Stomatal Characteristics Research Articles

Physiological Plasticity of Green Gram Stomata to Photosynthesis Traits under Interactive Effects of Elevated CO2, Drought and Heat Stress

Heat waves and droughts are projected to become more widespread as a result of climate change. At the same time, CO2 levels are predicted to have doubled by 2100. The stomatal regulation and gas exchange characteristics were assessed in 25 days old plants of green gram (var Co 8) by exposing them to six different treatments namely, T1: a [CO2] + a T+ irrigation (100%), T2: a [CO2] + a T+ irrigation (50%), T3: a [CO2] + e T (40ºC) + irrigation (100%), T4: e [CO2] – 800 ppm + a T+ irrigation (100%), T5: a [CO2] + combined stress [e T (40ºC) + irrigation (50%) T6: e [CO2] – 800 ppm + combined stress [e T (40ºC) + irrigation (50%)]. The experiment was carried out using Completely Randomized Design (CRD) with three replications. All gas exchange parameters viz., ((photosynthesis rate, stomatal conductance, and transpiration rate) were determined before imposing stress and two weeks after imposing stress. Stomatal characters was examined two weeks after imposing stress. Elevated CO2 stress caused a reduction in stomatal frequency accompanied by larger stomatal size. The study revealed the positive effect of higher CO2 concentration on gas exchange traits of the C3 crops viz., green gram.

Leaf surface microtopography shaping the bacterial community in the phyllosphere: evidence from 11 tree species

Phyllosphere bacteria are an important component of environmental microbial communities and are closely related to plant health and ecosystem stability. However, the relationships between the inhabitation and assembly of phyllosphere bacteria and leaf microtopography are still obscure. In this study, the phyllosphere bacterial communities and leaf microtopographic features (vein density, stomatal length, and density) of eleven tree species were fully examined. Both the absolute abundance and diversity of phyllosphere bacterial communities were significantly different among the tree species, and leaf vein density dominated the variation. TITAN analysis showed that leaf vein density also played more important roles in regulating the relative abundance of bacteria than stomatal features, and 6 phyla and 62 genera of phyllosphere bacteria showed significant positive responses to leaf vein density. Moreover, LEfSe analysis showed that the leaves with higher vein density had more bacterial biomarkers. Leaf vein density also changed the co-occurrence pattern of phyllosphere bacteria, and the co-occurrence network demonstrated more negative correlations and more nodes on the leaves with larger leaf vein density, indicating that higher densities of leaf veins improved the stability of the phyllosphere bacterial community. Phylogenetic analysis showed that deterministic processes (especially homogeneous selection) dominated the assembly process of phyllosphere bacterial communities. The leaf vein density increased the degree of bacterial clustering at the phylogenetic level. Therefore, the inhabitation and assembly of the phyllosphere bacterial community are related to leaf microtopography, which provides deeper insight into the interaction between plants and bacteria.

IMPACT OF CADMIUM TOXICITY ON LEAF AREA AND STOMATAL CHARACTERISTICS IN FABA BEAN

Although changes in stomatal response to elevated doses of cadmium has already been observed in several plants, few studies have focused on this phenomenon in more detail. The effects of different doses of cadmium Cd2+ (50 and 100 mg.kg-1 soil) on leaf area and stomatal characteristics (number of stomata, number of epidermal cells, stomatal index and size of stomata) of faba bean (Vicia faba L. cultivar Aštar) were studied after 15 days of heavy metal treatment. No visual changes on adaxial or abaxial side of leaves of the tested variety of faba bean were found. The leaf area was higher by 14.15 % at lower and by 12.23 % at the higher doses of Cd. The tested doses of Cd did not lead to a change in the number of stomata. The number of epidermal cells was increased on adaxial side by 4.98 % at dose Cd50. Stomatal index was decreased due to the effect of higher dose of cadmium by 11.38 % on adaxial side of leaves. In stomatal widths, decrease by 2.04 % (adaxial side) and 2.26 % (abaxial side) was observed at higher doses of Cd. In stomatal length decrease by 1.85 % was observed at higher dose of Cd on adaxial and decrease by 3.89 % (Cd50) and 4.63 % (Cd100) on abaxial side of leaves respectively. The variations of response could be signals of tolerance or adaptive mechanisms of the leaves of tested bean cultivar under the used concentrations of cadmium.

