Reponses of morphological and biochemical traits of bamboo trees under elevated atmospheric O3 enrichment.

Dwarf bamboo (Indocalamus decorus) is an O3-tolerant plant species. To identify the possible mechanism and response of leaf morphological, antioxidant, and anatomical characteristics to elevated atmospheric O3 (EO3) concentrations, we exposed three-year-old I. decorus seedlings to three O3 levels (low O3-LO: ambient air; medium O3-MO: Ambient air+70 ppb high O3-HO: Ambient air+140 ppb O3) over a growing season using open-top chambers. Leaf shape and stomatal characteristics, and leaf microscopic structure of I. decorus were examined. The results indicated that 1) the stomata O3 flux (Fst) of HO decreased more rapidly under EO3 as the exposure time increased. The foliar O3 injury of HO and MO occurred when AOT40 was 26.62 ppm h and 33.20 ppm h, respectively, 2) under EO3, leaf number, leaf mass per area, leaf area, and stomata length/width all decreased, while leaf thickness, stomatal density, width, and area increased compared to the control, 3) MDA and total soluble protein contents all showed significantly increase under HO (36.57% and 32.77%) and MO(31.91% and 19.52%) while proline contents only increased under HO(33.27%). 4) MO and HO increased bulliform cells numbers in the leaves by 6.28% and 23.01%, respectively. HO reduced the transverse area of bulliform cells by 13.73%, while MO treatments had no effect, and 5) the number of fusoid cells interspace, the transverse area of fusoid cells interspace, and mesophyll thickness of HO significantly increased by 11.16%, 28.58%, and 13.42%, respectively. In conclusion, I. decorus exhibits strong O3 tolerance characteristics, which stem from adaptions in the leaf's morphological, structural, antioxidant, and anatomical features. One critical attribute was the enlargement of the bulliform cell transverse area and the transverse area of fusoid cells interspace that drove this resistance to O3. Local bamboo species with high resistance to O3 pollution thus need to be promoted for sustained productivity and ecosystem services in areas with high O3 pollution.

Leaf morpho-anatomical adjustments in a Quercus pubescens forest after 10 years of partial rain exclusion in the field.

In the Mediterranean region, a reduction of annual precipitation and a longer and drier summer season are expected with climate change by the end of the century, eventually endangering forest survival. To cope with such rapid changes, trees may modulate their morpho-anatomical and physiological traits. In the present study, we focused on the variation in leaf gas exchange and different leaf morpho-anatomical functional traits of Quercus pubescens Willd. in summer using a long-term drought experiment in natura consisting of a dynamic rainfall exclusion system where trees have been submitted to amplified drought (AD) (~-30% of annual precipitation) since April 2012 and compared them with trees under natural drought (ND) in a Mediterranean forest. During the study, we analyzed net CO2 assimilation (An), stomatal conductance (gs), transpiration (E), water-use efficiency (WUE), stomatal size and density, density of glandular trichomes and non-glandular trichomes, thickness of the different leaf tissues, specific leaf area and leaf surface. Under AD, tree functioning was slightly impacted, since only An exhibited a 49% drop, while gs, E and WUE remained stable. The decrease in An under AD was regulated by concomitant lower stomatal density and reduced leaf thickness. Trees under AD also featured leaves with a higher non-glandular trichome density and a lower glandular trichome density compared with ND, which simultaneously limits transpiration and production costs. This study points out that Q. pubescens exhibits adjustments of leaf morpho-anatomical traits which can help trees to acclimate to AD scenarios as those expected in the future in the Mediterranean region.

Anatomical features of ecological importance and taxonomic value revealed by scanning electron microscopy and light microscopy in Camonea umbellata (L.) A.R. Simões & Staples (Convolvulaceae).

