Stomata Cells Research Articles

The anatomy, micromorphology, and essential oils of the Turkish endemic and endangered species Alchemilla orduensis

In this study, the anatomical and micromorphological characteristics of the vegetative organs and the essential oil constituents of the aerial and underground parts of the local and endangered endemic species A. orduensis Pawł. were evaluated. For anatomical study, sections of root, rhizome, stem, leaves and petiole were excised and stained with safranin/fast green mixture. Leaf and petiole structures were examined micromorphologically. Essential oil contents were determined by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) analysis. The results showed that rectangular meristematic cells were present in the root. The leaf is of the bifacial and amphistomatic type. Stomata cells are of the anomocytic type. The stomatal index for the upper surface of the leaves is 0.04, while the stomatal index for the lower surface is 0.17. Druse crystals were found in the rhizome, stem and leaves. Among the various compounds identified, the most abundant groups in the aboveground parts are alcohols (39.81%) and ketones (14.99%) with 1-Octen-3-ol, 1-octan-3-one and borane- methyl sulfide complex as the main compounds. Terpenes (23.44%) and alcohols (11.82%), in which myrtenolis was the main compound, were most abundant in the underground parts.

Modulation of abscisic acid signaling via endosomal TOL proteins.

The phytohormone abscisic acid (ABA) functions in the control of plant stress responses, particularly in drought stress. A significant mechanism in attenuating and terminating ABA signals involves regulated protein turnover, with certain ABA receptors, despite their main presence in the cytosol and nucleus, subjected to vacuolar degradation via the Endosomal Sorting Complex Required for Transport (ESCRT) machinery. Collectively our findings show that discrete TOM1-LIKE (TOL) proteins, which are functional ESCRT-0 complex substitutes in plants, affect the trafficking for degradation of core components of the ABA signaling and transport machinery. TOL2,3,5 and 6 modulate ABA signaling where they function additively in degradation of ubiquitinated ABA receptors and transporters. TOLs colocalize with their cargo in different endocytic compartments in the root epidermis and in guard cells of stomata, where they potentially function in ABA-controlled stomatal aperture. Although the tol2/3/5/6 quadruple mutant plant line is significantly more drought-tolerant and has a higher ABA sensitivity than control plant lines, it has no obvious growth or development phenotype under standard conditions, making the TOL genes ideal candidates for engineering to improved plant performance.

Seasonal variation of stomatal characteristics of Ficus species grown in Zaria, North Western Nigeria

Foliar stomatal characteristics are among the commonly used characters for the identificationand delimitation of taxa. This study was carried out to determine variations in stomatalcharacteristics of some members in the Genus Ficus grown in Zaria, part of the Sudan Savanna zone of Nigeria. Eight different Ficus species grown in Zaria were used for the study. Microscopic observations of foliar stomatal characteristics were carried out following standard established protocols during both the dry and rainy seasons. Stomatal preparations were obtained using matured leaves by treating each leaf with sodium hypochlorite to clear the chlorophyll contents. Measurements of stomatal characters were made with the aid of an ocular micrometer and stage micrometer. Photomicrographs were taken. The data obtainedwere subjected to analysis of variance (ANOVA) with Duncan’s New Multiple Range Test used to separate significant means at 5 % level. The result obtained revealed significant difference (P≤0.05) in the stomatal characteristics of the Ficus species with season. Anomocytic stomata was detected in all the species. There were variations with abaxial stomata cell length ranging from 23.32-50.24 μm in dry season and in the rainy season, the abaxial cell length ranged between 26.78-46.43 μm. Also, the stomatal index in the dry season ranged from 1.30% to 27.16% while in the rainy season, it ranged from 15.29 % to 23.19 %.

A charged existence: A century of transmembrane ion transport in plants.

If the past century marked the birth of membrane transport as a focus for research in plants, the past 50 years has seen the field mature from arcane interest to a central pillar of plant physiology. Ion transport across plant membranes accounts for roughly 30% of the metabolic energy consumed by a plant cell, and it underpins virtually every aspect of plant biology, from mineral nutrition, cell expansion, and development to auxin polarity, fertilization, plant pathogen defense, and senescence. The means to quantify ion flux through individual transporters, even single channel proteins, became widely available as voltage clamp methods expanded from giant algal cells to the fungus Neurospora crassa in the 1970s and the cells of angiosperms in the 1980s. Here, I touch briefly on some key aspects of the development of modern electrophysiology with a focus on the guard cells of stomata, now without dispute the premier plant cell model for ion transport and its regulation. Guard cells have proven to be a crucible for many technical and conceptual developments that have since emerged into the mainstream of plant science. Their study continues to provide fundamental insights and carries much importance for the global challenges that face us today.

