated anthocyanin levels by approximately 36%, reaching 362.97 mg/100 g FW. In contrast, 1 mM melatonin treatments resulted in more moderate increases, with pulsed application achieving 308.43 mg/100 g FW (15% increase) and continuous application reaching 344.88 mg/100 g FW (29% increase) (Fig. 1 i). Statistical analysis demonstrated a strong positive correlation between anthocyanin content and vase life (r = 0.81, p < 0.001), highlighting its pivotal role in enhancing color vibrancy and extending flower longevity (Table 1 ). 3.3. Physiological and water relations parameters Electrolyte leakage in the control group was measured at 37.81%. Melatonin treatments significantly reduced leakage, with continuous 0.1 mM melatonin achieving the greatest reduction to 21.72%, a 43% decrease, followed by pulsed 0.1 mM at 28.03%, a 26% decrease. The 1 mM treatments showed milder reductions, with 31.05% for pulsed, 18% lower, and 33.10% for continuous, 12% lower (Fig. 2a). A strong negative correlation with vase life was evident (r = − 0.71, p < 0.01), highlighting the importance of minimizing membrane damage for enhanced postharvest flower preservation (Table 1 ). Relative water content (RWC) in the control group averaged 71.84%. Treatment with 0.1 mM melatonin markedly increased RWC to 79.89% for pulsed application, an 11% rise, and 79.32% for continuous application, a 10% rise. The 1 mM treatments yielded smaller increases, reaching 75.20% for pulsed, a 5% rise, and 73.89% for continuous, a 3% rise (Fig. 2b). Solution uptake in the control samples was 34.33 mL. Melatonin treatments enhanced uptake, with pulsed 0.1 mM reaching 40.00 mL, a 16% increase, and continuous 0.1 mM reaching 39.67 mL, a 15% increase. The 1 mM treatments showed modest gains, with 37.00 mL for pulsed, an 8% increase, and 37.33 mL for continuous, a 9% increase (Fig. 2c). The fresh-to-dry weight ratio in the control group was recorded at 26.51. Application of 0.1 mM melatonin significantly raised this ratio to 31.25 for pulsed treatment, an 18% increase, and 30.29 for continuous treatment, a 14% increase. The 1 mM treatments resulted in smaller increments, reaching 28.94 for pulsed, a 9% increase, and 28.46 for continuous, a 7% increase (Fig. 2d). Strong positive correlations were observed between vase life and relative water content, solution uptake, and fresh-to-dry weight ratio (r > 0.8, p < 0.001), emphasizing their critical roles in sustaining hydration and prolonging postharvest flower longevity (Table 1 ). 3.4. Antioxidant enzyme activities Peroxidase (POD) activity in the control group was 2.29 U g⁻¹ FW, rising to 3.73 U g⁻¹ FW with pulsed 0.1 mM melatonin, a 63% increase, and 3.53 U g⁻¹ FW with continuous 0.1 mM melatonin, a 54% increase. The 1 mM treatments showed smaller rises, reaching 3.12 U g⁻¹ FW for pulsed, a 36% increase, and 3.18 U g⁻¹ FW for continuous, a 39% increase (Fig. 2e). Catalase (CAT) activity in the control was 3.60 U g⁻¹ FW, increasing to 3.93 U g⁻¹ FW with pulsed 0.1 mM melatonin, a 9% rise, and 3.90 U g⁻¹ FW with continuous 0.1 mM melatonin, an 8% rise. The 1 mM treatments reached 3.85 U g⁻¹ FW for pulsed, a 7% rise, and 3.73 U g⁻¹ FW for continuous, a 4% rise (Fig. 2f). Both POD and CAT activities exhibited strong positive correlations with vase life (r > 0.9, p < 0.001), underscoring their critical role in mitigating oxidative stress and extending flower longevity (Table 1 ). 4. Discussion The findings of this study provide compelling evidence that the exogenous application of melatonin, applied either as a pulse or in continuous form at concentrations of 0.1 and 1 mM, exerts profound positive effects on a wide range of postharvest attributes in cut rose flowers, with the exception of carotenoid content, which remained unaffected. Melatonin extended vase life and enhanced flower quality, with 0.1 mM pulsed treatment providing the greatest extension in vase life (9.67 days), and both 0.1 mM treatments achieving maximum quality scores (Fig. 1 a-b). A strong positive correlation existed between vase life and flower quality (r = 0.71, p < 0.01; Table 1 ). These results complement and extend existing literature: for instance, Mazrou et al. [ 21 ] reported that 0.2 mM melatonin nearly doubled the vase life of cut roses by improving RWC, reducing membrane damage, and delaying senescence. Similarly, Lezoul et al. [ 23 ] demonstrated that postharvest melatonin application at 0.1 mM lengthened carnation vase life by up to 10 days. Preharvest applications in tuberose ( Polianthes tuberosa ) were also shown to promote water balance and antioxidant activity, further extending floral longevity [ 55 ]. Comparable effects have also been reported in peony ( Paeonia lactiflora ), where melatonin delayed senescence by protecting chlorophyll molecules, reducing proline accumulation, and alleviating oxidative stress [ 27 ]. At the mechanistic level, the beneficial role of melatonin can be understood from its dual capacity as both a direct ROS scavenger and a modulator of plant hormonal pathways. Melatonin neutralizes reactive oxygen species such as superoxide radicals, hydrogen peroxide, and hydroxyl radicals, thereby protecting vital biomolecules like lipids, proteins, and nucleic acids from oxidative damage. In tandem, melatonin can fine-tune hormone signaling by suppressing ethylene biosynthesis, the primary hormonal driver of senescence, while simultaneously enhancing auxin-related activities that promote tissue vitality and delay cell death [ 38 ]. Moreover, melatonin has been shown to enhance the transcription of stress-related genes, including those encoding antioxidant enzymes, thereby strengthening cellular protection systems against oxidative stress [ 20 , 26 ]. This set of interconnected actions explains why melatonin-treated flowers not only live longer but also maintain superior visual and quality attributes. A key finding of this study is the clear superiority of the 0.1 mM pulse treatment [ 21 , 56 ]. We propose this is a classic example of hormetic priming. A brief, concentrated exposure to melatonin likely acts as a mild eustress signal, activating the flower's transcriptional defense machinery (e.g., genes for antioxidant enzymes, aquaporins, and heat-shock proteins) more potently than a continuous, low-level stimulus [ 57 , 58 ]. This 'primed' state then persists throughout the vase life, providing sustained protection against senescence triggers. In contrast, continuous exposure, particularly at the higher 1 mM concentration, could lead to receptor desensitization or negative feedback inhibition, diminishing its efficacy over time [ 59 ]. This priming hypothesis is consistent with observations in other plant systems where brief stress applications confer long-term resistance [ 60 , 61 ]. A clear and significant enhancement in flower diameter was also observed under 0.1 mM melatonin, with the continuous treatment producing the largest flowers (51.00 mm, or an 18% increase) (Fig. 1 c). Vase life strongly correlated with flower size (r = 0.84, p < 0.001; Table 1 ), suggesting that larger flowers are more likely to remain viable for longer when treated with melatonin. Parallel results have been reported by Wang et al. [ 27 ], where peonies maintained greater flower size under melatonin treatment due to enhanced water balance, membrane stability, and osmotic regulation. Cut chrysanthemums treated with 5 µM melatonin also displayed increased diameter, fresh weight, and water retention compared to untreated controls [ 27 ]. Similarly, marigold plants sprayed with 150 mg/L melatonin exhibited significant increases in both fresh and dry flower weights as well as yield, mainly attributed to improved morpho-physiological processes [ 62 ]. From a physiological perspective, melatonin contributes to enlarged flower diameter by promoting cell expansion and division, processes mediated in part by its interactions with auxin and gibberellin signaling pathways. Additionally, it promotes water absorption by upregulating aquaporin genes, which facilitate efficient water transport through membranes, ensuring adequate hydration to support cell enlargement [ 63 – 65 ]. Thus, melatonin reinforces both the hydraulic and biochemical mechanisms underlying floral opening, ensuring longer-lasting ornamental appeal. The observed increase in flower diameter is likely driven by enhanced cell expansion. This process is potentially mediated by melatonin's well-documented role in upregulating aquaporin genes (e.g., PIP2;1 , TIP1;1 ), which facilitate water influx into petal cells, thereby increasing turgor pressure and driving cell enlargement [ 36 , 66 ]. Chlorophyll content (including indices for chlorophyll a, chlorophyll b, and total chlorophyll) was significantly elevated by melatonin treatments, with the 0.1 mM pulse treatment producing the highest increases (22% for the chlorophyll index and ~ 28% for total chlorophyll) (Fig. 1 d–g). Chlorophyll levels correlated strongly with vase life (r > 0.75, p < 0.01; Table 1 ), highlighting their vital role in sustaining postharvest floral metabolism. Similar findings have been observed in chrysanthemums, where melatonin delayed chlorophyll degradation and preserved higher pigment content during storage [ 26 ]. Mechanistically, melatonin exerts its chlorophyll-protective effect by stabilizing chloroplast membranes, preventing ROS-mediated damage, and inhibiting chlorophyllase—the enzyme responsible for chlorophyll breakdown [ 67 ]. In addition, melatonin upregulates genes involved in chlorophyll biosynthesis, resulting in higher pigment accumulation [ 68 – 70 ]. Interestingly, carotenoids remained unaffected in this study (Fig. 1 h), suggesting that while melatonin selectively regulates chlorophyll metabolism, carotenoid biosynthesis may not be as responsive to melatonin or may