Spatial distribution characteristics of stomata at the areole level in Michelia cavaleriei var. platypetala (Magnoliaceae).

In hierarchically reticulate venation patterns, smaller orders of veins form areoles in which stomata are located. This study aimed to quantify the spatial relationship among stomata at the areole level. For each of 12 leaves of M. cavaleriei var. platypetala, we assumed that stomatal characteristics were symmetrical on either side of the midrib, and divided the leaf surface on one side of the midrib into six layers equidistantly spaced along the apical-basal axis. We then further divided each layer into three positions equidistantly spaced from midrib to leaf margin, resulting in a total of 18 sampling locations. In addition, for 60 leaves, we sampled three positions from midrib to margin within only the widest layer of the leaf. Stomatal density and mean nearest neighbour distance (MNND) were calculated for each section. A replicated spatial point pattern approach quantified stomatal spatial relationships at different distances (0-300 μm). A tendency towards regular arrangement (inhibition as opposed to attraction or clustering) was observed between stomatal centres at distances <100 μm. Leaf layer (leaf length dimension) had no significant effect on local stomatal density, MNND or the spatial distribution characteristics of stomatal centres. In addition, we did not find greater inhibition at the centre of areoles, and in positions farther from the midrib. Spatial inhibition might be caused by the one-cell-spacing rule, resulting in more regular arrangement of stomata, and it was found to exist at distances up to ~100 μm. This work implies that leaf hydraulic architecture, consisting of both vascular and mesophyll properties, is sufficient to prevent important spatial variability in water supply at the areole level.

Microsporangiophores from the Early Cretaceous (Berriasian) of Bornholm, Denmark, with comments on a pre-angiosperm xerophytic flora

A new taxon, Skyttegaardia galtieri, is described based on microsporangiophores with Monosulcites/Cycadopites pollen isolated from clays collected at the Skyttegård locality, island of Bornholm, Denmark, which are of earliest Cretaceous (Berriasian) age. Each microsporangiophore consists of a short, massive proximal fertile stalk-like portion with a truncate base, and a long sterile distal extension. A cavity on each side of the median line of the stalk-like portion, partially encloses a sporangium that dehisces by a longitudinal slit. The long distal extension tapers to a slender point and is curved toward the inferred adaxial side. The extension is irregularly angular in cross-section and the cuticle is thick with deep stomatal pits. The organization of the microsporangiophore, the in situ pollen and stomatal features suggest relationship with extant Cycadales. However, in all extant and fossil cycads there are usually many more sporangia per microsporangiophore, typically in groups of two to five, and they are borne on the surface of the proximal stalk-like portion rather than embedded in its tissues. These differences preclude secure inclusion of Skyttegaardia in Cycadales and open the possibility that these microsporangiophores were produced by a group of extinct plants, the other parts of which remain to be identified. The thick cuticle and sunken stomata of Skyttegaardia, together with the embedded sporangia, suggest adaptation to water stress, which is also consistent with the xeromorphic traits seen among the leaf fragments in the Skyttegaard flora and the arid conditions inferred from geological–geochemical proxies.

Species-specific and altitude-related variations in stomatal features of Berberis lycium Royle and B. parkeriana C.K. Schneid

ABSTRACT Epidermal micro-morphological investigations have drawn the consideration of many researchers because of their taxonomic usefulness, but their relationship with environment is not completely known. Keeping this in view, quantitative leaf epidermal features (number of epidermal cells and stomata, and stomata length and width) were examined in the species Berberis lycium Royle and B. parkeriana C.K. Schneid along an altitudinal gradient at three different altitudes in Manoor Valley (Himalaya), Pakistan. A significant variability was found in the size and type of epidermal cells and stomata on both sides of the understory plants leaves. Berberis parkeriana had two types of stomata (anomocytic, and anisocytic) while Berberis lycium possesses a single type of stomata (paracytic). Furthermore, both species had stomata on the abaxial surface only. Berberis parkeriana had higher values of all parameters analyzed; the number of epidermal cells and stomata increased with increasing altitude while the length and width of stomata decreased with increasing altitude. This approach proved extremely valuable for the assessment of environmental impacts on the adaptive potential of plants and subsequent eco-physiological changes.

