Stomatal Complex Research Articles

Leaf cuticle in Brazilian species of Cryptocarya (Lauraceae)

In this study, we analysed leaf cuticle characters of 61 collections from 13 Cryptocarya species recognised in Brazil, of which 11 are considered endemic, and one Costa Rican collection of an unidentified species. Most Cryptocarya species studied have predominantly undulate anticlinal epidermal walls on the adaxial surface, butterfly-shaped stomatal ledges and the stomatal complex protruding and arching over the stomatal slit with a rim resembling two kidneys facing each other (reniform rims). Analysis of a matrix of six leaf cuticle qualitative characters and 19 states, most of them illustrated here for the first time by light and scanning electron microscopy, allowed us to distinguish these taxa. Based on these characters, two Brazilian Cryptocarya species can be easily separated from the others by their predominantly straight anticlinal epidermal walls adaxially and the almost flat surface appearance of the stomatal complex.

Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants

The origin of plants and their colonization of land fundamentally transformed the terrestrial environment. Here we elucidate the basis of this formative episode in Earth history through patterns of lineage, gene and genome evolution. We use new fossil calibrations, a relative clade age calibration (informed by horizontal gene transfer) and new phylogenomic methods for mapping gene family origins. Distinct rooting strategies resolve tracheophytes (vascular plants) and bryophytes (non-vascular plants) as monophyletic sister groups that diverged during the Cambrian, 515–494 million years ago. The embryophyte stem is characterized by a burst of gene innovation, while bryophytes subsequently experienced an equally dramatic episode of reductive genome evolution in which they lost genes associated with the elaboration of vasculature and the stomatal complex. Overall, our analyses reveal that extant tracheophytes and bryophytes are both highly derived from a more complex ancestral land plant. Understanding the origin of land plants requires tracing character evolution across a diversity of modern lineages.

Stomatal Development and Gene Expression in Rice Florets.

Stomata play a fundamental role in modulating the exchange of gases between plants and the atmosphere. These microscopic structures form in high numbers on the leaf epidermis and are also present on flowers. Although leaf stomata are well studied, little attention has been paid to the development or function of floral stomata. Here, we characterize in detail the spatial distribution and development of the floral stomata of the indica rice variety IR64. We show that stomatal complexes are present at low density on specific areas of the lemma, palea and anthers and are morphologically different compared to stomata found on leaves. We reveal that in the bract-like organs, stomatal development follows the same cell lineage transitions as in rice leaves and demonstrate that the overexpression of the stomatal development regulators OsEPFL9-1 and OsEPF1 leads to dramatic changes in stomatal density in rice floral organs, producing lemma with approximately twice as many stomata (OsEPFL9-1_oe) or lemma where stomata are practically absent (OsEPF1_oe). Transcriptomic analysis of developing florets also indicates that the cellular transitions during the development of floral stomata are regulated by the same genetic network used in rice leaves. Finally, although we were unable to detect an impact on plant reproduction linked to changes in the density of floral stomata, we report alterations in global gene expression in lines overexpressing OsEPF1 and discuss how our results reflect on the possible role(s) of floral stomata.

Morphoanatomical study of some species from fabaceae family in Iraq

The current study dealt with comparative morphological and anatomical study of different species of Leguminosae family in Iraq. The study included seven species : Albizia lebbeck Benth. , Alhagi maurorum Medik. , Cassia sopheral Roxb. , Leucaena leucocephala Lam. , Medicago sativa Boiss., Trifolium repens Boiss, Vicia tenuifolia Roth. .The morpho-anatomical study is very important to distinguish between them. Samples of the study were collected from different areas in Iraq during flowering period between 2021-2022. In the present research, cuticular and epidermal anatomical features were described, in addition to the anatomical features of stems, leaves and petiole. Results showed that some of the morphological and anatomical characters of studied parts have good taxonomic value to distinguish between above studied species. Epidermis characters have taxonomic significance , espeically the nature of anticilinal walls and types of stomatal complexes , while dimensions of stem cells and the rates of the length of stomata were limited taxonomic importance . The general shapes of cross – sections of stem showed great taxonomic significance for isolation species , as well as cortex thickness .

