Mesophyll Tissue Research Articles

New sources of melon accessions with resistance to bacterial fruit blotch at different phenological stages of melon growth and to multiple strains of Acidovorax citrulli

Bacterial fruit blotch, which is caused by Acidovorax citrulli, is one of the most common diseases of melon crops. To date, there is no disease-resistant commercial cultivar, and management strategies have not been efficient. Therefore, the objectives of this study were to identify melon accessions with genetic resistance to bacterial fruit blotch at different phenological stages of plant growth and to multiple strains of the pathogen. The disease severity was estimated using descriptive scales and evaluated by inoculating A. citrulli into seeds (55 accessions), seedlings, and plants before flowering (38 accessions). After assessing the stability of seven accessions to three strains of the bacterium, two accessions were selected to evaluate their resistance at the flowering and fruiting stages and to perform a transmission assay and optical and scanning electron microscopic analyses. Most accessions showed varied responses (resistance vs. susceptibility) at the different phenological stages of melon growth. However, accessions I-136 and A-43 showed high levels of resistance in most assays and in the stability assay. The fruits of these accessions showed no symptoms of bacterial fruit blotch, and seed transmission of A. citrulli showed values of only 0.6% (I-136) and 2.5% (A-43). Microscopy showed few structural and temporal changes in the colonization of A. citrulli in the leaf mesophyll tissues of these accessions, which can be associated with resistance. The results suggest that accessions A-43 and I-136 can act as donors of bacterial fruit blotch resistance genes, which can be introduced into commercial cultivars through genetic improvement programs.

Ploidy influences wheat mesophyll cell geometry, packing and leaf function.

Leaf function is influenced by leaf structure, which is itself related not only to the spatial arrangement of constituent mesophyll cells, but also their size and shape. In this study, we used confocal microscopy to image leaves of Triticum genotypes varying in ploidy level to extract 3D information on individual mesophyll cell size and geometry. Combined with X‐ray Computed Tomography and gas exchange analysis, the effect of changes in wheat mesophyll cell geometry upon leaf structure and function were investigated. Mesophyll cell size and shape were found to have changed during the course of wheat evolution. An unexpected linear relationship between mesophyll cell surface area and volume was discovered, suggesting anisotropic scaling of mesophyll cell geometry with increasing ploidy. Altered mesophyll cell size and shape were demonstrated to be associated with changes in mesophyll tissue architecture. Under experimental growth conditions, CO2 assimilation did not vary with ploidy, but stomatal conductance was lower in hexaploid plants, conferring a greater instantaneous water‐use efficiency. We propose that as wheat mesophyll cells have become larger with increased ploidy, this has been accompanied by changes in cell geometry and packing which limit water loss while maintaining carbon assimilation.

A single-cell analysis of the Arabidopsis vegetative shoot apex.

The shoot apical meristem allows for reiterative formation of new aerial structures throughout the life cycle of a plant. We use single-cell RNA sequencing to define the cellular taxonomy of the Arabidopsis vegetative shoot apex at the transcriptome level. We find that the shoot apex is composed of highly heterogeneous cells, which can be partitioned into 7 broad populations with 23 transcriptionally distinct cell clusters. We delineate cell-cycle continuums and developmental trajectories of epidermal cells, vascular tissue, and leaf mesophyll cells and infer transcription factors and gene expression signatures associated with cell fate decisions. Integrative analysis of shoot and root apical cell populations further reveals common and distinct features of epidermal and vascular tissues. Our results, thus, offer a valuable resource for investigating the basic principles underlying cell division and differentiation in plants at single-cell resolution.

How cells and tissues of Daphnopsis fasciculata (Thymelaeaceae) react to the leaf-mining habit of Phyllocnistis hemera (Lepidoptera: Gracillariidae).

