Stomatal Area Research Articles

Co-application of silicon and biochar affected anatomical and biochemical properties of corn leaf (Zea mays L.) under soil nickel toxicity

Soil pollution with heavy metals is a threat to crop production. Practically, application of silicon (Si) with biochar can be a cost-effective approach to immobilize metals in contaminated soils. Investigation of the anatomical and biochemical changes of corn leaf is important for describing the mechanisms of Si and biochar soil application in alleviating the negative effects of nickel (Ni) toxicity. A factorial pot experiment was conducted to investigate the effect of Si (0, 250 and 500 mg Si kg-1 soil) in combination with rice husk biochar (RHB) or sheep manure biochar (SMB) prepared at two pyrolysis temperatures (300 and 500 °C) on anatomical and biochemical properties of corn leaves in a Ni-polluted soil. The length, width, area and weight of third-leaf, and metaxylem and protoxylem of midrib improved by application of Si250 with RHB more than SMB. At Si250, RHB300 and RHB500 improved the stomatal area by 31.7 and 27.7% compared to control (without biochar), respectively. The leaf membrane stability index was increased by increasing Si application level and reached 69% in RHB300. In contrast to total chlorophyll, the highest carotenoid content, catalase and peroxidase was obtained by control (without Si and biochar) followed by SMB. At Si250, the highest relative water content (RWC) was observed in RHB300 by 34.8% increase. Also, RHB300 had the highest total dry matter, with increases of 82.2, 120.0 and 83.1% at Si0, Si250 and Si500, respectively. By increasing the Si level and biochar application, the shoot Ni decreased between 42.1 to 133.3%. Combined application of Si250 with RHB300 resulted in the highest dry matter through improving the leaf dimensions, metaxylem and protoxylem areas of midrib, membrane stability index, total chlorophyll, and RWC, while Ni uptake was reduced.

Using the Montgomery-Koyama-Smith equation to calculate the stomatal area per unit lamina area for 12 Magnoliaceae species.

The Montgomery-Koyama-Smith (MKS) equation predicts that total leaf area per shoot is proportional to the product of the sum of individual leaf widths and maximum individual leaf length, which has been validated for some herbaceous and woody plants. The equation is also predicted to be valid in describing the relationship between the total stomatal area per micrograph (AT) and the product of the sum of individual stomatal widths (denoted as LKS) and maximum individual stomatal length (denoted by WKS) in any particular micrograph. To test the validity of the MKS equation, 69,931 stomata (from 720 stomatal micrographs from 12 Magnoliaceae species) were examined. The area of each stoma was calculated using empirical measurements of stomatal length and width multiplied by a constant. Six equations describing the relationships among AT, LKS, and WKS were compared. The root-mean-square (RMSE) and the Akaike information criterion (AIC) were used to measure the goodness of fit, and the trade-off between the goodness of fit and the structural complexity of each model, respectively. Analyses supported the validity of the MKS equation and the power-law equation AT ∝ (LKS∙WKS)α, where a is a scaling exponent. The estimated values of α at the species level and for the pooled data were all statistically smaller than unity, which did not support the hypothesis that AT ∝ LTS∙WTS. The power-law equation had smaller RMSE and AIC values than the MKS equation for the data from the 12 individual species and the pooled data. These results indicate that AT tends to allometrically scale with LKS∙WKS, and that increases in AT do not keep pace with increases in LTS∙WTS. In addition, using the product of LKS and WKS is better than using only one of the two variables.

