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Introduction: The identification of the physiological processes limiting carbon assimilation under water stress is crucial for improving model predictions and selecting drought-tolerant varieties. However, the influence of soil water availability on photosynthesis-limiting processes is still not fully understood. This study aimed to investigate the origins of photosynthesis limitations on potato (Solanum tuberosum) during a field drought experiment. Methods: Gas exchange and chlorophyll fluorescence measurements were performed at the leaf level to determine the response of photosynthesis-limiting factors to the decrease in the relative extractable water (REW) in the soil. Results: Drought induced a two-stage response with first a restriction of CO2 diffusion to chloroplasts induced by stomatal closure and a decrease in mesophyll conductance, followed by a decrease in photosynthetic capacities under severe soil water restrictions. Limitation analysis equations were revisited and showed that mesophyll conductance was the most important constraint on carbon and water exchanges regardless of soil water conditions. Discussion: We provide a calibration of the response of stomatal and non-stomatal factors to REW to improve the representation of drought effects in models. These results emphasize the need to revisit the partitioning methods to unravel the physiological controls on photosynthesis and stomatal conductance under water stress. [ABSTRACT FROM AUTHOR]

Introduction: The identification of the physiological processes limiting carbon assimilation under water stress is crucial for improving model predictions and selecting drought-tolerant varieties. However, the influence of soil water availability on photosynthesis-limiting processes is still not fully understood. This study aimed to investigate the origins of photosynthesis limitations on potato (Solanum tuberosum) during a field drought experiment. Methods: Gas exchange and chlorophyll fluorescence measurements were performed at the leaf level to determine the response of photosynthesis-limiting factors to the decrease in the relative extractable water (REW) in the soil. Results: Drought induced a two-stage response with first a restriction of CO2 diffusion to chloroplasts induced by stomatal closure and a decrease in mesophyll conductance, followed by a decrease in photosynthetic capacities under severe soil water restrictions. Limitation analysis equations were revisited and showed that mesophyll conductance was the most important constraint on carbon and water exchanges regardless of soil water conditions. Discussion: We provide a calibration of the response of stomatal and non-stomatal factors to REW to improve the representation of drought effects in models. These results emphasize the need to revisit the partitioning methods to unravel the physiological controls on photosynthesis and stomatal conductance under water stress. [ABSTRACT FROM AUTHOR]

Quantifying the effect of factors controlling CO2 assimilation is crucial for understanding plant functions and developing strategies to improve productivity. Methods exist in numerous variants and produce various indicators, such as limitations, contributions, and sensitivity, often causing confusion. Simplifications and common mistakes lead to overrating the importance of diffusion—whether across stomata or the mesophyll. This work develops a consistent set of definitions that integrates all previous methods, offering a generalised framework for quantifying restrictions. Ten worked examples are provided in a free downloadable spreadsheet, demonstrating the simplicity and applicability to a wide range of questions. [ABSTRACT FROM AUTHOR]

Salt stress is a significant abiotic stress that hinders the growth of rice (Oryza sativa L.) and reduces their yield. Previous research has examined the synthesis of γ-aminobutyric acid (GABA) and its role in plant resistance under various abiotic stresses. However, the synthesis of GABA and its ability to mitigate damage caused by salt stress—particularly its effects on osmotic adjustment, antioxidant defense, photosynthesis, and overall plant growth throughout the entire rice lifecycle—remains unclear. Therefore, we conducted two experiments using salt-tolerant rice cultivar Lianjian 5 (J-5) and salt-susceptible cultivar Lianjing 7 (L-7). In Experiment I, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. In Experiment II, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. Therefore, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. Subsequently, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. We measured the activities of superoxide dismutase, peroxidase, and catalase, as well as photosynthetic characteristics such as photosynthesis, transpiration, chlorophyll content, stomatal density and size, and leaf anatomical features. The RNA-seq analysis revealed that GABA production is enhanced via the glutamate decarboxylase (GAD) gene (LOC4333932) in the salt-resistant rice cultivar. Exogenous GABA application improves salt-stress tolerance by increasing endogenous ABA and GABA contents, which enhance osmotic adjustment, boost antioxidant defenses, and regulate ion balance. These combined effects help maintain photosynthetic efficiency and support overall plant growth under salt-stressed environments. Additionally, the increased proportion of mesophyll cell periphery covered by chloroplasts (Sc/Sm) indicated enhanced mesophyll conductance. These helped maintain photosynthesis under saline conditions while reducing water consumption. [ABSTRACT FROM AUTHOR]

Climate change-driven drought events are becoming unescapable in an increasing number of areas worldwide. Understanding how plants are able to adapt to these changing environmental conditions is a non-trivial challenge. Physiologically, improving a plant's intrinsic water use efficiency (WUEi) will be essential for plant survival in dry conditions. Physically, plant adaptation and acclimatisation are constrained by a plant's anatomy. In other words, there is a strong link between anatomical structure and physiological function. Former research predominantly focused on using 2D anatomical measurements to approximate 3D structures based on the assumption of ideal shapes, such as spherical spongy mesophyll cells. As a result of increasing progress in 3D imaging technology, the validity of these assumptions is being assessed, and recent research has indicated that these approximations can contain significant errors. We suggest to invert the workflow and use the less common 3D assessments to provide corrections and functions for the more widely available 2D assessments. By combining these 3D and corrected 2D anatomical assessments with physiological measurements of WUEi, our understanding of how a plant's physical adaptation affects its function will increase and greatly improve our ability to assess plant survival. Leaf mesophyll cells are often approximated by capsules and spheres to discuss structure-function relationships. These assumptions allow an easy assessments based on widely available 2D datasets of foliar tissue. However, this is a rough approximation of often irregularly shaped spongy mesophyll cells. We suggest to use more rare 3D assessments to provide corrections and functions to be used in 2D assessments, rather than scaling 2D analysis to 3D structures based on the assumption of ideal shapes. [ABSTRACT FROM AUTHOR]

Summary: Characterizing physiological and anatomical changes that underlie rapid evolution following climatic perturbation can broaden our understanding of how climate change is affecting biodiversity. It can also provide evidence of cryptic adaptation despite stasis at higher levels of biological organization.Here, we compared evolutionary changes in populations of Mimulus cardinalis from historically different climates in the north and south of the species' range following an exceptional drought. We grew seeds produced from predrought ancestral plants alongside peak‐drought descendants in a common glasshouse and exposed them to wet and dry conditions.Before the drought, northern ancestral populations expressed traits contributing to drought escape, while southern ancestral populations expressed drought avoidance. Following the drought, both regions evolved to reduce water loss and maintain photosynthesis in dry treatments (drought avoidance), but via different anatomical alterations in stomata, trichomes, and palisade mesophyll. Additionally, southern populations lost the ability to take advantage of wet conditions.These results reveal rapid evolution towards drought avoidance at an anatomical level following an exceptional drought, but suggest that differences in the mechanisms between regions incur different trade‐offs. This sheds light on the importance of characterizing underlying mechanisms for downstream life‐history and macromorphological traits. [ABSTRACT FROM AUTHOR]

Background. A study of morphological, anatomical and physiological parameters of plants obtained as a result of introgressive breeding is important for assessing the prospects of their further use. Materials and methods. Spring bread wheat plants of cv. ‘Dobrynya’ and a set of introgressive wheat lines with Аegilops columnaris Zhuk. genetic material were studied. The area of flag leaves was measured. Preparations of macerated leaf tissue were used to analyze mesophyll parameters. Spectrophotometric techniques were applied to determine the composition of photosynthetic pigments in the flag leaf. Results and conclusion. A negative effect of substitutions of chromosomes 2A, 5B, 6A and 6D for chromosomes of the U and X genomes on the size of the flag leaf area was disclosed. There were no significant differences in cell shape and size among the lines and in comparison with the recipient cultivar. Changes in the content of pigments in flag leaf laminae have been recorded. Increased content of all groups of pigments was observed in the lines containing substitutions 6A(6G), 6B(6X) and 5B(5X)6A(6X). Substitution 2A(2U) led to a decrease in the level of chlorophyll, the ratio of chlorophyll a to b, and the ratio of chlorophyll to carotenoids.