Plant cell and tissue responses to the attack of mining herbivores may be diagnosed by anatomical and histochemical analyses, herein investigated regarding the mining activity of Phyllocnistis hemera larvae in the leaf lamina of Daphnopsis fasciculata. The larva enters the leaf lamina through the adaxial epidermis, and feeds on palisade parenchyma cells. A healing tissue is produced after the larva passes, and its cells are reactive to histochemical tests for lignins and pectins. At first, the leaf mine is composed of a channel that is limited by palisade parenchyma cell wall fragments. Later, it is filled with a regenerative tissue constituted by isodiametric cells recruited from the spongy parenchyma, which fills up the mine channel. The cells differentiated inside the mine, regenerated the damage caused to leaf tissues, and may isolate the mine from the entrance of pathogens. Daphnopsis fasciculata is capable of reconstructing mesophyll tissues, which involves the totipotency of parenchyma cells and enables an important strategy for plant recovering after the attack of mining parasites.

Macro-Micromorphological, Antioxidant and Preliminary Phytochemical Studies on Two Terrestrial Orchids Eulophia Nuda Lindl. and Geodorum Densiflorum (Lam.) Schltr.

An attempt for study of two terrestrial orchids i.e. Eulophia nuda (Lindl.) and Geodorum densiflorum (Lam.) Schltr. were carried out. Main focus was on the corms of both the orchids due to its huge medicinal properties like anticancerous, antioxidant, antidiabetic, antimicrobial, phytotoxic, etc. This is one of the prime reasons behind their threatened status along with endemic habitat. The parameters which were analysed during the study include macro- and micro-morphology, preliminary phytochemistry, and antioxidant activity (DPPH activity). In macro-morphology of both the orchids, slight difference was reported and, thus sometimes Geodorum densiflorum is being used as an adulterant in place of Eulophia nuda. During micro-morphological analysis, the oxalate crystals, raphides, mucilage ducts, starch grains, and oil granules were observed from cortical region of corm and in the mesophyll tissue of leaves in both the orchids. Stomatal Index of leaf surface was calculated along with the type of stomata, i.e. Cyclic II type. Preliminary analysis of phytochemical constituents in both the orchids was performed with three different solvent systems. A comparative antioxidant activity between leaves extract of both the orchids was carried out.

Mechanical fragmentation of leaf litter by fine root growth contributes greatly to the early decomposition of leaf litter

Understory plant root proliferation into the litter layer occurs in many forest ecosystems and dramatically accelerates litter decomposition and nutrient release in the early stages. Mechanical fragmentation of leaf litter by fine roots could be one main reason, but its mechanism is poorly understood. To quantitatively assess the influence of fine roots on the mechanical fragmentation of leaf litter in the early decomposition process, we examined the effects of fine root mass of Lolium multiflorum on morphological and physical characteristics of decomposing litters of Symplocos setchuensis, a dominant species in a mid-subtropical evergreen broad-leaved forest of China, via a litter bag simulation experiment. The results showed that there were various fine root growth forms in/on decomposing litters, including the penetration and tearing of leaf epidermis, and the “walking or inserting” between the mesophyll tissue and the leaf veins. Fine root mass had a significant positive effect on the mass loss during litter decomposition (F = 8.543, P < 0.01). In a duration of 170-day leaf litter incubation, the mass remaining ration was significantly higher in no roots treatments and fewer roots treatments than that in more roots treatments. In the case of more roots, the physical tensile strength of leaf litter fragments was 0.156 N/mm, which was significantly lower than that under the treatments with fewer roots and no roots (P < 0.05). More fine roots penetrating the litter layer could significantly promote the intensity of mechanical fragmentation by changing the morphology, structure, and physical properties of the leaf litter. The fine root biomass in the litter layer was positively correlated with the decomposition rate, and the specific root length and specific root tip density were two important indicators related to decomposition. In conclusion, fine roots growing into litter promoted the intensity of mechanical fragmentation by increasing root length and producing new root tips and by actively regulating litter traits, so as to improve the utilization efficiency of nutrient release in the early decomposition process.

Metabolic profiling of epidermal and mesophyll tissues under water-deficit stress in Opuntia ficus-indica reveals stress-adaptive metabolic responses.