Comparative analysis of two Korean irises (Iris ruthenica and I. uniflora, Iridaceae) based on plastome sequencing and micromorphology.

Iris ruthenica Ker Gawl. and I. uniflora Pall. ex Link, which are rare and endangered species in Korea, possess considerable horticultural and medicinal value among Korean irises. However, discrimination of the species is hindered by extensive morphological similarity. Thus, the aim of the present study was to identify discriminating features by comparing the species’ complete plastid genome (i.e., plastome) sequences and micromorphological features, including leaf margins, stomatal complex distribution (hypostomatic vs. amphistomatic leaves), anther stomata density, and tepal epidermal cell patterns. Plastome comparison revealed slightly divergent regions within intergenic spacer regions, and the most variable sequences, which were distributed in non-coding regions, could be used as molecular markers for the discrimination of I. ruthenica and I. uniflora. Phylogenetic analysis of the Iris species revealed that I. ruthenica and I. uniflora formed a well-supported clade. The comparison of plastomes and micromorphological features performed in this study provides useful information for elucidating taxonomic, phylogenetic, and evolutionary relationships in Iridaceae. Further studies, including those based on molecular cytogenetic approaches using species specific markers, will offer insights into species delimitation of the two closely related Iris species.

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 24.8μm (I. rossii) to 56.0μm (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.

The plasma membrane aquaporin ZmPIP2;5 enhances the sensitivity of stomatal closure to water deficit.

Increasing stomatal movement is beneficial to improve plant water use efficiency and drought resilience. Contradictory results indicate that aquaporins might regulate stomatal movement. Here, we tested whether the maize plasma membrane PIP2;5 aquaporin affects stomatal closure under water deficit, abscisic acid (ABA)or vapour pressure deficit (VPD) treatment in intact plants, detached leavesor peeled epidermis. Transpiration, stomatal conductance (gs ) and apertureand reactive oxygen species (ROS) in stomatal complexes were studied in maize lines with increased or knocked down (KD) PIP2;5 gene expression. In well-watered conditions, the PIP2;5 overexpressing (OE) plants transpired more than wild types (WTs), while no significant difference in transpiration was observed between pip2;5 KD and WT. Upon mild water deficit or low ABA concentration treatments, transpiration and gs decreased more in PIP2;5 OElines and less in pip2;5 KD lines, in comparison with WTs. In the detached epidermis, ABA treatment induced faster stomatal closing in PIP2;5 OE lines compared to WTs, while pip2;5 KD stomata were ABA insensitive. These phenotypes were associated with guard cell ROS accumulation. Additionally, PIP2;5 is involved in the transpiration decrease observed under high VPD. These data indicate that maize PIP2;5 is a key actor increasing the sensitivity of stomatal closure to water deficit.

Leaf epidermal and petiole anatomical features as taxonomic characters in some Vernonia species in Nigeria

Foliar and petiole micro-morphological characteristics of some members of the genus Vernonia namely; Vernonia amygdalina Del. (bitter variety), Vernonia amygdalina Del. (non-bitter variety), Vernonia cinerea (L) Less., Vernonia galamensis (Cass.) Less., and Vernonia adoensis Sch. Bip. in Jos, Nigeria was investigated to provide additional micro-morphological characters to support existing taxonomic information regarding the species. Epidermal peels of fresh leaves were made and transverse sections of petioles were cut using a rotary microtome. Staining was done using Safranin and slides observed using a light microscope. Quantitative characters were measured and subjected to Duncan Multiple Range Test. Stomatal distribution was amphistomatic except for V. galamensis and V. cinerea with hypostomatic distribution; stomata type was mostly anomocytic except V. galamensis with paracytic stomata. Stomata index varied among taxa with V. adoensis and V. amygdalina (bitter variety) having the highest (10.84 %) and lowest (0.67%) respectively. Anticlinal cell wall patterns were straight to slightly undulate while wavy anticlinal cell wall pattern was diagnostic to V. cinerea. Trichome types observed were glandular and multicellular uniseriate with highest and lowest trichome indices recorded in V. adoensis (2.80%) and V. galamensis (0.02%) respectively. Petiole outline was convex to concave, epidermis was uniseriate, trichome multicellular uniseriate and vascular bundles bicollateral. Variations observed in the stomatal complex, epidermal cell complex, petiole outline, petiole vasculature type, trichome and stomata indices could be employed for species identification and delimitation.