Partitioning of transpiration to cut flower organs and its mediating role on vase life response to dry handling: A case study in chrysanthemum

The mediating role of water relations on vase life response to prior desiccation (dry handling) was addressed in cut chrysanthemum. In the first part of the study, the contribution of different organs to whole-cut flower transpiration was determined in 12 cultivars. During desiccation, leaf transpiration decreased owing to stomatal closure. Instead, no active regulation was apparent in either stem or flower. Cultivar differences in leaf transpiration were related to the weight loss required to induce stomatal closure (R2 = 0.919). A small portion of cut flower transpiration was through the flower (12.3 ± 0.3 %), with the major contributor being either leaves or stem, depending on the water status and the cultivar. Leaf transpiration was positively correlated with whole-cut flower transpiration (R2 = 0.879). In the second part of the study, the postharvest longevity upon arrival and following desiccation (5 or 10 % weight loss) was determined on six cultivars with contrasting whole-cut flower transpiration rates. In these cultivars, the rehydration ability following a dehydration event, petal carbohydrate and soluble protein contents, as well as leaf carbohydrate, soluble protein and mineral contents were also assessed. Impaired water transport, as a result of prior desiccation, was not associated with the vase life response to dry handling. A strong correlation between whole-cut flower transpiration in the desiccation experiment and the vase life response to prior desiccation was found. Low vase life decrease in response to prior desiccation was associated with decreased whole-cut flower transpiration during the postharvest period. In conclusion, cultivar differences in vase life response to prior desiccation were attributed to variation in leaf stomatal characteristics.

Exogenous melatonin improves the salt tolerance of cotton by removing active oxygen and protecting photosynthetic organs

BackgroundAs damage to the ecological environment continues to increase amid unreasonable amounts of irrigation, soil salinization has become a major challenge to agricultural development. Melatonin (MT) is a pleiotropic signal molecule and indole hormone, which alleviates the damage of abiotic stress to plants. MT has been confirmed to eliminate reactive oxygen species (ROS) by improving the antioxidant system and reducing oxidative damage under adversity. However, the mechanism by which exogenous MT mediates salt tolerance by regulating the photosynthetic capacity and ion balance of cotton seedlings still remains unknown. In this study, the regulatory effects of MT on the photosynthetic system, osmotic modulators, chloroplast, and anatomical structure of cotton seedlings were determined under 0–500 μM MT treatments with salt stress induced by treatment with 150 mM NaCl.ResultsSalt stress reduces the chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, PSII photochemical efficiency, PSII actual photochemical quantum yield, the apparent electron transfer efficiency, stomata opening, and biomass. In addition, it increases non-photochemical quenching. All of these responses were effectively alleviated by exogenous treatment with MT. Exogenous MT reduces oxidative damage and lipid peroxidation by reducing salt-induced ROS and protects the plasma membrane from oxidative toxicity. MT also reduces the osmotic pressure by reducing the salt-induced accumulation of Na+ and increasing the contents of K+ and proline. Exogenous MT can facilitate stomatal opening and protect the integrity of cotton chloroplast grana lamella structure and mitochondria under salt stress, protect the photosynthetic system of plants, and improve their biomass. An anatomical analysis of leaves and stems showed that MT can improve xylem and phloem and other properties and aides in the transportation of water, inorganic salts, and organic substances. Therefore, the application of MT attenuates salt-induced stress damage to plants. Treatment with exogenous MT positively increased the salt tolerance of cotton seedlings by improving their photosynthetic capacity, stomatal characteristics, ion balance, osmotic substance biosynthetic pathways, and chloroplast and anatomical structures (xylem vessels and phloem vessels).ConclusionsOur study attributes help to protect the structural stability of photosynthetic organs and increase the amount of material accumulation, thereby reducing salt-induced secondary stress. The mechanisms of MT-induced plant tolerance to salt stress provide a theoretical basis for the use of MT to alleviate salt stress caused by unreasonable irrigation, fertilization, and climate change.

Morphology, Photosynthetic Traits, and Nutritional Quality of Lettuce Plants as Affected by Green Light Substituting Proportion of Blue and Red Light.