Variations in the leaf economics spectrum, anatomical, ultrastructural, and stomatal traits of five tree species in the urban-rural air pollution environment

Rapid urbanization has contributed to global increases in air pollution derived from urban areas. Unlike natural forests, urban forests are exposed to higher concentrations of airborne pollutants due to the strong urban-suburban-rural pollutant emission gradients. However, there remains a pressing lack of available information pertaining to the urban air pollution-related effects on the leaf economics spectrum, anatomical, ultrastructural, and stomatal traits of tree species along an urban-rural gradient. Here, the degree to which urban air pollution impacts the adaption of greening tree species and associated service functions was assessed by sampling five common tree species (Acer pictum, Fraxinus chinensis, Koelreuteria paniculata, Salix babylonica, Sophora japonica) along urban-rural-natural forests in the Beijing metropolitan region of China. These analyses revealed a significant reduction in leaf mass per unit area (–13.4 %), leaf thickness (–16.7 %), and stomatal area (–27.5 %) with increasing proximity to areas of greater air pollution that coincide with significant increases in leaf tissue density (+12.6 %), leaf nitrogen content (+10.1 %), relative chlorophyll content (+2.7 %), and stomatal density (+11.9 %). Higher air pollution levels were associated with organelle changes including gradual disintegration of chloroplasts, larger intercellular spaces and apparent starch and plastoglobuli deposition. Air pollution was conducive to the strengthening of the trade-off potential and adaptation strategies of trees in urban ecosystems, which are associated with trees with a rapid investment return strategy associated with thick leaves and strong photosynthetic capacity. These results provide strong empirical evidence of the profound air pollution-induced changes in leaf functional traits and adaption ability of urban forest tree species.

Overexpression of RpKTI2 from Robinia pseudoacacia Affects the Photosynthetic Physiology and Endogenous Hormones of Tobacco.

Kunitz trypsin inhibitor genes play important roles in stress resistance. In this study, we investigated RpKTI2 cloned from Robinia pseudoacacia and its effect on tobacco. RpKTI2 was introduced into the tobacco cultivar NC89 using Agrobacterium-mediated transformation. Six RpKTI2-overexpressing lines were obtained. Transgenic and wild-type tobacco plants were then compared for photosynthetic characteristics and endogenous hormone levels. Transgenic tobacco showed minor changes in chlorophyll content, fluorescence, and photosynthetic functions. However, the maximum photochemical efficiency (Fv/Fm) increased significantly while intercellular CO2 concentration (Ci) decreased significantly. Stomatal size and hormone content (indole-3-acetic acid, zeatin riboside, gibberellin, and indole-3-propionic acid) were reduced, while brassinosteroid content increased. Random forest regression revealed that RpKTI2 overexpression had the biggest impact on carotenoid content, initial fluorescence, Ci, stomatal area, and indole-3-acetic acid. Overall, RpKTI2 overexpression minimally affected chlorophyll synthesis and photosynthetic system characteristics but influenced stomatal development and likely enhanced the antioxidant capacity of tobacco. These findings provide a basis for future in-depth research on RpKTI2.

Morpho-physiological traces of exogenous biogenic iron oxide nanoparticles in basil seedlings

Chemical fertilizers used in plant development and differentiation have become a global problem affecting the entire ecosystem, especially soil pollution. Food production demand with the increasing population has encouraged scientists to use biogenic nanoparticles in the agricultural field. Evaluation of growth, development, and differentiation processes of sweet basil (Ocimum basilicum L.) seedlings at gradually increasing concentrations of biogenic iron oxide nanoparticles (BIO-NPs) were identified by morphological and physiological parameters in this study. The results showed that growth parameters reached the maximum value at 100 mg/L but were less at other concentrations. At similar concentration, the stomatal density of the leaf was the maximum, while the stomatal area showed the lowest value. The levels of H2O2 and malondialdehyde (MDA) decreased in the treated seedlings. BIO-NPs increased the antioxidant defense and supported its growth by changing the antioxidant enzyme activities, H2O2, and MDA contents. The BIO-NP treatment provided positive improvements in phytochemical content in parallel with the growth and development of sweet basil seedlings. Different growth parameters, physiological results, supporting enzyme activities, and biochemical data revealed the contribution of the BIO-NP treatments to the growth and development of sweet basil seedlings. BIO-NPs improved higher phytochemical production of sweet basil, which may be suitable for its propagation on a commercial scale.