STRUCTURAL MODIFICATIONS IN BLACK PINE NEEDLES AS POTENTIAL BIOMARKERS OF ENVIRONMENTAL POLLUTION

This study presents micro-morphological characters and anatomical modifications detected in black pine needles collected from urban polluted areas in order to propose new biomarkers useful in air pollution biomonitoring. The plant samples were collected during the July 2021 from 10 different polluted sites from Bucharest and analyzed using light and scanning electron microscopy. When compared with the samples collected from less polluted sites, needle micromorphology and structure have showed significant alterations such as injured stomatal complex, eroded forms of tubular wax type and complete degradation of wax crystalline structure, raised peristomatal areas, early wax plugs perforations and abnormal epidermal teeth. The loads of heavy metal of samples were assessed by X-ray fluorescence spectrometry and the results showed a positive correlation between structural alteration incidence and needle heavy metal surface depositions.

Eco-evo-devo of plant stomata: the diversity of stomatal development and its evolution

Stomata have long been playing an important role since plant ancestor invaded the land. The stomatal guard cells are produced by a simple developmental process, in which the meristemoids, stomatal-lineage stem cells, undergo asymmetric divisions prior to differentiation. Since the 2000s, stomatal development has been lively studied in the model plant Arabidopsis, which led to the elucidation of its molecular basis, particularly the pivotal role of three stomatal key transcription factors, namely SPEECHLESS, MUTE, and FAMA. On the other hand, when looking at non-model plants, people will notice that the developmental process of stomata is considerably diverged among species. While such diversity in stomatal development has been well documented by plant morphologists from early times, its molecular basis and ecological significance remained poorly known. In recent years, however, accumulating knowledge in model plants and the development of research technologies applicable to non-model plants have made stomata accessible to studies of ecological evolutionary developmental biology (eco-evo-devo). This review provides an overview of the diversity in the form and development of stomata in land plants, introduces the eco-evo-devo research applied on stomata, such as (1) the research on the unique stomatal complex in grass species, and (2) our recent work on the intrageneric diversity of stomatal development in Callitriche (Plantaginaceae), and discusses the prospects of this emerging field.

Investigating the Phenotypic Plasticity of the Invasive Weed Trianthema portulacastrum L.

Phenotypic plasticity is frequently highlighted as a key factor in plant invasiveness, as it enables invasive species to adapt to diverse, complicated habitats. Trianthema portulacastrum is one of the most common aggressive species that threaten different crops around the world. Phenotypic plasticity in T. portulacastrum was investigated by comparing variation in germination, vegetative macromorphology, photosynthetic pigments, stomatal complexes, and seed micromorphological traits of 35 samples collected from 35 different localities. One-way cluster analysis and principal component analysis (PCA) were used to classify samples into homogeneous groups based on the measured traits. Pairwise statistical comparisons were conducted between the three resulting groups. The phenotypic plasticity index (PI) was calculated and compared among different groups of characters. Results showed that photosynthetic pigments and macromorphological characteristics had the highest PI, followed by seed micromorphology, and then stomatal complex traits, while germination parameters showed the lowest PI. We propose that soil moisture, salinity, and temperature are the most determinative and explanative variables of the variation between the three classified groups. We strongly believe that the phenotypic plasticity of T. portulacastrum will support species abundance and spread even under expected changes in climatic conditions, in contrast to the vulnerable traditional crops.