Green light, as part of the photosynthetically active radiation, has been proven to have high photosynthetic efficiency once absorbed by plant leaves and can regulate plant physiological activities. However, few studies have investigated the appropriate and efficient way of using the green light for plant production. Thus, the objective of this study was to investigate a moderate amount of green light, partially replacing red and blue light, for plant growth and development. In this experiment, four treatments were set up by adjusting the relative amount of green light as 0 (RB), 30 (G30), 60 (G60), and 90 (G90) μmol m−2 s−1, respectively, with a total photosynthetic photon flux density of 200 μmol m−2 s−1 and a fixed red-to-blue ratio of 4:1. Lettuce (Lactuca sativa cv. ‘Tiberius’) plant growth and morphology, stomatal characteristics, light absorptance and transmittance, photosynthetic characteristics, and nutritional quality were investigated. The results showed that: (1) shoot dry weight increased by 16.3 and 24.5% and leaf area increased by 11.9 and 16.2% under G30 and G60, respectively, compared with those under RB. Plant stem length increased linearly with increasing green-to-blue light ratio; (2) light transmittance of lettuce leaf under treatments employing green light was higher than that under RB, especially in the green region; (3) stomatal density increased, whereas stomatal aperture area decreased with the increase in the relative amount of green light; and (4) carbohydrate accumulation increased under G60 and G90. Soluble sugar contents under G60 and G90 increased by 39.4 and 19.4%, respectively. Nitrate contents under G30, G60, and G90 decreased by 26.2, 40.3, and 43.4%, respectively. The above results indicated that 15–30% green light replacing red and blue light effectively increased the yield and nutritional quality of lettuce plants.

Leaf epidermal anatomy of Cynodon dactylon (L.) Pers. in relation to ecotypic adaptation

Qualitative and quantitative studies were done on leaf epidermal characteristics with special reference to stomatal features to find out the impact of environmental condition on twenty four accessions of Cynodon dactylon (L.) Pers. collected from different ecological habitats of Bangladesh. The foliar epidermal peels from both surfaces of mature leaves were observed under microscope. The leaves were found to be amphistomatic and stomata were paracytic type. The epidermal cells in this study were found to be sinuous. Silica bodies were found to be saddle and cross shaped. Prickles angular were pointed at the tip. Macro-hairs were present in all the accessions, but no micro-hair was found both adaxially or abaxially. Stomatal frequency and stomatal index were found to vary from accession to accession on both adaxial and abaxial surface of leaves, and the differences were statistically significant in most of the cases.&#x0D; Bangladesh J. Plant Taxon. 28(1): 171-193, 2021 (June)

Postharvest storage of three chayote (Sechium edule (Jacq.) Sw.) varieties

The consumer demand for chayote (Sechium edule (Jacq.) Sw.) fruits has increased in recent years, virens levis being the most important variety, although other chayote varieties are gaining importance such as nigrum xalapensis and n. spinosum. However, the postharvest behavior of these varieties is different, so it is important to evaluate the factors that limit the shelf life of each variety. Therefore, in this study, fruits of each variety from the Mexican National Germplasm Bank of Sechium edule were used. The following fruit quality variables were evaluated: weight loss, humidity (%), color, chlorophyll, titratable acidity, total soluble solids (TSS), total sugars, and stomatal characteristics. In addition, the storage potential of each variety was evaluated for two weeks at different temperatures, 7°, 13° (85% RH) and 24 °C (60% RH), with the application of 1-methylcyclopropene (1-MCP). The variables evaluated were viviparism, disease severity, weight loss, dehydration and chilling injury (CI). The fruits of n. xalapensis and n. spinosum have a higher content of chlorophylls and carotenoids, but similar contents of TSS, acidity and total sugars than v. levis fruits. The use of 1-MCP reduced viviparism in all varieties, and the severity of blisters was higher in v. levis. The fruits of the three varieties presented severe CI when stored at 7 °C but the most susceptible to dehydration and diseases severity is n. spinosum.

Spray irrigation with microcystins-rich water affects plant performance from the microscopic to the functional level and food safety of spinach (Spinacia oleracea L.)

