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The niche of aphids is largely defined by their consumption of plant phloem sap and its composition, including nutrients and specialized metabolites. Niche construction is the change of the environment by organisms, which may influence the fitness of these organisms and their offspring. To better understand interactions between plants and aphids, it is necessary to investigate whether aphids modify the chemical composition of the phloem sap of their host plants and whether conspecifics are affected by previous infestation. In the current study, ears of wheat (Triticum aestivum) plants were infested with clonal lineages of the English grain aphid (Sitobion avenae) or were left uninfested. The metabolic composition of ear phloem sap exudates was analyzed through amino acid profiling and metabolic fingerprinting. Aphids of the clonal lineages were either put on previously aphid-infested or on uninfested ears and their colony sizes followed over time. Furthermore, it was investigated whether aphids choose one treatment group over another. Sitobion avenae infestation affected the relative concentrations of some metabolites in the phloem exudates of the ears. Compared to uninfested plants, the relative concentration of asparagine was higher after aphid infestation. Colonies grew significantly larger on previously aphid-infested ears, which the aphids also clearly chose in the choice experiment. The pronounced positive effect of previous infestation on aphid colonies indicates niche construction, while the choice of these constructed niches reveals niche choice by S. avenae on wheat. The interplay between these different niche realization processes highlights the complexity of interactions between aphids and their hosts. [ABSTRACT FROM AUTHOR]

SUMMARY: Soil salinity significantly limits rice productivity, but it is poorly understood how excess sodium (Na+) is delivered to the grains at the reproductive stage. Here, we functionally characterized OsHAK4, a member of the clade IV HAK/KUP/KT transporter subfamily in rice. OsHAK4 was localized to the plasma membrane and exhibited influx transport activity for Na+, but not for K+. Analysis of organ‐ and growth stage‐dependent expression patterns showed that very low expression levels of OsHAK4 were detected at the vegetative growth stage, but its high expression in uppermost node I, peduncle, and rachis was found at the reproductive stage. Immunostaining indicated OsHAK4 localization in the phloem region of node I, peduncle, and rachis. Knockout of OsHAK4 did not affect the growth and Na+ accumulation at the vegetative stage. However, at the reproductive stage, the hak4 mutants accumulated higher Na+ in the peduncle, rachis, husk, and brown rice compared to the wild‐type rice. Element imaging revealed higher Na+ accumulation at the phloem region of the peduncle in the mutants. These results indicate that OsHAK4 plays a crucial role in retrieving Na+ from the phloem in the upper nodes, peduncle, and rachis, thereby preventing Na+ distribution to the grains at the reproductive stage of rice. [ABSTRACT FROM AUTHOR]

Recently, more and more researchers have begun to consider using waste bark fractions to produce value-added biochemicals and materials, as well as for energy production. Extraction is often the first operation in biomass biorefineries. Here we obtained hydroethanolic extracts from waste cork and phloem fractions of Quercus cerris bark and analyzed them to determine their antioxidant, antimicrobial, and nitric oxide (NO) production inhibition properties and their hepatotoxicity. The antioxidant properties were investigated by ex vivo TBARSs as well as OxHLIA antioxidant assays, the antibacterial properties against Gram-positive and Gram-negative bacteria isolated from food and clinical sources, and antifungal properties against Aspergillus brasiliensis and A. fumigatus. The NO production inhibition activity was assessed in a lipopolysaccharide (LPS)-stimulated murine macrophage (RAW 264.7) cell line, and antiproliferative activities were determined against five different cell lines, including lung (NCI-H460), gastric (AGS), breast (MCF7), and colon (CaCo2) tumor cell lines, as well as a non-tumor cell line (PLP2). The hydroethanolic maceration of waste cork and phloem yielded 4.4% and 2.4% extracts, respectively. Gallic acid glucosides, phenolic acids, and ellagic acid were identified in both extracts. The waste cork and phloem extracts showed antioxidant, antimicrobial, antifungal, and antiproliferative properties but also showed hepatotoxicity in the case of waste cork. Both bark fractions varied in terms of their bioactivity, with waste cork extracts showing, in general, higher bioactivity than phloem extracts [ABSTRACT FROM AUTHOR]