This article describes detailed and novel data on the anatomy and histochemistry of leaves, stems, and roots of Camonea umbellata (L.) A.R.Simões & Staples in different environments for the identification of characters with taxonomical value and of ecological importance, with provision of light and scanning electron microscopy images. To analyze the characters, we collected samples of the vegetative organs of three individuals in each of three populations, which were in a grazing area, an urban environment, and a biological reserve. The main diagnostic anatomical markers for the identification of C. umbellata include amphistomatic leaves, tetracytic and brachyparatetracytic stomata, peltate trichomes, long simple trichomes, epidermis with striated cuticle ornamentation, mesophyll with acute borders, presence of druses, secretory channels, angular collenchyma, fibrous pericycle in the stem, intraxylary phloem in the vegetative organs, oil bodies throughout the midrib, petiole, stem and root, and epicuticular waxes of the crust and coiled rodlet types. Since the characters above did not show variation in the environments evaluated, we consider these characters taxonomically useful for the identification of C. umbellata. RESEARCH HIGHLIGHTS: The anatomy of the aerial vegetative organs of Camonnea umbellata retains common Convolvulaceae characters. The sinuosity of the epidermal cell walls and the density of trichomes in the epidermis of the petiole were visually variable characters among the analyzed individuals. Amphistomatic leaves, tetracytic and brachyparatetracytic stomata, peltate trichomes, epidermis with striated cuticle ornamentation, dorsiventral mesophyll with border acute, presence of druses, secretory structures, angular collenchyma, fibrous pericycle in the stem, intraxillary phloem, presence of oil bodies in all organs, and epicuticular waxes of the crust type and coiled rods were considered important anatomical markers for the recognition and correct identification of Camonea umbellata.

Endemic species analysis: Foliar epidermal anatomical characters of Aster glehnii F. Schmidt (Asteraceae).

The classification and identification of Aster glehnii F. Schmidt are determined from its foliar epidermal anatomical features. Scanning electronic microscopy has been used to determine the foliar epidermal anatomical characteristics of the species in detail. This study compared the qualitative and quantitative characteristics of the leaf epidermis of A. glehnii for taxonomic identification to be used as a reference for future studies on the species. A. glehnii has smooth, thin cuticles, depressed anomocytic stomata dispersed randomly throughout the leaf surface, polygonal epidermal cells with straight to slightly curved anticlinal walls, and no trichomes. There are obvious veins containing thick-walled bundle sheath cells. The stomatal density is between 100 and 150 stomata per millimeter. The vein density ranges from five to 10 veins per millimeter, and the epidermal cells are 10 to 20 µm long and 5 to 10 µm in width. Understanding the connections between the different A. glehnii species and categorizing and identifying them depend heavily on these foliar epidermal structural features. Taxonomy and conservation are closely intertwined because the former serves as the basis for comprehending and safeguarding biodiversity. RESEARCH HIGHLIGHTS: Optical microscopy of the A. glehnii leaf epidermis for taxonomic identification SEM was used to identify and authenticate endemic species Microscopic identification of endemic species can assist in the conservation.

Tolerance to mild shading levels in cattail as related to increased photosynthesis and changes in its leaf area and anatomy.

Shading is an environmental factor that has been little investigated regarding its effects on emergent aquatic plants. Typha domingensis Pers. is an emergent macrophyte that demonstrates some plasticity for self-shading, and as it can shade other species in the same area, the effect of shading on its traits deserves further investigation. The objective of the present study was to evaluate the gas exchange, leaf anatomy, and growth of T. domingensis cultivated under increasing shading intensities. The plants were collected and propagated in a greenhouse, and the clones were subjected to four shading intensities: 0% (unshaded), 35%, 73%, and 83% shading created by black nets. Growth traits, clonal production, photosynthesis, transpiration, and leaf anatomy were evaluated. The 73% and 83% shading promoted the death of all plants, but all plants survived in the 35% and unshaded treatments. Compared with the unshaded treatment, the 35% shading treatment promoted a higher photosynthetic rate and greater transpiration, supporting increased growth and production of clones. The increase in the photosynthetic rate in the 35% shading was related to the increase in leaf area which increased the photosynthesis of the whole plant. The 73% and 83% treatments inhibited the development of photosynthetic parenchyma and stomata in T. domingensis, leading to a drastic reduction in photosynthesis and energy depletion. Therefore, T. domingensis does not tolerate intense shading, but its photosynthetic characteristics and growth are favored by mild shading, a factor that may be of great importance for its competitiveness and invasive behavior.

How Important Are Functional and Developmental Constraints on Phenotypic Evolution? An Empirical Test with the Stomatal Anatomy of Flowering Plants.

