Leaf Vascular Bundles Research Articles

Effect of Persistent Salt Stress on the Physiology and Anatomy of Hybrid Walnut (Juglans major × Juglans regia) Seedlings.

Soil salinization has become one of the major problems that threaten the ecological environment. The aim of this study is to explore the mechanism of salt tolerance of hybrid walnuts (Juglans major × Juglans regia) under long-term salt stress through the dynamic changes of growth, physiological and biochemical characteristics, and anatomical structure. Our findings indicate that (1) salt stress inhibited seedling height and ground diameter increase, and (2) with increasing salt concentration, relative water content (RWC) decreased, and proline (Pro) and soluble sugar (SS) content increased. The Pro content reached a maximum of 549.64 μg/g on the 42nd day. The increase in superoxide dismutase (SOD) activity (46.80-117.16%), ascorbate peroxidase (APX) activity, total flavonoid content (TFC), and total phenol content (TPC) under salt stress reduced the accumulation of malondialdehyde (MDA). (3) Increasing salt concentration led to increases and subsequent decreases in the thickness of palisade tissues, spongy tissues, leaves, and leaf vascular bundle diameter. Upper and lower skin thickness, root periderm thickness, root diameter, root cortex thickness, and root vascular bundle diameter showed different patterns of change at varying stress concentrations and durations. Overall, the study concluded that salt stress enhanced the antireactive oxygen system, increased levels of osmotic regulators, and low salt concentrations promoted leaf and root anatomy, but that under long-term exposure to high salt levels, leaf anatomy was severely damaged. For the first time, this study combined the anatomical structure of the vegetative organ of hybrid walnut with physiology and biochemistry, which is of great significance for addressing the challenge of walnut salt stress and expanding the planting area.

Rice transcription factor OsWRKY37 positively regulates flowering time and grain fertility under copper deficiency.

Efficient uptake, translocation, and distribution of Cu to rice (Oryza sativa) spikelets is crucial for flowering and yield production. However, the regulatory factors involved in this process remain unidentified. In this study, we isolated a WRKY transcription factor gene induced by Cu deficiency, OsWRKY37, and characterized its regulatory role in Cu uptake and transport in rice. OsWRKY37 was highly expressed in rice roots, nodes, leaf vascular bundles, and anthers. Overexpression of OsWRKY37 promoted the uptake and root-to-shoot translocation of Cu in rice under -Cu condition but not under +Cu condition. While mutation of OsWRKY37 significantly decreased Cu concentrations in the stamen, the root-to-shoot translocation and distribution ratio in brown rice affected pollen development, delayed flowering time, decreased fertility, and reduced grain yield under -Cu condition. yeast one-hybrid, transient co-expression and EMSAs, together with in situ RT-PCR and RT-qPCR analysis, showed that OsWRKY37 could directly bind to the upstream promoter region of OsCOPT6 (copper transporter) and OsYSL16 (yellow stripe-like protein) and positively activate their expression levels. Analyses of oscopt6 mutants further validated its important role in Cu uptake in rice. Our study demonstrated that OsWRKY37 acts as a positive regulator involved in the uptake, root-to-shoot translocation, and distribution of Cu through activating the expression of OsCOPT6 and OsYSL16, which is important for pollen development, flowering, fertility, and grain yield in rice under Cu deficient conditions. Our results provide a genetic strategy for improving rice yield under Cu deficient condition.

Effect of levels of water stress on some physiological and chemical traits of wheat cultivars (Triticum aestivum L.)

