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Oxygen isotopic composition (Δ18OLW) of leaf water can help improve our understanding of how anatomy interacts with physiology to influence leaf water transport. Leaf water isotope models of Δ18OLW such as the Péclet effect model have been developed to predict Δ18OLW, and it incorporates transpiration rate (E) and the mixing length between unenriched xylem water and enriched mesophyll water, which can occur in the mesophyll (Lm) or veins (Lv). Here we used two cell wall composition mutants grown under two light intensities and RH to evaluate the effect of cell wall composition on Δ18OLW. In maize (Zea mays), the compromised ultrastructure of the suberin lamellae in the bundle sheath of the ALIPHATIC SUBERIN FERULOYL TRANSFERASE mutant (Zmasft) reduced barriers to apoplastic water movement, resulting in higher E and Lv and, consequently, lower Δ18OLW. In cellulose synthase-like F6 (Cslf6) mutants and wildtype of rice (Oryza sativa), the difference in Δ18OLW in plants grown under high and low growth light intensity co-varied with their differences in stomatal density. These results show that cell wall composition and stomatal density influence Δ18OLW by altering the Péclet effect and that stable isotopes can facilitate the development of a physiologically and anatomically explicit water transport model.

Background Even though some Dracaena species are used as medicine, their utilization as food is rather unusual. In northern Angola, however, leaves and underground tubers of Dracaena camerooniana Baker are frequently consumed. In particular, the leaves are of increasing economic value in the region. But the anatomy and nutritional aspects of the plant have not been studied so far. Therefore, a detailed anatomic description of the plant was conducted. In a second step the nutritional value of the defined material was analysed, providing a basis for the discussion of a more intensive utilisation of this rainforest shrub. Results The leaf anatomy of Dracaena camerooniana differs from the species of the genus that have been examined so far, in showing adaptations to wet climatic conditions. The stems produce a secondary thickening meristem with amphivasal secondary vascular bundles. During tuber formation, the parenchyma of the pith in the vascular cylinder of the root markedly increases. From a nutritional point of view, leaves do not noteworthy contribute to vitamin intake. The nutritional composition of the tubers is comparable to that of cassava (Manihot esculenta Crantz ) and potatoes (Solanum tuberosum L.). However, a high fructose value indicates inulin as a storage carbohydrate. Conclusion Inspite of its rather moderate nutritional values, Dracaena camerooniana is an indigenous addition to the diet of the Angolan population that could also be cultivated in the future due to the easy vegetative propagation.

Gall-inducing organisms change the development of their host plant organs, resulting in ontogenetic patterns not observed in the non-galled plants. Distinct taxa induce galls on Schinus spp., manipulating meristematic patterns in the host plant in distinct ways. Here we report ontogenetic novelties induced in the lateral buds of S. engleri by Eucecidoses minutanus, a Cecidosidae, whose galls have been poorly understood.The anatomy, histochemistry, and histometry of galls in distinct phases of development, non-galled buds, and stems of Schinus engleri were analyzed in parallel with the instars of E. minutanus to detail the morphogenetic changes in the host with each larval stage.Ontogenetic phases of the galls were intricately associated with larval development. First and second-instar larvae induced pericycle and pith cells to dedifferentiate into the gall inner meristem, where hyperplasia and cell hypertrophy characterized the growth and development phase of the gall. The innermost layers were lipid-rich nutritive cells that lined the larval chamber. Additional vascular bundle rows were produced in young galls. Third and fourth instar-larvae were associated with the gall maturation phase: centripetal lignification of the outer parenchyma cell layers, epidermal stratification, and activation of a cambium-like meristem (CLM). The CLM activity resulted in new layers of nutritive cells that differentiated inward as the first layers of nutritive cells were consumed by E. minutanus larvae, and, also, in more parenchyma cell layers that formed outward. All tissues between the innermost layer of nutritive tissue that surround the gall chamber and the outermost layer of the dermal system that externally covers the gall form the gall wall, and increased in thickness until the end of gall maturation.E. minutanus induces a structurally complex globoid stem gall, modifying all host plant tissues and stimulating a novel meristematic pattern in S. engleri. The gall developmental stages are each related to specific gall-inducing instars, as gall development progresses according to the development of E. minutanus.

Photosynthetic efficiency and sink demand are tightly correlated with rates of phloem loading where maintaining low cytosolic sugar concentrations is paramount to prevent downregulation of photosynthesis. Sugars Will Eventually be Exported Transporters (SWEETs) are thought to have a pivotal role in apoplastic phloem loading of C4 grasses. SWEETs have not been well-studied in C4 species, and their investigation is complicated by photosynthesis taking place across two cell types and therefore, photoassimilate export can occur out of either one. SWEET13 homologues in C4 grasses have been proposed to facilitate apoplastic phloem loading. Here we provide evidence for this hypothesis using the C4 grass Setaria viridis. Expression analyses on the leaf gradient of C4 species Setaria and sorghum show abundant transcript levels for SWEET13 homologues. Carbohydrate profiling along the Setaria leaf show total sugar content to be significantly higher in the mature leaf tip compared with the younger tissue at the base. We present the first known immunolocalization results for SvSWEET13a and SvSWEET13b using novel isoform-specific antisera. These results show localization to the bundle sheath and phloem parenchyma cells of both minor and major veins. We further present the first transport kinetics study of C4 monocot SWEETs by utilizing a Xenopus laevis oocyte heterologous expression system. We demonstrate that SvSWEET13a and SvSWEET13b are high-capacity transporters of glucose and sucrose with a higher apparent Vmax for sucrose than glucose, typical of clade III SWEETs. Collectively, these results provide evidence for an apoplastic phloem loading pathway in Setaria and possibly other C4 species.

Abroma augusta L. known as Devil’s cotton belongs to Malvaceae. The exploratory study aimed to study the morphological and anatomical characteristics of the aerial parts of A. augusta L. from Semarang. The transverse section of the aerial parts was made by a simple method (fresh preparation) and then observed under a binocular microscope with an optilab. All characteristics were observed and then compared with the references. The collected data were analyzed descriptively and quantitatively. In summary, the results showed that A. augusta L. was an evergreen shrub (small tree) with orthotropic and plagiotropic branches and polymorphous leaves. The inflorenscence was found in the terminal and axillar plagiotropic branching with bisex, actinomorphic, and pentamerous flowers. The fruit was unique (obconical capsule with a rounded base and truncate-tip with 5 angled wings) including cotton fibers and numerous black seeds. The petiole was composed of epidermis, collenchyma, cortical parenchyma, sclerenchyma, vascular bundle, mucilaginous ducts, and pith. The dorsiventral leaf was composed of upper and lower epidermis, palisade, and spongy parenchyma. The stomata type was ranunculaceous (anomocytic) while the guard cell was kidney-shaped. The stomata density on the abaxial leaf was higher than that of the adaxial leaf. The stellate and unicellular non-glandular trichomes, and capitate glandular trichomes were found abundantly on the petiole and leaf blade. These morphological and anatomical studies are important to support the identification as a part of the conservation effort of the plant. Further studies are recommended to investigate the root morphology and anatomy and also biochemical characteristics of each part of the plant in order to obtain complete plant identification.

Symbiotic N2 fixation depends on a steady supply of carbohydrate to nodules. Sucrose is the main carbohydrate translocated through the phloem to nodules. Some putative sucrose transporter genes have been found in legumes and are highly expressed in nodules. However, none of these are crucial for sucrose transport to nodules. In this study, we characterized a soybean sucrose transporter, GmSUT1, which was highly expressed in nodules and mainly localized in peripheral fixation zone and vascular bundles of nodules. Soybean transgenic composite plants overexpressing GmSUT1 exhibited increased nodule number and dry weight, and improved plant dry weight and N content compared to control plants when inoculated with rhizobia. Furthermore, the inoculated RNAi plants impaired sucrose transport and showed increased shoot sucrose concentration. In nodules, overexpression of GmSUT1 decreased the sucrose concentration and increased hextose concentrations, whereas RNAi plants decreased glucose concentration compared with the control plants. These results in combination with the subcellular localization of GmSUT1 at the plasma membrane indicate that GmSUT1 plays a role in sucrose transport to nodules to promote soybean nodulation.