AbstractQuantifying the relative contribution of functional and developmental constraints on phenotypic variation is a long-standing goal of macroevolution, but it is often difficult to distinguish different types of constraints. Alternatively, selection can limit phenotypic (co)variation if some trait combinations are generally maladaptive. The anatomy of leaves with stomata on both surfaces (amphistomatous) present a unique opportunity to test the importance of functional and developmental constraints on phenotypic evolution. The key insight is that stomata on each leaf surface encounter the same functional and developmental constraints but potentially different selective pressures because of leaf asymmetry in light capture, gas exchange, and other features. Independent evolution of stomatal traits on each surface imply that functional and developmental constraints alone likely do not explain trait covariance. Packing limits on how many stomata can fit into a finite epidermis and cell size-mediated developmental integration are hypothesized to constrain variation in stomatal anatomy. The simple geometry of the planar leaf surface and knowledge of stomatal development make it possible to derive equations for phenotypic (co)variance caused by these constraints and compare them with data. We analyzed evolutionary covariance between stomatal density and length in amphistomatous leaves from 236 phylogenetically independent contrasts using a robust Bayesian model. Stomatal anatomy on each surface diverges partially independently, meaning that packing limits and developmental integration are not sufficient to explain phenotypic (co)variation. Hence, (co)variation in ecologically important traits like stomata arises in part because there is a limited range of evolutionary optima. We show how it is possible to evaluate the contribution of different constraints by deriving expected patterns of (co)variance and testing them using similar but separate tissues, organs, or sexes.

Anatomical drivers of stomatal conductance in sorghum lines with different leaf widths grown under different temperatures.

Sustaining crop productivity and resilience in water-limited environments and under rising temperatures are matters of concern worldwide. We investigated the leaf anatomical traits that underpin our recently identified link between leaf width (LW) and intrinsic water use efficiency (iWUE), as traits of interest in plant breeding. Ten sorghum lines with varying LW were grown under three temperatures to expand the range of variation of both LW and gas exchange rates. Leaf gas exchange, surface morphology and cross-sectional anatomy were measured and analysed using structural equations modelling. Narrower leaves had lower stomatal conductance (gs ) and higher iWUE across growth temperatures. They also had smaller intercellular airspaces, stomatal size, percentage of open stomatal aperture relative to maximum, hydraulic pathway, mesophyll thickness, and leaf mass per area. Structural modelling revealed a developmental association among leaf anatomical traits that underpinned gs variation in sorghum. Growing temperature and LW both impacted leaf gas exchange rates, but only LW directly impacted leaf anatomy. Wider leaves may be more productive under well-watered conditions, but consume more water for growth and development, which is detrimental under water stress.

Implications of foliar epidermal micromorphology using light and scanning electron microscopy: A useful tool in taxonomy of Korean irises.

The genus Iris L., comprising approximately 210 species, is one of the most species-rich genera in the family Iridaceae. In this study, the first comprehensive leaf micromorphological characters of Korean irises were studied using light and scanning electron microscopy. Our objective was to evaluate the foliar micromorphological characteristics (namely epidermal cells, stomata types, and guard cell size) of Korean Iris taxa in a systematic context. All the investigated Korean Iris taxa had amphistomatic or hypostomatic leaves with anomocytic stomatal complexes. Guard cell length varied among species, ranging from 24.8 µm (I. rossii) to 56.0 µm (I. domestica). Although the presence of papillae on the outer periclinal wall is not of taxonomic significance, leaf margin pattern, guard cell size, and sunken stomata type were useful for species-level identification of Korean Iris species. The occurrence of polymorphic stomatal types was reported here for the first time, and the correlation between genome size and epidermal guard cell length was discussed.

Stomatal density in Pinus sylvestris as an indicator of temperature rather than CO2 : Evidence from a pan-European transect.

The commonly observed negative relationship between stomatal density (SD) and atmospheric CO2 has led to SD being proposed as an indicator of atmospheric CO2 concentration. The use of SD as a proxy for CO2 , however, has been hampered by an insufficient understanding of the intraspecific variation of this trait. We hypothesized that SD in Pinus sylvestris, a widely distributed conifer, varies geographically and that this variation is determined by major climatic variables. By sampling needles from naturally growing trees along a latitudinal range of 32.25°, equivalent to 13.7°C gradient of mean annual temperature (MAT) across Europe, we found that SD decreased from the warmest southern sites to the coldest sites in the north at a rate of 4 stomata per mm2 for each 1°C, with MAT explaining 44% of the variation. Additionally, samples from a provenance trial exhibited a positive relationship between SD and the MAT of the original localities, suggesting that high SD is an adaptation to warm temperature. Our study revealed one of the strongest intraspecific relationships between SD and climate in any woody species, supporting the utility of SD as a temperature, rather than direct CO2 , proxy. In addition, our results predict the response of SD to climate warming.