Microscopical observations of crystal deposits on the epidermis of leaves of Agave potatorum

Calcium oxalate crystals were observed on the leaf epidermis of Agave potatorum surrounding the stomatal complex. Their morphology corresponded to the styloid type, and the chemical composition using EDS spectrum confirms calcium oxalate. A significantly higher abundance of crystals was observed on the adaxial leaf side in comparison with the abaxial side (p < 0.05). Crystals grew up in bundles in a range of 6–8 elements into idioblasts. A light microscope reveals that these crystals reflect part of the incident light. Cuticle from the abaxial leaf side was thicker and had a special structure formed by six papillae surrounding a larger central papilla, which was observed as star-like. This could be related to the evolutionary adaptation of this Agave species to drought stress conditions.

Micromorphological Characteristics of Fruit Surfaces of Some Usable Species of the Genus Valeriana (Valerianaceae) Among Ukrainian Flora

Abstract The micromorphological features of the fruit surfaces of nine species of Ukrainian flora, namely Valeriana tuberosa L., Valeriana tripteris L., Valeriana rossica P. Smirn., Valeriana stolonifera Czern., Valeriana grossheimii Worosch, Valeriana sambucifolia Mikan fil., Valeriana officinalis L. s. str., Valeriana wolgensis Kazak. [ Valeriana officinalis var. nitida (Kreyer) Rostanski], and Valeriana simplicifolia (Rchb.) Kabath, were examined. Depending on the presence and localization of pubescence on the surface of the fruit, three groups of species were distinguished: those with glabrous fruits, those with fruits pubescent only on the adaxial side, and those with fruits pubescent on both sides. Scanning electron microscopy revealed the additional characteristics of the fruits (microsculpture of the fruit surface, shape of cuticular formations on the surface of the outer periclinal walls of epidermal cells and on the surface of hairs, and structure of the stomatal complex), which were useful for the identification of the species. At the supraspecific level, the revealed features of the fruit surfaces somewhat overlapped and could be used to identify series and sections only as additional features. Based on the studied samples from herbarium material (KW), V. officinalis var. nitida was considered synonymous with V. wolgensis since there were no micromorphological differences between their fruits. The detailed micromorphological characteristics of the fruit surfaces of all the studied species can be used for further comparative morphological investigations of different aerial parts to identify stable features independent of geographic and ecological conditions.

Palyno-anatomical characters and their systematic significance in the family Apiaceae from Chitral, eastern Hindu Kush, Pakistan.

The present study was performed to provide a detailed explanation of leaf epidermal anatomy and pollen micromorphological features of selected species of family Apiaceae from Chitral, eastern Hindu Kush region as the basis of forthcoming studies. In the present article pollen morphology of eight species and foliar epidermal of seven species of family Apiaceae have been examined through microscopic techniques. In results two types of pollen prolate (five species) and perprolate (three species) with three colpi have been recorded. The exine ornamentation was found to be regulate, striate, and cerebroid. Largest pollen was found in Heracleum leucocarpum with the polar diameter of 43.25 μm and equatorial diameter of 21.6μm. Smallest pollen was observed in Elaeosticta chitralica with the polar diameter of 18.4μm. The P/E ratio varied from 1.59 to 2.16. Regarding to foliar epidermal anatomy, three types of epidermal cells including rectangular, irregular, and polygonal with variation in anticlinal wall pattern were determined. In the selected species three kinds of stomata comprising anisocytic, anomocytic, and paracytic type were reported in the current research. The size of epidermal cells ranged from 106 × 42.50 μm in Bupleurum falcatum subsp. cernuum and 77.25 × 26.35 μm in Prangos pabularia in adaxial surface. Largest stomatal complex was found in Prangos pabularia both in adaxial 33.55 × 20.05 μm and abaxial 50.25 × 39.40 μm. All the observed quantitative and qualitative features of the species were proved to be useful in the delimitation of species at generic and species level.