Phloem-feeding insects cause massive losses in agriculture and horticulture. Host plant resistance to phloem-feeding insects is often mediated by changes in phloem composition, which deter insect settling and feeding and decrease viability. Here, we report that rice plant resistance to the phloem-feeding brown planthopper (BPH) is associated with fortification of the sclerenchyma tissue, which is located just beneath the epidermis and a cell layer or two away from the vascular bundle in the rice leaf sheath. We found that BPHs prefer to feed on the smooth and soft region on the surface of rice leaf sheaths called the long-cell block. We identified Bph30 as a rice BPH resistance gene that prevents BPH stylets from reaching the phloem due to the fortified sclerenchyma. Bph30 is strongly expressed in sclerenchyma cells and enhances cellulose and hemicellulose synthesis, making the cell walls stiffer and sclerenchyma thicker. The structurally fortified sclerenchyma is a formidable barrier preventing BPH stylets from penetrating the leaf sheath tissues and arriving at the phloem to feed. Bph30 belongs to a novel gene family, encoding a protein with two leucine-rich domains. Another member of the family, Bph40, also conferred resistance to BPH. Collectively, the fortified sclerenchyma-mediated resistance mechanism revealed in this study expands our understanding of plant-insect interactions and opens a new path for controlling planthoppers in rice.

This research was conducted to investigate the effect of garlic cloves extract (GCE) at 50 and 100 g l-1 and licorice root extract (LRE) at 25 and 50 g l-1 as foliar spray treatments on the vegetative growth and leaf anatomy of strawberry plants cultivated in different growing media, i.e. traditional soil (silt : sand 1:1 v/v), solid substrates (Peatmoss, Perlite and vermiculite 1:1:1 v/v/v), hydroponic (DFT technique) during 2017 and 2018 seasons. The growth of strawberry plants cv. festival cultivated in the three assigned growing media was significantly enhanced by the applied GCE and LRE treatments. Significant increases in the fresh and dry weights of root and shoots, root size, number of leaves and total leaves area / plant were obtained with all GCE and LRE treatments, while a significant reduction in roots / shoots ratio was occurred. In addition, both treatments caused a significant increase in the leaf content of photosynthetic pigments, nitrogen, phosphorous, potassium, calcium, magnesium and crude protein compared with the untreated plants. Anatomically, the applied concentrations of both GCE and LRE led to obvious increases in the thickness of mid vein, length and width of main vascular bundle, thickness of phloem and xylem tissues, number of xylem vessels/ bundle and thickness of lamina and its tissue components (upper and lower epidermis and mesophyll tissue). Furthermore, these positive effects of GCE and LRE treatments on the vegetative growth, chemical composition and leaf anatomy were most pronounced with the plants cultivated in solid substrate mixture followed by the plants cultivated hydroponically then those cultivated in traditional soil. Also, LRE at 50 g l-1 was the most effective treatment in this respect followed by LRE at 25 g l-1 then GCE at 50 g l-1 while GCE at 100 g l-1 was the least effective. Therefore, the present study strongly confirm the use of GCE and LRE as healthy safe and eco-friendly treatments to improve growth of strawberry plants whether cultivated in traditional soil or in soil alternatives and also to reduce the risks of using growth regulators for clean and safe agriculture.

Rapid commercialization, industrialization and the use of nanotechnology has led to an increase in the distribution of nanoparticles (NPs) in the environment. The most common metal oxide NPs which is present within products is Titanium dioxide (TiO(2)). TiO(2) NPs have photocatalytic nature and can affect plant growth. The current study investigated the morphological, anatomical and biochemical features of Baby sun rose (Aptenia cordifolia) after exposure to different concentrations of TiO(2) nanoparticles (0, 1, 5, 10 and 20 mg L(−1)). Treatment with TiO(2) NPs showed changes in the morphological features and increased photosynthetic pigmentation within the plant. An increase in the level of phenolics (12%) and flavonoid compounds (13%) was observed when plants were treated with moderate levels of TiO(2) NPs. A reduction in the diameter of the vascular bundles and increased thickening of the transverse wall were observed in several samples. The number of scattered vascular bundles in the stems increased. The morphological, biochemical, and anatomical responses of Baby sun rose indicates that plants can adapt to environments contaminated with up to 20 mg L(−1) TiO(2) NPs(.) The cultivation of Baby sun rose plants in environments polluted with TiO(2) NPs is recommended. This study enhances the knowledge of the effect of TiO(2) NPs on the growth of Baby sun rose which is an ornamental plant, widely cultivated in different regions of Iran. The results of this study suggest that contaminated environments up to 20 mg L(−1) TiO(2) NPs can be managed by phytoremediation. Further studies are needed to investigate this plant's tolerance strategies against stress caused by TiO(2) NPs and bulk TiO(2) as well as the effect of other nanoparticles on plant.

Jojoba, Simmondsia chinensis (Link) Schneider, is a slow-growing woody perennial shrub, whose production can be limited by soil salinity. Based on the fact that alterations of salinity stress can be reduced by biofertilization, the aim of this work was to study the effects of salinity and Azospirillum brasilense inoculation on the probable structural characteristics of leaves, stems, and roots of jojoba plants grown in vitro by light and scanning electron microscopy. Salt stress induces changes in anatomical characteristics of jojoba in vitro such as increment in mesophyll thickness on leaves, and increases in the cortex, pith, and xylem vessel diameters on stems. Cell density decreased in leaf and stem, and increased in roots. Azospirillum brasilense inoculations mitigated leaf succulence and prevent the root anatomical alterations caused by salinity displaying leaf mesophyll and chlorenchyma thickness, root diameter, cortex thickness, and vascular bundle diameter similar values to control plants in some treatments. Also improved the anatomical characteristic of the stem and increment the xylem vessels ratio between stem and root. The anatomical changes induced by A. brasilense could protect jojoba plants from the detrimental effects of saline stress and explain the higher tolerance to salinity of inoculated plants.

Machine transplanting and the application of slow-release nitrogen (N) fertilizer (SRNF) have played vital roles in the modernization of rice production. We aimed to determine the effects of potted-seedling transplanting—a new machine-transplanting method—and SRNF on hybrid rice yields. A 2-year split-plot experiment (2016–2017) was conducted in Meishan, Sichuan province, China, using two machine-transplanting methods (potted-seedling and blanket-seedling) and three N treatments. Total green leaf area, high-effective leaf area and its rate at heading, net photosynthetic rate of flag leaves 7 days after heading, glutamate synthase (GOGAT) and glutamine synthase (GS) activity after heading, dry matter production, and N accumulation at heading and maturity increased under the potted-seedling method or 70% SRNF as a base + 30% urea application at the panicle initiation stage (SBUP). Stem diameter and number of small and of all vascular bundles at the neck–panicle node in potted-seedling plants increased as a result of increasing numbers of effective panicles, secondary branches, and spikelets. In potted-seedling plants, treatment with SBUP increased the number of large and total vascular bundles at the panicle–neck internode and the number of differentiated and surviving secondary branches and spikelets and decreased the number of ineffective tillers and degenerated secondary branches and spikelets. We conclude that the potted-seedling machine transplanting method and SRNF combined with urea topdressing can strengthen the source–sink relationship in rice, resulting in higher yields.

Hybrids and planting density are the main factors affecting maize lodging resistance. Here, we aimed to elucidate the mechanism of the regulation of maize lodging resistance by comparing two hybrids at various planting densities from the perspective of lignin metabolism. Our results showed that compared to lodging-susceptible hybrid Xundan 20 (XD20), lodging-resistant hybrid Denghai 605 (DH605) showed a lower center of gravity and culm morphological characteristics that contributed to the higher lodging resistance of this hybrid. Lignin content, activities of key lignin synthesis-related enzymes and G-, S- and H-type monomer contents were significantly higher in hybrid DH605 than in hybrid XD20. Stalk mechanical strength, lignin accumulation and enzyme activity decreased significantly with increasing planting density in the two hybrids. While G-type monomers first decreased with increasing planting density but then remained stable, S-type monomers showed a decreasing trend, and H-type monomers showed an increasing trend. Correlation analysis showed that lodging rate was significantly correlated with plant traits and lignin metabolism. Therefore, maize hybrids characterized by high lignin accumulation, high lignin synthesis-related activities, high S-type monomer content, low center of gravity, high stem puncture strength, high cortical thickness, and small vascular bundle area are more resistant to lodging. High planting densities reduce stalk lignin accumulation, relevant enzyme activities and mechanical strength, thereby, ultimately increasing the lodging rate significantly.