Anatomy of the saltgrass (Distichlis spicata L.) leaves with irrigation and without irrigation

Distichlis spicata is a gramineous halophyte species that grow around the coastal areas. The objective of the study was to identify the modifications in the anatomical structure of stomates of the D. spicata leaf epidermis, cultivated with irrigation and without irrigation conditions. Two populations were selected, 1) plants of D. spicata with irrigation and 2) plants of D. spicata without irrigation. Ten plants per replication were selected from each population, and from each selected plant, the fourth leaf was taken. Each leaf was cut longitudinally into four segments which were dried and analyzed using an Electronic Scanning Microscope. The variables measured were the stomatal density, length, and width of stomates and pores, the stomatal area, the proportion of the pore area concerning the size of the stomata, and the stomata proportion per surface. The results showed that D. spicata populations with irrigation and without irrigation showed anatomical modifications in the structure of stomates in the adaxial epidermis but not in the abaxial epidermis. In the adaxial epidermis, the plants with irrigation showed higher values of stoma length, stoma width, stoma area and pore length, while plants without irrigation showed higher values of proportion pore/stoma and stomatal density. The D. spicata plants without irrigation showed small stomates than plants with irrigation, also, the plants without irrigation, increased the accumulation of salt crystals in the abaxial epidermis.

Plasma membrane intrinsic proteins SlPIP2;5 gene regulates tolerance to high VPD in tomato

Plasma membrane intrinsic proteins (PIPs) play important roles in plant growth, development, and abiotic stress responses. However, the functions and regulatory mechanisms of PIPs under high vapor pressure deficit (VPD) stress are not yet well understood. In this study, we used tobacco rattle virus (TRV) - mediated virus-induced gene silencing (VIGS) technology to discover that SlPIP2;5 is involved in the acclimation process of tomato plants to high VPD. Under high VPD, the TRV-SlPIP2;5 strain exhibited improved growth compared to the TRV strain, and silencing SlPIP2;5 increased the enzyme activities of the antioxidant system of tomato plants and reduced the sensitivity of plants to atmospheric drought stress by eliminating reactive oxygen species produced by the plants. Additionally, leaf structure was improved, with decreased thickness of the epidermis and spongy tissue, leading to enhanced water transport efficiency. Furthermore, the TRV-SlPIP2;5 strain had increased stomatal length and individual stomatal area, which changed net assimilation rate and stomatal conductance to air drought. In addition, SlPIP2;5 was localized on the plasma membrane, and its promoter region contained numerous core elements and V-myb avian myeloblastosis viral oncogene homolog (MYB) binding sites. Yeast One-Hybrid Assay (Y1H) and Dual Luciferase (LUC) assays showed that the transcription factor SlMYB110 can bind to SlPIP2;5 and regulate its expression. qRT-PCR analysis revealed that high VPD inhibited the expression of SlMYB110, consistent with the expression pattern of SlPIP2;5. Therefore, we speculate that under high VPD, SlMYB110 negatively regulates the expression of SlPIP2;5, thereby modulating the tolerance of tomato plants to atmospheric drought. These findings provide a theoretical basis for improving tomato response to high VPD, and SlPIP2;5 was added to the high VPD-responsive gene pool as a valuable gene that could be used to improve high VPD tolerance in tomato through genetic engineering.

Chromium stress influences several parameters of leaf dynamics and morphology in Oryza sativa L. genotypes

Chromium (Cr) stress is a prevalent abiotic stress that alters various physiological, growth and metabolic parameters in plants. The toxicity of chromium at concentrations up to 100 µM were studied in two common Indian Oryza sativa genotypes, Lalat upland and Swarnaprabha. More chromium accumulated in roots than in leaves in both genotypes, with Lalat upland taking up more chromium than Swarnaprabha. Higher chromium concentrations reduced various physiological traits including stomatal conductance, transpiration rate, photosynthetic water use efficiency, photosynthetic pigments content in both the genotypes, and this decline was more pronounced in Lalat upland. Increase in vapour pressure deficit, sub stomatal carbon dioxide concentration and malondialdehyde content was detected at 100 µM chromium treated genotypes, however the effects were higher in Lalat upland. Confocal microscopy showed stomatal guard cell deformation, greater stomatal area and closed stomatal aperture in the leaves of 100 µM chromium treated Lalat upland plants. Abscisic acid and Salicylic acid content and expression of NCED1 and NCED2 genes involved in stomata aperture regulation were enhanced in Lalat upland and down regulated in Swarnaprabha under chromium stress. Variation in glandular and non-glandular trichome density and length was found in the leaves of chromium stressed plants in both the genotypes. The results suggest that Lalat upland is more sensitive to chromium toxicity than Swarnaprabha at higher chromium concentrations.

