Unravelling the Stomatal Phenotype‒Function Relationships in Urban Trees Under Air Pollution Stress: A Multispecies Comparative Study

Unravelling the Stomatal Phenotype‒Function Relationships in Urban Trees Under Air Pollution Stress: A Multispecies Comparative Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Unravelling the Stomatal Phenotype‒Function Relationships in Urban Trees Under Air Pollution Stress: A Multispecies Comparative Study Md. Abul Kashem, Mohammad Ataur Rahman, Sirajum Munira Hussaini, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8415643/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Urban trees play a vital role in reducing the harmful effects of air pollution, yet their physiological and anatomical responses, especially stomatal plasticity, under long-term urban stress remain poorly understood. This study examined the stomatal phenotype‒function relationships in dominant urban tree species across two contrasting environments in Dhaka: the heavily polluted areas of Motijheel-Sayedabad and the relatively clean National Botanical Garden. We conducted a comparative analysis of key stomatal features, including stomatal density, size, area, perimeter, pore index, and stomatal opening status, across multiple species to assess their adaptive responses to air pollution. Two-way ANOVA showed that most stomatal structural and functional traits of urban plants were strongly affected by species, site, and their interaction, emphasizing distinct species-specific responses to pollution levels. Species such as Polyalthia longifolia , Swietenia mahagoni , and Ficus benghalensis exhibited significant stomatal alterations, indicating potential resilience under environmental stress. Pearson's correlation analysis found significant relationships among various stomatal traits. Principal component analysis of stomatal traits showed that the first two principal components (PC1 and PC2) together explained 69.71% of the total variance. PC1 alone accounted for 44.34%, while PC2 contributed a further 25.37%. This indicates that these two components effectively encapsulate the primary patterns of trait variation. The PCA results demonstrated a clear separation between stomatal morphological traits (e.g., SL, SB, SA, SP) and functional attributes (%OS, %CS), suggesting different physiological mechanisms control them. Overall, this study shows how important stomatal traits are as signs of how well plants can adapt to their environment and also provides useful information for choosing trees in cities for planning green infrastructure. Morphometric traits Stomata Polluted site Functional traits Control site PCA biplot Figures Figure 1 Figure 2 Figure 3 Figure 4 1 Introduction Urbanization, a hallmark of the 21st century, presents unparalleled environmental challenges for urban flora, especially trees, which constitute the foundation of green infrastructure in cities [ 1 – 3 ]. The rapid expansion of metropolitan areas, such as Dhaka, has led to significant alterations in atmospheric quality, microclimate, and hydrological regimes due to increased vehicular emissions, industrial activities, and urban heat island effects [ 4 – 6 ]. Urban trees are increasingly exposed to various anthropogenic stressors, including elevated levels of air pollutants, thermal stress, reduced soil moisture, and heavy metal contamination, all of which jeopardize their growth, physiological functions, and long-term survival [ 7 – 10 ]. To keep urban ecosystem services like regulating microclimates, cleaning the air, and storing carbon, it’s important to know how trees change their shape and function in these situations [ 11 – 13 ]. Among the many physiological adaptations that plants exhibit in response to stress, stomatal traits are particularly fundamental. Stomata are tiny holes on the surface of leaves that control the exchange of gases and the balance of water. They are crucial for the growth stress resistance of plants [ 14 – 17 ]. Genetic and environmental factors both affect important stomatal parameters like stomatal density (SD), stomatal length (SL), stomatal breadth (SB), stomatal area (SA), the stomatal pore index (SPI), and the proportion of open to closed stomata. These traits exhibit significant plasticity, enabling plants to adjust their physiology in response to fluctuating environmental conditions, including pollution and drought [ 18 – 21 ]. Intraspecific variation in stomatal traits signifies the ability of individuals to adapt to specific site conditions, frequently indicating local adaptation or phenotypic plasticity in response to microenvironmental heterogeneity [ 22 – 26 ]. Conversely, interspecific variation is primarily influenced by evolutionary history and life-history strategies, which govern species’ functional responses to urban stressors [ 8 , 22 , 23 , 27 ]. A comparative knowledge of intra- and interspecific variation in stomatal traits is thus crucial to consider species' ecological performances, and it will be useful for choosing resistant tree taxa for urban planting programs. Although stomatal responses have been studied under controlled environmental conditions or for a limited number of species, large-scale field observations comparing several plant species along pollution gradients within tropical megacities are scarce. In Dhaka city, with a still burgeoning population and increasingly being surrounded by polluted atmosphere, particulate-containing aerosols in the air, as well as water deprivation, assessing the variation pattern of trees dependent on dominant species with respect to stomatal traits is likely to provide insights into their functional performance scale and adaptive strategies. With such low green coverage and the consistently poor air quality in the city, trees in those highly polluted areas like Motijheel and Sayedabad are put under prolonged physiological stress [ 4 ]. Therefore, it is essential to evaluate whether tree species in these polluted environments exhibit notable stomatal and functional plasticity compared with those growing in cleaner areas, such as the National Botanical Garden. Such assessments are critical because not all species respond equally: some may display high stomatal density to maximize CO₂ uptake, whereas others may maintain smaller stomata to reduce transpirational water loss or minimize pollutant entry [ 15 , 28 – 31 ]. Comprehending this relationship is crucial for the development of urban green spaces, especially in the selection of resilient species for afforestation and pollution control. For instance, species exhibiting significant stomatal plasticity may more effectively balance the trade-offs between gas exchange and water conservation in contaminated environments [ 32 – 34 ]. Moreover, stomatal metrics such as the stomatal pore index, percentage of open stomata, and stomatal conductance proxies can serve as non-destructive indicators of tree health and pollution tolerance [ 32 , 35 ]. This study seeks to clarify the relationship between stomatal phenotype and function in selected urban tree species from contrasting locations in Dhaka, ranging from the heavily polluted zone, Motijheel-Sayedabad, to the relatively unpolluted National Botanical Garden. By quantifying a suite of stomatal traits and comparing interspecific variation, this study seeks to assess the intraspecific variability in stomatal traits of dominant urban tree species between relatively clean and highly polluted sites in Dhaka, evaluate the extent of interspecific variation among species, identify species that exhibit significant stomatal plasticity or trait stability across environments, and relate trait patterns to species’ potential ecological performance under urban stress. This study will support evidence-based decision-making for sustainable urban forestry in South Asian megacities. 2 Materials and methods 2.1 Study sites The study was conducted at two contrasting locations in Dhaka, Bangladesh, the National Botanical Garden, designated as the control (less polluted) site, and the Motijheel-Sayedabad areas, selected as the polluted site owing to their high levels of air pollution (Fig. 1 ). The National Botanical Garden, located in the Mirpur area of Dhaka, spans approximately 204 acres and is geographically positioned at 23.81660° N latitude and 90.34875° E longitude. It is one of the largest botanical gardens in Bangladesh [ 4 , 36 ]. Owing to its rich plant diversity and relatively low vehicular activity, this location offers a cleaner, less polluted environment, making it an ideal reference site for comparison. On the contrary, the Motijheel-Sayedabad areas were chosen as the polluted site because they represent some of the busiest and most traffic-congested parts of Dhaka city [ 4 ]. These areas experience heavy traffic throughout the day, which mainly consists of petrol-powered and diesel-operated vehicles. The continuous emissions from these vehicles release large amounts of airborne pollutants, including fine particulate matter, carbon monoxide, nitrogen oxides, and lead, which contribute to poor air quality. As a result, these areas are highly representative of urban air pollution hotspots, making them suitable for assessing the impact of pollution on urban vegetation. 2.2 Leaf collection The study was conducted in February 2024 and targeted the most frequently occurring tree species common to both the polluted and nonpolluted sites. Fresh leaf samples were collected from ten representative species, selected on the basis of their prevalence across both locations (Table 1 ). For each species, three healthy individuals were chosen per site. From each tree, ten fully expanded and physiologically active young leaves were sampled. This sampling strategy resulted in a total of 540 leaf samples (10 leaves × 3 trees × 10 species × 2 sites, polluted and nonpolluted). All the samples were immediately transported to the laboratory for further analysis. Table 1 List of tree species, including families and common names, selected from polluted and unpolluted sites in Dhaka city, Bangladesh, for the present study Common name Scientific name Family Jackfruit Artocarpus heterophyllus Moraceae Banyan tree Ficus benghalensis Moraceae Sacred fig tree Ficus religiosa Moraceae Spanish cherry Mimusops elengi Sapotaceae False Ashoka Polialthia longifolia Annonaceae Black plum tree Sizium cumini Myrtaceae Mahagony Swietenia mahagoni Meliaceae Arjun tree Terminalia arjuna Combretaceae Indian almond Terminalia catappa Combretaceae 2.3 Determination of leaf stomatal traits Stomatal properties were studied via the impression technique [ 37 , 38 ]. First, the leaf was spread gently upon a plain field of glass. A thick swath of clear nail polish was painted upon the ventral side of the leaf. After the nail polish had dried, the peel of the nail polish swath was gently removed from the leaf completely. A cloudy impression of the leaf surface attached to the nail polish was found. One drop of glycerin was added, and then, the leaf impressions were placed on a clean slide, covered with a cover slip and observed under a microscope. A photograph of the field of a leaf under a microscope (Axio Lab. A1 microscope (Carl Zeiss Microscopy GmbH, Germany) was used. Three images were taken from each leaf, and three stomata from each image were selected to study the stomatal parameters (Table 2 ). Three leaves were taken from each species at each site. Stomatal dimensions were quantified via ImageJ software (Ver: 1.45k). The captured images were opened in ImageJ, and the scale was calibrated by setting the line width tool in micrometers (µm) on the basis of the provided scale bar in the Analyse menu (Fig. 2 ). This calibrated scale was then added to the ROI Manager window. The stomatal length, width, area, and perimeter were subsequently measured by selecting individual stomata and clicking the "Measure" option, which processed the selected region of interest (ROI) data. For the measurement of stomatal density (individual mm − 2 ), the number of stomata per unit area (mm − 2 ) was counted from the images at a magnification of 10 × 40, and the visual field area was 32×22 µm 2 . The stomatal density was calculated via the following formula [ 39 , 40 ]: where the area of field of view (FOV) = ӆr 2 The stomatal pore index is an integrative parameter of stomatal density and stomatal length that reflects the stomatal conductance of leaves. The following formula calculates the SPI (%): SPI = Stomatal density × Stomatal length 2 × 10 − 4 Table 2 Morphometric and functional traits measured from the control and polluted sites during the study period Group name Trait name Short form Unit Description Morphometric Stomatal Length SL µm Linear length of the stomatal pore. Stomatal Breadth SB µm Width of the stomatal pore. Stomatal Area SA µm² Estimated area of the stomatal pore, often approximated as an ellipse. Stomatal Perimeter SP µm Total boundary length surrounding the stomatal pore. Stomatal Density SD no./mm² Number of stomata per unit leaf area. Stomatal Pore Index SPI % Product of stomatal density and stomatal area; reflects gas exchange potential. Functional Open Stomata OS % Proportion of stomata that are open under observed conditions. Closed Stomata CS % Proportion of stomata that are closed under observed conditions. 2.4 Statistical analysis To investigate differences in morphometric and functional traits among the nine plant species from both sites, one-way analysis of variance (ANOVA) was performed. Post hoc comparisons were conducted via Tukey’s honestly significant difference (HSD) test to determine significant differences between means. All the statistical analyses were conducted via JMP 4.0 software (SAS Institute, Cary, NC, USA). 