Dark septate endophytes (DSEs) appear to protect host plants against a variety of biotic and abiotic stresses; however, our knowledge of the roles played by DSEs in improving the drought tolerance of trees is poor. In this study, we inoculated sterile drought-stressed Ormosia hosiei seedlings with the DSE species Acrocalymma vagum to determine the role that the DSE plays in seedling growth and drought tolerance of O. hosiei. We investigated whether inoculation with DSE affected the leaf morphology, anatomical structure, pigments, photosynthesis, and chloroplast ultrastructure. Inoculated seedlings and non-inoculated seedlings were grown under three different soil water conditions (well-watered, 75% of field water capacity; moderate water, 55% of field water capacity; or low water, 35% of field water capacity) for 114 days. The leaf length, leaf width, leaf area, leaf dry weight, leaf palisade tissue thickness, vascular bundle area, and the inner diameter of vessels of the inoculated seedlings were significantly greater than those of non-inoculated seedlings. Furthermore, the content of pigments, net photosynthetic rate, stomatal conductance, and the transpiration rate of inoculated seedlings were significantly higher than those of the non-inoculated seedlings, whereas the intracellular CO2 concentration was significantly lower than that of non-inoculated seedlings. The mitochondria, chloroplasts, and cell membrane were well preserved under water stress in the inoculated seedlings, whereas the chloroplasts and other leaf cell organelles of the non-inoculated seedlings were severely damaged. Our results indicate that inoculating O. hosiei with a DSE could be a promising biological approach with the potential to promote the survival of these trees.

C-4 photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO2 concentration at the site of CO2 fixation. C-4 plants benefit from high irradiance but their efficiency decreases under shade, causing a loss of productivity in crop canopies. We investigated shade acclimation responses of Setaria viridis, a model monocot of NADP-dependent malic enzyme subtype, focussing on cell-specific electron transport capacity. Plants grown under low light (LL) maintained CO2 assimilation rates similar to high light plants but had an increased chlorophyll and light-harvesting-protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen-evolving activity and the PSII/PSI ratio were enhanced in LL BS cells, indicating a higher capacity for linear electron flow. Abundances of PSI, ATP synthase, Cytochrome b(6)f and the chloroplast NAD(P)H dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were also increased in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts were associated with a more oxidised plastoquinone pool in LL plants and the formation of PSII - light-harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results suggest that the supramolecular composition of PSII in BS cells is adjusted according to the redox state of the plastoquinone pool. This discovery contributes to the understanding of the acclimation of PSII activity in C-4 plants and will support the development of strategies for crop improvement, including the engineering of C-4 photosynthesis into C-3 plants.

Cucurbit phloem is complex, with large sieve tubes on both sides of the xylem (bicollateral phloem), and extrafascicular elements that form an intricate web linking the rest of the vasculature. Little is known of the physical interconnections between these networks or their functional specialization, largely because the extrafascicular phloem strands branch and turn at irregular angles. Here, export in the phloem from specific regions of the lamina of cucumber (Cucumis sativus L.) was mapped using carboxyfluorescein and 14 C as mobile tracers. We also mapped vascular architecture by conventional microscopy and X-ray computed tomography using optimized whole-tissue staining procedures. Differential gene expression in the internal (IP) and external phloem (EP) was analyzed by laser-capture microdissection followed by RNA-seq. The vascular bundles of the lamina form a nexus at the petiole junction, emerging in a predictable pattern, each bundle conducting photoassimilate from a specific region of the blade. The vascular bundles of the stem interconnect at the node, facilitating lateral transport around the stem. Elements of the extrafascicular phloem traverse the stem and petiole obliquely, joining the IP and EP of adjacent bundles. Using pairwise comparisons and weighted gene coexpression network analysis (WGCNA), we found differences in gene expression patterns between the petiole and stem and between IP and EP, and we identified hub genes of tissue-specific modules. Genes related to transport were expressed primarily in the EP while those involved in cell differentiation and development as well as amino acid transport and metabolism were expressed mainly in the IP.

C4 plants, such as maize, strictly compartmentalize Rubisco to bundle sheath chloroplasts. The molecular basis for the restriction of Rubisco from the more abundant mesophyll chloroplasts is not fully understood. Mesophyll chloroplasts transcribe the Rubisco large subunit gene and, when normally quiescent transcription of the nuclear Rubisco small subunit gene family is overcome by ectopic expression, mesophyll chloroplasts still do not accumulate measurable Rubisco. Here we show that a combination of five ubiquitin promoter-driven nuclear transgenes expressed in maize leads to mesophyll accumulation of assembled Rubisco. These encode the Rubisco large and small subunits, Rubisco assembly factors 1 and 2, and the assembly factor Bundle sheath defective 2. In these plants, Rubisco large subunit accumulates in mesophyll cells, and appears to be assembled into a holoenzyme capable of binding the substrate analog CABP (carboxyarabinitol bisphosphate). Isotope discrimination assays suggest, however, that mesophyll Rubisco is not participating in carbon assimilation in these plants, most probably due to a lack of the substrate ribulose 1,5-bisphosphate and/or Rubisco activase. Overall, this work defines a minimal set of Rubisco assembly factors in planta and may help lead to methods of regulating the C4 pathway.

In this study, we investigated the expression and functions of the transcription factor gene RDD4 (rice Dof daily fluctuations 4), which has sequence similarity to RDD1 that controls nutrient ion accumulation in rice. RDD4 protein was highly accumulated in leaf sheaths and localized to vascular bundles. RDD4-overexpressing plants (RDD4-OX) improved the accumulation of various nutrient ions, irrespective of nutrient concentration in a hydroponic solution. K+ and Cl- deficiencies induced the accumulation of other cations and anions, respectively. Interestingly, in RDD4-OX plants K+ and Cl- deficiencies increased PO4 3- and Mg2+ contents, respectively, despite opposite electric charges. Furthermore, PO4 3- deficiency induced NO3 - and Mg2+ accumulation in RDD4-OX plants. These data show that RDD4 is associated with the control of nutrient ion contents within plants. Also, photosynthetic CO2 assimilation in RDD4-OX plants was higher than in wild-type (WT) plants, although the sizes of shoots and panicles decreased in RDD4-OX plants. Subsequent microarray analysis indicated that OsFWL7, similar to maize CNR1 that negatively regulates plant size, showed the most significant difference in its expression levels between WT and RDD4-OX plants. Based on these results, it is hypothesized that a prominent increase in the OsFWL7 expression reduces plant size in RDD4-OX plants. This article is protected by copyright. All rights reserved.

The leaf vascular bundle sheath cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem sap water and solutes radially entering the mesophyll cells. Under normal conditions, xylem sap pH below 6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSC proton pump, AHA2, we now test the hypothesis that it regulates the xylem sap pH and leaf radial water fluxes. We monitored the xylem sap pH in the veins of detached leaves of wild-type Arabidopsis, AHA mutants and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor (vanadate) and stimulator (fusicoccin), and different pH buffers. We monitored their impact on the xylem sap pH and the leaf hydraulic conductance (Kleaf ), and the effect of pH on the water osmotic permeability (Pf ) of isolated BSCs protoplasts. We found that AHA2 is necessary for xylem sap acidification, and in turn, for elevating Kleaf . Conversely, AHA2 knockdown, which alkalinized the xylem sap, or, buffering its pH to 7.5, reduced Kleaf , and elevating external pH to 7.5 decreased the BSCs Pf . All these showed a causative link between AHA2 activity in BSCs and leaf radial hydraulic water conductance.