Plant functional traits are often considered as indicators of plant-environment relationship; however, some plant features can be highly taxonomic-specific. The study of intraspecific trait variation is essential to understand what functional traits are influenced by the phylogeny and what traits are more dependent on environment. We studied six common steppe plant species in two natural vegetation plots near lake Baikal in Southern Siberia different in climate aridity and grazing degree: site 1 - native true grass steppe under lower climate aridity, site 2 - high disturbed sagebrush steppe under higher aridity. Plant functional traits showed different relevance to species and environment. Plant height, leaf thickness (LT), mesophyll cell volume (Vcell), and the chloroplast number per cell had the greatest contribution to differences between species and varied slightly within a species. Photosynthesis (Amax) and transpiration (E) rates, chlorophyll content, mesophyll surface area per leaf area unit (Ames/A) were more dependent on environment than on species. Amax and E decreased in all studied species in more adverse conditions of site 2, however plants differed in mechanisms of these changes. In Stipa krylovii, Artemisia frigida and Potentilla acaulis, most abundant in true steppe (site 1) mesophyll cell sizes, cell and chloroplast number per leaf area decreased in site 2. Other species, Artemisia scoparia, Potentilla bifurca and Allium anisopodium which were more abundant in disturbed steppe (site 2), had larger cells and showed an increase in cell and chloroplast number per leaf area in site 2 and decrease in the photosynthetic capacity of a chloroplast. We concluded that the leaf thickness and cell size belong to species-specific features, whereas Amax, pigment content and integral mesophyll traits as Ames/A are more indicative for plant-environment relationships and their response to growth conditions depend on the ecological strategy of a species.

In the ontogenesis of woody plants in general, and magnolia species in particular, the virginal age is quite long, and therefore is critically important from the point of view of selecting optimal conditions for growing plants. The study was conducted on biennial plants of deciduous magnolias: Magnolia kobus Sarg., M. obovata Thunb., M. denudata Desr. The studied plants were at the beginning of the virginile stage of development. The material for the investigation is selected from plants, which were planted by us in the research area of A. V. Fomin Botanical Garden of the Taras Shevchenko National University of Kyiv. In this study, we used scanning electron and light microscopes to examine the ultrastructure of the surface of leaves of the studied species. The histological characteristics of the leaves of the studied species are similar. They are hypostomatic. Their stomata are of the paracytic type, they are evenly distributed on the abaxial surface of the leaves. The epidermal cells of the studied species of the genus Magnolia have tortuous (cells located on the periphery of the leaf) or straight (cells located on the veins) outlines and rectangular (cells located on the veins) or flattened (cells placed on the periphery of the leaf) projection. The cuticle is relatively thin, located on both the abaxial and adaxial surfaces of the leaves. Epicuticular wax is observed of three types in the studied species: films (M. denudata), crust (M. kobus, M. obovata) and wax granules (M. denudata, M. obovata). The amount of wax and pubescence is greater on the abaxial surface in M. obovata; very weak pubescence and waxy layer is observed only on the abaxial surface of the leaf in M. kobus, weak pubescence is present on both sides in M. denudata. In all species of the genus Magnolia pubescence is simple, formed by hairs that "accompany" the veins. There are two main types of lamina relief in the studied species: reticular (M. obovata, M. denudata (subtype reticular-collicular)) and pitted (M. kobus). The species clearly differ in this feature, so we believe that the type of relief of the lamina can be used as an additional diagnostic feature to distinguish species of the genus Magnolia. Magnolia denudata is characterized by a small number of stomata, while M. obovata and M. kobus are characterized by their average number. The Stomata Index varies from 2.8 in M. denudata to 1.02 in M. kobus. The lamina is the thickest in M. obovata, the thinnest is in M. kobus, but the total thickness of the epidermal tissue as a percentage of the thickness of the leaf is, in descending order: M. denudata (29%), M. kobus (24%), M. obovata (18%). The mesophyll varies from homogeneous-spongy (in M. kobus) to layered (in M. obovata, M. denudata) type. The number of layers of cells that form the mesophyll in all studied species is from 4 to 6. Thus, M. kobus is characterized by the least specialized type of mesophyll. The vascular system in the studied plants is represented by small central and lateral vascular bundles. The ground tissue is present only in the central and large side bundles. In the early stages of ontogenesis the studied plants are typical mesophytes with hypostomatic leaves adapted to exist in sufficiently moist conditions in soil and air. In practical terms, the results of investigation can be used to select optimal conditions for growing plants at the initial stages of ontogenesis.

Abstract Background Leaf variegation is an intriguing phenomenon observed in many plant species. However, questions remain on its mechanisms causing patterns of different colours. In this study, we describe a tomato plant detected in an M2 population of EMS mutagenised seeds, showing variegated leaves with sectors of dark green (DG), medium green (MG), light green (LG) hues, and white (WH). Cells and tissues of these classes, along with wild-type tomato plants, were studied by light, fluorescence, and transmission electron microscopy. We also measured chlorophyll a/b and carotene and quantified the variegation patterns with a machine-learning image analysis tool. We compared the genomes of pooled plants with wild-type-like and mutant phenotypes in a segregating F2 population to reveal candidate genes responsible for the variegation. Results A genetic test demonstrated a recessive nuclear mutation caused the variegated phenotype. Cross-sections displayed distinct anatomy of four-leaf phenotypes, suggesting a stepwise mesophyll degradation. DG sectors showed large spongy layers, MG presented intercellular spaces in palisade layers, and LG displayed deformed palisade cells. Electron photomicrographs of those mesophyll cells demonstrated a gradual breakdown of the chloroplasts. Chlorophyll a/b and carotene were proportionally reduced in the sectors with reduced green pigments, whereas white sectors have hardly any of these pigments. The colour segmentation system based on machine-learning image analysis was able to convert leaf variegation patterns into binary images for quantitative measurements. The bulk segregant analysis of pooled wild-type-like and variegated progeny enabled the identification of SNP and InDels via bioinformatic analysis. The mutation mapping bioinformatic pipeline revealed a region with three candidate genes in chromosome 4, of which the FtsH-like protein precursor (LOC100037730) carries an SNP that we consider the causal variegated phenotype mutation. Phylogenetic analysis shows the candidate is evolutionary closest to the Arabidopsis VAR1. The synonymous mutation created by the SNP generated a miRNA binding site, potentially disrupting the photoprotection mechanism and thylakoid development, resulting in leaf variegation. Conclusion We described the histology, anatomy, physiology, and image analysis of four classes of cell layers and chloroplast degradation in a tomato plant with a variegated phenotype. The genomics and bioinformatics pipeline revealed a VAR1-related FtsH mutant, the first of its kind in tomato variegation phenotypes. The miRNA binding site of the mutated SNP opens the way to future studies on its epigenetic mechanism underlying the variegation.