Measuring stomatal and guard cell metrics for plant physiology and growth using StoManager1.

Automated guard cell detection and measurement are vital for understanding plant physiological performance and ecological functioning in global water and carbon cycles. Most current methods for measuring guard cells and stomata are laborious, time-consuming, prone to bias, and limited in scale. We developed StoManager1, a high-throughput tool utilizing geometrical, mathematical algorithms, and convolutional neural networks to automatically detect, count, and measure over 30 guard cell and stomatal metrics, including guard cell and stomatal area, length, width, stomatal aperture area/guard cell area, orientation, stomatal evenness, divergence, and aggregation index. Combined with leaf functional traits, some of these StoManager1-measured guard cell and stomatal metrics explained 90% and 82% of tree biomass and intrinsic water use efficiency (iWUE) variances in hardwoods, making them substantial factors in leaf physiology and tree growth. StoManager1 demonstrated exceptional precision and recall (mAP@0.5 over 0.96), effectively capturing diverse stomatal properties across over 100 species. StoManager1 facilitates the automation of measuring leaf stomatal and guard cells, enabling broader exploration of stomatal control in plant growth and adaptation to environmental stress and climate change. This has implications for global gross primary productivity (GPP) modeling and estimation, as integrating stomatal metrics can enhance predictions of plant growth and resource usage worldwide. Easily accessible open-source code and standalone Windows executable applications are available on a GitHub repository (https://github.com/JiaxinWang123/StoManager1) and Zenodo (https://doi.org/10.5281/zenodo.7686022).

Characterization of stomatal density and size of different vitis vinifera L. cultivars growing in Mediterranean climate conditions

The stomatal traits of 13 red and white grapevine cultivars of Vitis vinifera L. established in a cultivar collection garden in central Chile were characterized in this study. The cultivars examined were ‘Cabernet Franc’, ‘Cabernet Sauvignon’, ‘Carmenere’, ‘Cot’, ‘Grenache’, ‘Merlot’, ‘Mourvedre’, ‘Pinot Noir’, ‘Syrah’, ‘Chardonnay’, ‘Marzanne’, ‘Roussane’, and ‘Sauvignon Blanc’. Transparent nail polish peel prints in four adult leaves per vine were obtained and examined under a light microscope at 10 ×. The number of stomata in 0.196 mm2 was counted, and their length and width were measured using image analysis software. With these variables, the stomatal area and stomatal density were obtained. The ‘Cot’ cultivar had the largest stomata and stomatal area, while the ‘Mourvedre’ cultivar had the smallest stomata and stomatal area. ‘Chardonnay’ had the highest number of stomata and stomatal density, while ‘Carmenere’ had the lowest. The red grapevine cultivars exhibited larger and fewer stomata than the white grapevine cultivars, corroborating different adaptations for the environmental modulation of stomatal conductance and transpiration.

Anatomical Structures of Saskatoon Berry (Amelanchier Medik.)Leaves Under Different Cultivation Conditions

AmelanchierMedik. belonging to the family Rosaceae includes about 30 species with a high content of biologically active substances. The aim of the study was to determine the morpho-anatomical features of leaves at the adaptation and ontogenesis stages of Saskatoon berry variety ‘Krasnoyarskaya’ (A. alnifolia) and variety ‘Prince William’ (A. canadensis). Saskatoon berry leaves are characterized by hypostomatic and anomocytic, less often anisocytic stomata at all stages of ontogenesis. The study revealed in the average length of the polar axis and the stomata equatorial diameter, depending on the cultivation conditions and genotype. A. canadensis had a larger average stomatal area, a thicker epidermis, a greater height of the palisade chlorenchyma cells, and a higher coefficient of palisade, which made it more resistant to changes in atmospheric precipitation, at all stages of ontogenesis, in comparison A. alnifolia. Bangladesh J. Plant Taxon. 30(2): 185-193, 2023 (December)