Dryocosmus kuriphilus (Hymenoptera: Cynipidae), the Asian chestnut gall wasp (ACGW), is an invasive pest that threatens native stands and orchards of European Sweet Chestnut (Castanea sativa Mill.). ACGW induces galls in stems, petioles, and midribs. These galls cause inhibition of tree growth and fruit production. An understanding of morphogenetic changes in host organs is important to evaluate how plant resources are redirected to galls. Structural divergences in C. sativa petioles, midribs, and respective galls were investigated. Larvae of D. kuriphilus are found in the central region of young petioles and midribs in the spring. They are positioned in the pith region of petioles and midribs, surrounded by vascular tissues. The increase in cell layers and volume is evident in the ground tissues of galls, i.e., parenchyma, collenchyma, and sclerenchyma that originate from ground meristem. Gall formation causes the separation of the original vascular system into several collateral and amphicribral vascular bundles. The vascular web branching likely favors the redirection of resources from developing leaf blades to the galls by compensatory hydraulic mechanisms. The rapid growth rates of galls are likely supported by an increased water supply to gall sites. Cytoplasmically dense and metabolically active nutritive linings of the larval chambers are the sole source of food for larvae. Nutritive cells are maintained by a rich vascular supply. The redifferentiation of mechanical tissue surrounding the nutritive tissue also requires energy and protects the D. kuriphilus larva until pupation. These vascular alterations impact the normal formation of tissues in distal regions of the leaf, which reduces the productivity of chestnut trees.

Tetrastigma hemsleyanum Diels & Gilg ex Diels is a liana plant with promising medicinal and ornamental values. Its calabash-shaped roots (CRs) are served as a traditional Chinese herb. However, it takes a long growth period to form CRs. In this study, three types of architectural roots, including fibrous roots (FRs), bar-shaped roots (BRs) and CRs, were employed as materials, and the characteristics of histo-anatomy and digital RNA-seq transcriptome profiles were analyzed. Among the three types of roots, the vascular bundles in FRs were intact, while some of the vascular bundles degenerated in BRs, and only few traces of vascular bundles existed in CRs. Meanwhile, no obvious cell inclusions were found in the cytoplasm of FRs, while a few inclusions were found in BRs, and abundant inclusions were detected in CRs, which might be the main source of medicinal components in roots. The transcriptome profiles and qRT-PCR validation indicated that seven upregulated genes, encoding xyloglucan glycosyltransferase, ACC oxidase, CYP711A1, SHORT-ROOT transcript factor, galacturonosyltransferas, WAT1 and WRKY, and two downregulated genes, encoding LRR receptor-like serine/threonine-protein kinase and CYP83B1, were probably involved in the formation and development of CRs. In addition, Gene Ontology terms of intrinsic component of membrane, integral component of membrane, cell periphery, membrane part, plasma membrane, membrane, intrinsic component of plasma membrane, cellular chemical homeostasis and plasma membrane part were probably related to the formation of CRs. Kyoto Encyclopedia of Genes and Genomes pathways related to the development of CRs probably included MAPK signaling pathway–plant, plant hormone signal transduction and circadian rhythm–plant. Our finding suggested a probable mode for the formation of CRs.

Verticillium wilt (Verticillium dahliae Kleb.) is a fungal disease of sunflower plants causing vascular bundle jamming, leaf wilt, and plant death, all of which affect sunflower production. We devised an artificial inoculation field test to investigate Verticillium wilt incidence during different stages of sunflower growth including seedling, flowering, and maturation stages, to assess the impact of different disease appearance period on plant growth and production. We hypothesized that time of symptom appearance may be a key factor for sunflower development. The results showed that Verticillium wilt dramatically inhibited sunflower growth and production in all three developmental stages. The disease incidence of Verticillium wilt, considered as percentage of symptomatic plants, was higher than 60% at the maturation stage and lower than 20% at the seedling stage. However, the greatest yield suppression was identified at the seedling stage, while yield inhibition was relatively limited during the flowering and maturation stages. Therefore, the earlier the symptom appearance is established in sunflower development, the greater is the suppression of plant growth, indicating that seedling management is crucial in controlling the Verticillium wilt. The outcomes of this study would contribute to the development of disease control strategies to improve sunflower production.

Plants can minimize the adverse effects of salinity by modifying morphological and anatomical features. Previous studies showed that endophytic Epichloe bromicola play an important role in improving wild barley (Hordeum brevisubulatum) salinity tolerance. The aim of this work is to understand whether Epichloe endophyte affects the anatomical structures of host H. brevisubulatum under salinity environments. Seedlings of E. bromicola infected (E+) and E. bromicola free (E-) H. brevisubulatum were treated with different NaCl concentrations, with the control seedlings being grown without NaCl. Anatomical structures of roots, stems and leaves were observed by making paraffin sections with double staining dehydration methods (safranin and fast green). NaCl treatments significantly affected the anatomical structure of H. brevisubulatum. Vascular tissue area throughout the leaf, stem and root decreased as the NaCl concentration increased. Thickness of epidermis in stems and leaves, and the cortex in roots also decreased with salt level increases. Endodermis thickness, epidermis thickness and stele area in roots were increased under salinity stress. The presence of Epichloe endophyte regulated some anatomical structure modifications. Epichloe infection was associated with significant higher conducting tissues (including leaf xylem, leaf phloem, stem vascular bundles, stem xylem vessels and root meta-xylem area). The increased thickness of leaf veins, epidermis in stems, cortex and endodermis in roots were also associated with Epichloe endophyte infection under NaCl stress. The presence of Epichloe endophyte ameliorated adverse effects of salinity on H. brevisubulatum. We observed specific changes of anatomical structures that may help in inhibiting water loss and inhibiting decrease of transport capacity for better conduction of water, nutrients, photosynthates and re-translocation of assimilates to suppress negative effects of salinity and enhance the tolerance of H. brevisubulatum to salt stress.

Leaves are asymmetric, with different functions for adaxial and abaxial tissue. The bundle sheath (BS) of C3 barley (Hordeum vulgare) is dorsoventrally differentiated into three types of cells: adaxial structural, lateral S-type, and abaxial L-type BS cells. Based on plasmodesmatal connections between S-type cells and mestome sheath (parenchymatous cell layer below bundle sheath), S-type cells likely transfer assimilates toward the phloem. Here, we used single-cell RNA sequencing to investigate BS differentiation in C4 maize (Zea mays L.) plants. Abaxial BS (abBS) cells of rank-2 intermediate veins specifically expressed three SWEET sucrose uniporters (SWEET13a, b, and c) and UmamiT amino acid efflux transporters. SWEET13a, b, c mRNAs were also detected in the phloem parenchyma (PP). We show that maize has acquired a mechanism for phloem loading in which abBS cells provide the main route for apoplasmic sucrose transfer toward the phloem. This putative route predominates in veins responsible for phloem loading (rank-2 intermediate), whereas rank-1 intermediate and major veins export sucrose from the PP adjacent to the sieve element companion cell complex, as in Arabidopsis thaliana. We surmise that abBS identity is subject to dorsoventral patterning and has components of PP identity. These observations provide insights into the unique transport-specific properties of abBS cells and support a modification to the canonical phloem loading pathway in maize.

The galls induced by hemipterans generally show hypertrophy of the phloem; these insects usually feed on the sap in the sieve tube elements, occasioning phloem bundle hypertrophy. However, there are some exceptions; for example, the phylloxerids feed on the gall wall parenchyma. It has remained unknown, however, whether Daktulosphaira vitifoliae (the vine phylloxera) also causes hypertrophy of the phloem bundles. The galls induced by D. vitifoliae in leaves of the rootstock variety Richter-110 (Vitis berlandieri × Vitis rupestris) were examined microscopically. D. vitifoliae was found capable of inducing vascular bundle hypertrophy, as well as the nutritional enrichment of the gall wall parenchyma cells upon which the insect feeds. The hypertrophy of the phloem bundles commonly seen in hemipteran-induced leaf galls also occurs in those induced by D. vitifoliae, even though these do not feed on the phloem contents, but rather on the gall wall parenchyma. The appearance of phloem bundle hypertrophy in hemipteran-induced leaf galls requires the remobilization of photoassimilates that might affect the productivity of the affected plant.