3 Results 3.1 Morphometric Traits 3.1.1 Stomatal length Two-way ANOVA revealed that stomatal length was significantly affected by species, site, and their interactions (Table 3 ). Most species presented a reduction in stomatal length under polluted conditions. For example, A. heterophyllus decreased from 2.25 ± 0.07 µm at the control site to 1.80 ± 0.09 µm at the polluted site. Similarly, F. benghalensis decreased in size from 2.38 ± 0.06 µm to 1.77 ± 0.05 µm. In contrast, some species, such as P. longifolia and T. catappa , presented an increase in stomatal length under polluted conditions, with P. longifolia increasing from 2.49 ± 0.04 µm to 2.59 ± 0.1 µm (Table 4 ). Significant differences in stomatal length across species suggest differential sensitivity or adaptation to atmospheric pollution. Table 3 Overall two-way ANOVA statistics (F ratios) of the effects of site, species, and their interaction on the leaf stomatal properties in Dhaka city. Asterisks denote significance levels: *p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, and ns indicates not significant. Source of variation Species (df = 8) Site (df = 1) Species × Site (df = 8) Stomatal Length 8.96*** 5.81* 2.91* Stomatal Breadth 13.72*** 10.10** 4.51*** Stomatal Area 12.54*** 13.32*** 4.31** Stomatal Perimeter 11.34*** 11.0** 4.78*** Stomatal Density 39.52*** 3.03ns 6.58*** Stomatal Pore Index 12.16*** 0.18ns 5.97*** Open Stomata 3.03* 1.8ns 10.34*** Closed Stomata 2.63* 6.45* 7.5*** 3.1.2 Stomatal breadth For most species, stomatal breadth was lower at the polluted site than at the control site (Table 4 ). For example, A. heterophyllus presented a stomatal breadth of 1.54 ± 0.03 µm at the control site and 1.44 ± 0.06 µm at the polluted site. Similarly, F. benghalensis was 1.76 ± 0.04 µm at the control site and 1.25 ± 0.07 µm at the polluted site. Notable exceptions included P. longifolia , which presented greater stomatal breadth at the polluted site (2.08 ± 0.11 µm) than at the control site (1.99 ± 0.02 µm), and T. catappa , which also presented greater stomatal breadth at the polluted site (1.49 ± 0.02 µm) than at the control site (1.33 ± 0.09 µm). F. religiosa and T. arjuna displayed very similar stomatal breadths between the two sites, with F. religiosa having 1.5 ± 0.01 µm at the control site and 1.55 ± 0.15 µm at the polluted site and T. arjuna having 1.61 ± 0.03 µm at both sites. Two-way ANOVA also revealed that stomatal breadth varied significantly with species, site, and their interactions (Table 3 ). Table 4 Stomatal morphometric traits of selected plant species from the control and polluted sites in Dhaka city Species Site SL (µm) SB (µm) SA (µm 2 ) SP (µm) SD (no./mm²) SPI (%) Artocarpus heterophyllus Control 2.25 ± 0.07 1.54 ± 0.03 3.32 ± 0.29 6.54 ± 0.28 251.67 ± 25.45 0.13 ± 0.021 Polluted 1.8 ± 0.09 1.44 ± 0.06 2.48 ± 0.06 5.65 ± 0.08 203.33 ± 27.66 0.067 ± 0.013 Ficus benghalensis Control 2.38 ± 0.06 1.76 ± 0.04 4.16 ± 0.2 7.34 ± 0.18 157 ± 10.97 0.09 ± 0.001 Polluted 1.77 ± 0.05 1.25 ± 0.07 2.26 ± 0.12 5.42 ± 0.12 169.67 ± 9.82 0.053 ± 0.007 Ficus religiosa Control 2.5 ± 0.07 1.5 ± 0.01 3.9 ± 0.16 7.18 ± 0.13 77.67 ± 7.54 0.05 ± 0.006 Polluted 2.49 ± 0.05 1.55 ± 0.15 3.51 ± 0.24 6.95 ± 0.22 94.33 ± 7.22 0.06 ± 0.006 Mimusops elengi Control 2.36 ± 0.04 1.64 ± 0.1 3.58 ± 0.13 6.83 ± 0.11 44 ± 3.46 0.02 ± 0.003 Polluted 2.27 ± 0.08 1.33 ± 0.1 3.12 ± 0.31 6.48 ± 0.29 54.33 ± 10.33 0.023 ± 0.003 Polialthia longifolia Control 2.49 ± 0.04 1.99 ± 0.02 4.79 ± 0.08 7.76 ± 0.06 117.33 ± 5.55 0.07 ± 0.007 Polluted 2.59 ± 0.1 2.08 ± 0.11 4.71 ± 0.27 7.77 ± 0.18 123.67 ± 2.33 0.08 ± 0.006 Sizium cumini Control 1.85 ± 0.01 1.59 ± 0.04 2.57 ± 0.09 5.7 ± 0.1 274.67 ± 22.05 0.09 ± 0.007 Polluted 2.05 ± 0.07 1.47 ± 0.04 2.93 ± 0.13 6.15 ± 0.14 199 ± 5.29 0.083 ± 0.009 Swietenia mahagoni Control 2.25 ± 0.09 1.71 ± 0.02 3.45 ± 0.2 6.66 ± 0.19 142.67 ± 5.61 0.07 ± 0.003 Polluted 1.91 ± 0.07 1.51 ± 0.08 2.58 ± 0.2 5.71 ± 0.22 243.33 ± 27.43 0.09 ± 0.006 Terminalia arjuna Control 2.54 ± 0.06 1.61 ± 0.03 3.58 ± 0.2 7.01 ± 0.22 123.67 ± 19.74 0.08 ± 0.012 Polluted 2.54 ± 0.12 1.61 ± 0.03 3.75 ± 0.11 7.05 ± 0.06 144.67 ± 9.49 0.093 ± 0.015 Terminalia catappa Control 2.42 ± 0.35 1.33 ± 0.09 2.92 ± 0.66 6.25 ± 0.69 58.67 ± 5.55 0.03 ± 0.009 Polluted 2.47 ± 0.17 1.49 ± 0.02 3.15 ± 0.23 6.64 ± 0.32 128 ± 12.74 0.08 ± 0.012 3.1.3 Stomatal area The stomatal areas of all the selected tree species from the control and polluted sites in Dhaka city were investigated (Table 4 ). Two-way ANOVA revealed highly significant effects of site (control vs. polluted), species and their interactions on stomatal area (Table 3 ). Specifically, A. heterophyllus exhibited a notable reduction in stomatal area from 3.32 ± 0.29 µm 2 at the control site to 2.48 ± 0.06 µm 2 at the polluted site. Similarly, F. benghalensis significantly decreased from 4.16 ± 0.2 µm 2 at the control site to 2.26 ± 0.12 µm 2 at the polluted site, and S. mahagoni decreased from 3.45 ± 0.2 µm 2 to 2.58 ± 0.2 µm 2 . These reductions indicate a significant impact of pollution on stomatal morphology in these species. In contrast, F. religiosa , M. elengi , and P. longifolia presented relatively stable stomatal areas between the control and polluted sites. For example, F. religiosa maintained stomatal areas of 3.9 ± 0.16 µm 2 at the control site and 3.51 ± 0.24 µm 2 at the polluted site, whereas P. longifolia had stomatal areas of 4.79 ± 0.08 µm 2 and 4.71 ± 0.27 µm 2 , respectively. Interestingly, S. cumini , T. arjuna , and T. catappa presented slight increases in stomatal area at the polluted site (2.93 ± 0.13 µm 2 , 3.75 ± 0.11 µm 2 , and 3.15 ± 0.23 µm 2 , respectively) compared with those at the control site (2.57 ± 0.09 µm 2 , 3.58 ± 0.2 µm 2 , and 2.92 ± 0.66 µm 2 , respectively). 3.1.4 Stomatal Perimeter For A. heterophyllus , the stomatal perimeter was significantly lower at the polluted site (5.65 ± 0.08 µm) than at the control site (6.54 ± 0.28 µm). Similarly, F. benghalensis and S. mahagoni also presented a reduction in the stomatal perimeter at the polluted site (5.42 ± 0.12 µm and 5.71 ± 0.22 µm, respectively) compared with the corresponding values at the control site (7.34 ± 0.18 µm and 6.66 ± 0.19 µm). In contrast, F. religiosa (6.95 ± 0.22 µm vs. 7.18 ± 0.13 µm), P. longifolia (7.77 ± 0.18 µm vs. 7.76 ± 0.06 µm), and T. arjuna (7.05 ± 0.06 µm vs. 7.01 ± 0.22 µm) presented relatively similar stomatal perimeters at both the polluted and control sites (Table 4 ). Interestingly, the stomatal perimeter of S. cumini and T. catappa slightly increased at the polluted site (6.15 ± 0.14 µm and 6.64 ± 0.32 µm, respectively) compared with that at the control site (5.7 ± 0.1 µm and 6.25 ± 0.69 µm, respectively). However, on the basis of the shared superscript letters, not all of these differences between the sites for each species are statistically significant at the p < 0.05 level (Table 4 ). The overall two-way ANOVA results revealed significant effects of site, species, and their interactions on the stomatal perimeter (Table 3 ). 3.1.5 Stomatal density The stomatal density of nine selected plant species from control and polluted sites in Dhaka city was investigated, and the findings are summarized in Table 4 . Two-way ANOVA revealed a highly significant effect of species and the interactions between species and site (control vs. polluted) on stomatal density (Table 3 ). Specifically, A. heterophyllus presented a reduction in stomatal density from 251.67 ± 25.45 at the control site to 203.33 ± 27.66 at the polluted site. Similarly, S. cumini showed a notable decrease from 274.67 ± 22.05 at the control site to 199 ± 5.29 at the polluted site. In contrast, several species presented greater stomatal density at the polluted site than at the control site. F. benghalensis increased from 157 ± 10.97 to 169.67 ± 9.82, F. religiosa from 77.67 ± 7.54 to 94.33 ± 7.22, and M. elengi from 44 ± 3.46 to 54.33 ± 10.33. P. longifolia also slightly increased from 117.33 ± 5.55 to 123.67 ± 2.33. A significant increase was observed in S. mahagoni , with the density increasing from 142.67 ± 5.61 at the control site to 243.33 ± 27.43 at the polluted site. Similarly, T. arjuna increased from 123.67 ± 19.74 to 144.67 ± 9.49, and T. catappa increased from 58.67 ± 5.55 to 128 ± 12.74 (Table 4 ). 3.1.6 Stomatal pore index Two-way ANOVA revealed a highly significant effect of species and the interactions between species and site on the stomatal pore index (Table 3 ). Specifically, A. heterophyllus exhibited a notable reduction in the stomatal pore index from 0.13 ± 0.021 at the control site to 0.067 ± 0.013 at the polluted site. Similarly, F. benghalensis decreased from 0.09 ± 0.001 at the control site to 0.053 ± 0.007 at the polluted site. In contrast, several species presented an increase in the stomatal pore index at the polluted site compared with the control site. F. religiosa increased slightly from 0.05 ± 0.006 to 0.06 ± 0.006, and Mi. elengi from 0.02 ± 0.003 to 0.023 ± 0.003. P. longifolia increased from 0.07 ± 0.007 to 0.08 ± 0.006. A more pronounced increase was observed in S. mahagoni , with the value increasing from 0.07 ± 0.003 at the control site to 0.09 ± 0.006 at the polluted site. Similarly, T. arjuna increased from 0.08 ± 0.012 to 0.093 ± 0.015, and T. catappa increased from 0.03 ± 0.009 to 0.08 ± 0.012. S. cumini showed a minor reduction from 0.09 ± 0.007 to 0.083 ± 0.009 (Table 4 ). 3.2 Functional Traits 3.2.1 Percentage of open stomata The percentage of open stomata was significantly affected by species and the interactions between species and sites (Table 3 ). Specifically, F. benghalensis (72.63 ± 2.17%) and F. religiosa (64.04 ± 3.3%) presented significantly lower percentages of open stomata at the polluted site than at the control site (90.59 ± 1.41% and 94.87 ± 5.13%, respectively). A similar significant decrease was observed for M. elengi at the polluted site (65.87 ± 8.73%) compared with the control site (91.07 ± 4.5%). Conversely, compared with the control, P. longifolia significantly increased the percentage of open stomata at the polluted site (79.65 ± 2.91%) (64.38 ± 2.44%). For the remaining species, A. heterophyllus , S. cumini , S. mahagoni , T. arjuna , and T. catappa , no highly significant differences were found in the percentage of open stomata between the polluted and control sites (Table 5 ). Table 5 Functional traits of the stomata of different plant species at the control and polluted sites Species Site OS (%) CS (%) Artocarpus heterophyllus Control 72.05 ± 2.58 27.95 ± 2.58 Polluted 73.89 ± 1.65 26.11 ± 1.65 Ficus benghalensis Control 90.59 ± 1.41 9.41 ± 1.41 Polluted 72.63 ± 2.17 27.37 ± 2.17 Ficus religiosa Control 94.87 ± 5.13 5.13 ± 5.13 Polluted 64.04 ± 3.3 35.96 ± 3.3 Mimusops elengi Control 91.07 ± 4.5 8.93 ± 4.5 Polluted 65.87 ± 8.73 34.13 ± 8.73 Polialthia longifolia Control 64.38 ± 2.44 35.62 ± 2.44 Polluted 79.65 ± 2.91 20.35 ± 2.91 Sizium cumini Control 83.97 ± 8.25 16.03 ± 8.25 Polluted 88.29 ± 2.48 11.71 ± 2.48 Swietenia mahagoni Control 83.69 ± 1.97 16.31 ± 1.97 Polluted 79.93 ± 4.99 20.07 ± 4.99 Terminalia arjuna Control 80.78 ± 2.36 19.22 ± 2.36 Polluted 85.39 ± 3.71 14.61 ± 3.71 Terminalia catappa Control 72.14 ± 4.33 27.86 ± 4.33 Polluted 79.41 ± 0.11 20.51 ± 0.11 3.2.2 Percentage of closed stomata The percentage of closed stomata was significantly affected by species and site, with a strong interaction effect among them (Table 3 ). F. religiosa presented the lowest percentage of closed stomata (5.13 ± 5.13%), which was significantly lower than that of P. longifolia (35.62 ± 2.44%), which presented the highest percentage. Other species presented intermediate values, with F. benghalensis (9.41 ± 1.41%) and M. elengi (8.93 ± 4.5%) also tending towards lower percentages, whereas A. heterophyllus (27.95 ± 2.58%) and T. catappa (27.86 ± 4.33%) presented relatively higher percentages of closed stomata than did F. religiosa (Table 5 ). At the polluted site, the range of the percentage of closed stomata also varied. S. cumini presented the lowest percentage (11.71 ± 2.48%), whereas F. religiosa presented the highest percentage (35.96 ± 3.3%). Notably, F. benghalensis (27.37 ± 2.17%) and M. elengi (34.13 ± 8.73%) presented considerably greater percentages of closed stomata at the polluted site than did their control counterparts, with some of the species having higher closure percentages in the polluted environment. P. longifolia (20.35 ± 2.91%) presented a decrease in the number of closed stomata at the polluted site, falling into a middle range among the species (Table 5 ). Overall, the response to the polluted environment in terms of stomatal closure was species specific. Some species exhibited increased closure, potentially as a protective mechanism, whereas others showed decreased closure. 3.3 Multivariate exploratory analysis Pearson's correlation analysis revealed significant relationships among various stomatal traits (Fig. 3 ). Stomatal morphological parameters, namely, stomatal area, stomatal perimeter, stomatal length, and stomatal breadth, exhibited strong positive correlations. Specifically, SA was strongly positively correlated with SP (r = 0.98∗∗∗), SL (r = 0.82∗∗∗), and SB (r = 0.78∗∗∗). Similarly, SP was strongly positively correlated with SL (r = 0.89∗∗∗) and SB (r = 0.71∗∗∗) (Fig. 3 ). SL also demonstrated a moderate positive correlation with SB (r = 0.47∗∗∗). In contrast to the morphological traits, SD was significantly negatively correlated with size-related parameters. SD was moderately negatively correlated with SL (r = − 0.54∗∗∗), SP (r = − 0.44∗∗∗), and SA (r = − 0.37∗∗) (Fig. 3 ). This indicates a trade-off where plants with larger individual stomata tend to have fewer stomata per unit area. The stomatal pore index (SPI) was strongly positively correlated with stomatal density (r = 0.77∗∗∗) and moderately positively correlated with stomatal breadth (r = 0.32∗∗) (Fig. 3 ). PCA of the stomatal traits revealed that the first two principal components (PC1 and PC2) collectively explained 69.71% of the total variance observed in the dataset. Specifically, PC1 accounted for 44.34%, whereas PC2 explained 25.37% of the total variation, indicating that these two components sufficiently summarize the major patterns of trait variability. The biplot (Fig. 4 ) illustrates a distinct grouping of stomatal morphological traits, including SA, SP, SL, and SB, which showed strong positive loadings along the PC1 axis. This clustering indicates a high degree of positive correlation among these variables, suggesting that they jointly represent the overall dimensions of stomatal size and shape. In contrast, SD was negatively loaded on PC1 and positioned oppositely to the size-related traits, implying a trade-off between stomatal size and density. PC2 primarily captured the functional status of the stomata. The %OS and SPI were strongly positively associated with the percentage of open stomata, whereas the %CS exhibited strong negative loading (Fig. 4 ). This opposition suggests that %OS and SPI are closely related, reflecting active stomatal function, whereas %CS represents an inverse physiological state characterized by stomatal closure. 