Cactus pear (Opuntia ficus-indica) is a high productivity species within the Cactaceae grown in many semiarid parts of the world for food, fodder, forage, and biofuels. O. ficus-indica utilises obligate crassulacean acid metabolism (CAM), an adaptation that greatly improves water-use efficiency (WUE) and reduces crop water usage. To better understand CAM-related metabolites and water-deficit stress responses of O. ficus-indica, comparative metabolic profiling was performed on mesophyll and epidermal tissues collected from well-watered and water-deficit stressed cladodes at 50% relative water content (RWC). Tissues were collected over a 24-h period to identify metabolite levels throughout the diel cycle and analysed using a combination of acidic/basic ultra-high-performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) and gas chromatography/mass spectrometry (GC/MS) platforms. A total of 382 metabolites, including 210 (55%) named and 172 (45%) unnamed compounds, were characterised across both tissues. Most tricarboxylic acid (TCA) cycle and glycolysis intermediates were depleted in plants undergoing water-deficit stress indicative of CAM idling or post-idling, while the raffinose family oligosaccharides (RFO) accumulated in both mesophyll and epidermal tissues as osmoprotectants. Levels of reduced glutathione and other metabolites of the ascorbate cycle as well as oxylipins, stress hormones such as traumatic acid, and nucleotide degradation products were increased under water-deficit stress conditions. Notably, tryptophan accumulation, an atypical response, was significantly (24-fold) higher during all time points in water-deficit stressed mesophyll tissue compared with well-watered controls. Many of the metabolite increases were indicative of a highly oxidising environment under water-deficit stress. A total of 34 unnamed metabolites also accumulated in response to water-deficit stress indicating that such compounds might play important roles in water-deficit stress tolerance.

Cellular autofluorescence and browning in trichomes of Chinese cabbage (Brassica campestris) in response to mechanical stimulation and senescence.

There is limited information concerning the formation of dot-like browning appearing at the base of trichomes on mature leaves on the Chinese cabbage (Brassica campestris L. ssp. pekinensis). This study confirmed for the first time that enhanced autofluorescence can be induced in the base of trichomes when pressure stimuli is applied to trichomes; the enhanced autofluorescence gradually moves to the top of trichomes and the neighbouring mesophyll tissue within 15min. The excitation of autofluorescence in trichomes was found to be more effective in mature leaves compared to newly emergent leaves. Increased polyphenol oxidase (PPO) activities and reactive oxygen species (ROS) accumulation were also detected in the basal region of trichomes that were subjected to mechanical stimuli. Enhanced fluorescence was observed at the top of the trichomes in senescencing leaves. A browning in the base of the trichomes during leaf senescence was observed. In contrast, no browning occurred at the base of the trichomes in leaves that were subject to pressure stimuli. The blue fluorescence in the trichomes in senescent leaves arises mainly from the condensed cytoplasm. No direct evidence was able to prove that the enhanced autofluorescent substances in the trichomes during leaf senescence are the cause of the browning at the early growth stages.

Leaf anatomical adaptation of eighteen mangrove plant species from the Sundarbans in Bangladesh

Investigation on leaf anatomical adaptation of 18 mangrove plant species was carried out. Among the 18 species 13 were dorsiventral and five were isobilateral type. All the species had special stomatal structure and variable cuticle layer to minimize transpiration. Most of the species had succulent leaves with leaf thickness ranging from around 232 to 1363 μm. As an indication of salt secretion, both glandular and non-glandular trichomes were observed in several species. Although presence of single to multilayered hypodermis might effectively function as water storage tissue, several studied mangrove plant species e.g. Cynometra ramiflora L., Phoenix paludosa Roxb., Pongamea pinnata (L.) Pierre, Sonneratia apetala Buch. - Ham., S. caseolaris (L.) Engl. and Xylocarpus moluccensis (Lamk.) M. Roem. showed complete absence of hypodermis. This might be due to moderate saline condition. In addition, marked terminal tracheids in mesophyll tissue of a number of species might help with capillary water storage within the leaf. To enhance mechanical support several species were found to develop considerable amount of diverse sclereids within the mesophyll tissue and surrounding vascular bundle. Although maximum anatomical adaptations are common for plants growing in saline habitat it may be suggested that these features were differentially developed in plants specifically grown in mesohaline zone.