MicroRNA319 (miR319) has been implicated in leaf development in a number of plant species. Here we study the roles of miR319a and its regulated network in leaf development in poplars. Over-expression of miR319a in Populus alba × Populus glandulosa caused dwarf statures, narrow leaf blades and serrated leaf margins. The vascular bundles and bundle sheaths in transgenic leaves had more layers of cells than those in the leaves of control plants, indicating enhanced lignification in these cells. Among the 93 putative targets of miR319a predicted with the psRNATarget tool, only three genes, TCP (TEOSINTE BRANCHED1, CYCLOIDEA, and PROLIFERATING CELL NUCLEAR ANTIGEN BINDING FACTOR), were differentially expressed in the leaves of MIR319a-over-expression transgenic lines. With the RNA-seq data sets from multiple MIR319a over-expression transgenic lines, we built a three-layered gene regulatory network mediated by miR319a using Top-down graphic Gaussian model (GGM) algorithm that is capable of capturing causal relationships from transcriptomic data. The results support that miR319a primarily regulates the lignin biosynthesis, leaf development and differentiation as well as photosynthesis via miR319-MEE35/TCP4, miR319-TCP2 and miR319-TCP2-1 regulatory modules.

Pear (Pyrus spp.) belongs to the genus Pyrus, in the family Rosaceae. Some varieties of pear fruit exhibit bulged surface, which seriously affects the quality and commodity value of the pear fruit. In this study, we performed anatomical, physiological, and transcriptomic analysis to explore the mechanism of paclobutrazol (PBZ) on the bulged surface of pear fruit. The vascular bundles of flesh were more evenly distributed, and the fruit cells were more compactly arranged and smaller in size treated with PBZ. However, the auxin (IAA) content of flesh was decreased in the treated group. Furthermore, the GO and KEGG analysis of differentially expressed genes (DEGs) showed that auxin, phenylpropanoid metabolic pathways, and transcriptional factor genes were significantly enriched on the relieved bulged surface of pear fruit. And it was analyzed that some genes contained auxin responded cis-elements from the selected DEGs in the promoter region. We conclude that PBZ plays a negative role in cell division, cell elongation, and vascular bundle development on the bulged surface of pear fruit through the involvement of auxin-related genes. This study will provide a theoretical basis for the regulation of the bulged surface of pear fruit by a growth retardant agent.

Drought decreases water transport capacity of leaves and limits gas exchange, which involves reduced leaf leaf hydraulic conductance (Kleaf) in both the xylem and outside-xylem pathways. Some literature suggests that grapevines are hyper-susceptible to drought-induced xylem embolism. We combined Kleaf and gas exchange measurements, micro-computed tomography of intact leaves, and spatially explicit modeling of the outside-xylem pathways to evaluate the role of vein embolism and Kleaf in the responses of two different grapevine cultivars to drought. Cabernet Sauvignon and Chardonnay exhibited similar vulnerabilities of Kleaf and gs to dehydration, decreasing substantially prior to leaf xylem embolism. Kleaf and gs decreased by 80% for both cultivars by Ψ leaf approximately –0.7 MPa and –1.2 MPa, respectively, while leaf xylem embolism initiated around Ψ leaf = –1.25 MPa in the midribs and little to no embolism was detected in minor veins even under severe dehydration for both cultivars. Modeling results indicated that reduced membrane permeability associated with a Casparian-like band in the leaf vein bundle sheath would explain declines in Kleaf of both cultivars. We conclude that during moderate water stress, changes in the outside-xylem pathways, rather than xylem embolism, are responsible for reduced Kleaf and gs. Understanding this mechanism could help to ensure adequate carbon capture and crop performance under drought.

Understanding vascular bundle systems in angiosperms is a challenge. On the one hand, the vascular tissue is extremely important in reconstructing the evolution and survivability of plants, but on the other hand, it forms a complicated three-dimensional system of controversially discussed phylogenetic and ontogenetic origin. To increase clarity, in this paper we briefly summarize histological, phylogenetic and molecular aspects of primary vascular bundle formation in angiosperms, adding histological data on early stages of vascular bundle formation, proposing a concept combining the different views and providing simplified illustrations to improve the understanding of primary vascular systems in angiosperms. Based on the auxin hypothesis, vascular bundle formation is stimulated by the development of leaf primordia. Provascular domains appear at the base of the leaf primordia and develop into two directions (leaf, internode). The low vs. high number of internodal bundles, their circular vs. scattered arrangement and the open vs. closed bundle construction in eudicots vs. monocots can be deduced to be due to processes below the shoot apical meristem. The most important processes distinguishing monocots from eudicots are the isolated bundle initiation outside the primary meristem, the enormous expansion of the leaf bases associated with a high number of vascular bundles and the early onset of primary thickening passively dislocating vascular bundles.

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

Host-induced gene silencing (HIGS) of insect growth and development is a promising measure for pest control in practice; the feasibility of disarming insect detoxification of toxic phytochemicals via HIGS of insect detoxification enzymes remains largely unexplored. In this study, a HIGS system was applied to interfere with glutathione S-transferase (GST) gene expression in brown planthopper (BPH, Nilaparvata lugens), a key insect pest in rice of Asia, and regulate rice resistance to the insect. The recombination vector in transgenic plants was expressed in almost all organs, especially in vascular bundle tissues, mesophyll, epidermal cells and leaf sheath sap, but not in xylem. Target BPH NlGST1-1 was successfully integrated into rice genome, the resultant transgenic rice lines harbored a single-copy of BPH NlGST1-1 dsRNA, and expression of NlGST1-1 dsRNA was detected in leaves and leaf sheaths of transgenic lines. However, the content of phytochemical gramine, an inherent alkaloid in gramineous plants, did not change in these transgenic plants. BPH nymphs reared on the transgenic rice expressing NlGST1-1 dsRNA displayed significant reductions in NlGST1-1 transcript expression and GST activity. The transgenic plants significantly retarded relative growth rate of the nymphs and the insect female fecundity, the plants also showed enhanced resistance when attacked by BPH. Our study demonstrated the feasibility of reinforcing gramine-mediated plant defense via HIGS of GSTs in herbivorous insects. HIGS-mediated suppression of the herbivore adaptive mechanism has significant implications for efficiently managing BPH and other pests in rice.

An ideal leaf shape is beneficial to the yield of rice. Molecular understanding of the leaf primordia and polarity establishment plays a significant role in exploring the genetic regulatory network of leaf morphogenesis. In recent years, researchers have cloned an array of coding genes and a few non-coding small RNAs involved in rice leaf development through regulating the development of leaf primordia, vascular bundles, sclerenchyma cells, bulliform cells, cell walls and epidermis cells. These genes and their interactions play critical roles in rice leaf development through the determination and regulatory role in gene expression, and their coordination with other genetic networks or signal pathways. But the relationship among these genes is poorly defined and the underlying network is still unclear. In this review, we introduced the regulatory pathways of leaf primordium development and leaf polarity establishment, mainly the relationship between cell development mechanism and leaf polarity establishment, focusing on how leaf tissue affects leaf shape. Hopefully, the regulation network reviewed here has immediate implications for future research and genomic design breeding.

High irradiance of a habitat in arid areas is usually associated with high temperature and dry air, which can cause water deficiency in plants. The Tulip tree (Liriodendron tulipifera) is a light-loving mesophytic species. This study showed that L. tulipifera forms shade or sun leaves depending on the light conditions. Some xeromorphic features were found in leaves of the trees in illuminated habitats. These sun leaves are smaller, denser, and thicker, with smaller epidermal cells and a thick cuticle; the spongy parenchyma consists of a larger number of rows of small cells; the cells of the columnar parenchyma are larger than the shade leaves. The sun leaf contains more total chlorophyll (by 20–30%), and the guard cells of the stomata of the sun leaf contain chloroplasts. The increased concentration of chlorophyll probably maintains the energy balance in the conditions of inhibited photosynthesis under high illumination and temperature. Decreased sizes of the sun leaf and epidermis cells, thickening of the cuticle and cell wall of epidermal cells, sunken stomata, compact mesophyll with small intercellular spaces, and multirow spongy parenchyma protect from overheating and passive loss of water and can be considered as xeromorphic features. Large numerous stomata and vascular bundles contribute to effective cooling of the surface by transpiration at high temperatures under sufficient water supply. Thus, the leaves of L. tulipifera have an ecological plasticity in relation to illumination and temperature, which contributed to the acclimation of the species to the habitat conditions in arid climates.