The use of microstructures in the authentication of powdered drug plants

Adulteration and substitution of herbal drugs are trending issues in the herbal industry, posing a serious threat to commercial natural product research. The anatomy of powdered and non-powdered samples of plant species were compared to ascertain their similarities. Air dried powdered leaf samples and unground or intact leaves, flowers and barks of eight medicinal plant species, namely, Vernonia amygdalina, Ocimum gratisimum, Trichilia monadelpha, Bridelia ferruginea, Lophira alata., Alstonia boonei, Dialium guineense and Enantia chlorantha were studied anatomically with the aim of identifying the original plant parts used in the preparation of the drugs. The microscopic studies of leaves of V. amygdalina and O. gratisimum revealed the presence of similar stomatal complex types and trichomes in both ground and unground samples. The anatomy and palynology of T. monadelpha flower revealed that bipolar, inaperturate, monopolar, monoporate, tetracolporate and triporate pollens are present in both the ground and unground samples. The microscopic study of the barks of L. alata, B. ferruginea, A. boonei, D. guineense and E. chlorantha also showed similar cells in ground and unground samples. The anatomical features are, therefore, elucidated for authentication of the originality of the medicinal plants studied.

Two galacturonosyltransferases function in plant growth, stomatal development, and dynamics.

The mechanical properties of guard cell (GC) walls are important for stomatal development and stomatal response to external stimuli. However, the molecular mechanisms of pectin synthesis and pectin composition controlling stomatal development and dynamics remain poorly explored. Here, we characterized the role of two Arabidopsis (Arabidopsis thaliana) galacturonosyltransferases, GAUT10 and GAUT11, in plant growth, stomatal development, and stomatal dynamics. GAUT10 and GAUT11 double mutations reduced pectin synthesis and promoted homogalacturonan (HG) demethylesterification and demethylesterified HG degradation, resulting in larger stomatal complexes and smaller pore areas, increased stomatal dynamics, and enhanced drought tolerance of plants. In contrast, increased GAUT10 or GAUT11 expression impaired stomatal dynamics and drought sensitivity. Genetic interaction analyses together with immunolabeling analyses suggest that the methylesterified HG level is important in stomatal dynamics, and pectin abundance with the demethylesterified HG level controls stomatal dimension and stomatal size. Our results provide insight into the molecular mechanism of GC wall properties in stomatal dynamics, and highlight the role of GAUT10 and GAUT11 in stomatal dimension and dynamics through modulation of pectin biosynthesis and distribution in GC walls.

OsBC1L1 and OsBC1L8 function in stomatal development in rice

Stomata that are bordered by pairs of guard cells are specialized for regulating gas exchange and transpiration in plants. The stomatal morphology of grass is unique, characterized by two dumbbell-shaped guard cells flanked by two lateral subsidiary cells. This morphology and developmental pattern enable grass stomata to respond to environmental signals efficiently. In this study, we demonstrated that knockout either OsBC1L1 or OsBC1L8, two close homologs of OsBC1L family causes no discernible defects in rice stomatal development, however, the double knockout mutant osbc1l1 osbc1l8 exhibits excess stomatal production and stomatal clustering. OsBC1L1 overexpression also causes abnormal stomatal patterning in rice. Moreover, osbc1l1 osbc1l8 has many defective stomata complexes with only one subsidiary cell. The expression of OsSPCH2 and OsFAMA, two genes key to stomatal development is both down-regulated in osbc1l1 osbc1l8. In contrast, overexpressing OsBC1L1 suppresses only the expression of OsSPCH2. Both OsBC1L1 and OsBC1L8 could be detected to be localized at the cell plate and plasma membrane during cell division of guard mother cells and subsidiary mother cells. Taken together, these results suggest that OsBC1L1 and OsBC1L8 play essential roles in the development of rice stomatal complex likely through their involvement in cell reproduction.