4 Discussion 4.1 Morphometric Traits Stomatal characteristics serve as essential anatomical indicators that reflect a plant’s capacity to modulate gas exchange and its ability to absorb pollutants when subjected to duress in urban environments. This study determined that nine prevalent urban tree species exhibited significantly diverse stomatal morphology and function. The morphometric and functional traits collectively inform us about species-specific strategies for tolerance or sensitivity to urban air pollution. The dimensions of the Stomata, particularly their length and width, function as primary measures of their overall size, which directly affects the aperture and, consequently, the capacity for gas exchange. P. longifolia exhibited comparatively greater stomatal length and width under polluted conditions, suggesting its potential ability to sustain gaseous exchange despite environmental stress. This response may function as a protective mechanism by reducing the stomatal aperture and surface area to limit the entry of pollutants [ 11 , 41 , 42 ]. On the other hand, A. heterophyllus, F. benghalensis, and S. mahagoni exhibited a decrease in both traits, indicating stomatal size plasticity in response to pollution, presumably to reduce pollutant entry and water loss, which may represent either a species-specific tolerance strategy or compensatory growth mechanisms under stress conditions [ 42 – 44 ]. The stomatal area and perimeter, which are based on length and width, were generally lower for species growing at polluted sites, with F. benghalensis and S. mahagoni showing pronounced reductions. These reductions may reflect adaptive anatomical modifications that restrict the exposure of the stomatal pore to ambient air, thus reducing the influx of pollutants such as SO₂, NOₓ, and particulate matter [ 45 ]. Reduced stomatal aperture may aid in excluding hazardous gases and particulates, thereby safeguarding mesophyll tissues and conserving water. This is particularly significant in urban microclimates where both pollution and thermal stress coexist. Furthermore, a reduction in perimeter is associated with reduced stomatal conductance and gas exchange, which may affect photosynthetic efficiency and overall plant productivity [ 10 , 42 , 46 ]. The perimeter of the stomata directly influences the dimensions of the stomatal aperture. Therefore, its reduction under stress conditions may be associated with hormonal variations, particularly increased abscisic acid synthesis, which is recognised to induce stomatal closure [ 17 ]. This morphological simplification corresponds to the defensive mechanisms employed by sensitive species in response to abiotic stress. Significant differences in stomatal density were observed among the species. F. benghalensis , S. cumini , T. catappa , and S. mahagoni sustained comparatively elevated stomatal densities under pollution stress, indicating a possible compensatory mechanism to preserve transpiration and photosynthesis, despite a potential decrease in pore size or the effects of heightened light intensity [ 47 , 48 ]. P. longifolia , by contrast, remained relatively stable at both sites. This indicates a conservative response, potentially involving a reduction in pollutant uptake and water loss [ 49 ]. A. heterophyllus and S. cumini exhibited a decrease in stomatal density at the contaminated site. This observed reduction in stomatal density attributable to pollution aligns with previous studies suggesting that plants respond to increased atmospheric pollutant levels, particularly particulate matter, by modifying their stomatal features as a protective mechanism [ 10 , 50 – 55 ]. The closure or constrictions of stomata can facilitate the prevention of hazardous gas ingress and reduce water loss through transpiration during stressful conditions [ 46 ]. The reduction in stomatal density may be associated with various pollution-induced physiological disturbances, such as oxidative stress and hormonal imbalances occurring during leaf development [ 56 ]. Pollutants have been shown to modify the levels of cytokinin and auxin, which are essential for the development and patterning of stomata [ 57 ]. The stomatal pore index (SPI) serves as a functional indicator of the overall gas exchange capacity of the leaf surface. S. mahagoni, T. catappa , and F. religiosa exhibited comparatively elevated SPI values even in contaminated habitats, indicating their physiological resilience and suitability as tolerant urban species. On the other hand, species like A. heterophyllus, F. benghalensis , and S. cumini exhibited markedly reduced SPIs in polluted environments. A reduction in the SPI under polluted conditions is a common adaptive response aimed at minimizing transpirational water loss and pollutant uptake through the stomatal aperture [ 10 , 30 , 50 , 58 , 59 ]. Pollution stress, particularly in urban settings dominated by NOx, SO₂, O₃, and PM, can disturb cellular homeostasis, resulting in altered guard cell physiology and restricted stomatal aperture [ 60 ]. This decrease in SPI is also correlated with a decline in photosynthetic efficiency, as a limited stomatal aperture and density directly hinder CO₂ uptake, consequently adversely affecting carbon assimilation and growth potential [ 61 , 62 ]. The SPI is considered a more accurate indicator of functional stomatal activity than mere stomatal density, as it accounts for both the number and size of stomata [ 17 , 63 ]. 4.2 Functional Traits The ratios of open to closed stomata further corroborated species-specific patterns of behaviour. S. cumini, T. catappa, T. arjuna, P. longifolia , and A. heterophyllus demonstrated a relatively high number of exposed stomata at polluted sites, potentially indicating increased tolerance to pollution or a reduced rate of stomatal closure. Compared with those at the control site, F. benghalensis and F. religiosa presented significantly lower percentages of open stomata at the polluted site. A similar significant reduction was observed for M. elengi at the polluted site compared with the control site. This reduction in stomatal opening may be attributed to the accumulation of particulate matter and gaseous pollutants on leaf surfaces and within stomatal pores [ 10 , 58 , 60 ]. Pollutants may directly influence the metabolic processes of guard cells or indirectly alter stomatal behavior by inducing oxidative stress, which can lead to stomatal closure [ 51 ]. The reduction in the stomatal aperture corroborates previous research indicating that air pollution can the capacity of gas exchange, potentially impacting photosynthesis and transpiration [ 49 ]. Conversely, a higher percentage of closed stomata was observed in M. elengi, F. religiosa , and S. mahagoni , indicating that stress-induced stomatal closure prevents further damage. Stomatal closure serves as a vital protective mechanism to reduce the entry of harmful pollutants within plant tissues [ 60 , 64 ]. This behavior aligns with research that emphasizes the functional significance of stomatal closure in mitigating pollutant entry and preserving water during stress conditions [ 42 , 59 , 60 ]. 4.3 Multivariate statistical approach The substantial positive correlations among stomatal size traits (SA, SP, SL, SB) indicate their inherent interdependence, collectively delineating the stomatal dimensions essential for gas exchange [ 20 , 21 ]. The inverse relationship between stomatal density and size characteristics affirms the well-established size-density trade-off, whereby plants control CO₂ uptake and water loss through the adjustment of stomatal number and dimensions [ 17 ]. The SPI showed a strong positive correlation with SD and a moderate correlation with SB. This means that it depends on both the number and width of the stomata, which are related to the potential for gas exchange. Conversely, %OS and %CS exhibited no significant correlation with morphological traits, indicating that stomatal size and density are structurally fixed, whereas aperture states are influenced by transient environmental factors such as light, humidity, and water availability [ 14 ]. The PCA results showed a clear difference between stomatal morphological traits including SL, SB, SA, SP, and functional attributes, %OS and %CS. This means that different physiological mechanisms control them. Traits associated with size exhibited a strong clustering on PC1, indicating their coordinated development and corroborating the well-established size–density trade-off [ 17 ]. Conversely, PC2 exhibited functional variation, with SPI and %OS demonstrating positive correlation and %CS exhibiting negative correlation. This indicates that the system is sensitive to immediate environmental conditions such as light and humidity. This differentiation between structure and function permits stomatal behavior to change independently of anatomical features, thereby improving its adaptivity under stress conditions. This suggests possible attribute combinations for identifying species capable of adapting to stress in developing urban settings. 5 Conclusion This study definitively shows that urban air pollution significantly influences the stomatal features of city trees, leading to two main adaptive responses: tolerance and avoidance. Certain species, such as S. mahagoni , P. longifolia , and S. cumini , possess stomatal characteristics that facilitate continued gas exchange and photosynthesis despite the presence of pollution. These characteristics encompassed larger pores, elevated pores, elevated SPIs, and more extensively exposed stomata. The sensitive species M. elengi and T. catappa utilised an avoidance strategy characterised by smaller pore sizes, a decreased SPI, and predominantly closed stomata. This probably obstructed the entry of contaminants, but it may have also impeded the assimilation of carbon. These findings demonstrate that stomatal traits serve as significant indicators of air pollution-induced stress in urban vegetation. The species-specific responses offer essential insights for urban planning and greening initiatives, highlighting the significance of choosing pollution-tolerant species to enhance air quality, ecological resilience, and promote sustainable urban development. Declarations Acknowledgements The authors are thankful to the University of Dhaka for providing funding and laboratory facilities to conduct this research. Authors' contributions M.A.K. - Sampling and data collection, writing of the original draft, review and editing, Resources, Methodology, Project supervisor. M.A.R. - Sampling and data collection, Methodology, Formal analysis, Software. S.M.H. - Writing – review & editing, Writing – original draft. M.Z.H . - Methodology, Formal analysis, Writing original draft Funding TheBiotechnology Research Centre (Grant # 08), University of Dhaka, conducted this research during 2023--2024. Data availability The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. Ethics approval and consent to participate No special permission was required to collect plant specimens from the polluted site (Motijheel-Sayedabad), as the area is not designated as a protected area. Sampling at the control site (National Botanical Garden) was conducted with permission from the relevant local authorities. The collection of plant parts (leaves) used in this study was conducted in compliance with local guidelines, and Dr. Ataur Rahman identified the species. 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Heath RL. (1980) Initial events in injury to plants by air pollutants. Annu. Rev. Plant Physiol. 1980;31: 395–431. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 12 Jan, 2026 Reviews received at journal 10 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers agreed at journal 05 Jan, 2026 Reviews received at journal 04 Jan, 2026 Reviewers agreed at journal 02 Jan, 2026 Reviewers invited by journal 02 Jan, 2026 Editor invited by journal 01 Jan, 2026 Editor assigned by journal 27 Dec, 2025 Submission checks completed at journal 26 Dec, 2025 First submitted to journal 26 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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09:16:15","extension":"xml","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":160380,"visible":true,"origin":"","legend":"","description":"","filename":"c4541290e3964f15969a962cd28735d51structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/ddba8616cf1a96cbc2752c7e.xml"},{"id":99509617,"identity":"a67a9327-0a65-443a-b0fe-974d3e019157","added_by":"auto","created_at":"2026-01-05 09:16:15","extension":"html","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":173374,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/2a3281ac535b2662cb3d938d.html"},{"id":99791100,"identity":"edddb233-74f6-4967-a294-e033336cf66a","added_by":"auto","created_at":"2026-01-08 12:59:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1740416,"visible":true,"origin":"","legend":"\u003cp\u003eMap showing the Botanical Garden as the control site and Motijheel-Sayedabad as the polluted site of the study area in Dhaka city, Bangladesh\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/68c9ae1e7898deb90c0fd95c.png"},{"id":99509597,"identity":"95d32c4d-d417-4c07-9424-445edc4a7569","added_by":"auto","created_at":"2026-01-05 09:16:14","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":598517,"visible":true,"origin":"","legend":"\u003cp\u003eImages of the leaf stomata of selected plants from the control and polluted sites for the determination of stomatal traits\u003c/p\u003e","description":"","filename":"2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/101a0d0588c1615a4b308c53.jpeg"},{"id":99509600,"identity":"aa04d716-52c1-42a3-9d8c-a8550acbfecb","added_by":"auto","created_at":"2026-01-05 09:16:14","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":167751,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation matrix of the stomatal traits of the studied plant species. Asterisks denote significance levels: ∗∗p\u0026lt;0.01, ∗∗∗p\u0026lt;0.001\u003c/p\u003e","description":"","filename":"3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/65fde1014da70d41041fcd2f.jpeg"},{"id":99509602,"identity":"813b88b4-f0c2-4610-8397-0864e8a8250a","added_by":"auto","created_at":"2026-01-05 09:16:15","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":28711,"visible":true,"origin":"","legend":"\u003cp\u003ePCA biplot of stomatal traits\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/2a5283f72fd61e4be93cece0.png"},{"id":100376306,"identity":"c38824cf-fc5a-4254-a630-deedb646e762","added_by":"auto","created_at":"2026-01-16 08:44:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3761798,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8415643/v1/c1129590-b2bb-4721-8273-06f2f21fb032.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Unravelling the Stomatal Phenotype‒Function Relationships in Urban Trees Under Air Pollution Stress: A Multispecies Comparative Study","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eUrbanization, a hallmark of the 21st century, presents unparalleled environmental challenges for urban flora, especially trees, which constitute the foundation of green infrastructure in cities [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The rapid expansion of metropolitan areas, such as Dhaka, has led to significant alterations in atmospheric quality, microclimate, and hydrological regimes due to increased vehicular emissions, industrial activities, and urban heat island effects [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Urban trees are increasingly exposed to various anthropogenic stressors, including elevated levels of air pollutants, thermal stress, reduced soil moisture, and heavy metal contamination, all of which jeopardize their growth, physiological functions, and long-term survival [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. To keep urban ecosystem services like regulating microclimates, cleaning the air, and storing carbon, it\u0026rsquo;s important to know how trees change their shape and function in these situations [\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAmong the many physiological adaptations that plants exhibit in response to stress, stomatal traits are particularly fundamental. Stomata are tiny holes on the surface of leaves that control the exchange of gases and the balance of water. They are crucial for the growth stress resistance of plants [\u003cspan additionalcitationids=\"CR15 CR16\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Genetic and environmental factors both affect important stomatal parameters like stomatal density (SD), stomatal length (SL), stomatal breadth (SB), stomatal area (SA), the stomatal pore index (SPI), and the proportion of open to closed stomata. These traits exhibit significant plasticity, enabling plants to adjust their physiology in response to fluctuating environmental conditions, including pollution and drought [\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIntraspecific variation in stomatal traits signifies the ability of individuals to adapt to specific site conditions, frequently indicating local adaptation or phenotypic plasticity in response to microenvironmental heterogeneity [\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Conversely, interspecific variation is primarily influenced by evolutionary history and life-history strategies, which govern species\u0026rsquo; functional responses to urban stressors [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. A comparative knowledge of intra- and interspecific variation in stomatal traits is thus crucial to consider species' ecological performances, and it will be useful for choosing resistant tree taxa for urban planting programs.\u003c/p\u003e \u003cp\u003eAlthough stomatal responses have been studied under controlled environmental conditions or for a limited number of species, large-scale field observations comparing several plant species along pollution gradients within tropical megacities are scarce. In Dhaka city, with a still burgeoning population and increasingly being surrounded by polluted atmosphere, particulate-containing aerosols in the air, as well as water deprivation, assessing the variation pattern of trees dependent on dominant species with respect to stomatal traits is likely to provide insights into their functional performance scale and adaptive strategies. With such low green coverage and the consistently poor air quality in the city, trees in those highly polluted areas like Motijheel and Sayedabad are put under prolonged physiological stress [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Therefore, it is essential to evaluate whether tree species in these polluted environments exhibit notable stomatal and functional plasticity compared with those growing in cleaner areas, such as the National Botanical Garden. Such assessments are critical because not all species respond equally: some may display high stomatal density to maximize CO₂ uptake, whereas others may maintain smaller stomata to reduce transpirational water loss or minimize pollutant entry [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eComprehending this relationship is crucial for the development of urban green spaces, especially in the selection of resilient species for afforestation and pollution control. For instance, species exhibiting significant stomatal plasticity may more effectively balance the trade-offs between gas exchange and water conservation in contaminated environments [\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Moreover, stomatal metrics such as the stomatal pore index, percentage of open stomata, and stomatal conductance proxies can serve as non-destructive indicators of tree health and pollution tolerance [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis study seeks to clarify the relationship between stomatal phenotype and function in selected urban tree species from contrasting locations in Dhaka, ranging from the heavily polluted zone, Motijheel-Sayedabad, to the relatively unpolluted National Botanical Garden. By quantifying a suite of stomatal traits and comparing interspecific variation, this study seeks to assess the intraspecific variability in stomatal traits of dominant urban tree species between relatively clean and highly polluted sites in Dhaka, evaluate the extent of interspecific variation among species, identify species that exhibit significant stomatal plasticity or trait stability across environments, and relate trait patterns to species\u0026rsquo; potential ecological performance under urban stress. This study will support evidence-based decision-making for sustainable urban forestry in South Asian megacities.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Study sites\u003c/h2\u003e\n \u003cp\u003eThe study was conducted at two contrasting locations in Dhaka, Bangladesh, the National Botanical Garden, designated as the control (less polluted) site, and the Motijheel-Sayedabad areas, selected as the polluted site owing to their high levels of air pollution (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The National Botanical Garden, located in the Mirpur area of Dhaka, spans approximately 204 acres and is geographically positioned at 23.81660\u0026deg; N latitude and 90.34875\u0026deg; E longitude. It is one of the largest botanical gardens in Bangladesh [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e]. Owing to its rich plant diversity and relatively low vehicular activity, this location offers a cleaner, less polluted environment, making it an ideal reference site for comparison. On the contrary, the Motijheel-Sayedabad areas were chosen as the polluted site because they represent some of the busiest and most traffic-congested parts of Dhaka city [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e]. These areas experience heavy traffic throughout the day, which mainly consists of petrol-powered and diesel-operated vehicles. The continuous emissions from these vehicles release large amounts of airborne pollutants, including fine particulate matter, carbon monoxide, nitrogen oxides, and lead, which contribute to poor air quality. As a result, these areas are highly representative of urban air pollution hotspots, making them suitable for assessing the impact of pollution on urban vegetation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Leaf collection\u003c/h2\u003e\n \u003cp\u003eThe study was conducted in February 2024 and targeted the most frequently occurring tree species common to both the polluted and nonpolluted sites. Fresh leaf samples were collected from ten representative species, selected on the basis of their prevalence across both locations (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). For each species, three healthy individuals were chosen per site. From each tree, ten fully expanded and physiologically active young leaves were sampled. This sampling strategy resulted in a total of 540 leaf samples (10 leaves \u0026times; 3 trees \u0026times; 10 species \u0026times; 2 sites, polluted and nonpolluted). All the samples were immediately transported to the laboratory for further analysis.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eList of tree species, including families and common names, selected from polluted and unpolluted sites in Dhaka city, Bangladesh, for the present study\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCommon name\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eScientific name\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFamily\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eJackfruit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eArtocarpus heterophyllus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMoraceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBanyan tree\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eFicus benghalensis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMoraceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSacred fig tree\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eFicus religiosa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMoraceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpanish cherry\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eMimusops elengi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSapotaceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFalse Ashoka\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ePolialthia longifolia\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAnnonaceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBlack plum tree\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eSizium cumini\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMyrtaceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMahagony\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eSwietenia mahagoni\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMeliaceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArjun tree\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eTerminalia arjuna\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCombretaceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIndian almond\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eTerminalia catappa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCombretaceae\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Determination of leaf stomatal traits\u003c/h2\u003e\n \u003cp\u003eStomatal properties were studied via the impression technique [\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]. First, the leaf was spread gently upon a plain field of glass. A thick swath of clear nail polish was painted upon the ventral side of the leaf. After the nail polish had dried, the peel of the nail polish swath was gently removed from the leaf completely. A cloudy impression of the leaf surface attached to the nail polish was found. One drop of glycerin was added, and then, the leaf impressions were placed on a clean slide, covered with a cover slip and observed under a microscope. A photograph of the field of a leaf under a microscope (Axio Lab. A1 microscope (Carl Zeiss Microscopy GmbH, Germany) was used. Three images were taken from each leaf, and three stomata from each image were selected to study the stomatal parameters (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Three leaves were taken from each species at each site.