Summary: Stomatal closure under high VPDL (leaf to air vapour pressure deficit) is a primary means by which plants prevent large excursions in transpiration rate and leaf water potential (Ψleaf) that could lead to tissue damage. Yet, the drivers of this response remain controversial. Changes in Ψleaf appear to drive stomatal VPDL response, but many argue that dynamic changes in soil‐to‐leaf hydraulic conductance (Ks‐l) make an important contribution to this response pathway, even in well‐hydrated soils.Here, we examined whether the regulation of whole plant stomatal conductance (gc) in response to typical changes in daytime VPDL is influenced by dynamic changes in Ks‐l. We use well‐watered plants of two species with contrasting ecological and physiological features: the herbaceous Arabidopsis thaliana (ecotype Columbia‐0) and the dry forest conifer Callitris rhomboidea.The dynamics of Ks‐l and gc were continuously monitored by combining concurrent in situ measurements of Ψleaf using an open optical dendrometer and whole plant transpiration using a balance. Large changes in VPDL were imposed to induce stomatal closure and observe the impact on Ks‐l.In both species, gc was observed to decline substantially as VPDL increased, while Ks‐l remained stable. Our finding suggests that stomatal regulation of transpiration is not contingent on a decrease in Ks‐l. Static Ks‐l provides a much simpler explanation for transpiration control in hydrated plants and enables simplified modelling and new methods for monitoring plant water use in the field. [ABSTRACT FROM AUTHOR]

In the ontogenesis of woody plants in general, and magnolia species in particular, the virginal age is quite long, and therefore is critically important from the point of view of selecting optimal conditions for growing plants. The study was conducted on biennial plants of deciduous magnolias: Magnolia kobus Sarg., M. obovata Thunb., M. denudata Desr. The studied plants were at the beginning of the virginile stage of development. The material for the investigation is selected from plants, which were planted by us in the research area of A.V. Fomin Botanical Garden of the Taras Shevchenko National University of Kyiv. In this study, we used scanning electron and light microscopes to examine the ultrastructure of the surface of leaves of the studied species. The histological characteristics of the leaves of the studied species are similar. They are hypostomatic. Their stomata are of the paracytic type, they are evenly distributed on the abaxial surface of the leaves. The epidermal cells of the studied species of the genus Magnolia have tortuous (cells located on the periphery of the leaf) or straight (cells located on the veins) outlines and rectangular (cells located on the veins) or flattened (cells placed on the periphery of the leaf) projection. The cuticle is relatively thin, located on both the abaxial and adaxial surfaces of the leaves. Epicuticular wax is observed of three types in the studied species: films (M. denudata), crust (M. kobus, M. obovata) and wax granules (M. denudata, M. obovata). The amount of wax and pubescence is greater on the abaxial surface in M. obovata; very weak pubescence and waxy layer is observed only on the abaxial surface of the leaf in M. kobus, weak pubescence is present on both sides in M. denudata. In all species of the genus Magnolia pubescence is simple, formed by hairs that "accompany" the veins. There are two main types of lamina relief in the studied species: reticular (M. obovata, M. denudata (subtype reticular-collicular)) and pitted (M. kobus). The species clearly differ in this feature, so we believe that the type of relief of the lamina can be used as an additional diagnostic feature to distinguish species of the genus Magnolia. Magnolia denudata is characterized by a small number of stomata, while M. obovata and M. kobus are characterized by their average number. The Stomata Index varies from 2.8 in M. denudata to 1.02 in M. kobus. The lamina is the thickest in M. obovata, the thinnest is in M. kobus, but the total thickness of the epidermal tissue as a percentage of the thickness of the leaf is, in descending order: M. denudata (29%), M. kobus(24%), M. obovata (18%). The mesophyll varies from homogeneous-spongy (in M. kobus) to layered (in M. obovata, M. denudata) type. The number of layers of cells that form the mesophyll in all studied species is from 4 to 6. Thus, M. kobus is characterized by the least specialized type of mesophyll. The vascular system in the studied plants is represented by small central and lateral vascular bundles. The ground tissue is present only in the central and large side bundles. In the early stages of ontogenesis the studied plants are typical mesophytes with hypostomatic leaves adapted to exist in sufficiently moist conditions in soil and air. In practical terms, the results of investigation can be used to select optimal conditions for growing plants at the initial stages of ontogenesis. [ABSTRACT FROM AUTHOR]

Summary: In leaves of C4 plants, the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C4 acids in mesophyll (M) cells and subsequent decarboxylation in the bundle sheath (BS). In C4 grasses, proliferation of plasmodesmata between these cell types is thought to increase cell‐to‐cell connectivity to allow efficient metabolite movement. However, it is not known whether C4 dicotyledons also show this enhanced plasmodesmal connectivity and so whether this is a general requirement for C4 photosynthesis is not clear. How M and BS cells in C4 leaves become highly connected is also not known.We investigated these questions using 3D‐ and 2D‐electron microscopy on the C4 dicotyledon Gynandropsis gynandra as well as phylogenetically close C3 relatives.The M–BS interface of C4G. gynandra showed higher plasmodesmal frequency compared with closely related C3 species. Formation of these plasmodesmata was induced by light. Pharmacological agents that perturbed photosynthesis reduced the number of plasmodesmata, but this inhibitory effect could be reversed by the provision of exogenous sucrose.We conclude that enhanced formation of plasmodesmata between M and BS cells is wired to the induction of photosynthesis in C4G. gynandra. [ABSTRACT FROM AUTHOR]

Plant functional traits are often considered as indicators of plant-environment relationship; however, some plant features can be highly taxonomic-specific. The study of intraspecific trait variation is essential to understand what functional traits are influenced by the phylogeny and what traits are more dependent on environment. We studied six common steppe plant species in two natural vegetation plots near lake Baikal in Southern Siberia different in climate aridity and grazing degree: site 1 - native true grass steppe under lower climate aridity, site 2 - high disturbed sagebrush steppe under higher aridity. Plant functional traits showed different relevance to species and environment. Plant height, leaf thickness (LT), mesophyll cell volume (Vcell), and the chloroplast number per cell had the greatest contribution to differences between species and varied slightly within a species. Photosynthesis (Amax) and transpiration (E) rates, chlorophyll content, mesophyll surface area per leaf area unit (Ames/A) were more dependent on environment than on species. Amax and E decreased in all studied species in more adverse conditions of site 2, however plants differed in mechanisms of these changes. In Stipa krylovii, Artemisia frigida and Potentilla acaulis, most abundant in true steppe (site 1) mesophyll cell sizes, cell and chloroplast number per leaf area decreased in site 2. Other species, Artemisia scoparia, Potentilla bifurca and Allium anisopodium which were more abundant in disturbed steppe (site 2), had larger cells and showed an increase in cell and chloroplast number per leaf area in site 2 and decrease in the photosynthetic capacity of a chloroplast. We concluded that the leaf thickness and cell size belong to species-specific features, whereas Amax, pigment content and integral mesophyll traits as Ames/A are more indicative for plant-environment relationships and their response to growth conditions depend on the ecological strategy of a species. [ABSTRACT FROM AUTHOR]

The mesophyll cells of grass leaves, such as rice, are traditionally viewed as displaying a relatively uniform pattern, in contrast to the clear distinctions of palisade and spongy layers in typical eudicot leaves. This quantitative analysis of mesophyll cell size and shape in rice leaves reveals that there is an inherent pattern in which cells in the middle layer of the mesophyll are larger and less circular and have a distinct orientation of their long axis compared to mesophyll cells in other layers. Moreover, this pattern was observed in a range of rice cultivars and species. The significance of this pattern with relation to potential photosynthetic function and the implication of the widespread use of middle layer mesophyll cells as typical of the rice leaf have been investigated and discussed. [ABSTRACT FROM AUTHOR]

This study was conducted in the lath house belonging to the College of Agriculture and Marshlands, the University of Dhi Qar on henna leaves seedlings during the 2020 growing season. The results can be summarized as follows: The results of the study showed that foliar spraying with Dionyfer had a positive, significant effect in improving the anatomical traits of the leaves of the henna plant. The foliar spraying treatment with Dionyfer at a concentration of (300 ml 100 L-1) recorded a significantly excelled in (cuticle thickness, Epidermis thickness, mesophyll cell diameter, vascular bundle diameter and tannin cell diameter) and the lowest averages with a significant difference compared to the control treatment. The interactions had a clear effect on the studied traits, where the spraying interaction (Foliar of Dionyfer 300 ml 100 L -1 + Azomin 350 ml 100 L-1) significantly excelled in giving the highest increase in cuticle thickness, Epidermis thickness, mesophyll cell diameter, vascular bundle diameter, and diameter tannin cells. [ABSTRACT FROM AUTHOR]