Aizoaceae is one of the most important and widespread succulent plant families in both tropical/subtropical regions and arid zones. In this study, 27 species were collected from various floristic regions in Egypt, Kingdom of Saudi Arabia and cactus farms (Kalupia - Egypt). The morphological characteristics of every taxon were recorded. The important morphological features included: the number of leaves per plant; leaf types; leaf position (cauline or radical; the latter indicates leaves arising from, or near, the roots); leaf arrangement; petiolate or sessile leaves; leaf sheath present or absent; leaf shape; leaf margin; leaf tip; presence of leaf 'window area'; leaf texture; and presence of white or dark miniscule dots (white miniscule dots from calcium carbonate and dark miniscule dots from tannin sacs). The investigated anatomical features were as follows: shape of the transverse section; the type of epidermal cells; the presence of large epidermal cells (bladder cells); presence of papilla and simple hairs; presence of tannin sacs; shapes of calcium oxalate crystals; shape of the xylem vessels; and the presence of Kranz unit (the unit that constitutes the vascular bundle/s, parenchyma sheath, and surrounding mesophyll) or collenchyma sheath. All data were recorded in a data matrix (as either text or numerical data), which was used to construct the identification key and phylogeny tree using a multi-variate statistical package. The results of our analysis may open the possibility of using the morphological and anatomical features of leaves to distinguish between the subfamilies, genera, and species of Aizoaceae. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.

The plants from two populations (P1 and P2) of xero-halophyte Sedobassia sedoides (Pall.) Freitag & G. Kadereit (Chenopodiaceae) with С3–С4 intermediate type of photosynthesis were examined. Morphophysiological parameters were determined: dry biomass of the above-ground organs, maximum quantum yield of photosystem II (PSII), ultra- and mesostructure of the leaf, carbon isotope discrimination (δ13С) in plants grown under normal conditions and exposed to moderate salinization (0 and 200 mM NaCl). By the values of δ13С and efficiency of PSII, we did not detect significant differences between the populations. Under control conditions, the chloroplasts and mitochondria were located in Kranz-like cells of the bundle sheath of both populations in the region adjacent to vascular bundle, which is characteristic of С2 type of photosynthesis (with photorespiratory СО2 concentrating mechanism). P2 plants were notable for a greater volume of Kranz-like cells of the bundle sheath and more numerous, larger chloroplasts and mitochondria than in P1 plants. By structural leaf parameters, P1 plants may be attributed to a proto-Kranz type of photosynthesis (intermediate between С3 and С2 types) and P2 plants to С2 photosynthesis. Under salinization, the accumulation of dry biomass was reduced in both populations but more considerably in P1. The ultrastructure of organelles in both populations showed different responses to salinization, which was especially pronounced in Kranz-like cells of the bundle sheath. In P1 plants, the area of chloroplasts and mitochondria rose, whereas the area and number of chloroplasts under stress did not change in P2 plants but the area and number of mitochondria decreased. In the cells of plants from both populations, signs of degradation were observed (more pronounced in P1 plants); they were shown in chloroplasts twisting and a disturbance of their granal stacking. In P2 plants, Kranz-like cells of the bundle sheath preserved safer organelles but there occurred the cells with complete degradation of a vacuolar type. Thus, intraspecific ultra- and mesostructural differences were detected in plants from two populations of С3–С4 intermediate species S. sedoides, which reflect different stages of development of photorespiratory СО2 concentrating mechanism. Under salinization, the plants from two different populations showed unlike strategies of adaptation on the level of leaf ultra- and mesostructure.

Systemic fungal endophytes may increase the adaptive potential of their hosts to different environmental conditions. However, the mechanisms involved in the adjustment are still an area of active inquiry. Considering that anatomical features in plants are the result of adaptation to different environments, this aspect of plants response to the symbionts deserves further research. In this work we investigated whether an asexual Epichloe endophyte modifies the foliar anatomy of symbiotic plants (E+) of its host grass with respect to endophyte-free plants (E-), using the Epichloe occultans–Lolium multiflorum system. The experiment was carried out in a greenhouse and plants were grown under benign, non-stressful (controlled) conditions. Symbiotic plants showed thinner leaf blades and lower mesophyll thickness. Likewise, the endophyte is associated with a greater number of vascular bundles. The stomatal density on the lower epidermis was higher in symbiotic plants than non-symbiotic plants. Our study reveals that Epichloe occultans modifies the foliar anatomy of Lolium multiflorum. Considering that leaf anatomy exhibits characters that were selected as a result of evolution in relation to specific environmental conditions, these results are promising since they can offer information about the mechanisms involved in the adaptive adjustment of symbiotic plants.

In plants, an elevation in ambient temperature induces adaptive morphological changes including elongated hypocotyls, which is predominantly regulated by a bHLH transcription factor, PIF4. Although PIF4 is expressed in all aerial tissues including the epidermis, mesophyll, and vascular bundle, its tissue-specific functions in thermomorphogenesis are not known. Here, we show that epidermis-specific expression of PIF4 induces constitutive long hypocotyls, while vasculature-specific expression of PIF4 has no effect on hypocotyl growth. RNA-Seq and qRT-PCR analyses reveal that auxin-responsive genes and growth-related genes are highly activated by epidermal, but not by vascular, PIF4. Additionally, inactivation of epidermal PIF4 or auxin signaling, and overexpression of epidermal phyB suppresses thermoresponsive growth, indicating that epidermal PIF4-auxin pathways are essential for the temperature responses. Further, we show that high temperatures increase both epidermal PIF4 transcription and the epidermal PIF4 DNA-binding ability. Taken together, our study demonstrates that the epidermis regulates thermoresponsive growth through the phyB-PIF4-auxin pathway., The PIF4 transcription factor along with the phyB photoreceptor, regulates growth responses to elevated temperature in plants. Here the authors show that PIF4 expression in the epidermis, rather than the vasculature, stimulates auxin responses and thermoresponsive growth in Arabidopsis.

Doubled-haploids are a great source of material for heterozygous coconuts to shorten the time taken for crop improvement through hybridization programs. However, low frequency of embryo conversion and formation of weak plantlets are the major limitations in the protocol. In the present study anther-derived embryos were analysed at cellular level through the histological observations to understand the occurrence of shoot differentiation in those embryos. Attempts were also made to optimise the 6-Benzylaminopurine (BAP) concentration in the regeneration medium. Among the tested BAP levels (5, 15, 25, 35, 45, 55 μM), the regeneration medium containing 25 and 35 μM gave rise to 51.5% sprouted embryos against the control that gave only 22.7%. Among the analysed anther-derived embryos sequential events of differentiation including the formation of provascular strands followed by vascular bundle, differentiation in to the growing point, giving rise to the secondary embryos and polarization in to the shoot and root pole were identified. The blunt embryos devoid any morphological sign of sprouting showed different cellular arrangement viz. haustorial structure without any meristematic point (47%), bipolar with shoot and root meristems (8%) and unipolar with either of the pole (45%). Thick haustorial cover lead to the physical dormancy inhibiting further development of the polar structures. The germinating embryos containing a single shoot gave rise to the healthy plants where as double, multiple or fused shoots formed the week plantlets. The findings can be used for further optimisation of the protocol to achieve a greater plant regeneration frequency. 1. Culture media supplemented with increased levels of 6-Benzylaminopurine (BAP) enhanced the regeneration frequency of anther-derived embryos. 2. Thick haustorial tissue created an obstacle effect on further development of the differentiated shoot apical meristem. 3. Formation of clustered plants through secondary embryogenesis or shoot multiplication at the early stage of plant regeneration caused to give rise to the week plants.