A field experiment was carried out at the second agricultural experiment station of the College of Agriculture - Al-Muthanna University during the agricultural season of 2022-2023. The objective of the study was to investigate the physiological and chemical responses of different bread wheat varieties to incomplete irrigation. The experiment was conducted utilising the randomised complete block design (RCBD) employing the split plot method, with three replications. The primary factors investigated in this study were related to irrigation deficiencies, which were represented by four different stages: D1 (control), D2 (tillering stage), D3 (elongation stage), and D4 (booting stage). The secondary factors examined in this research were different cultivars, denoted as V1 (Mawadah), V2 (Bohuth 22), V3 (Baraka), and V4 (Ibaa 99). The statistical analysis revealed significant variations among the stages of water stress. The D2 treatment exhibited the highest proline content at 41.692 mg per 100g, while the D4 treatment demonstrated the greatest thickness of vascular bundles in the roots at 201.23 μm. Regarding the cultivars under investigation, it was observed that the Baraka variety exhibited a higher chlorophyll content (54.24 SPAD units). In contrast, the Bohooth22 cultivar displayed a larger diameter of the vascular bundle in the roots (209.78 μm). Additionally, the Mawada variety demonstrated a greater thickness of the leaf vascular bundles (102.38 μm), while the cultivar IPA99 exhibited a higher content of Proline (35.481 mg per 100g). In terms of interference, treatment D3V1 exhibited a higher proline content of 48.607 mg/100g, indicating its superiority. The results of histological analysis showed the superiority of the combination D2V1 in the diameter of the vascular bundles of the roots (247.33) micrometers, and the occurrence of rupture and damage in the cells of the basal tissue of the root tissue in (D2V1, D3V1, D3V2) and in (D2V1, D2V2, D3V2), in addition to the occurrence of rupture and damage in the upper and lower epidermal cells in the tissue of its leaves, while the combination D2V3 wrinkled and damaged mesophyll cells, and excelled in the thickness of the leaf vascular bundles (142.40) µm, as well as showed that detachment and rupture of the upper epidermis from the mesophyll occurred in D2V4. The results of histological cutting of root cells showed that bundle damage appeared in the root tissue of combination D3V3. Also, fracture and separation occurred in the region of the vascular bundle from the underlying tissue, and some wood vessels were also damaged in the root tissue of the treatment D4V1, and in D4V3 there was a rupture in the lower epidermis of the leaf tissue, and a break in the cells of the cortex and epidermis of the root tissue, while in D4V4, damage was observed in the bundle and cells of the cortex, in addition to the occurrence of a tear in the lower epidermis of the leaves.

IlNRAMP5 is required for cadmium accumulation and the growth in Iris lactea under cadmium exposures

Iris lactea is potentially applied for remediating Cd-contaminated soils due to the strong ability of Cd uptake and accumulation. However, its molecular mechanism underlying Cd uptake pathway remains unknown. Here, we report a member of NRAMP (Natural Resistance-Associated Macrophage Protein) family, IlNRAMP5, is involved in Cd/Mn uptake and the growth in I. lactea response to Cd. IlNRAMP5 was localized onto the plasma membrane, and was induced by Cd. It was expressed in the root cortex rather than the central vasculature, and in leaf vascular bundle and mesophyll cells. Heterologous expression in yeast showed that IlNRAMP5 could transport Cd and Mn, but not Fe. Knockdown of IlNRAMP5 triggered a significant reduction in Cd uptake, further diminishing the accumulation of Cd. In addition, silencing IlNRAMP5 disrupted Mn homeostasis by lowering Mn uptake and Mn allocation, accompanied by remarkably inhibiting photosynthesis under Cd conditions. Overall, the findings suggest that IlNRAMP5 plays versatile roles in Cd accumulation by mediating Cd uptake, and contributes to maintain the growth via modulating Mn homeostasis in I. lactea under Cd exposures. This would provide a mechanistic understanding Cd phytoremediation efficiency in planta.

All together now: Cellular and molecular aspects of leaf development in lycophytes, ferns, and seed plants