A comparative study was conducted on the anatomical structure of the roots and leaves of Ferula tadshikorum, a rare plant species. The study included two groups: virginile plants introduced at the age of 4 years (located in the Tashkent Botanical Garden) and natural individuals aged 12-14 years (found in the Surkhandarya region, Babatag ridge). The main objective was to understand how the plant's anatomy changes with age and its adaptation to different environments. Common characteristics were identified in the leaves of both groups of plants. These included the isolateral palisade type of mesophyll, a rounded triangular shape around the central vein, and the presence of 2-layer elongated palisade tissue on the flattened lateral parts from the adaxial side. Regarding the root structure, significant differences were observed between the natural and introduced plants. In the natural samples, the woody part of the root exhibited groups of libriform cells, which seemed to be influenced by the edaphotype (soil conditions) and age of the plant. These findings suggest that the conductive system of the roots develops differently depending on the age and environment. The introduction of Ferula tadshikorum in the Tashkent Botanical Garden proved to be successful, as evident from the results. The leaves of the introduced plants showed adaptive characteristics, such as a thickened outer wall of the epidermis, collenchyma strands, bast fibers, and the isolateral palisade type of mesophyll. These adaptations are likely to help the plant cope with its new environment. In the roots of both natural and introduced plants, an important adaptive function was observed. The parenchymal cells were filled with starch grains, and there was an abundance of secretory ducts. This suggests that the root acts as an accumulating organ for organic substances, aiding the plant's survival and growth. In conclusion, the study provided valuable insights into the anatomical changes of Ferula tadshikorum at different stages of its life and in different environments. The observed adaptations in the leaves and roots contribute to the plant's ability to thrive in varying conditions.

Abstract The mesophyll cells of grass leaves, such as rice, are traditionally viewed as displaying a relatively uniform pattern, in contrast to the clear distinctions of palisade and spongy layers in typical eudicot leaves. This quantitative analysis of mesophyll cell size and shape in rice leaves reveals that there is an inherent pattern in which cells in the middle layer of the mesophyll are larger and less circular and have a distinct orientation of their long axis compared to mesophyll cells in other layers. Moreover, this pattern was observed in a range of rice cultivars and species. The significance of this pattern with relation to potential photosynthetic function and the implication of the widespread use of middle layer mesophyll cells as typical of the rice leaf have been investigated and discussed.

Changes in the ultrastructural organization of mesophyll cells during low-temperature adaptation (4°C, 7 days) were studied on seedlings of a frost-resistant variety of winter wheat (Triticum aestivum L.). It was found that, under the influence of low hardening temperature, wheat leaf cells increased in size, while the area of the cytoplasm increased and the size of the vacuole decreased. The electron density of the cytoplasm visually increased, and numerous vesicles appeared in it. In addition, the size of chloroplasts, as well as the number of chloroplasts, mitochondria, and peroxisomes per unit area of a cell section, increased. Accumulations of mitochondria and peroxisomes in the form of chains were noted near chloroplasts in the cells of hardened seedlings, and the mitochondria themselves changed their shape from round to elongated or dumbbell-shaped. The low temperature also affected the shape of chloroplasts, which became more rounded from lenticular, and outgrowths (stromules) were found in them. Significant changes under the influence of low temperature occurred in the ultrastructure of chloroplasts: the number and size of plastogbules increased; starch inclusions completely disappeared; the number of grana, the average number of thylakoids per grana, the height and area of the grana, the density of photosynthetic membranes in the chloroplast, and the index of grana stacking (ratio length of appressed membranes to the length of non-appressed membranes) decreased. At the same time, in the process of low-temperature hardening, an increased frost resistance of wheat was formed, which was analyzed by the survival rate of seedlings and the release of electrolytes from leaf tissues after testing freezing. The relationship between the found structural transformations in wheat leaf cells and functional and physiological-biochemical changes occurring in cold-tolerant plants in the process of low-temperature adaptation is shown. It is assumed that the observed ultrastructural reorganization of cells is one of the important components in a complex adaptation program as well as a link necessary for the formation of increased resistance of winter cereals to low temperatures. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the relationship between intercellular spaces and leaf gas exchange and the effect of total intercellular space on the growth of maize and sorghum under water restriction. The experiments were conducted in a greenhouse in a 2 × 3 factorial arrangement (two plant types and three water conditions: field capacity (FC = 100%), 75%FC, and 50%FC) with 10 replicates. The lack of water was a limiting factor for maize because it showed reductions in leaf area, leaf thickness, biomass, and gas exchange parameters, while sorghum remained unchanged, maintaining its water-use efficiency. This maintenance was correlated with the growth of intercellular spaces in sorghum leaves because the increased internal volume led to better CO2 control and prevented excessive water loss under drought stress. In addition, sorghum had more stomata than maize. These characteristics contributed to the drought tolerance of sorghum, while maize could not make the same adjustments. Therefore, changes in intercellular spaces promoted adjustments to avoid water loss and may have improved CO2 diffusion, characteristics that are important for drought-tolerant plants. [ABSTRACT FROM AUTHOR]

Amelanchier Medik. 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. [ABSTRACT FROM AUTHOR]

The leaf anatomy and chloroplast ultrastructure of Nepeta nuda L. plantlets regenerated in vitro from cryopreserved shoot apical meristem and in vitro-micropropagated plantlets were studied comparatively to assess whether cryoprocedure affected leaf morphogenesis. Both postcryo and in vitro plantlets failed to develop a distinguishable palisade layer, making the mesophyll appear homogeneous. Significant damage to the chloroplast envelope and substantial thylakoid ruptures were also observed. We assumed that the specific in vitro conditions more likely affected the structures than the cryotreatment itself. Light and transmission electron microscopy observations were also carried out on newly formed leaves of ex vitro-adapted plants. The examined leaf features were similar to those in the in situ plants -- bifacial leaf lamina, double-layered palisade parenchyma, loosely arranged spongy parenchyma cells, and chloroplasts with intact envelope and evenly distributed throughout the stroma internal membrane system. The obtained histological and ultrastructural results revealed the retained morphogenetic potential of N. nuda plants and proved cryopreservation as a suitable method for long-term storage. [ABSTRACT FROM AUTHOR]

Summary: Little is known about long‐distance mesophyll‐driven signals that regulate stomatal conductance. Soluble and/or vapor‐phase molecules have been proposed. In this study, the involvement of the gaseous signal ethylene in the modulation of stomatal conductance in Arabidopsis thaliana by CO2/abscisic acid (ABA) was examined.We present a diffusion model which indicates that gaseous signaling molecule/s with a shorter/direct diffusion pathway to guard cells are more probable for rapid mesophyll‐dependent stomatal conductance changes. We, therefore, analyzed different Arabidopsis ethylene‐signaling and biosynthesis mutants for their ethylene production and kinetics of stomatal responses to ABA/[CO2]‐shifts.According to our research, higher [CO2] causes Arabidopsis rosettes to produce more ethylene. An ACC‐synthase octuple mutant with reduced ethylene biosynthesis exhibits dysfunctional CO2‐induced stomatal movements. Ethylene‐insensitive receptor (gain‐of‐function), etr1‐1 and etr2‐1, and signaling, ein2‐5 and ein2‐1, mutants showed intact stomatal responses to [CO2]‐shifts, whereas loss‐of‐function ethylene receptor mutants, including etr2‐3;ein4‐4;ers2‐3, etr1‐6;etr2‐3 and etr1‐6, showed markedly accelerated stomatal responses to [CO2]‐shifts. Further investigation revealed a significantly impaired stomatal closure to ABA in the ACC‐synthase octuple mutant and accelerated stomatal responses in the etr1‐6;etr2‐3, and etr1‐6, but not in the etr2‐3;ein4‐4;ers2‐3 mutants.These findings suggest essential functions of ethylene biosynthesis and signaling components in tuning/accelerating stomatal conductance responses to CO2 and ABA. [ABSTRACT FROM AUTHOR]