\u003c/p\u003e\n \u003cp\u003eStomatal dimensions were quantified via ImageJ software (Ver: 1.45k). The captured images were opened in ImageJ, and the scale was calibrated by setting the line width tool in micrometers (\u0026micro;m) on the basis of the provided scale bar in the Analyse menu (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). This calibrated scale was then added to the ROI Manager window. The stomatal length, width, area, and perimeter were subsequently measured by selecting individual stomata and clicking the \u0026quot;Measure\u0026quot; option, which processed the selected region of interest (ROI) data. For the measurement of stomatal density (individual mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e), the number of stomata per unit area (mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) was counted from the images at a magnification of 10 \u0026times; 40, and the visual field area was 32\u0026times;22 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e. The stomatal density was calculated via the following formula [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cimg width=\"363\" height=\"40\" 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\" alt=\"image\"\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003ewhere the area of field of view (FOV) = ӆr\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003eThe stomatal pore index is an integrative parameter of stomatal density and stomatal length that reflects the stomatal conductance of leaves. The following formula calculates the SPI (%):\u003c/p\u003e\n \u003cp\u003eSPI\u0026thinsp;=\u0026thinsp;Stomatal density \u0026times; Stomatal length\u003csup\u003e2\u003c/sup\u003e \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMorphometric and functional traits measured from the control and polluted sites during the study period\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGroup name\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTrait name\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eShort form\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eUnit\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDescription\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"6\"\u003e\n \u003cp\u003e\u003cstrong\u003eMorphometric\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026micro;m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLinear length of the stomatal pore.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Breadth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026micro;m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWidth of the stomatal pore.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Area\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026micro;m\u0026sup2;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEstimated area of the stomatal pore, often approximated as an ellipse.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Perimeter\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026micro;m\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTotal boundary length surrounding the stomatal pore.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Density\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eno./mm\u0026sup2;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNumber of stomata per unit leaf area.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Pore Index\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSPI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProduct of stomatal density and stomatal area; reflects gas exchange potential.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eFunctional\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOpen Stomata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProportion of stomata that are open under observed conditions.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eClosed Stomata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProportion of stomata that are closed under observed conditions.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e\n \u003cp\u003eTo investigate differences in morphometric and functional traits among the nine plant species from both sites, one-way analysis of variance (ANOVA) was performed. Post hoc comparisons were conducted via Tukey\u0026rsquo;s honestly significant difference (HSD) test to determine significant differences between means. All the statistical analyses were conducted via JMP 4.0 software (SAS Institute, Cary, NC, USA).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Morphometric Traits\u003c/h2\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1 Stomatal length\u003c/h2\u003e\n \u003cp\u003eTwo-way ANOVA revealed that stomatal length was significantly affected by species, site, and their interactions (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Most species presented a reduction in stomatal length under polluted conditions. For example, \u003cem\u003eA. heterophyllus\u003c/em\u003e decreased from 2.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07 \u0026micro;m at the control site to 1.80\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 \u0026micro;m at the polluted site. Similarly, \u003cem\u003eF. benghalensis\u003c/em\u003e decreased in size from 2.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 \u0026micro;m to 1.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 \u0026micro;m. In contrast, some species, such as \u003cem\u003eP. longifolia\u003c/em\u003e and \u003cem\u003eT. catappa\u003c/em\u003e, presented an increase in stomatal length under polluted conditions, with \u003cem\u003eP. longifolia\u003c/em\u003e increasing from 2.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04 \u0026micro;m to 2.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 \u0026micro;m (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Significant differences in stomatal length across species suggest differential sensitivity or adaptation to atmospheric pollution.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eOverall two-way ANOVA statistics (F ratios) of the effects of site, species, and their interaction on the leaf stomatal properties in Dhaka city. Asterisks denote significance levels: *p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, \u0026lowast;\u0026lowast;p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, \u0026lowast;\u0026lowast;\u0026lowast;p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, and ns indicates not significant.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSource of variation\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSpecies (df\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSite (df\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSpecies \u0026times; Site (df\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.96***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.81*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.91*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Breadth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.72***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.10**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.51***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Area\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.54***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.32***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.31**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Perimeter\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.34***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.0**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.78***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Density\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e39.52***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.03ns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.58***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStomatal Pore Index\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.16***\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.18ns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.97***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOpen Stomata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.03*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.8ns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.34***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eClosed Stomata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.63*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.45*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.5***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2 Stomatal breadth\u003c/h2\u003e\n \u003cp\u003eFor most species, stomatal breadth was lower at the polluted site than at the control site (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). For example, \u003cem\u003eA. heterophyllus\u003c/em\u003e presented a stomatal breadth of 1.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03 \u0026micro;m at the control site and 1.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 \u0026micro;m at the polluted site. Similarly, \u003cem\u003eF. benghalensis\u003c/em\u003e was 1.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04 \u0026micro;m at the control site and 1.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07 \u0026micro;m at the polluted site. Notable exceptions included \u003cem\u003eP. longifolia\u003c/em\u003e, which presented greater stomatal breadth at the polluted site (2.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 \u0026micro;m) than at the control site (1.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 \u0026micro;m), and \u003cem\u003eT. catappa\u003c/em\u003e, which also presented greater stomatal breadth at the polluted site (1.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 \u0026micro;m) than at the control site (1.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 \u0026micro;m). \u003cem\u003eF. religiosa\u003c/em\u003e and \u003cem\u003eT. arjuna\u003c/em\u003e displayed very similar stomatal breadths between the two sites, with \u003cem\u003eF. religiosa\u003c/em\u003e having 1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 \u0026micro;m at the control site and 1.55\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 \u0026micro;m at the polluted site and \u003cem\u003eT. arjuna\u003c/em\u003e having 1.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03 \u0026micro;m at both sites. Two-way ANOVA also revealed that stomatal breadth varied significantly with species, site, and their interactions (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eStomatal morphometric traits of selected plant species from the control and polluted sites in Dhaka city\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"8\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSite\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSL (\u0026micro;m)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSB (\u0026micro;m)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSA (\u0026micro;m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSP (\u0026micro;m)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSD (no./mm\u0026sup2;)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSPI (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eArtocarpus heterophyllus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e251.67\u0026thinsp;\u0026plusmn;\u0026thinsp;25.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e203.33\u0026thinsp;\u0026plusmn;\u0026thinsp;27.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.067\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eFicus benghalensis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e157\u0026thinsp;\u0026plusmn;\u0026thinsp;10.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e169.67\u0026thinsp;\u0026plusmn;\u0026thinsp;9.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.053\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eFicus religiosa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e77.67\u0026thinsp;\u0026plusmn;\u0026thinsp;7.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.55\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e94.33\u0026thinsp;\u0026plusmn;\u0026thinsp;7.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eMimusops elengi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.83\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e44\u0026thinsp;\u0026plusmn;\u0026thinsp;3.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e54.33\u0026thinsp;\u0026plusmn;\u0026thinsp;10.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.023\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003ePolialthia longifolia\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e117.33\u0026thinsp;\u0026plusmn;\u0026thinsp;5.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e123.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eSizium cumini\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.85\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e274.67\u0026thinsp;\u0026plusmn;\u0026thinsp;22.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e199\u0026thinsp;\u0026plusmn;\u0026thinsp;5.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.083\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eSwietenia mahagoni\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e142.67\u0026thinsp;\u0026plusmn;\u0026thinsp;5.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e243.33\u0026thinsp;\u0026plusmn;\u0026thinsp;27.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eTerminalia arjuna\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e123.67\u0026thinsp;\u0026plusmn;\u0026thinsp;19.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e144.67\u0026thinsp;\u0026plusmn;\u0026thinsp;9.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.093\u0026thinsp;\u0026plusmn;\u0026thinsp;0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eTerminalia catappa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e58.67\u0026thinsp;\u0026plusmn;\u0026thinsp;5.