Recent advances in plant developmental genetics together with rapid accumulation of transcriptomic data on plants from divergent lineages provide an exciting opportunity to explore the evolution of plant morphology. To understand leaf origin in sporophytes of land plants, we have combined the available molecular and structural data on development of leaves with different morphologies in different plant lineages: clubmosses, spikemosses, leptosporangiate ferns, ophioglossioid ferns, marattioid ferns, whisk ferns, horsetails, and conifers. Specifically, we address the peculiarities of proximo-distal, ad/abaxial, and lateral development; presence/absence of mesophyll differentiation into palisade and spongy parenchyma; and type of leaf vascular bundles (collateral and bicollateral). Furthermore, taxon-specific and morphology-specific features of leaf development are considered in the context of the organization of shoot apical meristems (SAMs)—monoplex, simplex, or duplex—that produce leaf primordia. The data available imply that cellular patterns of leaf initiation correlate strongly with the structure of the SAMs but not with further leaf development or morphology. The later stages of leaf development are neither correlated with SAM structure nor with taxonomy. Occurrence and, if available, patterns of expression of homologs of the angiosperm genes responsible for the development of adaxial (ARPandC3HDZ) and abaxial (YABBYandKANADI) leaf domains, or establishment of the leaf marginal meristem (WOX) are discussed. We show that there is no correlation in the set of homologs of TFs that regulate abaxial and adaxial leaf domain development between leaves containing only spongy and no palisade mesophyll (of spikemosses, clubmosses, whisk ferns, horsetails, and most conifers), and leaves differentiated into palisade and spongy mesophyll (of leptosporangiate ferns,Ginkgo,Gnetum, and angiosperms). Expression of three out of four regulators of leaf development in primordia of both leaves and sporangia—C3HDZin spikemosses and whisk ferns,YABBYin clubmosses andKANADIin spikemosses and horsetails—indicates that a sporangium developmental program could have been co-opted as a “precursor program” for the origin of microphylls and euphylls. Additionally, expression of leaf development regulators in SAMs of spikemosses (ARP,C3HDZ, andKANADI), clubmosses (YABBY), leptosporangiate ferns (C3HDZ), and horsetails (C3HDZandKANADI) indicates that at least some mechanisms of SAM regulation were co-opted as well in the pre-program of leaf precursors.

Effects of high air temperature, drought, and both combinations on maize: A case study

High air temperature (HAT) and natural soil drought (NSD) have seriously affected crop yield and frequently take place in a HAT-NSD combination. Maize (Zea mays) is an important crop, thermophilic but not heat tolerant. In this study, HAT, NSD, and HAT-NSD effects on maize inbred line Huangzao4 -were characterized. Main findings were as follows: H2O2 and O- accumulated much more in immature young leaves than in mature old leaves under the stresses. Lateral roots were highly distributed near the upper pot mix layers under HAT and near root tips under HAT-NSD. Saccharide accumulated mainly in stressed root caps (RC) and formed a highly accumulated saccharide band at the boundary between RC and meristematic zone. Lignin deposition was in stressed roots under NSD and HAT-NSD. Chloroplasts increased in number and formed a high-density ring around leaf vascular bundles (VB) under HAT and HAT-NSD, and sparsely scattered in the peripheral area of VBs under NSD. The RC cells containing starch granules were most under NAD-HAT but least under HAT. Under NSD and HAT-NSD followed by re-watering, anther number per tassel spikelet reduced to 3. These results provide multiple clues for further distinguishing molecular mechanisms for maize to tolerate these stresses.

Disruption of tomato TGS machinery by ToLCNDV causes reprogramming of vascular tissue-specific TORNADO1 gene expression.