be less sensitive to oxidative stress, as reported by Xu et al. [ 71 ]. Anthocyanin concentrations also increased substantially under melatonin, particularly in 0.1 mM treatments (~ 36%), compared to 15–29% increases under 1 mM (Fig. 1 i). Vase life correlated strongly with anthocyanin levels (r = 0.81, p < 0.001), indicating that color retention is closely aligned with floral longevity. These results corroborate findings in amaryllis [ 72 ], litchi fruit [ 73 ], and cabbage seedlings [ 74 ]. Melatonin boosted anthocyanin biosynthesis through upregulation of structural genes such as phenylalanine ammonia-lyase ( PAL ), chalcone synthase ( CHS ), flavanone 3-hydroxylase ( F3H ), and anthocyanidin synthase ( ANS ), as well as transcription factors such as Myeloblastosis ( MYB ) and basic Helix-Loop-Helix ( bHLH ), which regulate the anthocyanin biosynthesis pathway [ 73 , 74 ]. The regulation of flavonoid biosynthetic genes, such as chalcone isomerase ( CHI ), also supports anthocyanin synthesis, ensuring enhanced pigmentation and prolonged flower freshness [ 75 ]. Electrolyte leakage, a key indicator of membrane integrity, decreased significantly under melatonin treatments, with continuous 0.1 mM yielding the most pronounced reduction (43%) (Fig. 2a). A negative correlation was observed with vase life (r = − 0.71, p < 0.01), highlighting the value of membrane stability for prolonging floral freshness. Similar outcomes have been observed in cut roses and carnations, where melatonin reduced leakage by enhancing ROS detoxification and preserving lipid bilayer structures (Ahmad et al., 2021; Liang et al., 2018). Mechanistically, melatonin can directly integrate into lipid membranes, reinforcing their stability, while also activating enzymatic antioxidants to suppress lipid peroxidation [ 78 , 79 ]. This reduction in ion leakage provides direct evidence of melatonin's role in preserving membrane stability. The significant upregulation of POD and CAT activities (Fig. 2e-f) offers a clear enzymatic mechanism for this protection, as these enzymes detoxify H₂O₂ and other ROS, preventing the lipid peroxidation that compromises membrane integrity [ 80 ]. Hydration-related traits, such as relative water content (RWC), solution uptake, and fresh-to-dry weight ratios, improved markedly with melatonin, with pulsed 0.1 mM performing slightly better than continuous application (Fig. 2b–d). All hydration parameters correlated strongly with vase life (r > 0.8, p < 0.001). These effects resonate with findings in tomato, where melatonin sprays increased RWC under heat and drought stress [ 81 ]. Hosseini et al. [ 82 ] also reported that melatonin extended postharvest longevity in roses and carnations by improving water retention and reducing ROS damage. The underlying mechanism involves aquaporin upregulation (plasma membrane intrinsic protein [ PIP ] and tonoplast intrinsic protein [ TIP ]) that facilitates water flow through cellular membranes [ 66 , 83 ]. By modulating stomatal closure, melatonin also optimizes transpiration rates, maintaining turgor pressure and preventing desiccation [ 84 , 85 ]. Studies also show melatonin maintains partially open stomata under drought stress, balancing transpiration and water retention [ 85 , 86 ]. Furthermore, melatonin improves biomass accumulation by enhancing photosynthesis and carbohydrate translocation, increasing fresh and dry weights in plants like grapefruit mint and cotton [ 87 , 88 ]. In petal tissues, melatonin reduces fresh and dry weight loss under drought, maintaining tissue hydration [ 89 ]. These mechanisms collectively enhance water status, biomass, and postharvest longevity in flowers. Finally, antioxidant enzyme activities—specifically POD and CAT—increased significantly under melatonin, with 0.1 mM pulse showing the greatest enhancement (POD by 63%) (Fig. 2e–f). These enzymes exhibited strong correlations with vase life (r > 0.8, p < 0.001). Such increases mirror other reports in Ranunculus asiaticus [ 56 ], mung bean [ 90 ], and roses [ 21 ], supporting melatonin’s strong ROS-scavenging roles. Beyond direct enzymatic upregulation, melatonin also promotes accumulation of non-enzymatic antioxidants such as glutathione and ascorbate [ 91 , 92 ]. Altogether, these multifaceted defense mechanisms protect membranes from peroxidation, maintain redox balance, and delay senescence [ 93 , 94 ]. It is important to acknowledge the limitations of this study. Our conclusions regarding the molecular mechanisms, such as the upregulation of aquaporins or specific signaling pathways, are based on logical inference from our phenotypic data and the existing literature. Future studies employing transcriptomic or proteomic analyses would be required to directly validate these hypothesized pathways. Furthermore, our study was conducted on a single rose cultivar; future work should validate the optimized protocol across different cultivars and species. 5. Conclusion This study identifies a 0.1 mM melatonin pulse treatment as a highly effective and resource-efficient strategy to significantly extend the vase life of 'Samurai' roses. The superiority of the pulse method suggests it acts as a potent priming agent, efficiently activating the flower's own defense systems with minimal resource input. Melatonin effectively mitigated major senescence triggers, including ROS accumulation, membrane damage, and water imbalance. Importantly, the pulse 0.1 mM treatment presents a practical, cost-efficient, and environmentally sustainable option for the floriculture industry. This foundational work paves the way for future studies to explore the molecular basis of melatonin's priming effect, further refining its application for sustainable floriculture. Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. 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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-8762944","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":593747694,"identity":"b7027a4a-6919-4c0d-b840-727c05480f9c","order_by":0,"name":"sara Shamsinejad","email":"","orcid":"","institution":"Shahid Bahonar University of Kerman","correspondingAuthor":false,"prefix":"","firstName":"sara","middleName":"","lastName":"Shamsinejad","suffix":""},{"id":593747695,"identity":"74f9a28f-acda-42d2-9429-e9b426da5405","order_by":1,"name":"Safoora Saadati","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYNACNiBib2CGsYnTIsHGc4BULQwSCczEKZZvYH/44UeZXR2f5BtjA4YaOwY+6QP4tRgc4DGW7DmXLMEmnWOcwHAsmYGNL4GAFgYeBgneNmawlgMMbEDEQ9hhj3/+bauXYJM8A9TyjwgtDAcYzKR52w5LsEnwGCcwthGhxeAwj5m1zLnjkm08acUGiX3JPIQd1t7++Oabsmp++fbDmyU+fLOTk+8h5DCUyEhgYCDok1EwCkbBKBgFRAAAhBYwppqPOmQAAAAASUVORK5CYII=","orcid":"","institution":"Shahid Bahonar University of Kerman","correspondingAuthor":true,"prefix":"","firstName":"Safoora","middleName":"","lastName":"Saadati","suffix":""},{"id":593747697,"identity":"f9fa245c-6df4-4b2a-be9f-5bc2aa961eab","order_by":2,"name":"Vahid Reza Saffari","email":"","orcid":"","institution":"Shahid Bahonar University of Kerman","correspondingAuthor":false,"prefix":"","firstName":"Vahid","middleName":"Reza","lastName":"Saffari","suffix":""},{"id":593747698,"identity":"db9c824e-9134-43b2-baa8-6758784a655c","order_by":3,"name":"Zahra Pakkish","email":"","orcid":"","institution":"Shahid Bahonar University of Kerman","correspondingAuthor":false,"prefix":"","firstName":"Zahra","middleName":"","lastName":"Pakkish","suffix":""}],"badges":[],"createdAt":"2026-02-02 09:24:04","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8762944/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8762944/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103506580,"identity":"10fa564f-d5e5-485c-bad7-3b9d946ee849","added_by":"auto","created_at":"2026-02-26 13:37:46","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":125113,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of melatonin treatments (pulse and continuous at 0.1 mM and 1 mM) on postharvest parameters of cut roses (\u003cem\u003eRosa hybrida\u003c/em\u003eL. cv. Samurai), including vase life (a), flower quality (b), flower diameter (c), chlorophyll index (d), chlorophyll a (e) chlorophyll b (f) total chlorophyll (g), carotenoid (h), anthocyanin (i) contents. Bars represent means ± SE (n = 3), with different letters indicating significant differences (Duncan’s test, P ≤ 0.05).\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8762944/v1/de299e814ba46d3f7e079970.jpg"},{"id":103263340,"identity":"d9271dd9-c4d8-4e78-9ed5-f55994648691","added_by":"auto","created_at":"2026-02-23 18:51:52","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":81983,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of melatonin treatments (pulse and continuous at 0.1 mM and 1 mM) on postharvest parameters of cut roses (Rosa hybrida L. cv. Samurai), including electrolyte leakage (a), relative water content (b), solution uptake (c), fresh-to-dry weight ratio (d), peroxidase (e) and catalase (f) activities. Bars represent means ± SE (n = 3), with different letters indicating significant differences (Duncan’s test, P ≤ 0.05).\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8762944/v1/22e3b19509b8480adfa7ec02.jpg"},{"id":103509916,"identity":"d3d216b8-347e-4d8d-91f5-18e770a5e8c6","added_by":"auto","created_at":"2026-02-26 14:02:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1227932,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8762944/v1/1b26ca4a-e1da-4c5a-9470-2899804b5ba2.pdf"},{"id":103263342,"identity":"62ab9c34-6953-4f7b-a28f-7493aea7816b","added_by":"auto","created_at":"2026-02-23 18:51:52","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":11005,"visible":true,"origin":"","legend":"","description":"","filename":"Book1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8762944/v1/a92a5be8929fe5cb0f9feb1f.