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e128\u0026thinsp;\u0026plusmn;\u0026thinsp;12.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.3 Stomatal area\u003c/h2\u003e\n \u003cp\u003eThe stomatal areas of all the selected tree species from the control and polluted sites in Dhaka city were investigated (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Two-way ANOVA revealed highly significant effects of site (control vs. polluted), species and their interactions on stomatal area (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Specifically, \u003cem\u003eA. heterophyllus\u003c/em\u003e exhibited a notable reduction in stomatal area from 3.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e at the control site to 2.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e at the polluted site. Similarly, \u003cem\u003eF. benghalensis\u003c/em\u003e significantly decreased from 4.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e at the control site to 2.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e at the polluted site, and \u003cem\u003eS. mahagoni\u003c/em\u003e decreased from 3.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e to 2.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e. These reductions indicate a significant impact of pollution on stomatal morphology in these species.\u003c/p\u003e\n \u003cp\u003eIn contrast, \u003cem\u003eF. religiosa\u003c/em\u003e, \u003cem\u003eM. elengi\u003c/em\u003e, and \u003cem\u003eP. longifolia\u003c/em\u003e presented relatively stable stomatal areas between the control and polluted sites. For example, \u003cem\u003eF. religiosa\u003c/em\u003e maintained stomatal areas of 3.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e at the control site and 3.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e at the polluted site, whereas \u003cem\u003eP. longifolia\u003c/em\u003e had stomatal areas of 4.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e and 4.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, respectively. Interestingly, \u003cem\u003eS. cumini\u003c/em\u003e, \u003cem\u003eT. arjuna\u003c/em\u003e, and \u003cem\u003eT. catappa\u003c/em\u003e presented slight increases in stomatal area at the polluted site (2.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, 3.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, and 3.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, respectively) compared with those at the control site (2.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, 3.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, and 2.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, respectively).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.4 Stomatal Perimeter\u003c/h2\u003e\n \u003cp\u003eFor \u003cem\u003eA. heterophyllus\u003c/em\u003e, the stomatal perimeter was significantly lower at the polluted site (5.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08 \u0026micro;m) than at the control site (6.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28 \u0026micro;m). Similarly, \u003cem\u003eF. benghalensis\u003c/em\u003e and \u003cem\u003eS. mahagoni\u003c/em\u003e also presented a reduction in the stomatal perimeter at the polluted site (5.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 \u0026micro;m and 5.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 \u0026micro;m, respectively) compared with the corresponding values at the control site (7.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18 \u0026micro;m and 6.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19 \u0026micro;m). In contrast, \u003cem\u003eF. religiosa\u003c/em\u003e (6.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 \u0026micro;m vs. 7.18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 \u0026micro;m), \u003cem\u003eP. longifolia\u003c/em\u003e (7.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18 \u0026micro;m vs. 7.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 \u0026micro;m), and \u003cem\u003eT. arjuna\u003c/em\u003e (7.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 \u0026micro;m vs. 7.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 \u0026micro;m) presented relatively similar stomatal perimeters at both the polluted and control sites (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eInterestingly, the stomatal perimeter of \u003cem\u003eS. cumini\u003c/em\u003e and \u003cem\u003eT. catappa\u003c/em\u003e slightly increased at the polluted site (6.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 \u0026micro;m and 6.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32 \u0026micro;m, respectively) compared with that at the control site (5.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 \u0026micro;m and 6.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69 \u0026micro;m, respectively). However, on the basis of the shared superscript letters, not all of these differences between the sites for each species are statistically significant at the p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 level (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). The overall two-way ANOVA results revealed significant effects of site, species, and their interactions on the stomatal perimeter (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.5 Stomatal density\u003c/h2\u003e\n \u003cp\u003eThe stomatal density of nine selected plant species from control and polluted sites in Dhaka city was investigated, and the findings are summarized in Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. Two-way ANOVA revealed a highly significant effect of species and the interactions between species and site (control vs. polluted) on stomatal density (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Specifically, \u003cem\u003eA. heterophyllus\u003c/em\u003e presented a reduction in stomatal density from 251.67\u0026thinsp;\u0026plusmn;\u0026thinsp;25.45 at the control site to 203.33\u0026thinsp;\u0026plusmn;\u0026thinsp;27.66 at the polluted site. Similarly, \u003cem\u003eS. cumini\u003c/em\u003e showed a notable decrease from 274.67\u0026thinsp;\u0026plusmn;\u0026thinsp;22.05 at the control site to 199\u0026thinsp;\u0026plusmn;\u0026thinsp;5.29 at the polluted site.\u003c/p\u003e\n \u003cp\u003eIn contrast, several species presented greater stomatal density at the polluted site than at the control site. \u003cem\u003eF. benghalensis\u003c/em\u003e increased from 157\u0026thinsp;\u0026plusmn;\u0026thinsp;10.97 to 169.67\u0026thinsp;\u0026plusmn;\u0026thinsp;9.82, \u003cem\u003eF. religiosa\u003c/em\u003e from 77.67\u0026thinsp;\u0026plusmn;\u0026thinsp;7.54 to 94.33\u0026thinsp;\u0026plusmn;\u0026thinsp;7.22, and \u003cem\u003eM. elengi\u003c/em\u003e from 44\u0026thinsp;\u0026plusmn;\u0026thinsp;3.46 to 54.33\u0026thinsp;\u0026plusmn;\u0026thinsp;10.33. \u003cem\u003eP. longifolia\u003c/em\u003e also slightly increased from 117.33\u0026thinsp;\u0026plusmn;\u0026thinsp;5.55 to 123.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.33. A significant increase was observed in \u003cem\u003eS. mahagoni\u003c/em\u003e, with the density increasing from 142.67\u0026thinsp;\u0026plusmn;\u0026thinsp;5.61 at the control site to 243.33\u0026thinsp;\u0026plusmn;\u0026thinsp;27.43 at the polluted site. Similarly, \u003cem\u003eT. arjuna\u003c/em\u003e increased from 123.67\u0026thinsp;\u0026plusmn;\u0026thinsp;19.74 to 144.67\u0026thinsp;\u0026plusmn;\u0026thinsp;9.49, and \u003cem\u003eT. catappa\u003c/em\u003e increased from 58.67\u0026thinsp;\u0026plusmn;\u0026thinsp;5.55 to 128\u0026thinsp;\u0026plusmn;\u0026thinsp;12.74 (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.6 Stomatal pore index\u003c/h2\u003e\n \u003cp\u003eTwo-way ANOVA revealed a highly significant effect of species and the interactions between species and site on the stomatal pore index (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Specifically, \u003cem\u003eA. heterophyllus\u003c/em\u003e exhibited a notable reduction in the stomatal pore index from 0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021 at the control site to 0.067\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013 at the polluted site. Similarly, \u003cem\u003eF. benghalensis\u003c/em\u003e decreased from 0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001 at the control site to 0.053\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007 at the polluted site.\u003c/p\u003e\n \u003cp\u003eIn contrast, several species presented an increase in the stomatal pore index at the polluted site compared with the control site. \u003cem\u003eF. religiosa\u003c/em\u003e increased slightly from 0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006 to 0.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006, and \u003cem\u003eMi. elengi\u003c/em\u003e from 0.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003 to 0.023\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003. \u003cem\u003eP. longifolia\u003c/em\u003e increased from 0.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007 to 0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006. A more pronounced increase was observed in \u003cem\u003eS. mahagoni\u003c/em\u003e, with the value increasing from 0.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003 at the control site to 0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006 at the polluted site. Similarly, \u003cem\u003eT. arjuna\u003c/em\u003e increased from 0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012 to 0.093\u0026thinsp;\u0026plusmn;\u0026thinsp;0.015, and \u003cem\u003eT. catappa\u003c/em\u003e increased from 0.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009 to 0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012. \u003cem\u003eS. cumini\u003c/em\u003e showed a minor reduction from 0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007 to 0.083\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009 (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Functional Traits\u003c/h2\u003e\n \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1 Percentage of open stomata\u003c/h2\u003e\n \u003cp\u003eThe percentage of open stomata was significantly affected by species and the interactions between species and sites (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Specifically, \u003cem\u003eF. benghalensis\u003c/em\u003e (72.63\u0026thinsp;\u0026plusmn;\u0026thinsp;2.17%) and \u003cem\u003eF. religiosa\u003c/em\u003e (64.04\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3%) presented significantly lower percentages of open stomata at the polluted site than at the control site (90.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41% and 94.87\u0026thinsp;\u0026plusmn;\u0026thinsp;5.13%, respectively). A similar significant decrease was observed for \u003cem\u003eM. elengi\u003c/em\u003e at the polluted site (65.87\u0026thinsp;\u0026plusmn;\u0026thinsp;8.73%) compared with the control site (91.07\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5%). Conversely, compared with the control, P. longifolia significantly increased the percentage of open stomata at the polluted site (79.65\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91%) (64.38\u0026thinsp;\u0026plusmn;\u0026thinsp;2.44%). For the remaining species, \u003cem\u003eA. heterophyllus\u003c/em\u003e, \u003cem\u003eS. cumini\u003c/em\u003e, \u003cem\u003eS. mahagoni\u003c/em\u003e, \u003cem\u003eT. arjuna\u003c/em\u003e, and \u003cem\u003eT. catappa\u003c/em\u003e, no highly significant differences were found in the percentage of open stomata between the polluted and control sites (Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eFunctional traits of the stomata of different plant species at the control and polluted sites\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSite\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eOS (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCS (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eArtocarpus heterophyllus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e72.05\u0026thinsp;\u0026plusmn;\u0026thinsp;2.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.95\u0026thinsp;\u0026plusmn;\u0026thinsp;2.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e73.89\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e26.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eFicus benghalensis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e90.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.41\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e72.63\u0026thinsp;\u0026plusmn;\u0026thinsp;2.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.37\u0026thinsp;\u0026plusmn;\u0026thinsp;2.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eFicus religiosa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e94.87\u0026thinsp;\u0026plusmn;\u0026thinsp;5.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.13\u0026thinsp;\u0026plusmn;\u0026thinsp;5.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e64.04\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e35.96\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eMimusops elengi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e91.07\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.93\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e65.87\u0026thinsp;\u0026plusmn;\u0026thinsp;8.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e34.13\u0026thinsp;\u0026plusmn;\u0026thinsp;8.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003ePolialthia longifolia\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e64.38\u0026thinsp;\u0026plusmn;\u0026thinsp;2.