An Accurate Phenotypic Study of The Foliar Epidermis for Some Species of Silene L. From Caryophyllaceae Family in Iraq

In the present research work, detailed micromorphological features study (investigated for foliar epidermal anatomy) for five species of the genus Silene L., belonging to the family Caryophyllaceae. One of the essential anatomical characteristics of the leaf in this genus observed two basic stomata types on both adaxial and abaxial epidermis, diacytic and anisocytic, from five species, three species have distinguished a diacytic type, exception two species S. chlorifolia and S. longipetala appeared to have both a diacytic and anisocytic, also has astrocytic crystals within epidermal cells. Also in the present work, 3 species out of 5 have trichomes on their both surfaces, observed having them multicellular uniseriate. All the taxa were the distinguished shape of the guard cells as reniform-like from a full short reniform in all species. So the general shape of ordinary epidermal cells, anticlinal wall of the epidermal cells, type of stomata cells, collar shape marginal of guard cells, and trichomes. Images enhanced the micromorphological characteristics under study. Information on the locations and dates of the collection was also confirmed. This study revealed that the micromorphological features of the family are taxonomically signi?cant in the accurate identi?cation of species.

Ploidy Determination in Banana Hybrids through Stomatal Studies and Chloroplast Count

Stomata are probably a viable taxonomy distinguishing feature. The study of stomata characteristics of synthetic banana hybrids and their parentage has been carried out. Ploidy determination is essential in banana breeding programs to understand the genetic makeup of hybrid plants. The purpose of this study was to determine the ploidy level of hybrids in contrast with the properties of plant stomata in synthetic banana hybrids with those of their parent plants. Therefore, by examining components such as stomata location, number of epidermal cells, number of stomata cells, stomata length, width, area, intensity and density, as well as chloroplast count, it is possible to compare and contrast the traits of synthetic banana hybrids and their parentage which have different genomes. The entire mount approach was used to make an incision for the purpose of observing stomata. By characterising the stomata traits of the synthetic hybrids and their parentage, the results were then descriptively and qualitatively assessed. Three different locations on the abaxial of the leaf were taken for the determination. The samples were collected from close to the petiole (R1), middle (R2), and distal end (R3), stomata were observed using the replica method. Results showed that more number of stomata was observed in R2of leaf abaxial. The chloroplast count in pairs of stomatal guard cells from the accessions was also measured. The chloroplast density was determined in pairs of stomatal guard cells from the accessions. Based on morphological descriptions, it was observed that 16.66% of the accessions were diploid, 50% were triploid and 33.33% were tetraploid. When considering the chloroplast count, the accessions were categorized into groups, certain accessions classified as tetraploids, others as triploids, and diploids.

Phenotypic variability of epidermis structure and silicon inclusions in the leaves of Quercus robur in the Feofaniya Park

The micromorphology of the leaf epidermis, localization, and silicon content in the epidermal cells of Quercus robur leaves growing in the shade and under direct sunlight in the Feofaniya Park (Kyiv, Ukraine) were studied using scanning electron microscopy and laser confocal microscopy. Silicon inclusions were found in the anticlinal and periclinal walls of adaxial epidermal cells, trichomes, guard cells of stomata, and walls of regular epidermal cells on the abaxial leaf surface, the amount of which varied according to the conditions of growth. Natural shading and the intensity of solar irradiation were found affecting the size of leaf blades, the ultrastructure of the leaf epidermis, and changes in the silicon content of oak leaves. Studies have shown that the anticlinal walls of the adaxial epidermis and the trichomes and stomata of the abaxial epidermis of leaves are the main silicon accumulators. The findings suggest that changes in leaf microstructure and silicon content contribute to maintaining optimal water balance in plants and can be regarded as signs of phenotypic plasticity in plants and an adaptive marker depending on the sunlight conditions of oak growth.

Intercellular Communication during Stomatal Development with a Focus on the Role of Symplastic Connection.