Effect of nanoparticle on growth, biochemical and anatomical characteristics of moringa plant (Moringa oleifera L.) under salinity stress condition

Two pot experiments were carried out at the Experimental Farm of the Agricultural Botany Department, Faculty of Agriculture, Al-Azhar University (Assiut branch), Assiut, Egypt, during two successive seasons of 2018 and 2019. The main aim of this study was to find out the effect of both of foliar application with some growth promoters (using nanotechnology) i.e., zinc, iron, copper oxide nanoparticles at 50, 100 and 150 mgl-1 of each and silica nanoparticles at 20, 40 and 60 mgl-1 as well as salinity stress level of irrigation water at 9000 mgl-1 individually and their interactions on growth, biochemical and anatomical characteristics of Moringa oliefera L. plant. The results showed that individually salinity stress level of irrigation water at 9000 mgl-1 decreased all studied vegetative growth parameters of moringa plant i.e., plant height (cm), stem diameter (cm), leaves number plant-1, leaf area plant-1 as well as root, stem and leaves dry weights plant-1 compared with the control. The same trend was obtained in photosynthetic pigments content (total chlorophyll) as well as the studied anatomical characteristics of root section (i.e., root diameter of V.C and length of xylem arch), stem section (i.e., stem diameter, O of V.C, length of V.B in the stem) and Leaf blade section (i.e., upper epidermis thickness, lower epidermis thickness and mesophyll tissue for leaflet) at 50 days of Moringa oliefera leaves compared with unstressed plant. On other hand, salinity stress level at 9000 mgl-1 resulted in increasing antioxidant activity as well as total phenolic contents at 60 days of Moringa oliefera leaves compared with unstressed plant. Data also indicated that the individually foliar application treatments with Zinc, Iron, Copper oxide nanoparticles at 50, 100, 150 of each and Silica at 20, 40, 60 mgl-1 nanoparticles increased studied vegetative growth as well as anatomical characteristics, chemical compositions, photosynthetic pigments (total chlorophyll), antioxidants activity and total phenolic contents of moringa plant compared with the control treatment. In this respect, Silica nanoparticles at 60 mgl-1 followed by zinc and iron oxide at 150 mgl-1 nanoparticles of each were the most effective treatments, respectively. Finally , Based on these results, it could be concluded that the foliar application with nanoparticles gave the highest Valois of morphological, chemical compositions and anatomical characteristics its that reduce the harmful effects of salinity stress of Moringa oliefera L. plant specially at silica 60 mgl-1,. Data recorded that this results using it under the same field conditions (Assiut governorate, Egypt).

Phenology of leaf optical properties and their relationship to mesophyll development in cool-temperate deciduous broad-leaf trees.

Leaf optical properties (reflectance and transmittance spectra of a single leaf) are the key to interpreting remote sensing data regarding the structure and functions of vegetation canopies. These properties are determined by leaf biochemical and anatomical traits, which change seasonally in deciduous species. To reveal the species-specific seasonal patterns in leaf optical properties and their relationship to chlorophyll content and/or mesophyll structure in deciduous trees, we examined these mechanistic relationships in a pioneer species, Betula ermanii, and in sunlit and shade leaves of a late-successional species, Quercus crispula, during their seasonal development. Leaf optical properties were measured from leaf emergence to leaf fall in four years. After leaf unfolding, reflectance in the photosynthetically active radiation (PAR) region decreased gradually, while transmittance dropped rapidly. Both reflectance and transmittance increased before leaf fall. In the near-infrared (NIR) region, reflectance increased and transmittance decreased during the development period. Values of parameter N (the number of compact layers within a leaf in PROSPECT-5 model) in young leaves was very low (1.1 for B. ermanii and 1.0 for sunlit and shade leaves of Q. crispula) but increased rapidly by 30% for B. ermanii and sunlit leaves of Q. crispula and by 20% for shade leaves. N was higher in the order of B. ermanii > Q. crispula sun leaves > shade leaves. The PROSPECT-5 simulation with our measured data showed that the development of mesophyll tissue increases reflectance and decreases transmittance in both NIR and PAR regions, and an increase in chlorophyll decreases both reflectance and transmittance in PAR region. Our results indicate that structural and biochemical development of leaf mesophyll and its interspecific variations are essential biological characteristics for understanding seasonal changes in canopy reflectance. The results of this study will help us to better analyze remotely sensed data.