The cambium and procambium generate the majority of biomass in vascular plants. These meristems constitute a bifacial stem cell population from which xylem and phloem are specified on opposing sides by positional signals. The PHLOEM INTERCALATED WITH XYLEM (PXY) receptor kinase promotes vascular cell division and organization. However, how these functions are specified and integrated is unknown. Here, we mapped a putative PXY-mediated transcriptional regulatory network comprising 690 transcription factor-promoter interactions in Arabidopsis (Arabidopsis thaliana). Among these interactions was a feedforward loop containing transcription factors WUSCHEL HOMEOBOX RELATED14 (WOX14) and TARGET OF MONOPTEROS6 (TMO6), each of which regulates the expression of the gene encoding a third transcription factor, LATERAL ORGAN BOUNDARIES DOMAIN4 (LBD4). PXY signaling in turn regulates the WOX14, TMO6, and LBD4 feedforward loop to control vascular proliferation. Genetic interaction between LBD4 and PXY suggests that LBD4 marks the phloem-procambium boundary, thus defining the shape of the vascular bundle. These data collectively support a mechanism that influences the recruitment of cells into the phloem lineage, and they define the role of PXY signaling in this context in determining the arrangement of vascular tissue.

The results of a study conducted by light microscopy of the anatomical structure of the leaf and thorns of Astragalus pterocephalus growing in the natural habitat of the Amankutan Mountains of the Samarkand region (Uzbekistan) are presented. The following diagnostic features were identified: leaf—isolateral-palisade type of mesophyll leaf; thick-walled outer walls of the epidermis; the outline of epidermal cells is rectilinear, the projection is polygonal; amphystomatic leaves; submerged numerous stomata of hemiparacitic and anomocytic type; chlorophyll-bearing palisade and spongy parenchyma; closed collateral type of vascular bundles and more sclerified, due to sclerenchymal cells. Thorn—parenchymal-beam type of structure; thin-walled outer walls of the epidermis; under the epidermis is a lamellar collenchyma; closed collateral type of vascular bundles and more sclerified, due to sclerenchymal cells. The complex of the above features reflects the species specificity of the structure of the leaf and spines. Identified and described features that can be used in the taxonomy of the studied tribes and can serve to identify plant materials.

Secondary stem growth develops different cambial variants in Convolvulaceae. Here, the cambial variant features of 17 species in seven genera (Convolvulaceae) in Taiwan are presented. The xylem rings produce various successive cambial types and the primary xylem and intraxylary phloem are produced in the outer and inner pith, respectively. The two Argyreia species have round or elliptical stems with continuous secondary xylem and phloem rings. In the eight Ipomoea species, secondary growth has two to four layers of successive cambia and xylem, dispersed with parenchyma tissue, except for I. nil and I. violacea with one layer of successive cambia. The first secondary xylem segments are separated by few or many xylem rays: I. cairica and I. obscura have three to five xylem rays and I. triloba has numerous xylem rays. The first secondary xylem of Erycibe henryi is divided by numerous rays in small stems, but develops more layers, as adjacent segments separated by xylem rays, in larger stems. Owing to continuous vascular bundle division, it has a dissected xylem. The secondary growth of Distimate tuberosa and Operculina turpethum produces two layers of successive cambia; the secondary successive cambium is divided evenly by rays into many arcs/segments. The stem thickness of I. pes-caprae subsp. brasiliensis increases via concentric successive cambia. Owing to shallowly lobed stems with directional successive cambia, I. obscura and I. triloba stems are irregularly shaped. I. littoralis and Stictocardia tilifolia stems are triangular without directional successive cambia. I. hederifolia and Merremia gemella stems have two to three deep lobes. Parenchyma proliferation results in thicker cortex with mucilaginous canals. The xylem vessels are dispersed and diffuse-porous; the vasicentric paratracheal parenchyma around them is common to all species. A bracketed key was developed comparing the secondary xylem structures of the 17 species, providing a basis for further morphological studies.

Summary Bundle Sheath Defective 2, BSD2, is a stroma‐targeted protein initially identified as a factor required for the biogenesis of ribulose 1,5‐bisphosphate carboxylase/oxygenase (RuBisCO) in maize. Plants and algae universally have a homologous gene for BSD2 and its deficiency causes a RuBisCO‐less phenotype. As RuBisCO can be the rate‐limiting step in CO2 assimilation, the overexpression of BSD2 might improve photosynthesis and productivity through the accumulation of RuBisCO. To examine this hypothesis, we produced BSD2 overexpression lines in Arabidopsis. Compared with wild type, the BSD2 overexpression lines BSD2ox‐2 and BSD2ox‐3 expressed 4.8‐fold and 8.8‐fold higher BSD2 mRNA, respectively, whereas the empty‐vector (EV) harbouring plants had a comparable expression level. The overexpression lines showed a significantly higher CO2 assimilation rate per available CO2 and productivity than EV plants. The maximum carboxylation rate per total catalytic site was accelerated in the overexpression lines, while the number of total catalytic sites and RuBisCO content were unaffected. We then isolated recombinant BSD2 (rBSD2) from E. coli and found that rBSD2 reduces disulfide bonds using reductants present in vivo, for example glutathione, and that rBSD2 has the ability to reactivate RuBisCO that has been inactivated by oxidants. Furthermore, 15% of RuBisCO freshly isolated from leaves of EV was oxidatively inactivated, as compared with 0% in BSD2‐overexpression lines, suggesting that the overexpression of BSD2 maintains RuBisCO to be in the reduced active form in vivo. Our results demonstrated that the overexpression of BSD2 improves photosynthetic efficiency in Arabidopsis and we conclude that it is involved in mediating RuBisCO activation., Significance Statement Catalytic properties of RuBisCO are susceptible to oxidation of its thiols, but the underlying process resulting in a change in RuBisCO activation has been largely elusive. Here we identify BSD2, known as a chaperone for RuBisCO assembly, as a protein that takes an essential role in the redox homeostasis of mature RuBisCO. We show that overexpression of BSD2 improves RuBisCO carboxylation efficiency through manipulating the redox potential.

Salsola crassa M.B. is one of the most successful plants used against industrial pollutants. In this study, we selected young Salsola crassa M.B. plants from their natural habitats. Some plants were irrigated with industrial wastewater containing Fe, Co, Ni, Cu, Pb, and Zn, and others were irrigated with tap water for 3-4 months. Afterwards, the shoots and roots were randomly cut, separated, fixed, dyed, and observed using light microscopy. Structural changes were analyzed by stereology. There were some differences in appearance and structure between the treated and control samples. For example, the number of leaves and flowers and the size of seeds and flowers in the treated plants were reduced. The diameter of the cortical parenchyma, the total area of each vascular bundle, surface area of the pith cells in the stem, leaf cuticle thickness, mechanical layer thickness of the anther, and diameter of pollen grains were reduced. A peculiar palisade chlorenchyma beneath the epidermis and unexpected small vascular bundles on the upper part of the cortex were features of both groups. Finally, we concluded that industrial waste water pollutants affected various aspects of plant development.

The "Specific Tissue" (ST) are proteins of unknown function present only in some plant families, mainly Fabaceae and Asteraceae. They are included in the PF10950 protein family and characterized by the presence of at least one domain of unknown function (DUF)2775. In this work we studied the involvement of the six members of the Medicago truncatula ST family (ST1 to ST6) in the development of flowers, fruits, and seeds by analysing the activity of their promoters (pST) after the construction of M. truncatula transgenic plants expressing the b-glucuronidase (GUS) reporter gene under the control of the six pSTs. The GUS activity was analysed in whole flowers and fruits and also in histological sections of these organs. The pST expression in the reproductive organs was mainly associated with the vascular bundles, especially throughout fruit development. These results pointed to an important role of ST proteins during the reproductive development stage, related to nutrient mobilization during the fruit and seed formation, that could be facilitated by their presence in the pod vascular bundles, as well as in the connective tissue of the anthers (ST3, ST4, ST6), in the placenta, the funiculus, and the outer parts of the developing seed (ST2, ST3, ST6). The observations made in this study were in agreement with the functions previously established for the three groups of M. truncatula ST proteins, as in the proposed function for ST1 in the transport and assimilation of nutrients, or the involvement of ST4, ST5, and ST6 in floral defence.