Stomata are microscopic pores on the plant epidermis that serve as a major passage for the gas and water exchange between a plant and the atmosphere. The formation of stomata requires a series of cell division and cell-fate transitions and some key regulators including transcription factors and peptides. Monocots have different stomatal patterning and a specific subsidiary cell formation process compared with dicots. Cell-to-cell symplastic trafficking mediated by plasmodesmata (PD) allows molecules including proteins, RNAs and hormones to function in neighboring cells by moving through the channels. During stomatal developmental process, the intercellular communication between stomata complex and adjacent epidermal cells are finely controlled at different stages. Thus, the stomata cells are isolated or connected with others to facilitate their formation or movement. In the review, we summarize the main regulation mechanism underlying stomata development in both dicots and monocots and especially the specific regulation of subsidiary cell formation in monocots. We aim to highlight the important role of symplastic connection modulation during stomata development, including the status of PD presence at different cell-cell interfaces and the function of relevant mobile factors in both dicots and monocots.

Frequency and spectrum of M2 mutants and genetic variability in cyto-agronomic characteristics of fenugreek induced by caffeine and sodium azide.

Trigonella foenum graecum L. (Fenugreek) is a valuable medicinal plant cultivated for decades for its therapeutic characteristics. Still no pronounced improvement concerning wild form was accomplished as it is a self-pollinating crop. Induced mutagenesis is encouraged as a remarkable tool on this plant to circumvent the genetic bottleneck of cultivated germplasms. As a result, novel allelomorphic combinations for short-term agronomic attributes were developed. Fenugreek cultivar Pusa Early Bunching, selected for the present experiment, was mutagenized with five doses (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) of caffeine and sodium azide (SA) to evaluate its impact on the qualitative and quantitative traits of M1 and M2 generation conducted in a Complete Randomized Block Design (CRBD), replicated five times during 2019-2020 and 2020-2021, respectively. The frequency of induced phenotypic variations was assessed in M2 progenies, resulting in the identification and isolation of a broad spectrum of mutants with altered phenotypes. Mutagenic effectiveness and efficiency were found to be maximum at lower concentrations of the mutagen treatments and highest in SA, followed by caffeine. Various morphological mutants with modified characters were observed at different concentrations in M2 generation. The spectrum of mutations was wider in SA than in caffeine, as caffeine produced 51 while SA produced 54 individual mutants under seven major categories. The maximum frequency of morphological mutants was associated with leaf, followed by plant size, plant growth habit, pod, seed size, seed shape, and seed color. Morphological and structural variations in the guard cells of stomata and seeds were observed through scanning electron microscopy. The variations created in the economically important traits may enrich the genetic diversity of this plant species. Moreover, these morphological mutants may serve as a source of elite genes in further breeding programs of fenugreek.

Observation of the development of leaf vein and stomata and identification candidate transcription factors related to vein/stoma development in grapevine leaf (Vitis vinifera L.)

The leaf functions through photosynthesis and determines the yield and quality of the grape (Vitis vinifera L.). Understanding the morphology, anatomy, and molecular regulation of leaf development can provide insight into the function of the leaf. In the present study, the microstructure of the vein and stomata was observed using an improved tissue clearing method, and differently expressed transcription factors (TFs) underlying leaf development were determined by transcriptome analysis in the ‘Pinot Noir’ grape. The process of stomata development from a single epidermal cell to a mature stomata cell was observed clearly under light microscopy by improving the method of tissue clearing. The onset of stomata formation in the leaf tip occurred prior to that in the central leaf, and developing stomata were observed in the center of the leaves at different development stages except for L5, when only mature stomata were present. The major vein was initiated before leaf unfolding (L1) and numbers of vessels increased underlying leaf growth. The shape of the vessel presented tapering. Freely ending veins were not observed until stages L4 and L5, and the vessels were different from other order veins in shape and ways of connection. Development-dependent differences between stomata and vein suggested differences in function during leaf development. A total of 445 TFs involved in leaf morphology and anatomy were identified. The members of the bHLH family (SCRM) and MYB family (MYB88) can contribute to stomata patterning during leaf development. Members of the TF families of ARF (ARF5), Dof (TMO6 and HCA2), HD-Zip III (HB14), and GRAS (SCR, SCL14, and SCL28) were potential regulators involved in vein development. The grape orthologs of WOX9, TCP4, and GRF1-9 can participate in leaf outgrowth and expansion. These results will be helpful for our further study of the molecular regulation of leaf development and the relation between leaf structure and function, which can be applied to improve grape production.