Mesophyll conductance: walls, membranes and spatial complexity.

A significant resistance to CO2 diffusion is imposed by mesophyll tissue inside leaves. Mesophyll resistance, rm (or its reciprocal, mesophyll conductance, gm ), reduces the rate at which Rubisco can fix CO2 , increasing the water and nitrogen costs of carbon acquisition. gm varies in proportion to the surface area of chloroplasts exposed to intercellular airspace per unit leaf area. It also depends on the thickness and effective porosity of the cell wall and the CO2 permeabilities of membranes. As no measurements exist for the effective porosity of mesophyll cell walls, and CO2 permeability values are too low to account for observed rates of CO2 assimilation, conclusions from modelling must be treated with caution. There is great variation in the mesophyll resistance per unit chloroplast area for a given cell wall thickness, which may reflect differences in effective porosity. While apparent gm can vary with CO2 and irradiance, the underlying conductance at the cellular level may remain unchanged. Dynamic changes in apparent gm arise for spatial reasons and because chloroplasts differ in their photosynthetic composition and operate in different light environments. Measurements of the temperature sensitivity of membrane CO2 permeability are urgently needed to explain variation in temperature responses of gm .

First Report of Black Spot Caused by Neoscytalidium dimidiatum on Sisal in Guangxi, China.

Sisal (Agave sisalana Perrine) is an important hard fiber crop that is widely planted in Guangxi, Guangdong, Hainan, Yunnan, and Fujian provinces, China. In July 2019, a new leaf disease of sisal with a disease incident of about 36% was found in Guangxi (Fig.1a~d). The oval or circular black lesions were 2.3 cm to 15.9 cm in length and 1.6 cm to 5.5 cm in width on both sides of the diseased leaves. The central part of the lesions was slightly hollow. The lesions continuously enlarged and ultimately penetrated the leaves. Reddish brown and dark mucus was secreted from the lesions. The junction of lesions and healthy parts was reddish brown to yellow. The diseased leaf fiber and mesophyll tissues were reddish brown and necrotic. Fresh leaf yield was reduced about 30% by the disease, and fiber quality was significantly compromised every year in Guangxi. Six kinds of fungi distinguished by their morphology, size and color of the colonies were isolated from diseased leaf tissues of 60 sisal plants sampled from five different farms in Guangxi. Isolate JMHB1 was isolated at a rate of 95.67%. The isolate JMHB1 was initially white with dense and hairy aerial mycelium, gradually turning dark grey to olive green on PDA (Fig. 2). Conidia, arthrospores, and chlamydospores were observed on PDA in culture (Fig. 3). The conidia formed arthric chains, disarticulating, cylindrical-truncate, oblong-obtuse to doliiform, colorless and transparent, zero- to one-septate, and averaging 4.4 to 13.8 µm × 2.2 to 5.6 µm (n=100). Arthrospores were short columnar, pigmented and transparent, single or formed arthric chains, averaging 5.5 to 17.9 µm × 2.1 to 3.5 µm (n=100). Chlamydospores were dark brown, round or oval, averaging 4.5 to 9.6 µm × 4.5 to 8.6 µm (n=100). Pathogenicity testing was conducted by inoculating 3-year-old healthy sisal plants with PDA plugs (5 × 5 mm) on which the fungus had grown for 5 days. Nine healthy plants were wounded on the leaves with a sterile needle, and mycelial plugs were placed on the wounds, covered with sterile moist cotton, and wrapped with parafilm. Nine control plants were wounded and treated with PDA plugs as the negative control. The test was repeated three times. All treated plants were kept in a greenhouse at ~28 ℃ and 40% RH. After 5 days, only leaves inoculated with isolate JMHB1 showed lesions similar to symptoms observed in the field (Fig.1e~f). The fungus was re-isolated from all nine diseased plants, and no symptoms were observed on the leaves of control plants. Molecular identification of the fungus was made by PCR amplification of the internal transcribed spacer (ITS) region of rDNA, EF1-α gene and β-tubulin gene using primers ITS1/ITS4 (White et al. 1990), EFl-728F/EF1-986R (Carbone and Kohn 1999), TUB2Fd/TUB4Rd (Aveskamp et al. 2009) respectively. The ITS (MT705646), EF1-α (MT733516) and β-tubulin (MT773603) sequences of JMHB1 were similar to the ITS (AY819727), EF1-α (EU144063) and β-tubulin (KF531800) sequences of the epitype of Neoscytalidium dimidiatum (CBS 499.66) with 100%, 99.65% and 99.02% identity, respectively. Based on pathogenicity testing, morphological characteristics, and molecular identification, the pathogen of sisal causing black spot was identified as N. dimidiatum (Penz.) Crous & Slippers (Crous et al. 2006). To our knowledge, this is the first report of black spot caused by N. dimidiatum on sisal in China. Sisal is the main economic crop in arid and semi-arid areas that is widely planted in several provinces of southern China. The serious occurrence of the disease caused by N. dimidiatum has greatly affected the development of sisal industry and local economic income in China. Identification of the pathogen of the disease is of great significance to guide disease control, increase farmers' income and promote the development of sisal industry.