Vascular development-related TRN1 transcription is suppressed by cytosine methylation in fully developed leaves of tomato. ToLCNDV infection disrupts methylation machinery and reactivates TRN1 expression - likely causing abnormal leaf growth pattern. Leaf curl disease of tomato caused by tomato leaf curl New Delhi virus (ToLCNDV) inflicts huge economical loss. Disease symptoms resemble leaf developmental defects including abnormal vein architecture. Leaf vein patterning-relatedTORNADO1gene's (SlTRN1) transcript level is augmented in virus-infected leaves. To elucidate the molecular mechanism of the upregulation ofSlTRN1in vivo, we have deployedSlTRN1promoter-reporter transgenic tomato plants and investigated the gene's dynamic expression pattern in leaf growth stages and infection. Expression of the gene was delimited in the vascular tissues and suppressed in fully developed leaves. WRKY16 transcription factor readily activated SlTRN1 promoter in varied sized leaves and upon virus infection, while silencing of WRKY16 gene resulted in dampened promoter activity. Methylation-sensitive PCR analyses confirmed the accumulation of CHH methylation at multiple locations in theSlTRN1promoter in older leaves. However, ToLCNDV infection reverses the methylation status and restores expression level in the leaf vascular bundle. The virus dampens the level of key maintenance and de novo DNA methyltransferases SlDRM5, SlMET1, SlCMT2 with concomitant augmentation of two DNA demethylases, SlDML1 and SlDML2 levels inSlTRN1promoter-reporter transgenics. Transient overexpression of SlDML2 mimics the virus-induced hypomethylation state of theSlTRN1promoter in mature leaves, while silencing of SlDML2 lessens promoter activity. Furthermore, in line with the previous studies, we confirm the crucial role of viral suppressors of RNA silencing AC2 and AC4 proteins in promoting DNA demethylation and directing it to restore activated transcription ofSlTRN1. Unusually elevated expression of SlTRN1 may negatively impact normal growth of leaves.

Growth and Morphological Responses of Kentucky Bluegrass to Homogeneous and Heterogeneous Soil Water Availabilities

Understanding the effect of water heterogeneity on the growth and water integration of clonal plants is important for scientific water management. In controlled field plots, we conducted a study by creating three different soil water treatments comprising four patches with different soil water supplies using Kentucky bluegrass (Poa pratensis L.) as the materials. The objective was to explore the differences in the growth indices and morphological attributes, and the possible water integration in ‘Arcadia’ Kentucky bluegrass in plots and patches with different soil water availabilities. Soil water deficit resulted in the declined biomass, root/shoot ratio and leaf relative water content of the whole genet, decreased leaf length and height of mother ramet, reduced leaf width and height of daughter ramets, and significant changes in the structures of vascular bundles in rhizomes and leaves. However, the leaf length, leaf width, height and leaf relative water content of daughter ramets in heterogeneous water-poor patches were recovered to the levels in water-rich patches. In addition, the diameter of the vessel in the xylem and percentage of the xylem area in leaf vascular bundles of daughter ramets in the heterogeneous water-poor patch were insignificantly different from those in water-rich patches. These results demonstrated that water integration among interconnected ramets promoted the growth status of daughter ramets in heterogeneous water-poor patches. However, the water translocation in interconnected ramets subjecting to heterogeneous water supplies was not investigated using stable isotope labelling in this study. Thus, the directions and patterns of water translocation among ramets necessitate further research.

Re-study of Guangdedendron micrum from the Late Devonian Xinhang forest

BackgroundGuangdedendron micrum is the Late Devonian tree lycopsid that made up Xinhang fossil forest in Anhui, China, showing the earliest stigmarian rooting system. Based on new specimens of this lycopsid, the roots bearing rootlets, terminal parts of stems, vegetative leaves and monosporangiate strobili containing megaspores are researched in detail.ResultsThe roots with four robust rhizomorphs are largely expanded and approach the size of those of the Late Carboniferous giant tree lycopsids in swampy forests. The rootlets along rhizomorphic axis leave oval to circular scars after abscission. Narrow-fusiform leaf cushions display a leaf scar, vascular bundle and ligule pit. Cylindrical megasporangiate strobili are borne singly, in pairs, or occasionally once-dichotomized. Of each megasporophyll, the pedicel consists of a keel and possibly undeveloped alations, and the long-triangular lamina presents a heel. Megasporangium is sessile and contains multiple Lagenicula megaspores with distinct spines and a large gula.ConclusionsG. micrum displays large terminal monosporangiate strobili probably adapted to turbulent condition, and its megasporophylls together with multiple Lagenicula-type megaspores hint a possible primitive evolutionary status. These characteristics provide new insights into the evolution of fertile traits of early lycopsids.

Histopathology of Corn Plants Infected by Endophytic Fungi.