Irrigation water coming from freshwater bodies that suffer toxic cyanobacterial blooms causes adverse effects on crop productivity and quality and raises concerns regarding food contamination and human exposure to toxins. The common agricultural practice of spray irrigation is an important exposure route to cyanotoxins, yet its impact on crops has received little attention. In the present study we attempted an integrated approach at the macro- and microscopic level to investigate whether spray or drip irrigation with microcystins (MCs)-rich water differently affect spinach performance. Growth and functional features, structural characteristics of stomata, and toxin bioaccumulation were determined. Additionally, the impact of irrigation method and water type on the abundance of leaf-attached microorganisms was assessed. Drip irrigation with MCs-rich water had detrimental effects on growth and photosynthetic characteristics of spinach, while spray irrigation ameliorated to various extents the observed impairments. The stomatal characteristics were differently affected by the irrigation method. Drip-irrigated spinach leaves showed significantly lower stomatal density in the abaxial epidermis and smaller stomatal size in the adaxial side compared to spray-irrigation treatment. Nevertheless, the latter deteriorated traits related to fresh produce quality and safety for human consumption; both the abundance of leaf-attached microorganisms and the MCs bioaccumulation in edible tissues well exceeded the corresponding values of drip-irrigated spinach with MC-rich water. The results highlight the significance of both the use of MCs-contaminated water in vegetable production and the irrigation method in shaping plant responses as well as health risk due to human and livestock exposure to MCs.

Spermine mediated improvements on stomatal features, growth, grain filling and yield of rice under differing water availability

Rice which belongs to the grass family is vulnerable to water stress. As water resources get limited, the productivity of rice is affected especially in granaries located at drought prone areas. It would be even worse in granaries located in drought prone areas such as KADA that receives the lowest rainfall in Malaysia. Spermine (SPM), a polyamine compound that is found ubiquitiosly in plants is involved in adaptation of biotic and abiotic stresses. The effect of SPM on growth,grain filling and yield of rice at three main granaries namely, IADA BLS, MADA and KADA representing unlimited water, limited water and water stress conditions respectively, were tested during the main season. Additinally, the growth enhancer was also tested during off season at KADA. Spermine increased plant height, number of tillers per hill and chlorophyll content in all three granaries. Application of SPM improved yield by 38, 29 and 20% in MADA, KADA and IADA BLS, respectively. Harvest index showed 2.6, 6 and 16% increases at IADA BLS, KADA and MADA, respectively in SPM treated plants as compared to untreated. Except for KADA which showed a reduction in yield at 2.54 tha−1, SPM improved yield at MADA, 7.21 tha−1 and IADA BLS, 9.13 tha−1 as compared to the average yield at these respective granaries. In the second trial, SPM increased the yield to 7.0 and 6.4 tha−1 during main and off seasons, respectively, indicating that it was significantly higher than control and the average yield reported by KADA. The yield of SPM treatments improved by 25 and 33% with an increment of farmer’s income at main and off seasons, respectively. Stomatal width was significantly higher than control at 11.89 µm. In conclusion, irrespective of the tested granaries and rice variety, spermine mediated plots displayed increment in grain yield.

Growth performance of ICCRI 06 H cocoa seedling in response to different microclimate and soil moisture conditions

Climate and environmental factors play an important role for cocoa (Theobroma cacao L.) optimal growth and production. This study aims to evaluate growth performance and stomatal characteristics of cocoa seedling in response to microclimate, i.e. temperature, relative humidity, light intensity and soil moisture condition. The cacao variety of ICCRI 06 H was used for greenhouse experiment arranged by a completely randomized design with three replications. The first factor was evapotranspiration (ETa) i.e. ETa-1 100% (control), ETa-2 50% (moderate stress), and ETa-3 25% (severe stress). The second factor was microclimate condition defined by its location in the greenhouse, i.e. inside the glass box (IB) and outside the glass box (OB). IB microclimate conditions were modified through the installation of 50-Watt LED artificial lamps. Our seven weeks observations demonstrated the specific microclimate condition created both in IB and OB. An insignificant effect of different soil moisture level to cocoa seedling growth was evidenced. Conversely, microclimate condition shows a significant effects especially the plant height and stem diameter. The multiple regression analysis suggests the presence of connection between microclimate and crop growth, i.e. plant height, stem diameter, and number of young cocoa leaves in IB. The stomatal characteristics indicate the more stressed condition created outside the box.