The flattened and needlelike leaves of the pine family (Pinaceae) share a conserved genetic network for adaxial-abaxial polarity but have diverged for photosynthetic adaptation

BackgroundLeaves have highly diverse morphologies. However, with an evolutionary history of approximately 200 million years, leaves of the pine family are relatively monotonous and often collectively called “needles”, although they vary in length, width and cross-section shapes. It would be of great interest to determine whether Pinaceae leaves share similar morpho-physiological features and even consistent developmental and adaptive mechanisms.ResultsBased on a detailed morpho-anatomical study of leaves from all 11 Pinaceae genera, we particularly investigated the expression patterns of adaxial-abaxial polarity genes in two types of leaves (needlelike and flattened) and compared their photosynthetic capacities. We found that the two types of leaves share conserved spatial patterning of vasculatures and genetic networks for adaxial-abaxial polarity, although they display different anatomical structures in the mesophyll tissue differentiation and distribution direction. In addition, the species with needlelike leaves exhibited better photosynthetic capacity than the species with flattened leaves.ConclusionsOur study provides the first evidence for the existence of a conserved genetic module controlling adaxial-abaxial polarity in the development of different Pinaceae leaves.

Exogenous implication of seismic stress in attenuation of in vitro induced morpho-anatomical aberrations in Hemidesmus indicus (L.) R. Br. ex Schult

Hemidesmus indicus (L.) R. Br. ex Schult. (Indian Sarsaparilla of the family Apocynaceae) is a perennial climber used in traditional and modern medicinal systems since ages due to presence of a phytoconstituent MBAlD (2-hydroxy 4-methoxy benzaldehyde) in its roots. The morphological and light microscopic examination of the foliar appendages of the in vitro regenerated plants revealed the presence of abnormalities in micro-morpho-anatomy of leaves, caused major shortfall to the acclimatization of in vitro raised plants and their survival success in the field. Therefore, the present study aimed to identify the effects of seismic stress treatment on the morphology, micro-morpho-anatomy and photosynthetic pigments development in tissue culture raised plants of H. indicus. The cultures were agitated at 80 rpm for 6.0 min using an incubator shaker for 4 wk twice a day. Significant phenotypic improvements with enhanced quality of shoots, roots and leaf number (14.0 ± 0.29), leaf area (3.2 ± 0.20 cm length and 1.0 ± 0.15 cm width), and growth ratio (4.8 ± 0.33 g fresh weight) were observed. The in vitro induced foliar micro-morpho-anatomical anomalies such as abnormal and non-functional stomata, underdeveloped cuticle, mesophyll tissues and vascular elements were mitigated by the seismic stress; and well organized tissues were developed. Seismic stress also enhanced the development of photosynthetic pigments in the leaves (8.20 μg g−1 FW) as compared with the control plantlets (6.89 μg g−1 FW). We postulate that the application of seismic stress alleviate in vitro induced morphological and anatomical anomalies at in vitro stage, and the developed plantlets exhibited improved survival rate during ex vitro and in vivo hardening processes.