Simple SummaryEndophytic fungi are fungi that live all or part of their life cycles within the tissues of their hosts. Although several endophyte-plant interactions are non-pathogenic in nature, it has been reported that upon infection, some endophytic fungi are able to adopt a pathogenic status resulting in disease symptoms in their host plants, ranging in severity from mild to severe. In the present study, light microscopy and transmission electron microscopy were used to investigate the tissue colonization and cell damage of corn plants by three endophytic fungi, Fusarium verticillioides, Fusarium sacchari, and Penicillium citrinum, causing disease symptoms in the roots, stems, and leaves of infected corn plants. Tissue deterioration and cell collapse were produced by endophytic F. verticillioides, while significant cell proliferation and wall thickening were observed in corn plants infected by endophytic F. sacchari. Corn plants infected by P. citrinum showed reductions in cell diameter of the vascular bundles of infected corn tissues. The ability of endophytic fungi recovered from healthy corn plants to cause disease when inoculated in healthy tissues of other corn plants signifies their importance as determinants of corn health and productivity.Endophytic fungi inhabiting plant tissues show extensive functional diversity, ranging from mutualism to pathogenicity. The present study evaluated the histological responses of corn plants to colonization by three species of endophytic fungi isolated from corn. Corn seedlings were inoculated with 1 × 106 conidia per mL spore suspensions of endophytic Fusarium verticillioides, Fusarium sacchari, and Penicillium citrinum and observed for 14 days for the emergence of disease symptoms. Histological examination of diseased root, stem, and leaf tissues was conducted using light and transmission electron microscopy. The results indicated that the mean diameters of root phloem, stem vascular bundles, and leaf vascular bundles, of corn plants infected with endophytic P. citrinum (18.91 µm, 146.96 µm, and 107.86 µm, respectively), F. verticillioides (18.75 µm, 85.45 µm, and 118.24 µm, respectively), and F. sacchari (24.15 µm root phloem, and 98.90 µm stem vascular bundle diameters), were significantly lower than the root phloem (33.68 µm), stem vascular bundle (186.77 µm), and leaf vascular bundle (155.88 µm) of the uninfected corn plants (p ≤ 0.05). Endophytic F. verticillioides was the most virulent, resulting in severe degradation and the eventual collapse of infected plant tissues. The study showed that endophytic fungi recovered from corn plants are capable of initiating significant disease responses in infected corn tissues.

Out of the blue: Phototropins of the leaf vascular bundle sheath mediate the regulation of leaf hydraulic conductance by blue light.

The Arabidopsis (Arabidopsis thaliana) leaf veins bundle-sheath cells (BSCs)-a selective barrier to water and solutes entering the mesophyll-increase the leaf radial hydraulic conductance (Kleaf) by acidifying the xylem sap by their plasma membrane H+-ATPase, AHA2. Based on this and on the BSCs' expression of phototropins PHOT1 and PHOT2, and the known blue light (BL)-induced Kleaf increase, we hypothesized that, resembling the guard cells, BL perception by the BSCs' phots activates its H+-ATPase, which, consequently, upregulates Kleaf. Indeed, under BL, the Kleaf of the knockout mutant lines phot1-5, phot2-1, phot1-5 phot2-1, and aha2-4 was lower than that of the wild-type (WT). BSC-only-directed complementation of phot1-5 or aha2-4 by PHOT1 or AHA2, respectively, restored the BL-induced Kleaf increase. BSC-specific silencing of PHOT1 or PHOT2 prevented such Kleaf increase. A xylem-fed kinase inhibitor (tyrphostin 9) replicated this also in WT plants. White light-ineffective in the phot1-5 mutant-acidified the xylem sap (relative to darkness) in WT and in the PHOT1-complemented phot1-5. These results, supported by BL increase of BSC protoplasts' water permeability and cytosolic pH and their hyperpolarization by BL, identify the BSCs as a second phot-controlled water conductance element in leaves, in series with stomatal conductance. Through both, BL regulates the leaf water balance.

Knock out of transcription factor WRKY53 thickens sclerenchyma cell walls, confers bacterial blight resistance.

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.