A stomata classification and detection system in microscope images of maize cultivars.

Plant stomata are essential structures (pores) that control the exchange of gases between plant leaves and the atmosphere, and also they influence plant adaptation to climate through photosynthesis and transpiration stream. Many works in literature aim for a better understanding of these structures and their role in the evolution process and the behavior of plants. Although stomata studies in dicots species have advanced considerably in the past years, even there is not much knowledge about the stomata of cereal grasses. Due to the high morphological variation of stomata traits intra- and inter-species, detecting and classifying stomata automatically becomes challenging. For this reason, in this work, we propose a new system for automatic stomata classification and detection in microscope images for maize cultivars based on transfer learning strategy of different deep convolution neural netwoks (DCNN). Our performed experiments show that our system achieves an approximated accuracy of 97.1% in identifying stomata regions using classifiers based on deep learning features, which figures out as a nearly perfect classification system. As the stomata are responsible for several plant functionalities, this work represents an important advance for maize research, providing an accurate system in replacing the current manual task of categorizing these pores on microscope images. Furthermore, this system can also be a reference for studies using images from different cereal grasses.

Macroscopic variation in Arabidopsis mutants despite stomatal uniformity across soil nutrient environments.

Stomata are essential pores flanked by guard cells that control gas exchange in plants. We can utilize stomatal size and density measurements as a proxy for a plant's capacity for gas exchange. While stomatal responses to stressful environments are well studied; data are lacking in the responses across mutant genotypes of the same species in these trait and treatment interactions or genetic variation in phenotypic plasticity. We evaluated the effects of soil nutrient variation on macroscopic and stomatal traits of Arabidopsis thaliana T-DNA insertion mutants for which prior performance in a single benign growing condition were available. Nutrient-induced stress significantly impacted traits including plant biomass, height, fruit number, and leaf number which we denote as macroscopic traits. We found evidence that genotype by environment effects exist for macroscopic traits, yet total stomatal area variation, or "microscopic variation" across environments was modest. Divergence from the wildtype line varied by mutant background and these responses were variable among traits. These findings suggest that Arabidopsis employs a strategy of physiological compensation, sacrificing morphological traits to maintain stomatal production.

Callitriche as a potential model system for evolutionary studies on the dorsiventral distribution of stomata.

Controlling the distribution of stomata is crucial for the adaptation of plants to new, or changing environments. While many plant species produce stomata predominantly on the abaxial leaf surface (hypostomy), some produce stomata on both surfaces (amphistomy), and the remaining few produce them only on the adaxial surface (hyperstomy). Various selective pressures have driven the evolution of these three modes of stomatal distribution. Despite recent advances in our understanding of stomatal development and dorsiventral leaf polarity, the genetic basis for the evolution of different stomatal distributions is still unclear. Here, we propose the genus Callitriche as a new model system to investigate patterns in the evolution of stomatal distribution. Callitriche comprises species with diverse lifestyles, including terrestrial, amphibious, and obligately aquatic plants. We found that species in this genus cover all three modes of dorsiventral stomatal distribution, making it a desirable model for comparative and evolutionary analyses on distribution modes. We further characterized the genetic basis of the different distribution modes, focusing on the stomatal key transcription factor SPEECHLESS. Future research using the promising model system Callitriche would open a new direction for evolutionary developmental biology studies on stomata.

Use of Synchrotron Phase-Sensitive Imaging for the Investigation of Magnetopriming and Solar UV-Exclusion Impact on Soybean (Glycine max) Leaves.