Analysis method of apparent quality of fair-faced concrete based on convolutional neural network machine learning

Fair-faced concrete has attracted much attention because of its noble texture, but the evaluation of its appearance quality often depends on personal subjective feelings (especially color difference) or complex image processing means, which hinders its development. Therefore, the accurate and objective evaluation of appearance quality is the key to fair-faced concrete engineering. This paper proposed a machine learning method to analyze the appearance quality of fair-faced concrete. Firstly, images of fair-faced concrete were collected by UAV (Unmanned Aerial Vehicle) or scanner for pretreatment. Then, based on the convolutional neural network algorithm, a visual quality database of fair-faced concrete including 2463 groups of information was established, and it was trained to recognize color difference and bubbles on the surface of fair-faced concrete pictures. The performance of the model is evaluated and optimized. The influence of environmental factors such as light intensity and surface moisture on the model is analyzed. Finally, the machine learning method is used to analyze the appearance quality of fair-faced concrete in engineering site. Compared with the traditional analysis methods, the accuracy of stomatal area rate and maximum stomatal diameter recognition was increased from 79.34 % to 93.83 %, and the accuracy of color difference recognition was increased by more than 10 %. At the same time, the identification method in this study still has strong robustness under light and surface moisture variation. The research results can provide useful thinking for evaluating fair-faced concrete engineering.

Coordination of hydraulic and functional traits in ten species of trees of the Sonoran Desert

Leave’s vein xylem and stomata hydraulic traits should be critically linked to modulating plant responses to drought in leaves of desert species, influencing traits at the whole-plant level and promoting adaptation. We tested for coordination among leaf vein xylem anatomical traits across different hierarchical orders (hydraulic vessel diameter, vein area, free veins per area, areolas per area, total free veins number, total areola number) and stomatal traits (stomatal size, stomatal density, stomatal index, leaf total stomatal area, leaf total stomatal number) as well as their relationship with the leaf area in ten tree species from the Sonoran Desert scrub, Mexico. Moreover, these traits were correlated with other hydraulic and functional traits associated with resource use strategies (hydroscape area, stem-specific density, leaf mass per area, and leaf phenology). Leaf total stomatal area and number were positively associated with vessel diameters at the midrib and with leaf total free terminal veins and areola number, indicating coordination between water transpiration and transport. Also, interspecific differences fit species along a physiological resource use spectrum, following an exploitative vs. conservative physiological axis. Accordingly, species with lower leaf longevity (LL) and foliage duration at the canopy (FD) displayed higher values of stomatal indices and free vein densities, higher stomata density; and anatomical traits related to higher hydraulic conductance and gas exchange in comparison to species with higher LL and FD. Therefore, in this community, species have been selected to take advantage of different temporal hydrological niches to enhance survival under unpredictable and highly seasonal water availability.

Structural and functional traits underlying the capacity of Calotropis procera to face different stress conditions

Calotropis procera (Aiton) W. T. Aiton, originally native to tropical and sub-tropical regions of northwestern Africa to southwest Asia through the Arabian Peninsula. The present study was engaged to uncover the underlying mechanism (structural and functional) of C. procera sampled from six different ecological regions. The population of normal irrigated agriculture field (IAF) had better growth, high K+ ion content, photosynthetic pigments (chl a chl b, Tchl and caro) and stomatal density. The population of dust and pollution stressed habitat (IWD) exhibited enlarged epidermal cells in stem and leaf, enhanced cortical proportion with largest cells in stem and phloem area in leaf. The population of drought and aridity stressed habitat (ARS) showed increased root cellular area, cortical region thickness and its cell area, and phloem region. The population from salt-affected habitat (SLF) possessed high root and shoot ionic contents (Na+ and Ca2+), total soluble sugars, total antioxidant activity, chlorophyll a/b, widened metaxylem vessels and phloem area in the stem, while intensive sclerification observed in both stem and leaf. The population native to waterlogged and salinity stressed habitat (APC) represented vigorous root growth, total free amino acids, well-developed metaxylem vessels and stomatal area in leaf. The population from drought and salinity-prone habitat (UBL) indicate increased storage of parenchymatous tissue (pith region and its cells area) and epidermal cell area in leaf. It is concluded that C. procera showed much outmost behavior in view of growth, structural and functional attributes in response to prevailing environmental condition.