The difficult forest conditions of the Volgograd region determine the relevance of research in the field of agroforestry. For the selection and use of tree species in plantations during the arrangement of agricultural land, it is necessary to identify the structural and functional features of the leaves, which are reliable indicators of the mechanism of plant adaptation to stress factors. The experiment was set up during June to September 2022 under field and laboratory conditions with the participation of the dendrological collections of the Nizhnevolzhskaya station for tree species breeding, a branch of the Federal Scientific Center for Agroecology of the Russian Academy of Sciences (50°078°N, 45°370°E). The objects of research are shrubs of different geographical origin: Berberis vulgaris L., Berberis heteropoda Schrenk., Ligustrum vulgare L., Cotinus coggygria Scop., Mahonia aquifolium Nutt., Corylus avellana L. and Ribes aureum Pursh. An optical method was used to assess the permeability of the epidermis of native mature leaves of the middle tier of the crown. The dynamics and variation of the content of photosynthetic pigments has been established. In Ligustrum vulgare, Mahonia aquifolium and Cotinus coggygria, a higher content of chlorophylls and a smaller number of palisade mesophyll cells were found than in heliophytes. The species specificity of the structural features of the palisade mesophyll, taking into account the ecological groups of shrubs, was revealed, as well as a positive correlation between the number of cells and the amount of chlorophyll of the palisade mesophyll in Cotinus coggygria (0.87) and Ribes aureum (0.85), Corylus avellana (0.63). The conducted studies allow obtaining new data on the adaptive capabilities of shrubs under the action of stress factors for their selection and further practical application in the field of agroforestry. [ABSTRACT FROM AUTHOR]

The leaf anatomy and chloroplast ultrastructure of Nepeta nuda L. plantlets regenerated in vitro from cryopreserved shoot apical meristem and in vitro-micropropagated plantlets were studied comparatively to assess whether cryoprocedure affected leaf morphogenesis. Both postcryo and in vitro plantlets failed to develop a distinguishable palisade layer, making the mesophyll appear homogeneous. Significant damage to the chloroplast envelope and substantial thylakoid ruptures were also observed. We assumed that the specific in vitro conditions more likely affected the structures than the cryotreatment itself. Light and transmission electron microscopy observations were also carried out on newly formed leaves of ex vitro-adapted plants. The examined leaf features were similar to those in the in situ plants – bifacial leaf lamina, double-layered palisade parenchyma, loosely arranged spongy parenchyma cells, and chloroplasts with intact envelope and evenly distributed throughout the stroma internal membrane system. The obtained histological and ultrastructural results revealed the retained morphogenetic potential of N. nuda plants and proved cryopreservation as a suitable method for long-term storage.

Abstract Background Blue Native polyacrylamide gel electrophoresis (BN PAGE) followed by denaturing PAGE is a widely used, convenient and time efficient method to separate thylakoid complexes and study their composition, abundance, and interactions. Previous analyses unravelled multiple monomeric and dimeric/oligomeric thylakoid complexes but, in certain cases, the separation of complexes was not proper. Particularly, the resolution of super- and megacomplexes, which provides important information on functional interactions, still remained challenging. Results Using a detergent mixture of 1% (w/V) n-dodecyl-β-d-maltoside plus 1% (w/V) digitonin for solubilisation and 4.3–8% gel gradients for separation as methodological improvements in BN PAGE, several large photosystem (PS) I containing bands were detected. According to BN(/BN)/SDS PAGE and mass spectrometry analyses, these PSI bands proved to be PSI-NADH dehydrogenase-like megacomplexes more discernible in maize bundle sheath thylakoids, and PSI complexes with different light-harvesting complex (LHC) complements (PSI-LHCII, PSI-LHCII*) more abundant in mesophyll thylakoids of lincomycin treated maize. For quantitative determination of the complexes and their comparison across taxa and physiological conditions, sample volumes applicable to the gel, correct baseline determination of the densitograms, evaluation methods to resolve complexes running together, calculation of their absolute/relative amounts and distribution among their different forms are proposed. Conclusions Here we report our experience in Blue/Clear-Native polyacrylamide gel electrophoretic separation of thylakoid complexes, their identification, quantitative determination and comparison in different samples. The applied conditions represent a powerful methodology for the analysis of thylakoid mega- and supercomplexes.

Summary: Leaf structure plays an important role in photosynthesis. However, the causal relationship and the quantitative importance of any single structural parameter to the overall photosynthetic performance of a leaf remains open to debate. In this paper, we report on a mechanistic model, eLeaf, which successfully captures rice leaf photosynthetic performance under varying environmental conditions of light and CO2.We developed a 3D reaction‐diffusion model for leaf photosynthesis parameterised using a range of imaging data and biochemical measurements from plants grown under ambient and elevated CO2 and then interrogated the model to quantify the importance of these elements.The model successfully captured leaf‐level photosynthetic performance in rice. Photosynthetic metabolism underpinned the majority of the increased carbon assimilation rate observed under elevated CO2 levels, with a range of structural elements making positive and negative contributions. Mesophyll porosity could be varied without any major outcome on photosynthetic performance, providing a theoretical underpinning for experimental data.eLeaf allows quantitative analysis of the influence of morphological and biochemical properties on leaf photosynthesis. The analysis highlights a degree of leaf structural plasticity with respect to photosynthesis of significance in the context of attempts to improve crop photosynthesis. [ABSTRACT FROM AUTHOR]

The article deals with the problems of induction of the anatomical and morphological structure of plants of different life forms under the conditions of a long-term chronic action of ionising radiation on the territory of the Northern nuclear power plant. Currently, the study and assessment of the radioecological situation on the territory of the former Semipalatinsk nuclear test site, taking into account the ecological state of natural plant and animal populations, is of particular importance. The study of the reaction of living organisms, be it plants or animals, to different doses of chronic ionising radiation makes it possible to assess and diagnose the state of environmental quality, and these organisms themselves can serve as bioindicators of pollution. On the territory of the Semipalatinsk test site, at the experimental site "Balapan", 3 sections with meadow type of soil were studied: polluted section no. 1 - the northwestern shore of Lake Chagan, polluted section no. 2 - the north-eastern shore of Lake Chagan, and control section no. 3. For structural analysis, the study recorded the vegetative organs of plant species with an increased radiation background. It was found that when the EDR (exposure dose rate) of gamma radiation increases and the plant growth is stimulated. In the conditions of radioactive contamination, with an increase in the activity of alpha, beta and gamma radiation, plants response and changes occur in the internal structure of their vegetative organs. Such adaptive features arise under the influence of a complex of environmental factors, including radiation pollution. [ABSTRACT FROM AUTHOR]

AbstractThe paper reports the results of a comparative study of the anatomical structures of the leaf blades of Waldsteinia ternata grown under different light conditions in the Siberian Botanical Garden of Tomsk State University. Waldsteinia ternata is a tertiary nemoral relict from the mountains of southern Siberia, which is found in a limited number of taiga communities due to narrow environmental tolerance to various factors. The species remains poorly studied; comprehensive studies of the anatomical features of its leaves have not been performed on the territory of Russia. Leaves of W. ternata are dorsoventral and amphistomatous with anomocytic type stomata. The plants are classified as mesophytes. The relationship between the development of the anatomical structure of leaves and light conditions was revealed. The W. ternata plants grown in the sun showed an increased number of stomata and epidermal cells, an increased thickness of the leaf and mesophyll, and an increased number of cells of the upper and lower epidermis, that is, the plants exhibited heliophytic features of plant adaptation to good light conditions. At the same time, the vascular tissues of the plants grown in the sun were less developed, which reflected their adaptation to unfavorable water conditions. A number of relative indicators, such as the stomatal index of the lower epidermis, the ratio of the palisade to spongy mesophyll, and the ratio of xylem to phloem, did not change under different growth conditions. Thus, under different light and water conditions, W. ternata acquires helioxeromorphic or sciomesomorphic features.