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Melatonin Pulse Treatment Optimization: Boosting Vase Life and Postharvest Quality in Cut Roses (Rosa hybrida cv. Samurai)","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eRoses (\u003cem\u003eRosa\u003c/em\u003e spp.), known as the \"queen of flowers\", are central to the global floriculture industry, valued for their aesthetic appeal, color diversity, and cultural significance [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The cut flower market exceeded \u003cspan\u003e$\u003c/span\u003e40\u0026nbsp;billion in 2024, with roses dominating due to their use in arrangements and gifting [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, postharvest longevity is limited by rapid senescence, causing economic losses and reduced consumer satisfaction [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This complex deterioration process is driven by an interplay of physiological and biochemical stressors, including: (1) oxidative damage from reactive oxygen species (ROS), which compromises membrane integrity, lipids, and proteins [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]; (2) ethylene-induced petal abscission and senescence via upregulation of biosynthetic genes [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]; (3) vascular occlusions from microbial proliferation and physiological plugging, impeding water uptake [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]; and (4) loss of hydraulic conductivity and turgor pressure, resulting in wilting [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Conventional postharvest interventions, such as chemical preservatives (e.g., silver thiosulfate, 8-hydroxyquinoline) and cold storage, mitigate these issues to varying degrees but are limited by inconsistent efficacy, high costs, and environmental concerns from chemical residues [\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This necessitates innovative, sustainable strategies to enhance vase life while aligning with eco-friendly floriculture practices [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMelatonin (N-acetyl-5-methoxytryptamine), a pleiotropic indoleamine, has emerged as a promising biostimulant in postharvest horticulture, extending beyond its established role in circadian regulation to exhibit potent antioxidant and regulatory functions in plants [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Its efficacy in delaying senescence is well-documented across cut flowers, including roses [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], anthurium [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], carnations [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], gerberas [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], Chrysanthemum [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], and peonies [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], as well as fruits like sweet cherries [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], and pears [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Melatonin's multifaceted mechanisms include: (1) direct scavenging of ROS (e.g., superoxide, hydrogen peroxide) and upregulation of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), mitigating oxidative stress [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].; (2) suppression of ethylene biosynthesis through downregulation of ACC synthase (ACS) and ACC oxidase (ACO) genes, reducing petal abscission [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]; (3) enhancement of hydraulic conductivity via upregulation of aquaporin genes (PIP, TIP), improving water relations and turgor maintenance [\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]; and (4) antimicrobial activity that curbs bacterial growth in vase solutions, preventing vascular blockages [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Additionally, melatonin modulates phytohormone crosstalk, elevating indole-3-acetic acid (IAA) to counteract abscisic acid (ABA)-mediated stress and sustaining carbohydrate reserves to support energy demands [\u003cspan additionalcitationids=\"CR38\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. These actions collectively preserve chlorophyll content, delay petal senescence, and enhance visual quality [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. However, for widespread commercial adoption, understanding \u003cem\u003ehow\u003c/em\u003e to apply melatonin is as critical as knowing \u003cem\u003ethat\u003c/em\u003e it works. Previous studies have demonstrated its efficacy but often using a single application method, leaving a significant gap in our knowledge of optimized protocols. Specifically, the comparative efficacy of a brief, resource-saving pulse treatment versus a continuous vase solution application, and the interaction of these methods with concentration, remains unexplored. This study was therefore designed not merely to reconfirm the benefits of melatonin, but to directly address this applied knowledge gap. We hypothesize that a short pulse treatment acts as a priming stimulus, triggering a more robust and sustained endogenous defense response compared to continuous exposure. This study systematically compares pulse versus continuous methods at two concentrations to identify an optimized protocol for commercial scalability.\u003c/p\u003e \u003cp\u003eDespite these advances, the optimal application strategy for melatonin in cut roses remains underexplored. Pulse treatments (short-term immersion) may prime defense and antioxidant systems, offering a rapid, cost-effective intervention, while continuous exposure in vase solutions could provide sustained protection against oxidative and microbial stress. The comparative efficacy of these methods, particularly at varying physiological concentrations (e.g., 0.1 and 1 mM), is a critical knowledge gap [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. This study investigates the effects of pulse versus continuous melatonin treatments at 0.1 and 1 mM on the postharvest vase life of cut roses, hypothesizing that application method and concentration interactively modulate senescence pathways. By elucidating an optimized melatonin application protocol, this research aims to deliver a sustainable, cost-effective strategy to enhance the postharvest quality and commercial value of cut roses, contributing to greener floriculture practices.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Plant material\u003c/h2\u003e \u003cp\u003eCut roses (\u003cem\u003eRosa hybrida\u003c/em\u003e L. cv. Samurai) were harvested at the commercial maturity stage (tight bud, outer petals unfurling) from a commercial greenhouse in Zarand, Kerman province, Iran. Stems were uniformly selected for length (approximately 50 cm), free from defects or diseases, and immediately transported to the laboratory under hydrated conditions (wrapped in moist paper and placed in buckets with distilled water). Upon arrival, stems were re-cut underwater to a uniform length of 40 cm to remove air emboli, basal leaves were removed to prevent microbial contamination in vase solutions, and 4 leaves were retained per stem to standardize foliage load and minimize variability in physiological measurements. Each treatment was replicated three times, with each replicate consisting of 10 cut stems (one stem per vase), resulting in a total of 150 stems (5 treatments \u0026times; 3 replicates \u0026times; 10 stems).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Preparation of melatonin solutions\u003c/h2\u003e \u003cp\u003eMelatonin (N-acetyl-5-methoxytryptamine, purity\u0026thinsp;\u0026ge;\u0026thinsp;98%, Sigma-Aldrich, USA) was dissolved in absolute ethanol (0.1% v/v) as a co-solvent to enhance solubility, then diluted to the desired concentrations (0.1 mM and 1 mM) using distilled water. Control solutions consisted of distilled water with 0.1% ethanol to account for any solvent effects. All solutions were freshly prepared on the day of treatment and adjusted to pH 5.5\u0026ndash;6.0 using 0.1 M HCl or NaOH to mimic typical vase water conditions [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Treatment applications\u003c/h2\u003e \u003cp\u003eThe experiment followed a completely randomized design (CRD) with a 2 \u0026times; 2 factorial arrangement (method: pulse/continuous; concentration: 0.1/1 mM) plus a control, resulting in five treatments: (1) control (distilled water with 0.1% ethanol), (2) 0.1 mM melatonin pulse, (3) 1 mM melatonin pulse, (4) 0.1 mM melatonin continuous, and (5) 1 mM melatonin continuous. All treatments were applied immediately after stem preparation. For pulse treatments, stems were immersed up to 10 cm from the base in melatonin solutions (0.1 or 1 mM) for 30 minutes at 20\u0026deg;C in the dark, then rinsed with distilled water and transferred to vases with fresh distilled water, refreshed every 48 hours. For continuous treatments, stems were placed in vases with melatonin-infused solutions (0.1 or 1 mM), replaced every 48 hours to maintain concentration. To prevent melatonin degradation under light, all vases were covered with opaque material [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Vases were maintained at 20\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C, 60\u0026ndash;70% relative humidity, and a 12-hour photoperiod (15\u0026ndash;20 \u0026micro;mol m⁻\u0026sup2; s⁻\u0026sup1; PPFD). Each treatment had three replicates of 10 stems (one per vase).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Measurement of postharvest parameters\u003c/h2\u003e \u003cp\u003ePostharvest parameters were assessed primarily at the conclusion of the vase life period, with the exception of vase life, flower quality, and solution uptake, which were evaluated dynamically throughout the experiment. Physiological and biochemical parameters were measured on leaf tissues, while anthocyanin content was quantified specifically in petals.