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e35.62\u0026thinsp;\u0026plusmn;\u0026thinsp;2.44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.65\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.35\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eSizium cumini\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e83.97\u0026thinsp;\u0026plusmn;\u0026thinsp;8.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.03\u0026thinsp;\u0026plusmn;\u0026thinsp;8.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e88.29\u0026thinsp;\u0026plusmn;\u0026thinsp;2.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.71\u0026thinsp;\u0026plusmn;\u0026thinsp;2.48\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eSwietenia mahagoni\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e83.69\u0026thinsp;\u0026plusmn;\u0026thinsp;1.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.31\u0026thinsp;\u0026plusmn;\u0026thinsp;1.97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.93\u0026thinsp;\u0026plusmn;\u0026thinsp;4.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.07\u0026thinsp;\u0026plusmn;\u0026thinsp;4.99\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eTerminalia arjuna\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e80.78\u0026thinsp;\u0026plusmn;\u0026thinsp;2.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.36\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e85.39\u0026thinsp;\u0026plusmn;\u0026thinsp;3.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.61\u0026thinsp;\u0026plusmn;\u0026thinsp;3.71\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eTerminalia catappa\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eControl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e72.14\u0026thinsp;\u0026plusmn;\u0026thinsp;4.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.86\u0026thinsp;\u0026plusmn;\u0026thinsp;4.33\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolluted\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2 Percentage of closed stomata\u003c/h2\u003e\n \u003cp\u003eThe percentage of closed stomata was significantly affected by species and site, with a strong interaction effect among them (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). \u003cem\u003eF. religiosa\u003c/em\u003e presented the lowest percentage of closed stomata (5.13\u0026thinsp;\u0026plusmn;\u0026thinsp;5.13%), which was significantly lower than that of \u003cem\u003eP. longifolia\u003c/em\u003e (35.62\u0026thinsp;\u0026plusmn;\u0026thinsp;2.44%), which presented the highest percentage. Other species presented intermediate values, with \u003cem\u003eF. benghalensis\u003c/em\u003e (9.41\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41%) and \u003cem\u003eM. elengi\u003c/em\u003e (8.93\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5%) also tending towards lower percentages, whereas \u003cem\u003eA. heterophyllus\u003c/em\u003e (27.95\u0026thinsp;\u0026plusmn;\u0026thinsp;2.58%) and \u003cem\u003eT. catappa\u003c/em\u003e (27.86\u0026thinsp;\u0026plusmn;\u0026thinsp;4.33%) presented relatively higher percentages of closed stomata than did \u003cem\u003eF. religiosa\u003c/em\u003e (Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eAt the polluted site, the range of the percentage of closed stomata also varied. \u003cem\u003eS. cumini\u003c/em\u003e presented the lowest percentage (11.71\u0026thinsp;\u0026plusmn;\u0026thinsp;2.48%), whereas \u003cem\u003eF. religiosa\u003c/em\u003e presented the highest percentage (35.96\u0026thinsp;\u0026plusmn;\u0026thinsp;3.3%). Notably, \u003cem\u003eF. benghalensis\u003c/em\u003e (27.37\u0026thinsp;\u0026plusmn;\u0026thinsp;2.17%) and \u003cem\u003eM. elengi\u003c/em\u003e (34.13\u0026thinsp;\u0026plusmn;\u0026thinsp;8.73%) presented considerably greater percentages of closed stomata at the polluted site than did their control counterparts, with some of the species having higher closure percentages in the polluted environment. \u003cem\u003eP. longifolia\u003c/em\u003e (20.35\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91%) presented a decrease in the number of closed stomata at the polluted site, falling into a middle range among the species (Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). Overall, the response to the polluted environment in terms of stomatal closure was species specific. Some species exhibited increased closure, potentially as a protective mechanism, whereas others showed decreased closure.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Multivariate exploratory analysis\u003c/h2\u003e\n \u003cp\u003ePearson\u0026apos;s correlation analysis revealed significant relationships among various stomatal traits (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Stomatal morphological parameters, namely, stomatal area, stomatal perimeter, stomatal length, and stomatal breadth, exhibited strong positive correlations. Specifically, SA was strongly positively correlated with SP (r\u0026thinsp;=\u0026thinsp;0.98\u0026lowast;\u0026lowast;\u0026lowast;), SL (r\u0026thinsp;=\u0026thinsp;0.82\u0026lowast;\u0026lowast;\u0026lowast;), and SB (r\u0026thinsp;=\u0026thinsp;0.78\u0026lowast;\u0026lowast;\u0026lowast;). Similarly, SP was strongly positively correlated with SL (r\u0026thinsp;=\u0026thinsp;0.89\u0026lowast;\u0026lowast;\u0026lowast;) and SB (r\u0026thinsp;=\u0026thinsp;0.71\u0026lowast;\u0026lowast;\u0026lowast;) (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). SL also demonstrated a moderate positive correlation with SB (r\u0026thinsp;=\u0026thinsp;0.47\u0026lowast;\u0026lowast;\u0026lowast;). In contrast to the morphological traits, SD was significantly negatively correlated with size-related parameters. SD was moderately negatively correlated with SL (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.54\u0026lowast;\u0026lowast;\u0026lowast;), SP (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.44\u0026lowast;\u0026lowast;\u0026lowast;), and SA (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.37\u0026lowast;\u0026lowast;) (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). This indicates a trade-off where plants with larger individual stomata tend to have fewer stomata per unit area. The stomatal pore index (SPI) was strongly positively correlated with stomatal density (r\u0026thinsp;=\u0026thinsp;0.77\u0026lowast;\u0026lowast;\u0026lowast;) and moderately positively correlated with stomatal breadth (r\u0026thinsp;=\u0026thinsp;0.32\u0026lowast;\u0026lowast;) (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003ePCA of the stomatal traits revealed that the first two principal components (PC1 and PC2) collectively explained 69.71% of the total variance observed in the dataset. Specifically, PC1 accounted for 44.34%, whereas PC2 explained 25.37% of the total variation, indicating that these two components sufficiently summarize the major patterns of trait variability. The biplot (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) illustrates a distinct grouping of stomatal morphological traits, including SA, SP, SL, and SB, which showed strong positive loadings along the PC1 axis. This clustering indicates a high degree of positive correlation among these variables, suggesting that they jointly represent the overall dimensions of stomatal size and shape. In contrast, SD was negatively loaded on PC1 and positioned oppositely to the size-related traits, implying a trade-off between stomatal size and density.\u003c/p\u003e\n \u003cp\u003ePC2 primarily captured the functional status of the stomata. The %OS and SPI were strongly positively associated with the percentage of open stomata, whereas the %CS exhibited strong negative loading (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). This opposition suggests that %OS and SPI are closely related, reflecting active stomatal function, whereas %CS represents an inverse physiological state characterized by stomatal closure.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Morphometric Traits\u003c/h2\u003e \u003cp\u003eStomatal characteristics serve as essential anatomical indicators that reflect a plant\u0026rsquo;s capacity to modulate gas exchange and its ability to absorb pollutants when subjected to duress in urban environments. This study determined that nine prevalent urban tree species exhibited significantly diverse stomatal morphology and function. The morphometric and functional traits collectively inform us about species-specific strategies for tolerance or sensitivity to urban air pollution.\u003c/p\u003e \u003cp\u003eThe dimensions of the Stomata, particularly their length and width, function as primary measures of their overall size, which directly affects the aperture and, consequently, the capacity for gas exchange. \u003cem\u003eP. longifolia\u003c/em\u003e exhibited comparatively greater stomatal length and width under polluted conditions, suggesting its potential ability to sustain gaseous exchange despite environmental stress. This response may function as a protective mechanism by reducing the stomatal aperture and surface area to limit the entry of pollutants [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. On the other hand, \u003cem\u003eA. heterophyllus, F. benghalensis, and S. mahagoni\u003c/em\u003e exhibited a decrease in both traits, indicating stomatal size plasticity in response to pollution, presumably to reduce pollutant entry and water loss, which may represent either a species-specific tolerance strategy or compensatory growth mechanisms under stress conditions [\u003cspan additionalcitationids=\"CR43\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. The stomatal area and perimeter, which are based on length and width, were generally lower for species growing at polluted sites, with \u003cem\u003eF. benghalensis\u003c/em\u003e and \u003cem\u003eS. mahagoni\u003c/em\u003e showing pronounced reductions. These reductions may reflect adaptive anatomical modifications that restrict the exposure of the stomatal pore to ambient air, thus reducing the influx of pollutants such as SO₂, NOₓ, and particulate matter [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Reduced stomatal aperture may aid in excluding hazardous gases and particulates, thereby safeguarding mesophyll tissues and conserving water. This is particularly significant in urban microclimates where both pollution and thermal stress coexist. Furthermore, a reduction in perimeter is associated with reduced stomatal conductance and gas exchange, which may affect photosynthetic efficiency and overall plant productivity [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. The perimeter of the stomata directly influences the dimensions of the stomatal aperture. Therefore, its reduction under stress conditions may be associated with hormonal variations, particularly increased abscisic acid synthesis, which is recognised to induce stomatal closure [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. This morphological simplification corresponds to the defensive mechanisms employed by sensitive species in response to abiotic stress.\u003c/p\u003e \u003cp\u003eSignificant differences in stomatal density were observed among the species. \u003cem\u003eF. benghalensis\u003c/em\u003e, \u003cem\u003eS. cumini\u003c/em\u003e, \u003cem\u003eT. catappa\u003c/em\u003e, and \u003cem\u003eS. mahagoni\u003c/em\u003e sustained comparatively elevated stomatal densities under pollution stress, indicating a possible compensatory mechanism to preserve transpiration and photosynthesis, despite a potential decrease in pore size or the effects of heightened light intensity [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. \u003cem\u003eP. longifolia\u003c/em\u003e, by contrast, remained relatively stable at both sites. This indicates a conservative response, potentially involving a reduction in pollutant uptake and water loss [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. \u003cem\u003eA. heterophyllus\u003c/em\u003e and \u003cem\u003eS. cumini\u003c/em\u003e exhibited a decrease in stomatal density at the contaminated site. This observed reduction in stomatal density attributable to pollution aligns with previous studies suggesting that plants respond to increased atmospheric pollutant levels, particularly particulate matter, by modifying their stomatal features as a protective mechanism [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR51 CR52 CR53 CR54\" citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. The closure or constrictions of stomata can facilitate the prevention of hazardous gas ingress and reduce water loss through transpiration during stressful conditions [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. The reduction in stomatal density may be associated with various pollution-induced physiological disturbances, such as oxidative stress and hormonal imbalances occurring during leaf development [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e]. Pollutants have been shown to modify the levels of cytokinin and auxin, which are essential for the development and patterning of stomata [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe stomatal pore index (SPI) serves as a functional indicator of the overall gas exchange capacity of the leaf surface. \u003cem\u003eS. mahagoni, T. catappa\u003c/em\u003e, and \u003cem\u003eF. religiosa\u003c/em\u003e exhibited comparatively elevated SPI values even in contaminated habitats, indicating their physiological resilience and suitability as tolerant urban species. On the other hand, species like \u003cem\u003eA. heterophyllus, F. benghalensis\u003c/em\u003e, and \u003cem\u003eS. cumini\u003c/em\u003e exhibited markedly reduced SPIs in polluted environments. A reduction in the SPI under polluted conditions is a common adaptive response aimed at minimizing transpirational water loss and pollutant uptake through the stomatal aperture [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e]. Pollution stress, particularly in urban settings