For the first time, the morphological and anatomical structures of the leaves of different age individuals of the medicinal and rare species F. tadshikorum were studied in Tashkent Botanical Garden. Currently, natural populations of the species are in decline, and for the preservation and production of medicinal raw materials, research on the ex situ development conditions is needed. According to the results, adaptive responses to new habitat conditions in the anatomical structures of the vegetative organs were found. Plants of juvenile and immature development stages retained the the mesophyll's isolateral-palisade type, but differed in other quantitative and qualitative indicators of leaf tissues. Immature plants of the second year of life with more developed leaves showed modifications in the anatomical structure of the leaves, with powerfully developed vascular bundles, mechanical tissue, secretory ducts, as well as the presence of deep fibers both above the phloem of peripheral bundles, and also above the phloem of the central bundles of the petiole.

We aimed to effciently enhance plant Hg(II) tolerance by the transgenic approach utilizing a bacterial mercury transporter MerC, an Arabidopsis mesophyll specific promoter pRBCS1A, and a vacuolar membrane targeting syntaxin AtVAM3/SYP22. We generated two independent homozygous Arabidopsis pRBCS1A-TCV lines expressing mT-Sapphire-MerC-AtVAM3 under the control of pRBCS1A. Quantitative RT-PCR showed that the transgene was expressed specifically in shoots of pRBCS1A-TCV lines. Confocal analyses further demonstrated the leaf mesophyll specific expression of mT-Sapphire-MerC-AtVAM3. Confocal observation of the protoplast derived from the F1 plants of the pRBCS1A-TCV line and the tonoplast marker line p35S-GFP-dTIP showed the tonoplast colocalization of mT-Sapphire-MerC-AtVAM3 and GFP-dTIP. These results clearly demonstrated thatmT-Sapphire-MerC-AtVAM3 expression in Arabidopsis is spatially regulated as designed at the transcript and the membrane traffcking levels. We then examined the Hg(II) tolerance of the pRBCS1A-TCV lines as well as the p35S-driven MerC-AtVAM3 expressing line p35S-CV under the various Hg(II) stress conditions. Short-term (12 d) Hg(II) treatment indicated the enhanced Hg(II) tolerance of both pRBCS1A-TCV and p35S-CV lines. The longer (3 weeks) Hg(II) treatment highlighted the better shoot growth of the transgenic plants compared to the wild-type Col-0 and the pRBCS1A-TCV lines were more tolerant to Hg(II) stress than the p35S-CV line. These results suggest that mesophyll-specific expression of MerC-AtVAM3 is suffcient or even better to enhance the Arabidopsis Hg(II) tolerance. The Hg accumulation in roots and shoots did not di􀀀er between the wild-type Col-0 and the MerC-AtVAM3 expressing plants, suggesting that the boosted Hg(II) tolerance of the transgenic lines would be attributed to vacuolar Hg-sequestration by the tonoplast-localized MerC. Further perspectives of the MerC-based plant engineering are also discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Climate change shown to have a significant impact on the forest ecosystem due to increased and more frequent occurrence of extreme drought. However, in order to successfully adjust to the xeric environments, plants can usually adopt a variety of adaptation strategies. Here, we investigated the morpho-anatomical traits and biomass allocation patterns as acclimation mechanisms in drought conditions. We found that the interrelation between leaf morphological and anatomical traits were equally affected by drought conditions across all species. This suggests that there is no convincing evidence to classify taxa based on drought resistance vs. drought tolerance. However, based on the biomass allocation pattern, we found that P. koraiensis and F. mandshurica had the higher RMF and total PB, but lower LFM, suggesting higher drought tolerance than those of the other species. Therefore, our dataset revealed some easily measurable traits, such as LMF, RMF, and PB, which demonstrated the seedling's ability to cope with drought and which could be utilized to choose drought-tolerant species for reforestation in the temperate forest. Drought is a critical and increasingly common abiotic factor that has impacts on plant structures and functioning and is a challenge for the successful management of forest ecosystems. Here, we test the shifts in leaf morpho-anatomical or hydraulic traits and plant growth above ground caused by drought. A factorial experiment was conducted with two gymnosperms (Larix gmelinii and Pinus koraiensis) and two angiosperms (Fraxinus mandshurica and Tilia amurensis), tree species grown under three varying drought intensities in NE China. Considering all the species studied, the plant height (PH), root collar diameter (RCD), and plant biomass (PB) were significantly decreased by drought. The leaf thickness (LT) increased, while the leaf area (LA) decreased with drought intensity. In the gymnosperms, the mesophyll thickness (MT) increased, and the resin duct decreased, while in the angiosperms the palisade mesophyll thickness (PMT), the spongy mesophyll thickness (SMT), and the abaxial (ABE) and adaxial epidermis (ADE) thickness were increased by drought. The correlation analysis revealed that P. koraiensis and F. mandshurica had the higher RMF and total plant biomass, but the least LMF, suggesting drought tolerance. In contrast, the L. gmelinii had the least RMF and higher LMF, suggesting vulnerability to drought. Similarly, T. amurensis had the higher leaf size, which increased the evaporative demand and depleted the soil water quickly relative to the other species. The interrelation among the morpho-anatomical leaf traits was equally affected by drought across all the studied species, suggesting that there is no clear evidence to differentiate the taxa based on drought resistance vs. drought tolerance. Thus, we have identified some easily measurable traits (i.e., LMF, RMF, and PB) which evidenced the seedling's ability to cope with drought and which therefore could be used as proxies in the selection of drought tolerant species for reforestation in the temperate forest. [ABSTRACT FROM AUTHOR]

Plants have been affected by water stress ever since they settled on dry land. In severe and persisting drought, plant leaves are wilting. However, a documentation at the anatomical level of the minute changes that occur before wilting is challenging. On the other hand, understanding the anatomical alteration in plant leaves with respect to water stress provides a stronger basis to study molecular and submolecular processes through which plants enhance drought tolerance. In this work, we applied an affordable method to visualise mesophyll layers of Arabidopsis thaliana cell lines without preparation steps that would alter the volume of the cells. We rapidly plunge-froze the leaves in liquid nitrogen, cut them while in the N 2 bath, and immediately imaged the mesophyll cross sections in a scanning electron microscope. We applied a reduction of watering from 60 to 40 to 20 mL per day and investigated two time points, 7 and 12 days, respectively. Interestingly, the overall thickness of leaves increased in water stress conditions. Our results showed that the palisade and spongy layers behaved differently under varying watering regimes. Moreover, the results showed that this method can be used to image leaf sections after drought stress without the risk of artefacts or swelling caused by contact to liquids as during chemical fixation., (© 2024 The Author(s). Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.)

Worldwide, there are thousands of Vitis vinifera grape cultivars used for wine production, creating a large morphological, anatomical, physiological and molecular diversity that needs to be further characterised and explored, with a focus on their capacity to withstand biotic and abiotic stresses. This knowledge can then be used to select better adapted genotypes in order to help face the challenges of the expected climate changes in the near future. It will also assist grape growers in choosing the most suitable cultivar(s) for each terroir; with adaptation to drought and heat stresses being a fundamental characteristic. The leaf blade of grapevines is the most exposed organ to abiotic stresses, therefore its study regarding the tolerance to water and heat stress is becoming particularly important, mainly in Mediterranean viticulture. This review focuses on grapevine leaf morphoanatomy - leaf blade form, leaf epidermis characteristics (cuticle, indumentum, pavement cells and stomata) and anatomy of mesophyll - and their adaptation to abiotic stresses. V. vinifera xylem architecture and its adaptation capacity when the grapevine is subjected to water stress is also highlighted since grapevines have been observed to exhibit a large variability in responses to water availability. The hydraulic properties of the petiole, shoot and trunk are also reviewed. Summarising, this paper reviews recent advances related to the adaptation of grapevine leaf morphoanatomical features and hydraulic architecture to abiotic stresses, mainly water and heat stress, induced primarily by an ever-changing global climate.