Conditional stomatal closure in a fern shares molecular features with flowering plant active stomatal responses

Stomata evolved as plants transitioned from water to land, enabling carbon dioxide uptake and water loss to be controlled. In flowering plants, the most recently divergent land plant lineage, stomatal pores actively close in response to drought. In this response, the phytohormone abscisic acid (ABA) triggers signaling cascades that lead to ion and water loss in the guard cells of the stomatal complex, causing a reduction in turgor and pore closure. Whether this stimulus-response coupling pathway acts in other major land plant lineages is unclear, with some investigations reporting that stomatal closure involves ABA but others concluding that closure is passive. Here, we show that in the model fern Ceratopteris richardii active stomatal closure is conditional on sensitization by pre-exposure to either low humidity or exogenous ABA and is promoted by ABA. RNA-seq analysis and de novo transcriptome assembly reconstructed the protein-coding complement of the C.richardii genome, with coverage comparable to other plant models, enabling transcriptional signatures of stomatal sensitization and closure to be inferred. In both cases, changes in abundance of homologs of ABA, Ca2+, and ROS-related signaling components were observed, suggesting that the closure-response pathway is conserved in ferns and flowering plants. These signatures further suggested that sensitization is achieved by lowering the threshold required for a subsequent closure-inducing signal to trigger a response. We conclude that the canonical signaling network for active stomatal closure functioned in at least a rudimentary form in the stomata of the last common ancestor of ferns and flowering plants.

Tetraploidization Increases the Contents of Functional Metabolites in Cnidium officinale

Cnidium officinale is an important medicinal crop grown in Asia for its pharmacological properties. In this study, tetraploid breeding was conducted to increases the content of medicinal compound and tolerance to the environmental conditions using in vitro shoot culture of C. officinale. For this, we generated tetraploid C. officinale plants using oryzalin, a chromosome doubling agent, and compared the morphological traits, cytological characteristics, and heat stress-responsive gene expression levels between tetraploid and diploid genotypes. Chromosome doubling efficiency was the highest in plantlets treated with 4.0 mg∙L−1 oryzalin for 2 days. Compared with diploids, the plant height of tetraploids was reduced, while the petiole diameter was increased by approximately 39%. The dry matter of tetraploid leaves was significantly higher than that of diploid leaves. Compared with diploids, tetraploids showed higher chloroplast number and stomatal complex size but lower chlorophyll and carotenoid contents. The phenolic content of tetraploid plantlets was significantly higher than that of diploid plantlets. Contents of naringin as well as salicylic acid and gentisic acid, which are strong antioxidant compounds, were dramatically increased upon tetraploidization. Interestingly, liquid chromatography–mass spectrometry (LC–MS) analyses revealed increased levels of senkyunolide F and phthalide in tetraploid roots but not in tetraploid or diploid leaves.

Optical topometry and machine learning to rapidly phenotype stomatal patterning traits for maize QTL mapping

Stomata are adjustable pores on leaf surfaces that regulate the tradeoff of CO2 uptake with water vapor loss, thus having critical roles in controlling photosynthetic carbon gain and plant water use. The lack of easy, rapid methods for phenotyping epidermal cell traits have limited discoveries about the genetic basis of stomatal patterning. A high-throughput epidermal cell phenotyping pipeline is presented here and used for quantitative trait loci (QTL) mapping in field-grown maize (Zea mays). The locations and sizes of stomatal complexes and pavement cells on images acquired by an optical topometer from mature leaves were automatically determined. Computer estimated stomatal complex density (SCD; R2 = 0.97) and stomatal complex area (SCA; R2 = 0.71) were strongly correlated with human measurements. Leaf gas exchange traits were genetically correlated with the dimensions and proportions of stomatal complexes (rg = 0.39–0.71) but did not correlate with SCD. Heritability of epidermal traits was moderate to high (h2 = 0.42–0.82) across two field seasons. Thirty-six QTL were consistently identified for a given trait in both years. Twenty-four clusters of overlapping QTL for multiple traits were identified, with univariate versus multivariate single marker analysis providing evidence consistent with pleiotropy in multiple cases. Putative orthologs of genes known to regulate stomatal patterning in Arabidopsis (Arabidopsis thaliana) were located within some, but not all, of these regions. This study demonstrates how discovery of the genetic basis for stomatal patterning can be accelerated in maize, a C4 model species where these processes are poorly understood.