Leaf veins play an important role in plant growth and development, and the bundle sheath (BS) is believed to greatly improve the photosynthetic efficiency of C4 plants. The OBV mutation in tomato (Solanum lycopersicum) results in dark veins and has been used widely in processing tomato varieties. However, physiological performance has difficulty explaining fitness in production. In this study, we confirmed that this mutation was caused by both the increased chlorophyll content and the absence of bundle sheath extension (BSE) in the veins. Using genome-wide association analysis and map-based cloning, we revealed that OBV encoded a C2H2L domain class transcription factor. It was localized in the nucleus and presented cell type-specific gene expression in the leaf veins. Furthermore, we verified the gene function by generating CRISPR/Cas9 knockout and overexpression mutants of the tomato gene. RNA sequencing analysis revealed that OBV was involved in regulating chloroplast development and photosynthesis, which greatly supported the change in chlorophyll content by mutation. Taken together, these findings demonstrated that OBV affected the growth and development of tomato by regulating chloroplast development in leaf veins. This study also provides a solid foundation to further decipher the mechanism of BSEs and to understand the evolution of photosynthesis in land plants.

Increasing crop yield has always been an important goal in agriculture. Brassinosteroids (BRs) are growth‐promoting steroid hormones with vital roles in many root developmental processes. Sugar beet ( Beta vulgaris L.) is a root crop with a tertiary root structure. The differentiation of vascular bundles and the division of cambial cells increase root diameter. However, little is known about how BRs regulate the transverse growth of beetroot. Therefore, sugar beet with eight leaves was grown in medium containing epibrassinolide or brassinazole, an inhibitor of BR biosynthesis. BRs increased the spacing between the cambial rings by increasing the size of parenchyma cells between the rings and ultimately increasing root diameter. BRs also promoted secondary xylem differentiation. Moreover, the gene expression analysis of BvXTH33, BvSHV3, BvCESA6, BvPARVUS, and BvCEL1, which were related to the cell wall biosynthesis, indicated that BR could promote the growth of cell wall. These findings showed that BRs function in transverse development in beetroot.

Nigella sativa was widely used for nutritional and medicinal purposes. The present study investigated the effect of drought and salinity stresses on anatomical leaves structure and some biochemical properties to increase the secondary metabolites. For salt stress plants were treated with NaCl (30, 60 mM), and for drought stress plants were irrigated daily (control), once every two days (2DI) and once every three days (3DI). Compared to control plants, 2DI, 3DI, and NaCl 60 mM treatments increase significantly leaf rutin content, while the amount of rutin in seeds of NaCl 60 mM treated plants showed a significant decrease. 3DI treatment also significantly increased rutin content in seeds compared to NaCl 30 mM and control plants. The maximum level of quercetin (0.58 mg g−1 DW), kaempferol (0.16 mg g−1 DW), and myricetin (0.04 mg g−1 DW) in leaves were gained in both NaCl treatments. However, the flavonol components were affected more at salinity conditions rather than drought. In all treated plants, the amount of these compounds in leaves was more than in seeds. The highest amount of total phenol (130 mg g−1 DW), flavonoids (11.4 mg g−1 DW), and carotenoid content (1.55 mg g−1 DW) of leaves were observed under 2DI stress. Treated plants probably encountered different changes in the anatomical structure of leaves, including the decrease of phloem area, reducing vascular bundles and diameters, decreasing the number, and increasing the volume of cortex cells. The study also corroborates the cooperation between increasing the antioxidant capacity with the total flavonoid, rutin, and quercetin. Results indicated a higher sensitivity of N. sativa to drought stress than salinity stress and indicated that moderate salinity and drought could enhance secondary metabolites of seeds in this plant. The formation of potent antioxidants via the treatments could be worthy for pharmaceutical industries.

Drought and salinity are the two major abiotic stresses constraining the crop yield worldwide. Both of them trigger cellular dehydration and cause osmotic stress which leads to cytosolic and vacuolar volume reduction. However, whether plants share a similar tolerance mechanism in response to these two stresses under natural conditions has seldom been comparatively reported. There are three different ecotypes of reed within a 5 km2 region in the Badanjilin desert of Northwest China. Taking the typical swamp reed (SR) as a control, we performed a comparative study on the adaption mechanisms of the two terrestrial ecotypes: dune reed (DR) and heavy salt meadow reed (HSMR) by physiological and proteomic approaches coupled with bioinformatic analysis. The results showed that HSMR and DR have evolved C4-like photosynthetic and anatomical characteristics, such as the increased bundle sheath cells (BSCs) and chloroplasts in BSCs, higher density of veins, and lower density and aperture of stomata. In addition, the thylakoid membrane fluidity also plays an important role in their higher drought and salinity tolerance capability. The proteomic results further demonstrated that HSMR and DR facilitated the regulation of proteins associated with photosynthesis and energy metabolism, lipid metabolism, transcription and translation, and stress responses to well-adapt to the drought and salinity conditions. Overall, our results demonstrated that HSMR and DR shaped a similar adaption strategy from the structural and physiological levels to the molecular scale to ensure functionality in a harsh environment.

Plant cell walls are the first physical barrier against pathogen invasion, and plants thicken the cell wall to strengthen it and restrain pathogen infection. Bacterial blight is a devastating rice (Oryza sativa) disease caused by Xanthomonas oryzae pv. oryzae (Xoo), which typically enters the rice leaf through hydathodes and spreads throughout the plant via the xylem. Xoo interacts with cells surrounding the xylem vessel of a vascular bundle, but whether rice strengthens the sclerenchyma cell walls to stop pathogen proliferation is unclear. Here, we found that a WRKY protein, OsWRKY53, negatively confers resistance to Xoo by strengthening the sclerenchyma cell walls of the vascular bundle. OsMYB63 acts as a transcriptional activator and promotes the expression of three secondary cell wall-related cellulose synthase genes to boost cellulose accumulation, resulting in thickened sclerenchyma cell walls. Both OsWRKY53 and OsMYB63 are abundantly expressed in sclerenchyma cells of leaf vascular bundles. OsWRKY53 functions as a transcriptional repressor and acts genetically upstream of OsMYB63 to suppress its expression. The OsWRKY53-overexpressing and OsMYB63 knockout plants had thinner sclerenchyma cell walls, showing susceptibility to Xoo, while the OsWRKY53 knockout and OsMYB63-overexpressing plants had thicker sclerenchyma cell walls, exhibiting resistance to Xoo. These results suggest that modifying these candidate genes provides a strategy to improve rice resistance to bacterial pathogens.

Phytohormones are known to play crucial role in growth and development of plants. Effect of phytohormones is diverse in different plant species depending on its concentration, type of species and environmental factors where plant is growing. To know the influence of phytohormones on germination and vegetative growth physiology of Caesalpina crista present research work was designed. Initially seeds of Caesalpina crista were treated with different hormones Indole Acetic Acid (IAA), Gibberellic Acid (GA) and Benzyl Amino Purine (BAP)) and its effect on growth of embryo and tissue pattern formation was observed. Further, germinated plants were allowed to grow in soil and phytohormonal treatment was given at an interval of 15 days. Changes in vegetative growth physiology of plants were observed. On the basis of this analysis, it was concluded that Benzylaminopurine (BAP) treatment increases germination rate and shoot length of Caesalpina crista plants by promoting growth of pumule in embryo. IAA increases the leaf area and number of leaflets in plants. From the microscopic anatomical analysis of stem, it was observed that Although the number of vascular bundles were more in BAP treated plants, cambium activity was low as compared to GA and IAA treated plants. Endarch xylem differentiation was observed in GA and IAA treated plants whereas random xylem differentiation was observed in control and BAP treated plants.

In this study, micro computed tomography (Micro-CT) was employed to scan the leaf buds of walnut, and 898 scanning pictures with a total of 3.4 GB were obtained. The shape, size, external characteristics and internal structure of walnut leaf buds were clearly displayed by reconstructing the 3D virtual leaf buds based on the scanning images. Our results showed that the structure of the leaf bud, in successive order from outside to inside, was composed of squamae, young leaves and vascular bundles, and there were 8 bud scales and 5 young leaves for each leaf bud. The results suggested that this technology would provide an effective way for the realization of 3D visualization of walnut leaf bud, and the video production of virtual observation of fruit tree leaf bud, as well as the construction of digital leaf bud.