Microstructural Feature of Salvia glutinosa L. vegetative and generative organs

 It has been studied perspective medicinal plant S. glutinosa  aboveground parts vegetative and generative organs internal diagnostic features. The aboveground vegetative and generative organs of the plant are lined with unicellular or multicellular, conical trichomes, glands, unicellular or multicellular, also conical, spherical, secretory trichomes; Basal layer cells of curved and curved wall epidermal tissue is characteristic feature for leaf. The leaf is bifacial, amphistomatic, dorsoventral structure. Folium and axial organs cover tissue are presented diacytic type stomata. Lentil-like Guard cells of stomata, subsidiary cells stomata are curvilinear structure.In the internal structure of aboveground part polygonal structure tissue and mechanical tissue are actively represented, fiber and collenchyma existence are particularly characteristic sign for mechanical tissue. The transport system is monocyclic, collateral vascular bundles reflected in the stem, leaf stalk, and midrib. Longitudinally arranged, spherically shaped vascular vessel and tracheid element is in the transport system cortex. The axis organs xylem vessel mainly is spiral type, rarely  porous wall thickening.

Microscopic Evaluation and Antioxidant Activity of Glyphaea brevis (Spreng.) Monach. (Family Tiliaceae)

Background: Glyphaea brevis has been used traditionally to treat a variety of ailments, some of which are linked to oxidative stress. Despite the numerous studies on the biological activities of G. brevis, no literature was found on the microscopic study of this plant, which is essential for preparation of its monograph. As a result, the antioxidant activity of G. brevis and its qualitative microscopic characteristics were investigated in this study. Methods: The adaxial and abaxial epidermal layers of the G. brevis leaf, as well as transverse sections of the midrib and petiole, were obtained, cleared, and examined under a light microscope at X100 and X400 magnifications. The antioxidant activity of the crude methanol extract and fractions of G. brevis was evaluated via bioautographic method using 1,1-diphenyl-2-picrylhydrazyl- hydrate (DPPH) free radical scavenging activity (FRSA), total phenolic content (TPC) and the total flavonoid content (TFC). Results: Microscopic examination of the leaf revealed the presence of straight and few wavy thin-walled polygonal epidermal cells in the adaxial and abaxial layers, numerous stomata cells ranging from anisocytic, anomocytic, to paracytic in the abaxial layer, and various types of trichomes in both adaxial and abaxial layers. The FRSA and TFC were highest in the crude extract. The ethyl acetate fraction of G. brevis had highest FRSA, whereas the hexane fraction had the least. Conclusion: The microscopic study revealed characters that can be used to identify Glyphaea brevis, while the free radical scavenging activity supports its use in the treatment of many oxidative stress related diseases

Taxonomic implications of anatomical characteristics of the genus Tulipa (Liliaceae) in Turkey and their place in the historical subgeneric classifications

This paper comprehensively discusses anatomical features of the genus Tulipa (Liliaceae) in Turkey. These are compared with the current subgeneric classification. Anatomical structures, including transverse sections of the root, stem (scape) and leaf, and surface sections of the leaves are illustrated based on the 420 preparations obtained from 42 OTUs (populations) belonging to 18 taxa. Densities of stomata and epidermis cells per unit leaf area (mm2), stomatal index and ratio of stomata index on the leaf surfaces were also calculated. Cluster and principal component analyses (PCA) were employed, and all results were compared at the population level. In this anatomical study, some significant differences were found among Tulipa taxa, especially at the infrageneric and interspecific levels. The results of anatomical investigations are consistent with published results of previous morphological and molecular analyses. The results of cluster analysis and PCA support the classifications of Veldkamp & Zonneveld and Christenhusz et al. including three subgenera, Eriostemones, Tulipa and Clusianae, but subgenus Orithyia was not included in this study because it is absent from Turkey. Subgenus Eriostemones is divided into two sections, Sylvestres and Saxatiles, following treatments by Baker and Eker et al. In subgenus Tulipa, although morphometric analyses partially supported the taxonomic grouping previously proposed as three separate sections, Tulipa, Tulipanum and Eichleres, it also clearly indicates that considering them as a single section (Tulipa) is perhaps a better option.