StomataTracker: Revealing circadian rhythms of wheat stomata with in-situ video and deep learning

Plant stomata are essential channels for gas exchange between plants and the environment. The infrared gas-exchange system has greatly accelerated the studies of stomatal conductance (gs). Nevertheless, due to the lack of in-situ monitoring techniques, the behavior of stomata themselves remains poorly understood, especially in nocturnal environmental conditions. Here, a deep-learning-based stoma tracking pipeline (StomataTracker) was first proposed to continuously monitor stoma traits from unprecedentedly long-term, continuous, and non-destructive video data. Compared to the semi-automatic method (ImageJ), the open-source StomataTracker could greatly improve the extraction efficiency from 207 s to 1.47 s of stomatal traits, including stomatal area, perimeter, length, and width. The R2 adjusted of the four stomatal traits ranged from 0.620 to 0.752. In addition, the rhythm of wheat stomata opening in a completely dark environment was first reported from long-term video data. The closed time of stoma at night was negatively correlated with stomatal traits, and the R ranged from −0.583 to −0.855. The heterogeneity of stomatal behavior also highlighted that smaller stomata have the rhythm pattern of longer closure time at night. Overall, our study provides a novel perspective for stomatal study, and it is conducive to accelerating the application of stomatal circadian rhythm in wheat breeding.

Growth and Morpho-Stomatal Response of Kenaf (Hibiscus cannabinus) to Varying Water, Light, and Soil Conditions

This study investigated the stomatal responses of kenaf (Hibiscus cannabinus) to varying water, light, and soil conditions to explain how the species acclimatize to the changes in growing conditions. Seedlings were subjected to different watering regimes (daily – CON, 2 days interval – W2, 3 days interval – W3), light intensities (high, moderate, low), and soil conditions (garden soil – GS, Mt Makiling soil – MAK, UP Land Grant soil – UPL). The biomass, stomatal density (SD), epidermal cell density (ECD), stomatal index (SI), stomatal aperture length (SAL), guard cell length (GCL), stomatal area (SA), and potential conductance index (PCI) were measured across treatments. Water and light treatments had significant effects, but soil treatment did not affect most of the parameters measured. CON and/or W2 and high light intensity resulted in a higher SD, SI, SAL, and GCL, which resulted in a higher PCI, compared with the other water and light treatments. Contrarily, W3-treated seedlings had lower SD but significantly lower SAL, GCL, PCI, and aboveground biomass, compared to CON and W2-treated ones. Biomass allocation to root was also significantly higher in W3-treated seedlings. Therefore, kenaf seedlings exhibited a degree of stomatal plasticity in response to contrasting water, light, and soil conditions. Keywords: biomass allocation, potential conductance index, shade tolerance, stomatal index, water stress

Stomatal shape described by a superellipse in four Magnoliaceae species

ABSTRACT Stomata are essential for the exchange of water vapour and atmospheric gases between vascular plants and their external environments. The stomatal geometries of many plants appear to be elliptical. However, prior studies have not tested whether this is a mathematical reality, particularly since many natural shapes that appear to be ellipses are superellipses with greater or smaller edge curvature than predicted for an ellipse. Compared with the ellipse equation, the superellipse equation includes an additional parameter that allows generation of a larger range of shapes. We randomly selected 240 stomata from each of four Magnoliaceae species to test whether the stomatal geometries are superellipses or ellipses. The stomatal geometries for most stomata (943/960) were found to be described better using the superellipse equation. The traditional “elliptical stomata hypothesis” resulted in an underestimation of the area of stomata, whereas the superellipse equation accurately predicted stomatal area. This finding has important implications for the estimation of stomatal area in studies looking at stomatal shape, geometry, and function.