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Vase life\u003c/h2\u003e \u003cp\u003eVase life was determined as the number of days from the start of the experiment until flowers exhibited senescence, defined as wilting of \u0026gt;\u0026thinsp;50% of petals, petal discoloration, or bent neck (peduncle bending\u0026thinsp;\u0026gt;\u0026thinsp;45\u0026deg;). Daily visual assessments were conducted by two independent observers, and the average was recorded [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Flower quality\u003c/h2\u003e \u003cp\u003eFlower quality was evaluated daily on a subjective scale from 1 to 5, where: 5\u0026thinsp;=\u0026thinsp;excellent (fully turgid, vibrant color, no wilting); 4\u0026thinsp;=\u0026thinsp;good (minor petal edge curling, slight color fading); 3\u0026thinsp;=\u0026thinsp;moderate (noticeable wilting on 25\u0026ndash;50% petals); 2\u0026thinsp;=\u0026thinsp;poor (severe wilting, significant discoloration); and 1\u0026thinsp;=\u0026thinsp;unacceptable (complete wilting or abscission). Scores were averaged across replicates [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7. Flower diameter\u003c/h2\u003e \u003cp\u003eFlower diameter was measured using a digital caliper (accuracy\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 mm) at the end of the vase life period. The maximum diameter of the flower head was recorded as the distance across the outermost petals at their widest point. Measurements were taken in two perpendicular directions, and the average was calculated for each flower [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8. Chlorophyll content index\u003c/h2\u003e \u003cp\u003eChlorophyll content index was indirectly assessed as the chlorophyll index using a SPAD-502 chlorophyll meter (Konica Minolta, Japan) at the end of the vase life period. Measurements were taken on the middle portion of three leaves per stem, and the average SPAD value was recorded [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.9. Pigment content (chlorophyll, carotenoids, and anthocyanins)\u003c/h2\u003e \u003cp\u003eFresh leaf tissue was pulverized in 70% acetone and centrifuged at 350 \u0026times; g for 15 min at ambient temperature to produce a clarified supernatant. The absorbance of this extract was recorded spectrophotometrically at 663.2 nm, 646.8 nm, and 470 nm. Pigment levels were determined using equations derived from Lichtenthaler, (1987) and expressed as mg g⁻\u0026sup1; fresh weight (FW).\u003c/p\u003e \u003cp\u003eAnthocyanin content was measured in petal samples collected at the end of the vase life period. A 0.5 g sample of fresh petal tissue was extracted in 10 mL of acidified methanol (1% HCl v/v) overnight at 4\u0026deg;C in the dark. After centrifugation (10,000 \u0026times; g, 10 min), absorbance was measured at 530 nm and 657 nm using a spectrophotometer [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.10. Electrolyte leakage\u003c/h2\u003e \u003cp\u003eElectrolyte leakage, an indicator of membrane integrity, was measured using leaf discs (1 cm diameter, 10 discs per replicate) excised at the end of the vase life period. Discs were washed with distilled water, immersed in 20 mL distilled water, and shaken at 100 rpm for 24 hours at 25\u0026deg;C. Initial conductivity (EC\u003csub\u003e1\u003c/sub\u003e) was measured using a conductivity meter (Apera EC20, Apera Instruments, China). Samples were then autoclaved at 121\u0026deg;C for 20 min to release total electrolytes, cooled, and final conductivity (EC\u003csub\u003e2\u003c/sub\u003e) was measured. Ion leakage (%) was calculated as: (EC\u003csub\u003e1\u003c/sub\u003e / EC\u003csub\u003e2\u003c/sub\u003e) \u0026times; 100 [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e2.11. Relative water content (RWC)\u003c/h2\u003e \u003cp\u003eRelative water content was assessed on leaf samples collected at the end of the vase life period. Fresh weight (F\u003csub\u003eW\u003c/sub\u003e) was recorded immediately after sampling. Leaves were floated in distilled water for 24 hours at 4\u0026deg;C to achieve turgid weight (T\u003csub\u003eW\u003c/sub\u003e), then oven-dried at 70\u0026deg;C for 48 hours to obtain dry weight (D\u003csub\u003eW\u003c/sub\u003e). RWC (%) was calculated as: [(F\u003csub\u003eW\u003c/sub\u003e \u0026ndash; D\u003csub\u003eW\u003c/sub\u003e) / (T\u003csub\u003eW\u003c/sub\u003e \u0026ndash; D\u003csub\u003eW\u003c/sub\u003e)] \u0026times; 100 [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e2.12. Solution uptake\u003c/h2\u003e \u003cp\u003eSolution uptake was measured daily by recording the volume of solution consumed per stem. Vases were initially filled with 500 mL of treatment solution or distilled water (control). Each day, the volume of solution remaining in each vase was measured, and the consumed volume was replenished to maintain 500 mL. The total volume consumed per stem was calculated as the sum of daily consumption over the vase life period, adjusted for evaporative losses using control vases without stems. Solution uptake was expressed as mL stem⁻\u0026sup1; and averaged across replicates [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e2.13. Fresh-to-dry weight ratio\u003c/h2\u003e \u003cp\u003eThe fresh-to-dry weight ratio was determined to assess the plant's hydration status at the end of the vase life period. Leaf samples were collected and immediately weighed to obtain the fresh weight (F\u003csub\u003eW\u003c/sub\u003e). The samples were then oven-dried at 70\u0026deg;C for 48 hours until a constant dry weight (D\u003csub\u003eW\u003c/sub\u003e) was achieved. The fresh-to-dry weight ratio was calculated using the formula F\u003csub\u003eW\u003c/sub\u003e / D\u003csub\u003eW\u003c/sub\u003e [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e2.14. Antioxidant enzyme activities\u003c/h2\u003e \u003cp\u003ePeroxidase (POD) and catalase (CAT) activities were measured using leaf samples collected at the end of the vase life period. For both enzymes, 0.5 g of fresh leaf tissue was homogenized in 5 mL of 50 mM phosphate buffer (pH 7.0) containing 1% polyvinylpyrrolidone (PVP) at 4\u0026deg;C, centrifuged at 12,000 \u0026times; g for 15 min at 4\u0026deg;C, and the supernatant used as the enzyme extract.\u003c/p\u003e \u003cp\u003ePOD activity was determined by measuring guaiacol oxidation at 470 nm (UV-1800, Shimadzu, Japan) in a reaction mixture containing 50 mM phosphate buffer (pH 7.0), 20 mM guaiacol, 10 mM H₂O₂, and 0.1 mL enzyme extract. Activity was expressed as U g⁻\u0026sup1; FW, where one unit (U) represents the amount of enzyme causing a 0.01 increase in absorbance per minute [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCAT activity was measured by monitoring H₂O₂ decomposition at 240 nm in a reaction mixture containing 50 mM phosphate buffer (pH 7.0), 15 mM H₂O₂, and 0.1 mL enzyme extract. Activity was expressed as U g⁻\u0026sup1; FW, where one unit (U) represents the amount of enzyme causing a 0.01 increase in absorbance per minute, calculated using the extinction coefficient of 39.4 mM⁻\u0026sup1; cm⁻\u0026sup1; [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e2.15. Statistical analysis\u003c/h2\u003e \u003cp\u003eData were analyzed using analysis of variance (ANOVA) in SAS software (version 9.4, SAS Institute, USA). The factorial arrangement included two factors: application method (pulse vs. continuous) and concentration (0.1 mM vs. 1 mM), with a control treatment. Means were separated using Duncan\u0026rsquo;s multiple range test at P\u0026thinsp;\u0026le;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThe effects of melatonin applied via pulsed or continuous methods at 0.1 mM and 1 mM concentrations on postharvest characteristics of cut rose flowers were evaluated against an untreated control. All measured parameters, except carotenoid content, exhibited statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Vase life and overall quality\u003c/h2\u003e\n \u003cp\u003eThe control group had an average vase life of 6.00 days. Melatonin treatments extended vase life, with pulsed 0.1 mM melatonin achieving the longest duration at 9.67 days (a 61% increase), followed by continuous 0.1 mM melatonin at 9.00 days (a 50% increase). The 1 mM treatments were less effective, with vase lives of 8.67 days for pulsed and 8.00 days for continuous applications (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). Flower quality, rated on a 1\u0026ndash;5 scale, averaged 3.33 in the control. Both pulsed and continuous 0.1 mM melatonin treatments achieved the maximum score of 5.00, while 1 mM treatments yielded lower scores of 3.67 for pulsed and 3.33 for continuous applications (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb). Correlation analysis revealed a strong positive association between vase life and flower quality (r\u0026thinsp;=\u0026thinsp;0.71, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), indicating that enhanced quality contributes significantly to prolonged longevity (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eTable 1. Pearson correlation coefficients among postharvest parameters of cut roses (\u003cem\u003eRosa hybrida\u003c/em\u003e L. cv. Samurai) treated with melatonin.