Functional characterization of 5'-regulatory region of flavonoid 3',5'-hydroxylase-1 gene of banana plants.

Generation of crops with broad-spectrum tolerance to biotic and abiotic stress conditions depends upon availability of genetic elements suitable for varied situations and diverse genotypes. Here, we characterize the 5'-upstream regulatory region of flavonoid 3'5'-hydroxylase-1 (F3'5'H-1) gene from banana and analyzed its tissue-specific and stress-mediated activation in genetic background of tobacco plants. MusaF3'5'H-1 is a stress-responsive gene as its expression is induced in banana after application of salicylic acid and methyl jasmonate while its transcript levels were drastically reduced in response to drought, high salinity and abscisic acid. PMusaF3'5'H-1 harbours cis-elements associated with stress conditions and those responsible for tissue-specific expression. Transgenic lines harbouring PMusaF3'5'H-1-GUS displays strong GUS expression in guard cells of stomata indicating guard cell preferred activity of PMusaF3'5'H-1 while its activity was undetectable in roots. Drought and high salinity induce strong expression of GUS in transgenic tobacco lines and exposure to abscisic acid, salicylic acid and methyl jasmonate revealed distinct profiles of GUS expression in transgenic lines confirming involvement of F3'5'H-1 in plant stress responses. Fluorescent β-galactosidase assay revealed induction profiles of PMusaF3'5'H-1 at different time points in transgenic lines exposed to salicylic acid and abscisic acid while strong suppression in GUS expression was observed after application of methyl jasmonate. The guard cell preferred activity of PMusaF3'5'H-1 and stress-mediated expression profiles of MusaF3'5'H-1 indicated the suitability of PMusaF3'5'H-1 for generating stress-enduring crops and analyzing guard cell functions.

Study of Stomata Characteristics of Plantain and Horn Plants AAB genome

The study of stomata characteristics of plantain and horn plants has been carried out. This study aimed to compare the characteristics of plant stomata by plantain and horn banana AAB genome. Therefore, it is possible to find out the similarities and differences in characteristics between plantain and horn banana that have the same genome, including by stomata location, cover cell shape, stomatal type, number of epidermal cells, number of stomata cells, stomata length, stomata width, stomata area, stomata index, and stomatal density. Stomata observations were made by making an incision using the whole mount method. The results obtained were then analyzed descriptively qualitatively by describing the stomata characteristics of the plantain and horn banana plants

Degradation of oxalic acid produced by Botrytis elliptica infection in two ploidy levels of Lilium rosthornii Diels.

Oxalic acid (OA) is a crucial pathogenic factor for Sclerotinia spp. fungi, which is closely related to Botrytis spp. fungi. Whether OA is a pathogenic factor for the causal agent of grey mould in lily, Botrytis elliptica, and the response of lily to OA are poorly understood. To address these questions, lesion tissues and deposition of calcium oxalate (CaOX) and callose were observed in diploid and tetraploid leaves of L. rosthornii after inoculation with B. elliptica. Oxalate oxidase (OXO) activity and the transcript levels of some genes related to OA degradation (LrGLP1, LrGLP2 and LrWRKY4), reactive oxygen species (ROS) production/scavenging systems (LrRBOHD, LrGST, LrPOD and LrAPX1) and pathogen-related protein (PR) synthesis (LrCHI, LrBGL and LrPR10) were compared. After diploid and tetraploid leaves inoculation, lesion tissue and callose and CaOX were separately observed around in guard cells and stomata rather than the epidermis in the infected area. OXO activity was triggered at 2 h post-inoculation (hpi) in both ploidy leaves, and it was higher in the latter from 12-48 hpi. Expression of LrGLP1, LrGLP2, LrRBOHD, LrGST, LrPOD, LrCHI, LrBGL and LrPR10 was higher in tetraploids than in diploids from 24(12)-36(48) hpi. In conclusion, for B. elliptica, OA mainly chelates Ca2+ from the stomata cell wall. The strong capability to degrade OA and higher expression levels of some genes related to ROS accumulation/scavenging and PR synthesis may partially explain the relatively higher grey mould resistance of tetraploid L. rosthornii.