The combined response of exclusion of solar ultraviolet radiation (UV-A+B and UV-B) and static magnetic field (SMF) pre-treatment of 200 mT for 1 h were studied on soybean (Glycine max) leaves using synchrotron imaging. The seeds of soybean with and without SMF pre-treatment were sown in nursery bags kept in iron meshes where UV-A+B (280-400 nm) and UV-B (280-315 nm) from solar radiation were filtered through a polyester filters. Two controls were planned, one with polythene filter controls (FC)- which allows all the UV (280-400 nm); the other control had no filter used (open control-OC). Midrib regions of the intact third trifoliate leaves were imaged using the phase-contrast imaging technique at BL-4, Indus-2 synchrotron radiation source. The solar UV exclusion results suggest that ambient UV caused a reduction in leaf growth which ultimately reduced the photosynthesis in soybean seedlings, while SMF treatment caused enhancement of leaf growth along with photosynthesis even under the presence of ambient UV-B stress. The width of midrib and second-order veins, length of the second-order veins, leaf vein density, and the density of third-order veins obtained from the quantitative image analysis showed an enhancement in the leaves of plants that emerged from SMF pre-treated seeds as compared to untreated ones grown in open control and filter control conditions (in the presence of ambient UV stress). SMF pre-treated seeds along with UV-A+B and UV-B exclusion also showed significant enhancements in leaf parameters as compared to the UV excluded untreated leaves. Our results suggested that SMF-pretreatment of seeds diminishes the ambient UV-induced adverse effects on soybean.

Understanding airspace in leaves: 3D anatomy and directional tortuosity.

The leaf intercellular airspace is a tortuous environment consisting of cells of different shapes, packing densities, and orientation, all of which have an effect on the travelling distance of molecules from the stomata to the mesophyll cell surfaces. Tortuosity, the increase in displacement over the actual distance between two points, is typically defined as encompassing the whole leaf airspace, but heterogeneity in pore dimensions and orientation between the spongy and palisade mesophyll likely result in heterogeneity in tortuosity along different axes and would predict longer traveling distance along the path of least tortuosity, such as vertically within the columnar cell matrix of the palisade layer. Here, we compare a previously established geometric method to a random walk approach, novel for this analysis in plant leaves, in four different Eucalyptus species. The random walk method allowed us to quantify directional tortuosity across the whole leaf profile, and separately for the spongy and palisade mesophyll. For all species tortuosity was higher in the palisade mesophyll than the spongy mesophyll and horizontal (parallel to the epidermis) tortuosity was consistently higher than vertical (from epidermis to epidermis) tortuosity. We demonstrate that a random walk approach improves on previous geometric approaches and is valuable for investigating CO2 and H2 O transport within leaves.

Exogenous 1',4'-trans-Diol-ABA Induces Stress Tolerance by Affecting the Level of Gene Expression in Tobacco (Nicotiana tabacum L.).

1',4'-trans-diol-ABA is a key precursor of the biosynthesis of abscisic acid (ABA) biosynthesis in fungi. We successfully obtained the pure compound from a mutant of Botrytis cinerea and explored its function and possible mechanism on plants by spraying 2 mg/L 1',4'-trans-diol-ABA on tobacco leaves. Our results showed that this compound enhanced the drought tolerance of tobacco seedlings. A comparative transcriptome analysis showed that a large number of genes responded to the compound, exhibiting 1523 genes that were differentially expressed at 12 h, which increased to 1993 at 24 h and 3074 at 48 h, respectively. The enrichment analysis demonstrated that the differentially expressed genes (DEGs) were primarily enriched in pathways related to hormones and resistance. The DEGs of transcription factors were generally up-regulated and included the bHLH, bZIP, ERF, MYB, NAC, WRKY and HSF families. Moreover, the levels of expression of PYL/PYR, PP2C, SnRK2, and ABF at the ABA signaling pathway responded positively to exogenous 1',4'-trans-diol-ABA. Among them, seven ABF transcripts that were detected were significantly up-regulated. In addition, the genes involved in salicylic acid, ethylene and jasmonic acid pathways, reactive oxygen species scavenging system, and other resistance related genes were primarily induced by 1',4'-trans-diol-ABA. These findings indicated that treatment with 1',4'-trans-diol-ABA could improve tolerance to plant abiotic stress and potential biotic resistance by regulating gene expression, similar to the effects of exogenous ABA.

Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms.

Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%) and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.

Stomatal morphology and physiology explain varied sensitivity to abscisic acid across vascular plant lineages.