Heavy metal Hg stress detection in tobacco plant using hyperspectral sensing and data-driven machine learning methods.

Accurate detection of heavy metal stress on the growth status of plants is of great concern for agricultural production and management, food security, and ecological environment. A proximal hyperspectral imaging (HSI) system covered the visible/near-infrared (Vis/NIR) region of 400-1000nm coupled with machine learning methods were employed to discriminate the tobacco plants stressed by different concentration of heavy metal Hg. After acquiring hyperspectral images of tobacco plants stressed by heavy metal Hg with concentration solutions of 0mg·L-1 (non-stressed groups), 1, 3, and 5mg·L-1 (3 stressed groups), regions of interest (ROIs) of canopy in tobacco plants were identified for spectra processing. Meanwhile, tobacco plant's appearance and microstructure of mesophyll tissue in tobacco leaves were analyzed. After that, clustering effects of the non-stressed and stressed groups were revealed by score plots and score images calculated by principal component analysis (PCA). Then, loadings of PCA and competitive adaptive reweighted sampling (CARS) algorithm were employed to pick effective wavelengths (EWs) for discriminating non-stressed and stressed samples. Partial least squares discriminant analysis (PLS-DA) and least-squares support vector machine (LS-SVM) were utilized to estimate the stressed tobacco plants status with different concentrations Hg solutions. The performances of those models were evaluated using confusion matrixes (CMes) and receiver operating characteristics (ROC) curves. Results demonstrated that PLS-DA models failed to offer relatively good result, and this algorithm was abandoned to classify the stressed and non-stressed groups of tobacco plants. Compared to LS-SVM model based on full spectra (FS-LS-SVM), the LS-SVM model established EWs selected by CARS (CARS-LS-SVM) carried 13 variables provided an accuracy of 100%, which was promising to achieve the qualitative discrimination of the non-stressed and stressed tobacco plants. Meanwhile, for revealing the discrepancy between 3 stressed groups of tobacco plants, the other FS-LS-SVM, PCA-LS-SVM, and CARS-LS-SVM models were setup and offered relatively low accuracies of 55.56%, 51.11% and 66.67%, respectively. Performance of those 3 LS-SVM discriminative models was also poorly performing to differentiate 3 stressed groups of tobacco plants, which might be caused by low concentration of heavy metal and similar canopy (especially in fresh leaves) of plant. The achievements of the research indicated that HSI coupled with machine learning methods had a powerful potential to discriminate tobacco plant stressed by heavy metal Hg.

Receptor-like kinase OsCR4 controls leaf morphogenesis and embryogenesis by fixing the distribution of auxin in rice

Cell differentiation is a key event in organ development; it involves auxin gradient formation, cell signaling, and transcriptional regulation. Yet, how these processes are orchestrated during leaf morphogenesis is poorly understood. Here, we demonstrate an essential role for the receptor-like kinase OsCR4 in leaf development. oscr4 loss-of-function mutants displayed short shoots and roots, with tiny, crinkly, or even dead leaves. The delayed outgrowth of the first three leaves and seminal root in oscr4 was due to defects in plumule and radicle formation during embryogenesis. The deformed epidermal, mesophyll, and vascular tissues observed in oscr4 leaves arose at the postembryo stage; the corresponding expression pattern of proOsCR4:GUS in embryos and young leaves suggests that OsCR4 functions in these tissues. Signals from the auxin reporter DR5rev:VENUS were found to be altered in oscr4 embryos and disorganized in oscr4 leaves, in which indole-3-acetic acid accumulation was further revealed by immunofluorescence. OsWOX3A, which is auxin responsive and related to leaf development, was activated extensively and ectopically in oscr4 leaves, partially accounting for the observed lack of cell differentiation. Our data suggest that OsCR4 plays a fundamental role in leaf morphogenesis and embryogenesis by fixing the distribution of auxin.

From one side to two sides: the effects of stomatal distribution on photosynthesis.