Arabidopsis leaf hydraulic conductance is regulated by xylem sap pH, controlled, in turn, by a P-type H+ -ATPase of vascular bundle sheath cells.

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.

Genome-wide identification of the GATA gene family in potato (Solanum tuberosum L.) and expression analysis

The aim of this study was to identify members of potato GATA gene (StGATA) family and to provide information for further study on the regulatory role of StGATA transcription factors in potato growth and development and biotic and abiotic stresses. Based on the whole potato genome data, the members of potato GATA transcription factor family were identified and systematically analyzed by bioinformatics online analysis website and software. In total, forty-nine GATA proteins from Solanum tuberosum were identified. Phylogenetic analysis revealed that these GATA proteins could be divided into 5 subfamilies. The gene structure and conserved motif analysis revealed that many genes have more than one intron. Forty-nine StGATA genes were distributed on 12 chromosomes randomly. A cis-element analysis inferred that StGATAs contain abiotic stress-related elements. A heatmap showed that many StGATAs are generally expressed in tissues at different developmental stages. A representative member StGATA9 was selected for screening its expression characteristics to identify whether it was induced by Ralstonia solanacearum, abscisic acid (ABA) and methyl jasmonate (MJ) treatment. Quantitative real-time polymerase chain reaction (qRT-PCR) assays indicated that StGATA9 was induced by R. solanacearum. And StGATA9 was up-regulated by different concentrations of ABA and MJ. Tissue localization showed that StGATA9 was mainly expressed in phloem of leaf vascular bundles and stem vascular system. These results provide a theoretical basis for further experimental cloning and functional verification of the gene, while provides a theoretical basis for the study of molecular mechanism of resistance to bacterial wilt in potato.

Salinity stress mitigation of some canola cultivars grown under South Sinai conditions using magnetic water technology

Salinity stresses either in irrigation water and/or soil is one of the most serious agricultural problems facing farmers in arid and semi-arid regions included Egypt. Many are as in the Sinai region depend mainly on the underground water of various degrees of salinity that prevent cultivated crops from reach to the full yield.Under these conditions,a split-plot field experiment using three canola cultivars; Pactol, Serw-4 and Serw-6under three irrigation water treatments:i) Brackish-water (BW), ii) Magnetic-BW1; brackish water after magnetization through passing a three inch static-magnetic unit,3.75 mT,produced by Delta Water Company, Egypt and iii) Magnetic-BW2;brackish water after magnetization through passing a three inch static magnetic unit, 0.75 mT,produced by Magnetic-Technologies Company, UAE,was carried out at Agricultural Experimental Station of Desert Research Centre, Ras Sidr region, South Sinai Governorate, Egypt during the 2017/18 winter season. The results showed that irrigation with M-BW1or M-BW2surpassed irrigation with BW in all tested growth parameters (plant height, branches and leaf number/plant, leaf area, dry matter of leaves, stem and total plant,and total chlorophyll); leaf anatomy(instance, mid vein and lamina thickness, length and width of leaf vascular bundle and lower and upper epidermis thickness); stem anatomy(stem diameter and thickness of cortex, xylem and phloem in addition pith diameter)and chemical analysis for mineral content (N, P, K, Mg, Fe, Cu, Zn ) at 85 days after sowing (DAS). As an average of both magnetically brackish-water treatments over tested three canola varieties, the percent of improvement compared to irrigation with brackish-water ranged between 10.78-16.02% for growth parameters, 28.33-31.76% for dry matter of plant; 15.58 -80.81% for leaf;10.71-63.88% for stems and2.42-54.48% for mineral content of leaves at 85 DAS.Reverse trends were observed in the best indicators for alleviation salinity stress (Na, and proline),where these decrease dunder both magnetic brackish water treatments by 66.08 and 43.75%, respectively (average of both magnetically brackish-water treatments compared to BW water treatment). Generally, the three tested canola varieties showed a positive response under magnetic brackish water treatments. The positive results in above-mentioned parameters of vegetative growth reflected improvement in canola yield and its components. The percent of improvement ranged between 9.35and35.98 for yield components and reached1.29,19.66 and21.30% in seed oil percentage, seeds and oil yield (kg fed-1;fed=4200m2), respectively compared to brackish water.