Identifikasi Stomata Pteridophyta di Kawasan Air Terjun Parangkikis Pagerwojo Tulungagung Jawa Timur

The aim of this study was to identifiy the stomata morphological characters of Pteridophyta in the ​​Parangkikis Pagerwojo Waterfall area, Tulungagung. The first step of stomata observation was preparation of the abaxial leaf slice. The preparation was carried out by the replica method. Stomata character studied include types and size of stomata, the number of stomata and epidermis cells, and value of the stomatal index. The result of this study showed that stomata types of Pteridophyta were polocytic and anomocytic. Of the 15 Pteridophyta species observed, the all of stomata type were polocytic, except Selaginella which had type stomata anomocytic. Stomata oval was found in Selaginella intermedia and Phymatosorus sp., slightly oval (kidney) was found in Asplenium apogamum, Dryopteris sp., Asplenium normale, Nephrolepis bisserata, Nephrolepis davallioides, Asplenium nidus, and Pteris longipinnula sp., spherical was found in Dicranopteris linearis, Cyclosorus arida, Goniophlebium percussom, and Goniophlebium manmiense, and nonconcave was found in Coniogramme fraxinea. Stomata size affected the number of stomata. If the size of the stomata was small, the number of stomata was increasing. The highest number of stomata was found in D. linearis, which was 362, while the least number of stomata was S. intermedia, which was 18. Data on the number of stomata and epidermal cells were used to determine the stomatal index. The highest stomata index was found in D. linearis, which was 22.05% and the lowest was C. fraxinea, which was 5.44 %.
 
 Keywords: Anomocytic, Parangkikis, polocytic, Pteridophyta, stomata

Anatomy of the leaf blades of Waldsteinia ternata (Stephan) Fritsch (Rosaceae) grown under different light conditions

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.

Postharvest senescent dark spot development mechanism of Musa acuminata ("Khai" banana) peel associated with chlorophyll degradation and stomata cell death.

The occurrence of the postharvest physiological disorder of dark spots on the peel of the ripened "Khai" banana has led to a reduction in its commercial value. The objective of the present study was to investigate the development mechanisms of senescence dark spots of the "Khai" (Musa AA group) banana peel in relation to chlorophyll degradation and stomata cell death. Freshly harvested bananas (commercial mature green stage) were let to ripened at 25±2°C (90%-95% RH). Peel color, senescent spots, DNA degradation, chlorophyll content, chlorophyll-degrading enzyme activities were assessed. The senescent dark spots developed on the ripened bananas right after 6days of storage, which coincided with remarkably increased DNA degradation, and a rapid decreased of hue angle value and total chlorophyll content which indicated the chlorophyll degradation. The activities of chlorophyllase, chlorophyll-degrading peroxidase and pheophytinase increased gradually to the highest point where the chlorophyll content drastically reduced and the appearance of the dark spots was first recorded after 6days of storage. These dark spots were observed to be surrounded with a bright luminescent ring of hypermodified fluorescent chlorophyll catabolites (FCCs), the product of chlorophyll breakdown. Additionally, the scanning electron microscope (SEM) revealed that the dark spots were found to have originated from the collapsed cells around the stomata of the ripened banana peel whereby the chlorophyll was entirely diminished. PRACTICAL APPLICATIONS: This research revealed the senescent dark spot development mechanisms of the "Khai" banana peel. The dark spot development symptom on the banana peel surface was caused by the senescence and cell death of the relevant stomata, further associated with chlorophyll degradation. Therefore, any further research into minimizing the dark spot symptom must focus on preventing or delaying stomata senescence and cell death.

Arabidopsis cysteine-rich receptor-like protein kinase CRK33 affects stomatal density and drought tolerance

ABSTRACT Cysteine-rich receptor-like protein kinases (CRKs) are transmembrane proteins containing two domains of unknown function 26 (DUF26) RLKs in their ectodomain. Despite that CRKs control important aspects of plant development, only few proteins have functionally been characterized. In this work, we analyzed the function of CRK33 by characterizing two insertional lines. The stomatal density and stomatal index were decreased in crk33-2 and crk33-3 plants in comparison to wild-type plants, correlating with a decreased transpiration in transgenic plants and a higher drought tolerance. Furthermore, photosynthesis and stomatal conductance changed. Finally, all four stomata cell fate genes were upregulated, especially the expression of TMM and SPCH in the mutant background, suggesting a role for CRK33 in stomatal spacing.