The functions of stomata have been studied for a long time; however, a clear understanding of the influences of stomatal distribution on photosynthesis, especially the CO2 diffusion, is still unclear. Here, we investigated the stomatal morphology, distribution on leaf surfaces, vein traits and gas exchange parameters of 61 species, of which 29 were amphistomatous, spanning 32 families. Photosynthesis (A) was tightly coupled with operational stomatal conductance (gs ) and mesophyll conductance (gm ) regardless of whether phylogenetic relationships were accounted for. Although the enhancement of gs from ferns and gymnosperms to angiosperms could largely be explained by the increase in leaf vein density (VLA) and stomatal density (SD), the gs was decoupled from VLA and SD across angiosperm species. Instead, A in angiosperms was further influenced by the allocation of stomatal pores on leaf surfaces, which dramatically increased gs and gm . Moreover, the ratio of gs to anatomically based maximum gs was, on average, 0.12 across species. Our results show that the shift of stomatal pores from one leaf side to both sides played an important role in regulating CO2 diffusion via both stomata and mesophyll tissues. Modifications of stomata distribution have potential as a functional trait for photosynthesis improvement.

STRUKTUR ANATOMI DAUN SEBAGAI BUKTI DALAM PEMBATASAN TAKSON TUMBUHAN BERBUNGA: STUDI KASUS 12 SUKU TUMBUHAN BERBUNGA INDONESIA

Keanekaragaman tumbuhan tidak hanya terlihat secara morfologi, tetapi dapat dibedakan pula secara anatomi. Ciri anatomi dapat digunakan sebagai pendukung dan penguat pengklasifikasian jenis tumbuhan. Penelitian ini bertujuan untuk mengetahui ciri anatomi daun yang dapat digunakan sebagai penciri taksonomi dalam suatu tingkatan taksa melalui perwakilan jenis. Jenis yang digunakan berjumlah 15, yang merupakan perwakilan dari 12 suku tumbuhan berbunga Indonesia. Metode parafin digunakan untuk mendapatkan penampang transversal dan metode perendaman dengan asam nitrit (HNO3) digunakan untuk mendapatkan penampang epidermis daun. Sebagian ciri anatomi pada penelitian dapat digunakan sebagai penciri suku hingga jenis. Hasil penelitian menunjukkan bahwa 15 jenis yang diamati memiliki kesamaan ciri anatomi dengan data penelitian terdahulu yang telah dilakukan baik pada tingkat suku, marga maupun jenis. Kesamaan ciri anatomi tersebut mencakup satu hingga beberapa ciri seperti tipe stomata, dinding antiklinal sel epidermis, jaringan mesofil, dan berkas pengangkut (tangkai daun dan tulang tengah daun). Kesamaan ciri yang didapatkan pada masing-masing jenis menunjukkan bahwa ciri pada struktur anatomi daun dapat menjadi bukti pembatasan takson pada tumbuhan berbunga.

Isolation and characterization of chloroplastic glutamine synthetase gene (CsGS2) in tea plant Camellia sinensis

Tea plant (Camellia sinensis) is an ammonium preferring plant species. However, little is known about the mechanism underlying this preference. Herein, a chloroplastic glutamine synthetase gene (CsGS2), which is vital for nitrogen assimilation in mesophyll tissue, was isolated from tea cultivar C. sinensis cv. ‘Longjing43’. The full length cDNA of CsGS2 was 1622 bp, having a 1299 bp open reading frame encoding a 432-amino acid protein. Homology search and sequence analysis demonstrated that CsGS2 protein carried the basic characteristics of a canonical GS2 domain and shared high identity with GS2s from other plant species. Subcellular localization and immunolocalization of CsGS2 revealed that it is localized in chloroplast. qRT-PCR and Western blot analyses showed that CsGS2 was expressed in a leaf-specific pattern, such that both CsGS2 and its protein were most abundant in mature leaves. Temporal expression patterns of CsGS2 showed minor differences in response to ammonium and nitrate nutrition. The transcript level of CsGS2 was significantly induced in mature leaves during the development of new shoots, whereas darkness inhibited this induction significantly. These results suggested that CsGS2 does not play a role in the differential utilization mechanisms of differing nitrogen forms in tea, and imply a light dependent transcription regulation in mature leaves during the development of new shoots.