Влияние засоления на устьичную и гидравлическую проводимость, а также на уровень аквапоринов в клетках листьев растений ячменя, различающихся по солеустойчивости

We studied participation of aquaporins in the regulation of leaf hydraulic conductivity and relationship of hydraulic conductivity with accumulation of ABA and stomatal closure during salt stress. Using the method of immunohistochemical localization we showed that salinity led to greater decline in the level of aquaporins in the region of the vascular leaf bundles of the more salt-tolerant Prairia cultivar, accompanied by a noticeable decrease in hydraulic conductivity of the leaf. In the less salt-tolerant plants of the Mikhailovsky cultivar, significant changes in the level of aquaporins under the influence of salt stress were not found. The degree of decrease in the hydraulic conductivity of the leaf in plants of two cultivars under the influence of salt stress correlated with a decrease in transpiration. Immunohistochemical localization of abscisic acid (ABA) in leaf cells showed that during salt stress this hormone accumulated in leaf mesophyll cells and stomata. The uptake of exogenous hormone from the nutrient solution and its entry into the leaf through the vascular bundles was accompanied by an increase in staining for aquaporins and the hydraulic conductivity of the leaves, which is characteristic of the ABA action. Differences in the localization of exogenous and endogenous hormones were obviously the cause of the opposite directions of changes in hydraulic conductivity: its increase under the influence of an exogenous ABA and a decrease - under the influence of salt stress. ABA concentration assessment in xylem showed the absence of its increase during salt stress, which explains the absence changes of staining for this hormone in the region of the leaf vascular bundles and indicates that accumulation of ABA in a short-term salt stress is not the result of its delivery from the roots, but the result of its synthesis in the shoot itself.

Assessment of differences in morphological and physiological leaf lodging characteristics between two cultivars of Hippeastrum rutilum

BackgroundEnvironmental lodging stress, which is a result of numerous factors, is characterized by uncertainty. However, several studies related to lodging in cereal crops have reported that lodging in the Hippeastrum rutilum environment is very rare. Hippeastrum rutilum is a garden flower with high ornamental value and abundant germplasm resources. Under past cultivation practices, it was found that the plant types of ‘Red Lion’, with red flowers, and ‘Apple Blossom’, with pink flowers, are quite different. The leaves of ‘Red Lion’ are upright, while the leaves of ‘Apple Blossom’ show lodging, which seriously affects its ornamental value. The aims of this study were to compare the differences between the two varieties with leaf lodging and upright leaves according to morphological and physiological attributes. In this study, karyotype analysis and phenotypic morphological and physiological characteristics were compared to explore the differences between the two plant types.ResultsThe karyotype analysis of the two cultivars showed that their chromosome types were both tetraploid plants. The results showed that the lignin content in the leaves of ‘Red Lion’ was high, the cross-sectional structure of the leaf vascular bundle was more stable, and the chlorophyll content was high. In addition, significantly less energy was transferred to the electron transport chain (ETR) during the photoreaction. Similarly, the results regarding the maximum photosynthetic rate (Fv/Fm), nonphotochemical quenching (NPQ) and effective quantum yield of photosystem II photochemistry (△F/Fm′) all indicated that the photosynthetic capacity of “Red Lion” was greater than that of “Apple Blossom”, which was affected by leaf lodging. The size of the leaves was significantly smaller, and the leaf sag angle, leaf width, and leaf tip angle presented significantly lower values in ‘Red Lion’ than in ‘Apple Blossom’, which exhibits leaf sag. The difference in these factors may be the reason for the different phenotypes of the two cultivars.ConclusionThe results of this study proved that lodging affects the photosynthetic capacity of Hippeastrum rutilum and revealed some indexes that might be related to leaf lodging, laying a theoretical foundation for cultivating and improving new varieties.