Summary: Many plant leaves have two layers of photosynthetic tissue: the palisade and spongy mesophyll. Whereas palisade mesophyll consists of tightly packed columnar cells, the structure of spongy mesophyll is not well characterized and often treated as a random assemblage of irregularly shaped cells.Using micro‐computed tomography imaging, topological analysis, and a comparative physiological framework, we examined the structure of the spongy mesophyll in 40 species from 30 genera with laminar leaves and reticulate venation.A spectrum of spongy mesophyll diversity encompassed two dominant phenotypes: first, an ordered, honeycomblike tissue structure that emerged from the spatial coordination of multilobed cells, conforming to the physical principles of Euler's law; and second, a less‐ordered, isotropic network of cells. Phenotypic variation was associated with transitions in cell size, cell packing density, mesophyll surface‐area‐to‐volume ratio, vein density, and maximum photosynthetic rate.These results show that simple principles may govern the organization and scaling of the spongy mesophyll in many plants and demonstrate the presence of structural patterns associated with leaf function. This improved understanding of mesophyll anatomy provides new opportunities for spatially explicit analyses of leaf development, physiology, and biomechanics. [ABSTRACT FROM AUTHOR]

Little is known on how karst plants adapt to highly heterogeneous habitats via adjusting leaf anatomical structures. Phyllostachys glauca McClure is a dominant species that grow across different microhabitats in the limestone mountains of Jiangxi Province, China. We investigated the leaf anatomical structures, plant biomass, soil water content, soil total nitrogen (TN), and soil total phosphorus (TP) from three habitats characterized by different rock exposure, including high rock exposure (HRE), medium rock exposure (MRE) and low rock exposure (LRE), and aimed to discern the relationships between the leaf anatomical plasticity and edaphic factors. The leaves of P. glauca in different habitats showed significant anatomical plasticity in two aspects. First, the leaves adjusted cuticle thickness, papillae length, bulliform cell size and mesophyll thickness to lower water loss and then adapt to the water-deficient habitats (HRE). Second, the leaves enlarged vessels and vascular bundles (first-order and second-order parallel veins) to improve water and nutrient transportation and then enhance plant growth in nitrogen-rich habitats (HRE). Soil water and soil nutrients purely explained the total variation of leaf anatomical traits by 21.7% and 15.7%, respectively, and had a shared proportion of 15.8%. Our results indicated that the leaf anatomical variations in different habitats were associated with both soil water and soil nutrients. Moreover, we found that leaf anatomical structures were more affected by TN than TP. The present study advanced the current understanding of the strategies employed by karst plants to cope with highly heterogeneous habitats via leaf anatomical plasticity. [ABSTRACT FROM AUTHOR]

Iron (Fe) is an essential transition metal. Based on its redox-active nature under biological conditions, various Fe compounds serve as cofactors in redox enzymes. In plants, the photosynthetic machinery has the highest demand for Fe. In consequence, the delivery and incorporation of Fe into cofactors of the photosynthetic apparatus is the focus of Fe metabolism in leaves. Disturbance of foliar Fe homeostasis leads to impaired biosynthesis of chlorophylls and composition of the photosynthetic machinery. Nevertheless, mitochondrial function also has a significant demand for Fe. The proper incorporation of Fe into proteins and cofactors as well as a balanced intracellular Fe status in leaf cells require the ability to sense Fe, but may also rely on indirect signals that report on the physiological processes connected to Fe homeostasis. Although multiple pieces of information have been gained on Fe signalling in roots, the regulation of Fe status in leaves has not yet been clarified in detail. In this review, we give an overview on current knowledge of foliar Fe homeostasis, from the chemical forms to the allocation and sensing of Fe in leaves. [ABSTRACT FROM AUTHOR]

Background: Blue Native polyacrylamide gel electrophoresis (BN PAGE) followed by denaturing PAGE is a widely used, convenient and time efficient method to separate thylakoid complexes and study their composition, abundance, and interactions. Previous analyses unravelled multiple monomeric and dimeric/oligomeric thylakoid complexes but, in certain cases, the separation of complexes was not proper. Particularly, the resolution of super- and megacomplexes, which provides important information on functional interactions, still remained challenging. Results: Using a detergent mixture of 1% (w/V) n-dodecyl-β-d-maltoside plus 1% (w/V) digitonin for solubilisation and 4.3–8% gel gradients for separation as methodological improvements in BN PAGE, several large photosystem (PS) I containing bands were detected. According to BN(/BN)/SDS PAGE and mass spectrometry analyses, these PSI bands proved to be PSI-NADH dehydrogenase-like megacomplexes more discernible in maize bundle sheath thylakoids, and PSI complexes with different light-harvesting complex (LHC) complements (PSI-LHCII, PSI-LHCII*) more abundant in mesophyll thylakoids of lincomycin treated maize. For quantitative determination of the complexes and their comparison across taxa and physiological conditions, sample volumes applicable to the gel, correct baseline determination of the densitograms, evaluation methods to resolve complexes running together, calculation of their absolute/relative amounts and distribution among their different forms are proposed. Conclusions: Here we report our experience in Blue/Clear-Native polyacrylamide gel electrophoretic separation of thylakoid complexes, their identification, quantitative determination and comparison in different samples. The applied conditions represent a powerful methodology for the analysis of thylakoid mega- and supercomplexes. [ABSTRACT FROM AUTHOR]

Plants are exposed to high light intensity, high leaf temperatures and high air-to-leaf water vapor pressure deficit (ALVPD) during the day. These environmental stresses cause stomatal closure and photoinhibitory damage, leading to midday depression of photosynthesis. Chloroplast positioning is essential for the efficient operation of photosynthesis. However, chloroplast behavior before, during, and even after the midday depression of photosynthesis remains unknown. We investigated changes in the intracellular positioning of chloroplasts and photosynthetic traits under a diurnal pattern of light. Sorghum leaves were exposed to a 12-h regime of light mimicking the natural light environment, with constant leaf temperature and ALVPD. Net photosynthetic rate (Pn) showed a diurnal pattern, and midday depression in Pn was observed at 3.8 h of irradiation. Depression in Pn was attributed to stomatal limitation because the decrease in Pn was in accordance with the decrease in stomatal conductance. The maximum efficiency of photosystem II decreased with the increase in light intensity and remained low after 12 h of irradiation. Bundle sheath chloroplasts swelled after 8 h of irradiation, representing the accumulation of starch. Conversely, mesophyll chloroplasts exhibited avoidance response after 4 h of irradiation, and the avoidance position was maintained during the remainder of the daytime. These data suggest that chloroplasts are subject to light stress during and after the midday depression of photosynthesis. The intensity of natural light is excessive for most of the day and this light stress induces chloroplast avoidance response and depression of photosynthesis.