First report on genome size and ploidy determination of five indigenous coffee species using flow cytometry and stomatal analysis

The nuclear 2C DNA content and ploidy level determination of five indigenous coffee species from India was carried out using flow cytometry and by assessing the stomatal characteristics. The nuclear DNA content (2C/pg) analyzed varied from 1.29 pg in Coffea wightiana Wall. ex Wight & Arn. to 1.48 pg in Coffea jenkinsii Hook.f. Based on the genome size, all five species were divided into two groups. The first group comprises Coffea travancorensis Wight & Arn and C. wightiana with lower genome size (2C DNA 1.29–1.30 pg), and the second group consists of Coffea bengalensis Roxb.ex Schult, Coffea khasiana (Korth.) Hook.f and C. jenkinsii with larger genome size (2C DNA 1.45–1.48 pg). The species included in the first group were inhabited in dry environmental conditions in contrast to the species included in the second group which was predominantly from mesic habitat. Among the stomatal characteristics, no significant variation in stomatal density was observed among the species, although stomatal guard cell length and stomatal chloroplast number recorded significant variation among some species. Based on flow cytometry and stomatal characteristics, all five endangered coffee species analyzed in the study were identified as diploids. The study revealed that stomatal guard cell length and stomatal chloroplast number could be fast, inexpensive, and reliable methods for determining the ploidy status of indigenous coffee species.

PENGARUH PENCEMARAN DEBU SEMEN PADA STRUKTUR DAN FUNGSI DAUN BEBERAPA JENIS TANAMAN BERDAUN LEBAR

The stomatal features of the leaves of several species of various life forms that grow around the cement factory are investigated with the aim of examining the anatomical modifications of the leaves which increase their tolerance and survival in the presence of cement dust pollution. In addition, the chlorophyll content in the leaves has also been examined. In comparison, the same study has also been carried out for the composition of the same species in unaffected locations. Three different life forms of the plant were investigated over two sites: trees, represented by Polyalthia longifolia, Acacia auriculiformis, Persea americana, and Mangifera indica; shrubs by Syzygium myrtifolium, and Ixora javanica; and herbs by Rhoe and Aglaonema. The average stomata density in the affected area was 173.16 /mm2, while it could reach 244.96 /mm2 at the control site. The same trend was also shown by the chlorophyll content. The Independent T-test revealed a significant difference (p-value = 0.037). Adaptability in terms of having chlorophyll content from all three life forms at different sites was also available in this discussion. Herbs has the greatest difference between sites (0.33 μg/mL), followed by shrubs (0.31 μg/mL) and then trees (0.2 μg/mL). The Two way ANOVA test showed that both life forms and sites significantly influenced the content of chlorophyll (p-value = 0.00). However, there was no interaction between sites and life forms in influencing chlorophyll content (p value=0.652). In conclusion, In all three life forms, either stomatal density or chlorophyll content decreases with pollution.

Understanding the mechanistic basis of adaptation of perennial Sarcocornia quinqueflora species to soil salinity

Succulent halophytes can be used as convenient models for understanding the mechanistic basis of plant adaptation to salt stress. In this work, effects of salinity (0-1000 mM NaCl range) on growth, ion accumulation, and stomatal features were investigated in the succulent halophyte Sarcocornia quinqueflora. Elevated salinity levels up to 400 mM NaCl largely promoted dry matter yield, succulence, shoot surface area, and stomatal characteristics. Plant growth was optimal at 200 mM NaCl and reduced at concentrations exceeding 600 mM NaCl. Osmotic adjustment in a succulent shoot was achieved by a massive accumulation of inorganic ions, with Na+ and Cl- contributing approximately 85% of its osmolality, while organic compatible solutes and K+ were responsible for only approximately 15%. Shoot K+ was unchanged across the entire range of salinity treatments (200-1000 mM NaCl) and positively correlated with the transpiration rate (R=0.98). Carbohydrates were not reduced at high salinity compared to plants at optimal conditions, implying that growth retardation at severe salt dosages was attributed to limitations in a vacuolar Na+ and Cl- sequestrations capacity rather than inadequate photosynthesis and/or substrate limitation. It is concluded that the superior salt tolerance of S. quinqueflora is achieved by the effective reliance on Na+ and Cl- accumulation for osmoregulation and turgor maintenance, and efficient K+ homeostasis for adequate stomatal functioning over the entire salinity range. The above findings could be instrumental in developing strategies to improve salinity stress tolerance in perennial horticultural crops and optimize their water-use efficiency.