Leaf Response to Different Light Spectrum Compositions during Micropropagation of Gerbera Axillary Shoots

The experiment evaluated the influence of different light qualities and 6-benzyladenine (BA) concentration in a medium on the leaf response of multiplied Gerbera jamesonii Bolus ex Hook. f.‘Big Apple’ shoots. Three different light-emitting diode (LED) spectra—100% blue (B), 100% red (R) and red and blue mixture (7:3, RB)—were used, and a fluorescent lamp was used as a control (Fl). Concentrations of BA in Murashige and Skoog (MS) medium were 1, 2.5 and 5 µM. Leaves developed under 100% blue light had a lower frequency of stomata and a smaller area as compared with those from plants exposed to light with red in spectrum. Under 100% red light, the leaf area and the frequency of stomata increased along with growing concentration of BA in the medium. The thickest mesophyll was spotted in the cross-section of leaves exposed to the blue LED light. Leaves developed under the 100% red light had the thinnest mesophyll layers. Increasing concentration of BA in the medium resulted in enhanced leaf blade thickness. The cross-section of leaf vascular bundles was only half of that in petioles. The leaves under the LED combinations had larger vascular bundles than those under fluorescent light. The highest level of photosynthetic pigments was noticed in the leaves grown under LED R and RB lights. Our study demonstrated that 2.5 µM BA and a mixture of blue and red light provided by LED improved leaf quality during multiplication of gerbera shoots.

Cold acclimation has a differential effect on leaf vascular bundle structure and carbon export rates in natural Arabidopsis accessions originating from southern and northern Europe.

Acclimation to low but non‐freezing temperature represents an ecologically important process for Arabidopsis thaliana but also for many other plant species from temperate regions. Cold acclimation comprises and affects numerous molecular and physiological processes and the maintenance of sugar supply of sink tissue by photosynthetically active source tissue is essential for plant survival. Here, changes in vascular bundle (VB) structure at the leaf petiole were analysed together with sucrose exudation rates before and after cold acclimation. Six natural Arabidopsis accessions originating from southern and northern Europe were compared. Photosynthetic efficiency, that is, maximum and effective quantum yield of photosystem II, revealed a significant effect of environmental condition. Only for northern accessions was a highly significant negative correlation observed between leaf sucrose exudation rates, xylem, and petiole cross‐sectional areas. Furthermore, only for northern accessions was a significant increase of VB and leaf petiole cross‐sectional area observed during cold acclimation. In contrast, variance of cross‐sectional areas of cold acclimated southern accessions was strongly reduced compared to control plants, while mean areas remained similar under both conditions. In summary, these findings suggest that natural Arabidopsis accessions from northern Europe significantly adjust sink strength and leaf VB structure to maintain plant growth and photosynthesis under low temperature.

Nickel tolerance, translocation and accumulation in a Cd/Zn co-hyperaccumulator plant Sedum alfredii

Multi-elements hyperaccumulators are of high scientific interest to be applied in remediation of mix-contaminated soils. Sedum alfredii is a well-known Cd/Zn co-hyperaccumulator with high Pb and Cu tolerance. This study investigated the ability of the hyperaccumulating ecotype (HE) S. alfredii to tolerate and accumulate Ni. Differed from the non-hyperaccumulating ecotype (NHE), HE plants grew healthy after 50 μM Ni exposure for 4 weeks. The HE plants translocated up to 40 % Ni to the shoots under high Ni stress and accumulated >3000 and 200 mg kg−1 Ni in roots and shoots, respectively. Micro-XRF image showed that Ni was highly restricted within the HE stem and leaf vascular bundles, especially the xylem tissues. The HE roots were of high Ni tolerance, showing much less pronounced Ni-induced phytotoxicity as compared with the NHEs. Ni-induced O2– was observed in the apoplastic part of HE root cells, but both Ni and the induced O2– were highly accumulated in the sensitive zone (root cap, meristem, and cylinder) of NHE roots. These results suggest that although low Ni mobility out of vascular tissues limits the metal accumulation in stems and leaves, HE S. alfredii is highly tolerant towards Ni stress by metal homeostasis in root cells.