Enhanced ultraviolet-B radiation alleviates structural damages on rice leaf caused by Magnaporthe oryzae infection.

Enhanced ultraviolet-B (UV-B) radiation can change the interaction between crops and pathogens. The effects of single and compound stresses of enhanced UV-B radiation (5.0kJ·m-2) and Magnaporthe oryzae on the morphology, anatomy, and ultrastructure of rice leaves were investigated. M. oryzae infection decreased the leaf area and thickness, reduced the stomatal area and density, and caused damages to the leaf ultrastructure, such as cytoplasm-cell wall separation, atrophy and sinking of fan-shaped bulliform cells, and chloroplast deformation. The enhanced UV-B radiation supplied before or during M. oryzae infection remarkably decreased the mycelia number of M. oryzae in leaf epidermis, increased the leaf area, leaf thickness, stomatal density, and mastoid number; and alleviated the ultrastructural damages induced by M. oryzae to keep an integral chloroplast. While the UV-B radiation was supplied after M. oryzae infection, its alleviation effects on the damages induced by M. oryzae infection on the morphology and structure of rice leaf were attenuated. Thus, the alleviation of enhanced UV-B radiation on damages induced by M. oryzae infection on rice leaves was related to its application period. The enhanced UV-B radiation supplied before or during M. oryzae infection allowed the rice leaf to resist M. oryzae infection.

Morphological and Structural Responses of Albizia lebbeck to Different Lead and Nickel Stress Levels

Lead (Pb) and nickel (Ni) are serious soil pollutants that adversely affect plant growth and development and need to be removed through phytoremediation. The present study aimed to assess the morphological indices of Albizia lebbeck (L.) (Benth.) in relation to anatomical modifications for survival under both Pb and Ni stress. The seedlings of A. lebbeck were established and then subjected to four different concentrations, viz. 0 mM, 25 mM, 50 mM and 75 mM, of Pb and Ni for 14 days in two phases. Morphological traits such as shoot length (70.93%), fresh weight (79.27%), dry weight (83.9%), number of root hairs (65.7%), number of leaves per plant (67.4%) and number of leaflets per plant greatly reduced under Pb or Ni stress. Surprisingly, root length increased rather than decreased with the increase in Pb or Ni concentrations, along with an increase in leaflet width, leaflet length and leaflet area. Moreover, root cortical cell area, metaxylem area and phloem area decreased at 75 mM of Pb and Ni while epidermal thickness and cell area increased. Stem epidermal thickness, cell area and phloem area significantly decreased with the consistent increase in metaxylem area and cortical region thickness under both Pb and Ni stress. Leaf anatomical traits such as midrib thickness, abaxial epidermal thickness and stomatal density and adaxial epidermal thickness and stomatal area significantly increased with increasing Pb or Ni stress. Correlation analysis revealed close relations among morphological and anatomical traits (such as root length with cortical region thickness) for better plant survival under Pb or Ni stress, and a PCA-biplot further verified these correlation analyses. Cluster analyses demonstrated the associations among the morphological and anatomical traits based on different stress levels. Furthermore, we found that the longer exposure (from phase 1 to phase 2) of heavy metals stress is more dangerous for plant survival and can ultimately lead to plant death. Moreover, our results also confirmed that Ni is more harmful or dangerous to plants than Pb at high and moderate concentrations. The anatomical modifications ensured the survival of A. lebbeck in extreme heavy metals stress and therefore unlocked its potential to be used as a natural source of phytoremediation. We also recommend that the genetic potential of A. lebbeck associated with its survival under heavy metal stress be investigated.

Stomatal area estimation based on stomatal length and width of four Magnoliaceae species: even “kidney”-shaped stomata are not elliptical

Stomatal area estimation based on stomatal length and width of four Magnoliaceae species: even “kidney”-shaped stomata are not elliptical