\u0026nbsp;\u003c/p\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eVF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eFQ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eFD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eCI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eChl a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eChl b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eChl T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eCar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003eAnt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003eEL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eRWC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eSU\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eFW/FD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003ePOD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eCAT\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eVF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eFQ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.71 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eFD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.84 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.82 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eCI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.90 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.75 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.77 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eChl a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.76 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.84 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.88 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.74 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eChl b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.81 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.82 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.91 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.78 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.98 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eChl T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.78 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.84 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.87 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.76 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.99 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.99 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eCar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.58 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.48 \u003csup\u003ens\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.68 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.60 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.62 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.66 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.64 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eAnt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.81 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.67 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.84 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.74 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.65 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.70 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.67 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.64 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eEL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.71 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.61 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.88 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.59 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.65 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.74 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.68 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e-0.50 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e-0.70 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eRWC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.83\u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.87 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.93 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.87 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.88 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.92 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.89 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.60 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e0.81 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e-0.79 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eSU\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.80 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.71 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.84 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.80 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.74 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.78 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.75 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.72 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e0.85 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e-0.777 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.85 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eFW/FD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.86 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.76 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.86 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.91 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.78 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.83 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.80 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.74 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e0.85 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e-0.75 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.92 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.93 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003ePOD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.94 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.70 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.89 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.86 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.78 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.83 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.80 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.69 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e0.93 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e-0.75 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.87 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.88 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.91 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003eCAT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.92 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.74 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.88 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.89 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.82 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.86 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.83 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.66 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e0.76 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e-0.77 \u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.87 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.88 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.91 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e0.90 \u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 54px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003eSignificance levels are denoted as: * (P \u0026lt; 0.05), ** (P \u0026lt; 0.01), *** (P \u0026lt; 0.001), ns (non-significant, P \u0026gt; 0.05).\u003c/p\u003e\n \u003cp\u003eVF: Vase life; FQ: Flower quality; FD: flower diameter; CI: Chlorophyll index; Chl a: Chlorophyll a; Chl b: Chlorophyll b; Chl T: Chlorophyll T; Car: Carotenoids; Ant: Anthocyanins; EL: Electrolyte leakage; RWC: Relative water content; SU: Solution uptake; FW/FD: Fresh-to-dry weight ratio; c: Peroxidase activity; CAT: Catalase activity.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Morphological and pigment-related parameters\u003c/h2\u003e\n \u003cp\u003eThe control group exhibited an average flower diameter of 43.33 mm. Melatonin treatments increased flower diameter, with continuous 0.1 mM melatonin yielding the highest value at 51.00 mm (an 18% increase), followed by pulsed 0.1 mM melatonin at 49.67 mm. The 1 mM treatments resulted in intermediate diameters of 46.67 mm for pulsed and 45.67 mm for continuous applications (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ec). Flower diameter showed a strong positive correlation with vase life (r\u0026thinsp;=\u0026thinsp;0.84, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), highlighting its role in extending postharvest longevity (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe chlorophyll index in the control group was 45.50, with pulsed 0.1 mM melatonin showing the highest increase of 22%, followed by continuous 0.1 mM melatonin at approximately 14%. The 1 mM treatments exhibited smaller gains: about 13% for pulsed and 7% for continuous applications (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ed). Similarly, chlorophyll contents in the control were Chl a: 1.22 mg g⁻\u0026sup1; FW, Chl b: 0.47 mg g⁻\u0026sup1; FW, and total: 1.69 mg g⁻\u0026sup1; FW. Pulsed 0.1 mM melatonin yielded the greatest enhancements\u0026mdash;Chl a by roughly 27%, Chl b by 32%, and total by 28%\u0026mdash;while continuous 0.1 mM melatonin followed closely with increases of about 25% for Chl a, 30% for Chl b, and 26% for total. The 1 mM treatments showed more modest improvements: pulsed with around 11% for Chl a, 15% for Chl b, and 12% for total; and continuous with minimal rises of 1% for Chl a, 4% for Chl b, and 2% for total (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ee-g). Overall, chlorophyll content displayed a strong positive correlation with vase life(r\u0026thinsp;\u0026gt;\u0026thinsp;0.75, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), highlighting its role in extending flower longevity (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eCarotenoid content in the control was 0.29 mg g⁻\u0026sup1; FW, with slight increases for pulsed and continuous 0.1 mM melatonin treatments, and even smaller changes for 1 mM treatments. These differences were not statistically significant (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eh).