Ozone Response of Leaf Physiological and Stomatal Characteristics in Brassica juncea L. at Supraoptimal Temperatures

Plants are affected by the features of their surrounding environment, such as climate change and air pollution caused by anthropogenic activities. In particular, agricultural production is highly sensitive to environmental characteristics. Since no environmental factor is independent, the interactive effects of these factors on plants are essential for agricultural production. In this context, the interactive effects of ozone (O3) and supraoptimal temperatures remain unclear. Here, we investigated the physiological and stomatal characteristics of leaf mustard (Brassica juncea L.) in the presence of charcoal-filtered (target concentration, 10 ppb) and elevated (target concentration, 120 ppb) O3 concentrations and/or optimal (22/20 °C day/night) and supraoptimal temperatures (27/25 °C). Regarding physiological characteristics, the maximum rate of electron transport and triose phosphate use significantly decreased in the presence of elevated O3 at a supraoptimal temperature (OT conditions) compared with those in the presence of elevated O3 at an optimal temperature (O conditions). Total chlorophyll content was also significantly affected by supraoptimal temperature and elevated O3. The chlorophyll a/b ratio significantly reduced under OT conditions compared to C condition at 7 days after the beginning of exposure (DAE). Regarding stomatal characteristics, there was no significant difference in stomatal pore area between O and OT conditions, but stomatal density under OT conditions was significantly increased compared with that under O conditions. At 14 DAE, the levels of superoxide (O2-), which is a reactive oxygen species, were significantly increased under OT conditions compared with those under O conditions. Furthermore, leaf weight was significantly reduced under OT conditions compared with that under O conditions. Collectively, these results indicate that temperature is a key driver of the O3 response of B. juncea via changes in leaf physiological and stomatal characteristics.

Responses of stomatal features and photosynthesis to porewater N enrichment and elevated atmospheric CO2inPhragmites australis, the common reed

Biological invasions increasingly threaten native biodiversity and ecosystem services. One notable example is the common reed, Phragmites australis, which aggressively invades North American salt marshes. Elevated atmospheric CO2 and nitrogen pollution enhance its growth and facilitate invasion because P. australis responds more strongly to these enrichments than do native species. We investigated how modifications to stomatal features contribute to strong photosynthetic responses to CO2 and nitrogen enrichment in P. australis by evaluating stomatal shifts under experimental conditions and relating them to maximal stomatal conductance (gwmax ) and photosynthetic rates. Plants were grown in situ in open-top chambers under ambient and elevated atmospheric CO2 (eCO2 ) and porewater nitrogen (Nenr ) in a Chesapeake Bay tidal marsh. We measured light-saturated carbon assimilation rates (Asat ) and stomatal characteristics, from which we calculated gwmax and determined whether CO2 and Nenr altered the relationship between gwmax and Asat . eCO2 and Nenr enhanced both gwmax and Asat , but to differing degrees; gwmax was more strongly influenced by Nenr through increases in stomatal density while Asat was more strongly stimulated by eCO2 . There was a positive relationship between gwmax and Asat that was not modified by eCO2 or Nenr , individually or in combination. Changes in stomatal features co-occur with previously described responses of P. australis to eCO2 and Nenr . Complementary responses of stomatal length and density to these global change factors may facilitate greater stomatal conductance and carbon gain, contributing to the invasiveness of the introduced lineage.

The effect of shadow conditions on stomatal characters of several plants used in landscape design

The present study aims to determine the changes in stomatal characters of several plants depending on the shadow conditions. Within this scope, the leaf samples were collected from Platanus orientalis, Cercis siliquastrum, Eonymus japonica, Cotoneaster franchettii, and Buxus sempervirens species grown in open spaces. Scales images of leaf samples were taken using Scanning Electron Microscope and measurements were performed on these images in order to determine the micro-morphological characteristics such as stoma length (µm), stoma width (µm), pore opening length (µm), and pore opening width (µm) in the statistical analyses. The changes of these characteristics depending on the species, individuals, and shadow conditions were determined. The results showed that the differences in stomatal characteristics were statistically significant only between the individuals, whereas the effects of light and individual were statistically non-significant.