Summary: Vegetative storage proteins (VSPs) are known to serve as nitrogen reserves in many dicot plants but remain undiscovered in grasses, most widely grown group of crops globally. We identified and characterized a VSP in maize and demonstrated that its overexpression improved drought tolerance. Nitrogen supplementation selectively induced a mesophyll lipoxygenase (ZmLOX6), which was targeted to chloroplasts by a novel N‐terminal transit peptide of 62 amino acids. When ectopically expressed under the control of various tissue‐specific promoters, it accumulated to a fivefold higher level upon expression in the mesophyll cells than the wild‐type plants. Constitutive expression or targeted expression specifically to the bundle sheath cells increased its accumulation by less than twofold. The overexpressed ZmLOX6 was remobilized from the leaves like other major proteins during grain development. Evaluated in the field over locations and years, transgenic hybrids overexpressing ZmLOX6 in the mesophyll cells significantly outyielded nontransgenic sibs under managed drought stress imposed at flowering. Additional storage of nitrogen as a VSP in maize leaves ameliorated the effect of drought on grain yield. [ABSTRACT FROM AUTHOR]

SUMMARY: C4 plants partition photosynthesis enzymes between the bundle sheath (BS) and the mesophyll (M) cells for the better delivery of CO2 to RuBisCO and to reduce photorespiration. To better understand how C4 photosynthesis is regulated at the transcriptional level, we performed RNA‐seq, ATAC‐seq, ChIP‐seq and Bisulfite‐seq (BS‐seq) on BS and M cells isolated from maize leaves. By integrating differentially expressed genes with chromatin features, we found that chromatin accessibility coordinates with epigenetic features, especially H3K27me3 modification and CHH methylation, to regulate cell type‐preferentially enriched gene expression. Not only the chromatin‐accessible regions (ACRs) proximal to the genes (pACRs) but also the distal ACRs (dACRs) are determinants of cell type‐preferentially enriched expression. We further identified cell type‐preferentially enriched motifs, e.g. AAAG for BS cells and TGACC/T for M cells, and determined their corresponding transcription factors: DOFs and WRKYs. The complex interaction between cis and trans factors in the preferential expression of C4 genes was also observed. Interestingly, cell type‐preferentially enriched gene expression can be fine‐tuned by the coordination of multiple chromatin features. Such coordination may be critical in ensuring the cell type‐specific function of key C4 genes. Based on the observed cell type‐preferentially enriched expression pattern and coordinated chromatin features, we predicted a set of functionally unknown genes, e.g. Zm00001d042050 and Zm00001d040659, to be potential key C4 genes. Our findings provide deep insight into the architectures associated with C4 gene expression and could serve as a valuable resource to further identify the regulatory mechanisms present in C4 species. Significance Statement: C4 plants have better light‐use efficiency than C3 as they partition photosynthetic enzymes between the bundle sheath and the mesophyll cells to concentrate CO2 around RuBisCO. To understand the regulatory mechanisms behind this process, we investigated chromatin and regulatory differentiation between bundle sheath and mesophyll cells in maize leaves and found that chromatin accessibility coordinates with epigenetic features to fine‐tune cell type‐preferentially enriched gene expression. [ABSTRACT FROM AUTHOR]

With over 100 species indigenous to the Philippines, Hoya R. Br. is the most species-rich genus of Family Apocynaceae in the archipelago. Most species of this genus are epiphytic, and some species are hemiepiphytic or terrestrial. Epiphytic species must have adaptive features that help them survive water shortages caused by not having their roots anchored to the soil. The anatomical features of the leaf blades of six species native to the Philippines [H. espaldoniana Kloppenb., Siar, and Cajano; H. halconensis Schltr. ex Kloppenb.; H. lacunosa Blume; H. lucardenasiana Kloppenb., Siar, and Cajano; H. madulidii Kloppenb.; and H. meliflua (Blanco) Merr.] were investigated, and emphasis was placed on the comparison between the epiphytic and non-epiphytic species. Diversity was observed among the six species. Two species (H. lacunosa and H. meliflua) have multiple upper epidermis consisting of two cell layers, contrary to the other species, which have simple epidermis. The three epiphytic species (H. espaldoniana, H. lacunosa, and H. lucardenasiana) have relatively thick cuticle on both upper and lower sides as well as homogeneous mesophyll with few air spaces. This feature helps prevent excessive water loss, thus, partially explaining how these species survive as epiphytes. On the other hand, the non-epiphytic species (H. halconensis, H. madulidii, and H. meliflua) have thinner cuticle layers. It was also observed that the epiphytic species have homogeneous mesophyll while the non-epiphytic species have heterogeneous mesophyll. Anatomical diversity in the Philippine species of Hoya must have played a role in the diversification of the genus in the archipelago. Examining the anatomy of their roots and stems will help in further understanding this. [ABSTRACT FROM AUTHOR]

Goji berry (Lycium barbarum L.) is widely used as food and medicine in Asian countries and recently had a dramatic gain in popularity on American and European continents. Due to their complex composition and recommendations in traditional Chinese Medicine, goji berry is also one of the most studied species in the recent years. The species grow wild in Romania, being appreciated for its bush density for hedges and fences. Initially, imported L. barbarum varieties were used by goji berry growers for commercial plantations, while in the last year five new varieties were homologated. The morpho-anatomical structure of leaves and flowers of the wild and cultivated goji berry from the Bucharest area was compared, to determine important traits that could be relevant for goji breeders but also for taxonomists. Morphological differences were found regarding the leaves shape, position, and leaves width. The wild L. barbarum has cuticle-covered leaves, highly developed vascular bundles and vascular bundle sheaths were present in the mesophyll. The palisade cells appeared to be very large. These characteristics of the leaf's anatomy are also relevant in the context of biotic stressors, as eriophyid mites, that are one of the most important pests of goji berry shrubs. [ABSTRACT FROM AUTHOR]

Drought stress is one of the major environmental factors that limited crop's growth and production. Cassava known as a tropical crop that is widely distributed in Sub-Saharan Africa. It has a strong drought tolerance and can grow well under tough environmental conditions. Therefore, understanding how cassava responds to drought stress and coordinates survival and accumulation has great theoretical significance for improving crop drought resistance breeding. Many studies on cassava drought responses mainly focused on the leaf and whole seedling. Nevertheless, how the vasculature plays an important role in plant response to water deficiency remains to be fully elucidated. Here, comparative transcriptome analysis was performed on isolated mesophyll tissue and leaf vein vascular tissue of cassava variety KU50 after mild drought treatment to determine the molecular mechanism behind drought resistance in cassava vasculature. Our results showed that KU50 leaves had increased leaf temperature, with characters of rapidly decreased net photosynthetic rate, stomatal conductance, and transpiration rate in leaves, and the intercellular CO2 concentration accumulated under drought stress. Comparative transcriptome profiling revealed that under drought stress, leaf mesophyll tissue mainly stimulated the biosynthesis of amino acids, glutamic acid metabolism, and starch and sucrose metabolism. In particular, the arginine biosynthesis pathway was significantly enhanced to adapt to the water deficiency in leaf mesophyll tissue. However, in vascular tissue, the response to drought mainly involved ion transmembrane transport, hormone signal transduction, and depolymerization of proteasome. Concretely, ABA signaling and proteasome metabolism, which are involved in ubiquitin regulation, were changed under drought stress in KU50 leaf vascular tissue. Our work highlights that the leaf vasculature and mesophyll in cassava have completely different drought response mechanisms. [ABSTRACT FROM AUTHOR]

The responses of stomatal aperture to light intensity and CO2 concentration were studied in both Vicia faba (C3) and Kalanchoë fedtschenkoi (Crassulacean acid metabolism; CAM), in material sampled from both light and dark periods. Direct comparison was made between intact leaf segments, epidermises grafted onto exposed mesophyll, and isolated epidermal peels, including transplantations between species and between diel periods. We reported the stomatal opening in response to darkness in isolated CAM peels from the light period, but not from the dark. Furthermore, we showed that C3 mesophyll has stimulated CAM stomata in transplanted peels to behave as C3 in response to light and CO2. By using peels and mesophyll from plants sampled in the dark and the light period, we provided clear evidence that CAM stomata behaved differently from C3. This might be linked to stored metabolites/ions and signalling pathway components within the guard cells, and/or a mesophyll-derived signal. Overall, our results provided evidence for both the involvement of guard cell metabolism and mesophyll signals in stomatal responses in both C3 and CAM species.

Petals are typified by their conical epidermal cells that play a predominant role for the attraction and interaction with pollinators. However, cell identities in the petal can be very diverse, with different cell types in subdomains of the petal, in different cell layers, and depending on their adaxial-abaxial or proximo-distal position in the petal. In this mini-review, we give an overview of the main cell types that can be found in the petal and describe some of their functions. We review what is known about the genetic basis for the establishment of these cellular identities and their possible relation with petal identity and polarity specifiers expressed earlier during petal development, in an attempt to bridge the gap between organ identity and cell identity in the petal.