dominated by NOx, SO₂, O₃, and PM, can disturb cellular homeostasis, resulting in altered guard cell physiology and restricted stomatal aperture [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. This decrease in SPI is also correlated with a decline in photosynthetic efficiency, as a limited stomatal aperture and density directly hinder CO₂ uptake, consequently adversely affecting carbon assimilation and growth potential [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. The SPI is considered a more accurate indicator of functional stomatal activity than mere stomatal density, as it accounts for both the number and size of stomata [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Functional Traits\u003c/h2\u003e \u003cp\u003eThe ratios of open to closed stomata further corroborated species-specific patterns of behaviour. \u003cem\u003eS. cumini, T. catappa, T. arjuna, P. longifolia\u003c/em\u003e, and \u003cem\u003eA. heterophyllus\u003c/em\u003e demonstrated a relatively high number of exposed stomata at polluted sites, potentially indicating increased tolerance to pollution or a reduced rate of stomatal closure. Compared with those at the control site, \u003cem\u003eF. benghalensis\u003c/em\u003e and \u003cem\u003eF. religiosa\u003c/em\u003e presented significantly lower percentages of open stomata at the polluted site. A similar significant reduction was observed for \u003cem\u003eM. elengi\u003c/em\u003e at the polluted site compared with the control site. This reduction in stomatal opening may be attributed to the accumulation of particulate matter and gaseous pollutants on leaf surfaces and within stomatal pores [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. Pollutants may directly influence the metabolic processes of guard cells or indirectly alter stomatal behavior by inducing oxidative stress, which can lead to stomatal closure [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. The reduction in the stomatal aperture corroborates previous research indicating that air pollution can the capacity of gas exchange, potentially impacting photosynthesis and transpiration [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Conversely, a higher percentage of closed stomata was observed in \u003cem\u003eM. elengi, F. religiosa\u003c/em\u003e, and \u003cem\u003eS. mahagoni\u003c/em\u003e, indicating that stress-induced stomatal closure prevents further damage. Stomatal closure serves as a vital protective mechanism to reduce the entry of harmful pollutants within plant tissues [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. This behavior aligns with research that emphasizes the functional significance of stomatal closure in mitigating pollutant entry and preserving water during stress conditions [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e4.3 Multivariate statistical approach\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eThe substantial positive correlations among stomatal size traits (SA, SP, SL, SB) indicate their inherent interdependence, collectively delineating the stomatal dimensions essential for gas exchange [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The inverse relationship between stomatal density and size characteristics affirms the well-established size-density trade-off, whereby plants control CO₂ uptake and water loss through the adjustment of stomatal number and dimensions [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The SPI showed a strong positive correlation with SD and a moderate correlation with SB. This means that it depends on both the number and width of the stomata, which are related to the potential for gas exchange. Conversely, %OS and %CS exhibited no significant correlation with morphological traits, indicating that stomatal size and density are structurally fixed, whereas aperture states are influenced by transient environmental factors such as light, humidity, and water availability [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe PCA results showed a clear difference between stomatal morphological traits including SL, SB, SA, SP, and functional attributes, %OS and %CS. This means that different physiological mechanisms control them. Traits associated with size exhibited a strong clustering on PC1, indicating their coordinated development and corroborating the well-established size\u0026ndash;density trade-off [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Conversely, PC2 exhibited functional variation, with SPI and %OS demonstrating positive correlation and %CS exhibiting negative correlation. This indicates that the system is sensitive to immediate environmental conditions such as light and humidity. This differentiation between structure and function permits stomatal behavior to change independently of anatomical features, thereby improving its adaptivity under stress conditions. This suggests possible attribute combinations for identifying species capable of adapting to stress in developing urban settings.\u003c/p\u003e \u003c/div\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThis study definitively shows that urban air pollution significantly influences the stomatal features of city trees, leading to two main adaptive responses: tolerance and avoidance. Certain species, such as \u003cem\u003eS. mahagoni\u003c/em\u003e, \u003cem\u003eP. longifolia\u003c/em\u003e, and \u003cem\u003eS. cumini\u003c/em\u003e, possess stomatal characteristics that facilitate continued gas exchange and photosynthesis despite the presence of pollution. These characteristics encompassed larger pores, elevated pores, elevated SPIs, and more extensively exposed stomata. The sensitive species \u003cem\u003eM. elengi\u003c/em\u003e and \u003cem\u003eT. catappa\u003c/em\u003e utilised an avoidance strategy characterised by smaller pore sizes, a decreased SPI, and predominantly closed stomata. This probably obstructed the entry of contaminants, but it may have also impeded the assimilation of carbon. These findings demonstrate that stomatal traits serve as significant indicators of air pollution-induced stress in urban vegetation. The species-specific responses offer essential insights for urban planning and greening initiatives, highlighting the significance of choosing pollution-tolerant species to enhance air quality, ecological resilience, and promote sustainable urban development.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are thankful to the University of Dhaka for providing funding and laboratory facilities to conduct this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eM.A.K.\u003c/strong\u003e - Sampling and data collection, writing of the original draft, review and editing, Resources, Methodology, Project supervisor. \u003cstrong\u003eM.A.R.\u003c/strong\u003e - Sampling and data collection, Methodology, Formal analysis, Software. \u003cstrong\u003eS.M.H.\u0026nbsp;\u003c/strong\u003e- Writing \u0026ndash; review \u0026amp; editing, Writing \u0026ndash; original draft. \u003cstrong\u003eM.Z.H\u003c/strong\u003e. - Methodology, Formal analysis, Writing original draft\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTheBiotechnology Research Centre (Grant # 08), University of Dhaka, conducted this research during 2023--2024.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo special permission was required to collect plant specimens from the polluted site (Motijheel-Sayedabad), as the area is not designated as a protected area. Sampling at the control site (National Botanical Garden) was conducted with permission from the relevant local authorities. The collection of plant parts (leaves) used in this study was conducted in compliance with local guidelines, and Dr. Ataur Rahman identified the species. Voucher specimens were deposited in the Ecology and Environment Laboratory herbarium with accession numbers (Control site plants, EELH3021-EELH3029 and Polluted site plants, EELH3030-EELH3038) for reproducibility. Not applicable. This study did not involve human participants or animals.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. \u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eButt AN, Rigoni C. The Green Blueprint: designing future cities with urban green infrastructure and ecosystem services in the UK. Land. 2025;14(6):1306.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRusso A, Cirella GT. 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Evaluation of ambient air pollution impact on carrot plants at a suburban site using open top chambers. Environ Monit Assess. 2006;119:15\u0026ndash;30.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFlexas J, Medrano H. Drought-inhibition of photosynthesis in C3 plants: Stomatal and nonstomatal limitations revisited. Ann Bot. 2022;89(2):183\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarquhar GD, Sharkey TD. (1982) Stomatal conductance and photosynthesis. Annu Rev Plant Physiol. 1982;33(1): 317\u0026ndash;345.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAgbaire PO, Esiefarienrhe E. (2009) Air pollution tolerance indices (APTI) of some plants around Otorogun gas plant in Delta State, Nigeria. J. Appl. Sci. Environ. Manag. 2009;13(1): 11\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeath RL. (1980) Initial events in injury to plants by air pollutants. Annu. Rev. Plant Physiol. 1980;31: 395\u0026ndash;431.\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":"discover-plants","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Plants](https://link.springer.com/journal/44372)","snPcode":"44372","submissionUrl":"https://submission.springernature.com/new-submission/44372/3","title":"Discover Plants","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Morphometric traits, Stomata, Polluted site, Functional traits, Control site, PCA biplot","lastPublishedDoi":"10.21203/rs.3.rs-8415643/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8415643/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUrban trees play a vital role in reducing the harmful effects of air pollution, yet their physiological and anatomical responses, especially stomatal plasticity, under long-term urban stress remain poorly understood. This study examined the stomatal phenotype‒function relationships in dominant urban tree species across two contrasting environments in Dhaka: the heavily polluted areas of Motijheel-Sayedabad and the relatively clean National Botanical Garden. We conducted a comparative analysis of key stomatal features, including stomatal density, size, area, perimeter, pore index, and stomatal opening status, across multiple species to assess their adaptive responses to air pollution. Two-way ANOVA showed that most stomatal structural and functional traits of urban plants were strongly affected by species, site, and their interaction, emphasizing distinct species-specific responses to pollution levels. Species such as \u003cem\u003ePolyalthia longifolia\u003c/em\u003e, \u003cem\u003eSwietenia mahagoni\u003c/em\u003e, and \u003cem\u003eFicus benghalensis\u003c/em\u003e exhibited significant stomatal alterations, indicating potential resilience under environmental stress. Pearson's correlation analysis found significant relationships among various stomatal traits. Principal component analysis of stomatal traits showed that the first two principal components (PC1 and PC2) together explained 69.71% of the total variance. PC1 alone accounted for 44.34%, while PC2 contributed a further 25.37%. This indicates that these two components effectively encapsulate the primary patterns of trait variation. The PCA results demonstrated a clear separation between stomatal morphological traits (e.g., SL, SB, SA, SP) and functional attributes (%OS, %CS), suggesting different physiological mechanisms control them. Overall, this study shows how important stomatal traits are as signs of how well plants can adapt to their environment and also provides useful information for choosing trees in cities for planning green infrastructure.\u003c/p\u003e","manuscriptTitle":"Unravelling the Stomatal Phenotype‒Function Relationships in Urban Trees Under Air Pollution Stress: A Multispecies Comparative Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-05 09:16:10","doi":"10.21203/rs.3.rs-8415643/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-12T10:02:20+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-10T09:01:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"162956898397599331763023101066707457129","date":"2026-01-07T12:45:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"172053315461443601406951174115766034642","date":"2026-01-05T05:05:43+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-04T15:05:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"256557542141690440425217610643903189905","date":"2026-01-02T12:11:51+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-02T11:54:01+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-01T09:13:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-27T08:47:56+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-27T00:35:29+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Plants","date":"2025-12-27T00:29:09+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-plants","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Plants](https://link.springer.com/journal/44372)","snPcode":"44372","submissionUrl":"https://submission.springernature.com/new-submission/44372/3","title":"Discover Plants","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ad941f35-3030-4109-b3fd-2f3e7a777ab0","owner":[],"postedDate":"January 5th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-13T10:54:20+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-05 09:16:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8415643","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8415643","identity":"rs-8415643","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}