\u003c/p\u003e\n \u003cp\u003eAnthocyanin content in the control group was measured at 267.41 mg/100 g fresh weight (FW). Application of 0.1 mM melatonin, both pulsed and continuous, significantly elevated anthocyanin levels by approximately 36%, reaching 362.97 mg/100 g FW. In contrast, 1 mM melatonin treatments resulted in more moderate increases, with pulsed application achieving 308.43 mg/100 g FW (15% increase) and continuous application reaching 344.88 mg/100 g FW (29% increase) (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ei). Statistical analysis demonstrated a strong positive correlation between anthocyanin content and vase life (r\u0026thinsp;=\u0026thinsp;0.81, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), highlighting its pivotal role in enhancing color vibrancy and extending flower longevity (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Physiological and water relations parameters\u003c/h2\u003e\n \u003cp\u003eElectrolyte leakage in the control group was measured at 37.81%. Melatonin treatments significantly reduced leakage, with continuous 0.1 mM melatonin achieving the greatest reduction to 21.72%, a 43% decrease, followed by pulsed 0.1 mM at 28.03%, a 26% decrease. The 1 mM treatments showed milder reductions, with 31.05% for pulsed, 18% lower, and 33.10% for continuous, 12% lower (Fig. 2a). A strong negative correlation with vase life was evident (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.71, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), highlighting the importance of minimizing membrane damage for enhanced postharvest flower preservation (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eRelative water content (RWC) in the control group averaged 71.84%. Treatment with 0.1 mM melatonin markedly increased RWC to 79.89% for pulsed application, an 11% rise, and 79.32% for continuous application, a 10% rise. The 1 mM treatments yielded smaller increases, reaching 75.20% for pulsed, a 5% rise, and 73.89% for continuous, a 3% rise (Fig.\u0026nbsp;2b).\u003c/p\u003e\n \u003cp\u003eSolution uptake in the control samples was 34.33 mL. Melatonin treatments enhanced uptake, with pulsed 0.1 mM reaching 40.00 mL, a 16% increase, and continuous 0.1 mM reaching 39.67 mL, a 15% increase. The 1 mM treatments showed modest gains, with 37.00 mL for pulsed, an 8% increase, and 37.33 mL for continuous, a 9% increase (Fig.\u0026nbsp;2c).\u003c/p\u003e\n \u003cp\u003eThe fresh-to-dry weight ratio in the control group was recorded at 26.51. Application of 0.1 mM melatonin significantly raised this ratio to 31.25 for pulsed treatment, an 18% increase, and 30.29 for continuous treatment, a 14% increase. The 1 mM treatments resulted in smaller increments, reaching 28.94 for pulsed, a 9% increase, and 28.46 for continuous, a 7% increase (Fig. 2d). Strong positive correlations were observed between vase life and relative water content, solution uptake, and fresh-to-dry weight ratio (r\u0026thinsp;\u0026gt;\u0026thinsp;0.8, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), emphasizing their critical roles in sustaining hydration and prolonging postharvest flower longevity (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\n \u003ch2\u003e\u003cstrong\u003e3.4. Antioxidant enzyme activities\u003c/strong\u003e\u003c/h2\u003e\n \u003cp\u003ePeroxidase (POD) activity in the control group was 2.29 U g⁻\u0026sup1; FW, rising to 3.73 U g⁻\u0026sup1; FW with pulsed 0.1 mM melatonin, a 63% increase, and 3.53 U g⁻\u0026sup1; FW with continuous 0.1 mM melatonin, a 54% increase. The 1 mM treatments showed smaller rises, reaching 3.12 U g⁻\u0026sup1; FW for pulsed, a 36% increase, and 3.18 U g⁻\u0026sup1; FW for continuous, a 39% increase (Fig. 2e). Catalase (CAT) activity in the control was 3.60 U g⁻\u0026sup1; FW, increasing to 3.93 U g⁻\u0026sup1; FW with pulsed 0.1 mM melatonin, a 9% rise, and 3.90 U g⁻\u0026sup1; FW with continuous 0.1 mM melatonin, an 8% rise. The 1 mM treatments reached 3.85 U g⁻\u0026sup1; FW for pulsed, a 7% rise, and 3.73 U g⁻\u0026sup1; FW for continuous, a 4% rise (Fig. 2f). Both POD and CAT activities exhibited strong positive correlations with vase life (r\u0026thinsp;\u0026gt;\u0026thinsp;0.9, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), underscoring their critical role in mitigating oxidative stress and extending flower longevity (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe findings of this study provide compelling evidence that the exogenous application of melatonin, applied either as a pulse or in continuous form at concentrations of 0.1 and 1 mM, exerts profound positive effects on a wide range of postharvest attributes in cut rose flowers, with the exception of carotenoid content, which remained unaffected. Melatonin extended vase life and enhanced flower quality, with 0.1 mM pulsed treatment providing the greatest extension in vase life (9.67 days), and both 0.1 mM treatments achieving maximum quality scores (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-b). A strong positive correlation existed between vase life and flower quality (r\u0026thinsp;=\u0026thinsp;0.71, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These results complement and extend existing literature: for instance, Mazrou et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] reported that 0.2 mM melatonin nearly doubled the vase life of cut roses by improving RWC, reducing membrane damage, and delaying senescence. Similarly, Lezoul et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] demonstrated that postharvest melatonin application at 0.1 mM lengthened carnation vase life by up to 10 days. Preharvest applications in tuberose (\u003cem\u003ePolianthes tuberosa\u003c/em\u003e) were also shown to promote water balance and antioxidant activity, further extending floral longevity [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. Comparable effects have also been reported in peony (\u003cem\u003ePaeonia lactiflora\u003c/em\u003e), where melatonin delayed senescence by protecting chlorophyll molecules, reducing proline accumulation, and alleviating oxidative stress [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. At the mechanistic level, the beneficial role of melatonin can be understood from its dual capacity as both a direct ROS scavenger and a modulator of plant hormonal pathways. Melatonin neutralizes reactive oxygen species such as superoxide radicals, hydrogen peroxide, and hydroxyl radicals, thereby protecting vital biomolecules like lipids, proteins, and nucleic acids from oxidative damage. In tandem, melatonin can fine-tune hormone signaling by suppressing ethylene biosynthesis, the primary hormonal driver of senescence, while simultaneously enhancing auxin-related activities that promote tissue vitality and delay cell death [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Moreover, melatonin has been shown to enhance the transcription of stress-related genes, including those encoding antioxidant enzymes, thereby strengthening cellular protection systems against oxidative stress [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This set of interconnected actions explains why melatonin-treated flowers not only live longer but also maintain superior visual and quality attributes.\u003c/p\u003e \u003cp\u003eA key finding of this study is the clear superiority of the 0.1 mM pulse treatment [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. We propose this is a classic example of hormetic priming. A brief, concentrated exposure to melatonin likely acts as a mild eustress signal, activating the flower's transcriptional defense machinery (e.g., genes for antioxidant enzymes, aquaporins, and heat-shock proteins) more potently than a continuous, low-level stimulus [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. This 'primed' state then persists throughout the vase life, providing sustained protection against senescence triggers. In contrast, continuous exposure, particularly at the higher 1 mM concentration, could lead to receptor desensitization or negative feedback inhibition, diminishing its efficacy over time [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. This priming hypothesis is consistent with observations in other plant systems where brief stress applications confer long-term resistance [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA clear and significant enhancement in flower diameter was also observed under 0.1 mM melatonin, with the continuous treatment producing the largest flowers (51.00 mm, or an 18% increase) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Vase life strongly correlated with flower size (r\u0026thinsp;=\u0026thinsp;0.84, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), suggesting that larger flowers are more likely to remain viable for longer when treated with melatonin. Parallel results have been reported by Wang et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], where peonies maintained greater flower size under melatonin treatment due to enhanced water balance, membrane stability, and osmotic regulation. Cut chrysanthemums treated with 5 \u0026micro;M melatonin also displayed increased diameter, fresh weight, and water retention compared to untreated