Abscisic acid (ABA) can induce rapid stomatal closure in seed plants, but the action of this hormone on the stomata of fern and lycophyte species remains equivocal. Here, ABA-induced stomatal closure, signaling components, guard cell K+ and Ca2+ fluxes, vacuolar and actin cytoskeleton dynamics, and the permeability coefficient of guard cell protoplasts (Pf) were analyzed in species spanning the diversity of vascular land plants including 11 seed plants, 6 ferns, and 1 lycophyte. We found that all 11 seed plants exhibited ABA-induced stomatal closure, but the fern and lycophyte species did not. ABA-induced hydrogen peroxide elevation was observed in all species, but the signaling pathway downstream of nitric oxide production, including ion channel activation, was only observed in seed plants. In the angiosperm faba bean (Vicia faba), ABA application caused large vacuolar compartments to disaggregate, actin filaments to disintegrate into short fragments and Pf to increase. None of these changes was observed in the guard cells of the fern Matteuccia struthiopteris and lycophyte Selaginella moellendorffii treated with ABA, but a hypertonic osmotic solution did induce stomatal closure in fern and the lycophyte. Our results suggest that there is a major difference in the regulation of stomata between the fern and lycophyte plants and the seed plants. Importantly, these findings have uncovered the physiological and biophysical mechanisms that may have been responsible for the evolution of a stomatal response to ABA in the earliest seed plants.

Stomatal size, ploidy and polyembryony in Eriotheca Stellate Trichome Species Complex (Bombacoideae - Malvaceae) in the Cerrados of Brazil.

Geographic parthenogenesis, range expansion of apomictic plants after climate changes, has been described for Northern Hemisphere gametophytic apomicts. But similar trends have been observed for sporophytic apomicts of Cerrado, the savannas in Brazil. Eriotheca pubescens is a common Cerrado tree, an agamic complex of either hexaploid/polyembryonic apomicts or tetraploid/monoembryonic sexual individuals. Some populations have been described as a new species, Eriotheca estevesiae, all included in the Eriotheca Stellate Trichome Species Complex (ESTSC). Since breeding systems and ploidy are clearly associated with polyembryony and stomatal size, we used these ancillary features to map the reproductive and ploidy level traits of E. pubescens and E. estevesiae. Leaves and seeds were collected from individuals of 19 populations. Seeds were evaluated for the presence of polyembryony and leaves for stomatal measurements. Eight populations were monoembryonic while another eight were polyembryonic and for other three, the embryonic pattern was not readily verified. E. pubescens polyembryonic and hexaploid populations formed a homogeneous group, but monoembryonic plants were more variable. E. estevesiae populations were monoembryonic with smaller stomata. In contrast, some E. pubescens monoembryonic populations further south presented larger stomata. Despite these outliers, possibly mixed populations, stomatal size and embryonic pattern differed from northern to southern populations. Embryonic pattern and stomatal size indicated that northernmost populations of Eriotheca STSC (E. estevesiae) are diploid and sexual. Southernmost populations, mostly polyembryonic and with large stomata, are hexaploid and apomictic. This is in agreement with geographic parthenogenesis and range expansion of apomictic lineages to southern habitats available after the last glacial maximum.

Revisiting the physical mutagenesis for sugarcane improvement: a stomatal prospective.

This study was conducted to investigate the influence of gamma rays on stomatal parameters and the interaction of these traits with agronomy of the sugarcane crop. Three genotypes of sugarcane (NIA-0819, NIA-98, and BL4) were exposed to four doses of gamma radiation (10, 20, 30, and 40 Gy) and then subjected to field trials. Stomatal length, width, and density were observed using scanning electron microscopy. Moreover, agronomic and sugar-related characteristics of the crop were determined at maturity. The stomatal parameters augmented at two lower doses of gamma radiation (10 and 20 Gy) and declined under higher doses (30 and 40 Gy). The maximum stomatal length was observed in NIA-0819 at 10 Gy (63.71 µm), whereas NIA-98 and BL4 demonstrated highest stomatal length under 20 Gy (54.11 and 57.40 µm, respectively), indicating a role of genetic factors in varietal response. Similar trend was noticed for stomatal width and density as well. The lowermost treatment (10 Gy) of NIA-0819 produced maximum stomatal density (115.31 stomata mm-2 on the abaxial surface). Adaxial stomatal density was significantly lower than the abaxial one. Sugar quality attributes revealed a different tendency. Sucrose contents of BL4 increased gradually from 12.33% at control to 14.54% at 40 Gy. Yield and yield-contributing traits of genotypes indicated a strong positive correlation with the stomatal parameters. The present study suggested that gamma radiations cause variations in stomatal characteristics of sugarcane. These changes further influence the photosynthetic activity and instigate a direct impact on the agronomic performance of the crop.