controls [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Similarly, marigold plants sprayed with 150 mg/L melatonin exhibited significant increases in both fresh and dry flower weights as well as yield, mainly attributed to improved morpho-physiological processes [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. From a physiological perspective, melatonin contributes to enlarged flower diameter by promoting cell expansion and division, processes mediated in part by its interactions with auxin and gibberellin signaling pathways. Additionally, it promotes water absorption by upregulating aquaporin genes, which facilitate efficient water transport through membranes, ensuring adequate hydration to support cell enlargement [\u003cspan additionalcitationids=\"CR64\" citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]. Thus, melatonin reinforces both the hydraulic and biochemical mechanisms underlying floral opening, ensuring longer-lasting ornamental appeal. The observed increase in flower diameter is likely driven by enhanced cell expansion. This process is potentially mediated by melatonin's well-documented role in upregulating aquaporin genes (e.g., \u003cem\u003ePIP2;1\u003c/em\u003e, \u003cem\u003eTIP1;1\u003c/em\u003e), which facilitate water influx into petal cells, thereby increasing turgor pressure and driving cell enlargement [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eChlorophyll content (including indices for chlorophyll a, chlorophyll b, and total chlorophyll) was significantly elevated by melatonin treatments, with the 0.1 mM pulse treatment producing the highest increases (22% for the chlorophyll index and ~\u0026thinsp;28% for total chlorophyll) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed\u0026ndash;g). Chlorophyll levels correlated strongly with vase life (r\u0026thinsp;\u0026gt;\u0026thinsp;0.75, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), highlighting their vital role in sustaining postharvest floral metabolism. Similar findings have been observed in chrysanthemums, where melatonin delayed chlorophyll degradation and preserved higher pigment content during storage [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Mechanistically, melatonin exerts its chlorophyll-protective effect by stabilizing chloroplast membranes, preventing ROS-mediated damage, and inhibiting chlorophyllase\u0026mdash;the enzyme responsible for chlorophyll breakdown [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e]. In addition, melatonin upregulates genes involved in chlorophyll biosynthesis, resulting in higher pigment accumulation [\u003cspan additionalcitationids=\"CR69\" citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e]. Interestingly, carotenoids remained unaffected in this study (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eh), suggesting that while melatonin selectively regulates chlorophyll metabolism, carotenoid biosynthesis may not be as responsive to melatonin or may be less sensitive to oxidative stress, as reported by Xu et al. [\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAnthocyanin concentrations also increased substantially under melatonin, particularly in 0.1 mM treatments (~\u0026thinsp;36%), compared to 15\u0026ndash;29% increases under 1 mM (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ei). Vase life correlated strongly with anthocyanin levels (r\u0026thinsp;=\u0026thinsp;0.81, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), indicating that color retention is closely aligned with floral longevity. These results corroborate findings in amaryllis [\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e], litchi fruit [\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e], and cabbage seedlings [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e]. Melatonin boosted anthocyanin biosynthesis through upregulation of structural genes such as phenylalanine ammonia-lyase (\u003cem\u003ePAL\u003c/em\u003e), chalcone synthase (\u003cem\u003eCHS\u003c/em\u003e), flavanone 3-hydroxylase (\u003cem\u003eF3H\u003c/em\u003e), and anthocyanidin synthase (\u003cem\u003eANS\u003c/em\u003e), as well as transcription factors such as Myeloblastosis (\u003cem\u003eMYB\u003c/em\u003e) and basic Helix-Loop-Helix (\u003cem\u003ebHLH\u003c/em\u003e), which regulate the anthocyanin biosynthesis pathway [\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e, \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e]. The regulation of flavonoid biosynthetic genes, such as chalcone isomerase (\u003cem\u003eCHI\u003c/em\u003e), also supports anthocyanin synthesis, ensuring enhanced pigmentation and prolonged flower freshness [\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eElectrolyte leakage, a key indicator of membrane integrity, decreased significantly under melatonin treatments, with continuous 0.1 mM yielding the most pronounced reduction (43%) (Fig.\u0026nbsp;2a). A negative correlation was observed with vase life (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.71, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), highlighting the value of membrane stability for prolonging floral freshness. Similar outcomes have been observed in cut roses and carnations, where melatonin reduced leakage by enhancing ROS detoxification and preserving lipid bilayer structures (Ahmad et al., 2021; Liang et al., 2018). Mechanistically, melatonin can directly integrate into lipid membranes, reinforcing their stability, while also activating enzymatic antioxidants to suppress lipid peroxidation [\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e, \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e]. This reduction in ion leakage provides direct evidence of melatonin's role in preserving membrane stability. The significant upregulation of POD and CAT activities (Fig.\u0026nbsp;2e-f) offers a clear enzymatic mechanism for this protection, as these enzymes detoxify H₂O₂ and other ROS, preventing the lipid peroxidation that compromises membrane integrity [\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHydration-related traits, such as relative water content (RWC), solution uptake, and fresh-to-dry weight ratios, improved markedly with melatonin, with pulsed 0.1 mM performing slightly better than continuous application (Fig.\u0026nbsp;2b\u0026ndash;d). All hydration parameters correlated strongly with vase life (r\u0026thinsp;\u0026gt;\u0026thinsp;0.8, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). These effects resonate with findings in tomato, where melatonin sprays increased RWC under heat and drought stress [\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e]. Hosseini et al. [\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e] also reported that melatonin extended postharvest longevity in roses and carnations by improving water retention and reducing ROS damage. The underlying mechanism involves aquaporin upregulation (plasma membrane intrinsic protein [\u003cem\u003ePIP\u003c/em\u003e] and tonoplast intrinsic protein [\u003cem\u003eTIP\u003c/em\u003e]) that facilitates water flow through cellular membranes [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e, \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e]. By modulating stomatal closure, melatonin also optimizes transpiration rates, maintaining turgor pressure and preventing desiccation [\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e, \u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e]. Studies also show melatonin maintains partially open stomata under drought stress, balancing transpiration and water retention [\u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e, \u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e]. Furthermore, melatonin improves biomass accumulation by enhancing photosynthesis and carbohydrate translocation, increasing fresh and dry weights in plants like grapefruit mint and cotton [\u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e87\u003c/span\u003e, \u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e]. In petal tissues, melatonin reduces fresh and dry weight loss under drought, maintaining tissue hydration [\u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e89\u003c/span\u003e]. These mechanisms collectively enhance water status, biomass, and postharvest longevity in flowers.\u003c/p\u003e \u003cp\u003eFinally, antioxidant enzyme activities\u0026mdash;specifically POD and CAT\u0026mdash;increased significantly under melatonin, with 0.1 mM pulse showing the greatest enhancement (POD by 63%) (Fig.\u0026nbsp;2e\u0026ndash;f). These enzymes exhibited strong correlations with vase life (r\u0026thinsp;\u0026gt;\u0026thinsp;0.8, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Such increases mirror other reports in \u003cem\u003eRanunculus asiaticus\u003c/em\u003e [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e], mung bean [\u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e90\u003c/span\u003e], and roses [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], supporting melatonin\u0026rsquo;s strong ROS-scavenging roles. Beyond direct enzymatic upregulation, melatonin also promotes accumulation of non-enzymatic antioxidants such as glutathione and ascorbate [\u003cspan citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e, \u003cspan citationid=\"CR92\" class=\"CitationRef\"\u003e92\u003c/span\u003e]. Altogether, these multifaceted defense mechanisms protect membranes from peroxidation, maintain redox balance, and delay senescence [\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e, \u003cspan citationid=\"CR94\" class=\"CitationRef\"\u003e94\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt is important to acknowledge the limitations of this study. Our conclusions regarding the molecular mechanisms, such as the upregulation of aquaporins or specific signaling pathways, are based on logical inference from our phenotypic data and the existing literature. Future studies employing transcriptomic or proteomic analyses would be required to directly validate these hypothesized pathways. Furthermore, our study was conducted on a single rose cultivar; future work should validate the optimized protocol across different cultivars and species.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study identifies a 0.1 mM melatonin pulse treatment as a highly effective and resource-efficient strategy to significantly extend the vase life of 'Samurai' roses. The superiority of the pulse method suggests it acts as a potent priming agent, efficiently activating the flower's own defense systems with minimal resource input. Melatonin effectively mitigated major senescence triggers, including ROS accumulation, membrane damage, and water imbalance. Importantly, the pulse 0.1 mM treatment presents a practical, cost-efficient, and environmentally sustainable option for the floriculture industry. This foundational work paves the way for future studies to explore the molecular basis of melatonin's priming effect, further refining its application for sustainable floriculture.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests, financial or non-financial.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eAuthors\u0026rsquo; information (optional)\u003c/h2\u003e \u003cp\u003eNot provided.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eSS: Methodology, Data curation, SS: Formal analysis, Writing \u0026ndash; review \u0026amp; editing, VRS: designed the research, Supervision, ZP: Methodology, Supervision.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data supporting the findings of this study are available within the paper and its Supplementary Information.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSchmidt G. 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Front Plant Sci. 2021;12:779382. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/FPLS.2021.779382/BIBTEX\u003c/span\u003e\u003cspan address=\"10.3389/FPLS.2021.779382/BIBTEX\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJensen NB, Ottosen CO, Zhou R. Exogenous Melatonin Alters Stomatal Regulation in Tomato Seedlings Subjected to Combined Heat and Drought Stress through Mechanisms Distinct from ABA Signaling. Plants. 2023;12:1156. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/PLANTS12051156/S1\u003c/span\u003e\u003cspan address=\"10.3390/PLANTS12051156/S1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRezaei S, Javanmard A, Sabaghnia N, Morshedloo MR. Exogenous melatonin modulates physiological responses, phytochemical profiles and essential oil production in grapefruit mint under drought stress. Sci Rep. 2025;15:1\u0026ndash;12. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/S41598-025-99281-5;SUBJMETA\u003c/span\u003e\u003cspan address=\"10.1038/S41598-025-99281-5;SUBJMETA\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAhmad I, Guanglong Z, Zhou G, Younas MU, Yan X. Melatonin and mepiquat chloride impact on cotton growth, physiological and yield at different growth stages. 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Front Plant Sci. 2022;13:902694. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/FPLS.2022.902694/FULL\u003c/span\u003e\u003cspan address=\"10.3389/FPLS.2022.902694/FULL\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSati H, Chinchkar AV, Kataria P, Pareek S, Melatonin. A potential abiotic stress regulator. Plant Stress. 2023;10:100293. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/J.STRESS.2023.100293\u003c/span\u003e\u003cspan address=\"10.1016/J.STRESS.2023.100293\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhan Z, Jan R, Asif S, Farooq M, Jang Y-H, Kim E-G, et al. Exogenous melatonin induces salt and drought stress tolerance in rice by promoting plant growth and defense system. Sci Rep. 2024;14:1214.\u003c/span\u003e\u003c/li\u003e\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":"bmc-plant-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pbio","sideBox":"Learn more about [BMC Plant Biology](http://bmcplantbiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pbio/default.aspx","title":"BMC Plant Biology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Melatonin, Postharvest, Roses, Vase life, Quality","lastPublishedDoi":"10.21203/rs.3.rs-8762944/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8762944/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCut roses (\u003cem\u003eRosa hybrida\u003c/em\u003e L. cv. Samurai) undergo rapid postharvest senescence, limiting vase life and quality. While the preservative effect of melatonin is established, a critical barrier to its commercial adoption is the lack of standardized, cost-effective application protocols. This study evaluated melatonin's efficacy as a biostimulant, applied via pulse (30-min immersion) or continuous (vase solution) methods at 0.1 mM and 1 mM concentrations, testing the hypothesis that a brief pulse treatment acts as a priming stimulus for a more efficient defense response. Assessed parameters included vase life, flower quality, diameter, chlorophyll and anthocyanin contents, electrolyte leakage, relative water content, solution uptake, and antioxidant enzyme activities. The 0.1 mM pulse treatment extended vase life by 61% (9.67 vs. 6.00 days), improved flower quality (5.00 vs. 3.33), increased diameter by 18% (51.00 vs. 43.33 mm), enhanced chlorophyll by 22% and anthocyanin by 36%, and reduced electrolyte leakage by 43%, with strong correlations to vase life (r\u0026thinsp;=\u0026thinsp;0.71\u0026ndash;0.94, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The 0.1 mM continuous treatment was less effective, and 1 mM concentrations showed minimal benefits. These results suggest that a brief pulse treatment effectively primes the rose's endogenous defense systems, offering a highly efficient strategy. Melatonin's antioxidant and anti-senescence properties provide a sustainable, cost-effective strategy for extending rose vase life, with 0.1 mM pulse application as the most effective method for commercial floriculture.\u003c/p\u003e \u003cp\u003eCut roses (\u003cem\u003eRosa hybrida\u003c/em\u003e L. cv. Samurai) undergo rapid postharvest senescence, limiting vase life and quality. This study evaluated melatonin's efficacy as a biostimulant, applied via pulse (30-min immersion) or continuous (vase solution) methods at 0.1 mM and 1 mM concentrations, in a completely randomized design with three replicates of 10 stems per treatment. Assessed parameters included vase life, flower quality, diameter, chlorophyll and anthocyanin contents, electrolyte leakage, relative water content, solution uptake, and antioxidant enzyme activities. The 0.1 mM pulse treatment extended vase life by 61% (9.67 vs. 6.00 days), improved flower quality (5.00 vs. 3.33), increased diameter by 18% (51.00 vs. 43.33 mm), enhanced chlorophyll by 22% and anthocyanin by 36%, and reduced electrolyte leakage by 43%, with correlations to vase life (r\u0026thinsp;=\u0026thinsp;0.71\u0026ndash;0.94, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The 0.1 mM continuous treatment was less effective, and 1 mM concentrations showed minimal benefits. Melatonin's antioxidant and anti-senescence properties provide a sustainable, cost-effective strategy for extending rose vase life, with 0.1 mM pulse application as the most effective method for commercial floriculture.\u003c/p\u003e","manuscriptTitle":"Melatonin Pulse Treatment Optimization: Boosting Vase Life and Postharvest Quality in Cut Roses (Rosa hybrida cv. Samurai)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-23 18:51:47","doi":"10.21203/rs.3.rs-8762944/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-13T18:22:02+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-13T11:17:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-12T13:46:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"6082305070050994346368521581598018769","date":"2026-04-08T09:23:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"171236629714346865652657194648438461145","date":"2026-04-07T08:49:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"102997071095226573365160248738268826513","date":"2026-04-06T10:21:55+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-26T12:57:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-25T11:36:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"83603892011492745388301539064815674964","date":"2026-02-19T07:42:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"300219102818404416177097331405625288441","date":"2026-02-17T03:23:02+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-17T03:10:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-12T01:54:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-09T23:17:07+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-07T06:52:46+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Plant Biology","date":"2026-02-07T06:43:39+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-plant-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pbio","sideBox":"Learn more about [BMC Plant Biology](http://bmcplantbiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pbio/default.aspx","title":"BMC Plant Biology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4d6ec6bf-fe45-4dc2-b8e7-07771a90fdd1","owner":[],"postedDate":"February 23rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-04T06:40:13+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-23 18:51:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8762944","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8762944","identity":"rs-8762944","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}