There's a lack of studies on the structure–function aspect of linking non-structural carbohydrates to temperature, in particular phloem structure is yet a largely neglected subject. We studied gas exchange parameters and in parallel examined functional anatomy and non-structural carbohydrates status in leaf blades, petioles and branches in 'Cabernet Sauvignon' grapevines grown under three temperature regimes (22/16 °C, 28/22 °C, 34/28 °C day/night). After two months of growth, water use efficiency was the highest at 34 ºC. The individual organs size became progressively smaller as the temperatures increased, and was the smallest at 34 ºC for branch and petiole diameter, and for leaf thickness. The relative xylem cross-sectional area was largely not influenced by the temperature regime. In contrast, phloem cross-sectional area was significantly increased at high temperature in branches and petioles, and became 30% higher at 34 ºC in branches compared to 22 °C. The leaves had the highest non-structural carbohydrates concentration compared to petioles and branches. Sucrose content exhibited a temperature-dependent increase both in branches and petioles, and to some extent also in leaves, while starch, fructose and glucose content did not exhibit any statistically significant temperature trends. In grapevine, sucrose is the main non-structural carbohydrate used for long-distance transport. Our results indicate temperature dependent increased investment in phloem development in parallel with increased main long-distance transported sugar (sucrose) accumulation. Phloem and xylem development were apparently uncoupled, implying a differential cambium activity for each tissue. Our study could have wide structural–functional implications in the ongoing climate change scenario. [ABSTRACT FROM AUTHOR]

Background. Wildfires may cause serious injuries to the anatomical structure of trees that can lead to tree death or long-lasting injury recovery, limiting their growth and vitality for several years. Post-fire management involves a wide range of measures aimed at recovering and restoring burnt areas. Usually, the first step is "salvage logging", i.e., the removal of irremediably injured trees. The burn severity depends on several parameters and is variable within the burnt area. For this reason, in some areas, the death of apparently healthy individuals has often been observed even after several years. This study aims to assess delayed/latent mortality by analyzing glucose like a tracer in wood by using a blood glucometer and HPLC. Results. The glucose in the phloem, cambium, and last xylem rings was measured using a glucometer developed for measuring glucose in the blood. The adopted approach detected glucose concentrations that were recognizable for different functional levels of the trees. Conclusions. The glucometer was suitable to detect the glucose in wood and phloem in order to define the death or health of the disturbed and undisturbed trees post-fire. Further investigations are required to find new solutions for a rapid evaluation of the abiotic and biotic factors that influence tree functionality in the forest. This approach will be used to predict the probability of the death of the individuals injured, which would improve the efficiency and the economy of recovery operations. [ABSTRACT FROM AUTHOR]

Some species of the genus Passiflora have leaf morphological adaptations that grow to influence the development of the plant in producing areas. Hence, the objective of this work is to quantify and characterize the leaf anatomy of passion fruit species distributed in the South American region, which can become an important strategy in the selection of species more adapted to the environment where they will be grown. This work evaluates the abaxial and adaxial cuticle thickness (ABCT and ADCT), abaxial and adaxial epidermis thickness (ABET and ADET), xylem diameter (XD), phloem diameter (PD), and thickness of the palisade parenchyma (TPP), of the species Passiflora quadrangularis L., Passiflora foetida L., Passiflora edulis Sims, Passiflora gibertii N.E Brown, Passiflora coccinea Aubl, Passiflora alata Curtis, Passiflora tenuifila Killip, Passiflora caerulea L., and Passiflora cincinnata Mast. Passion fruit species present differences in leaf anatomy, which may influence the plant's development. The species Passiflora quadrangularis L. showed a greater thickness of cuticles, epidermis, conducting vessels, and palisade parenchyma. The species Passiflora edulis has higher density and stomatal functionality. All Passiflora species formed druses on their leaves. [ABSTRACT FROM AUTHOR]

Cotton aphids (Aphis gossypii Glover) are important pests of cucurbit crops. Plant defenses at different cell layers, including the leaf surface, mesophyll cells, and phloem, are employed to defend aphids. Here, we assessed differences in aphid resistance among six watermelon varieties and elucidated the defense mechanisms underlying aphid-resistant/susceptible watermelon varieties. The population abundance, offspring number per female, and meantime of phloem-feeding (E2 phase) of aphids were the highest on XiNong (XN), followed by JingXin (JX), TianWang (TW), ZaoJia (ZJ), and MeiFuLai (MFL), and these parameters were the lowest on JinMeiDu (JMD). Further analyses showed that there was no correlation between the aphid resistance of six watermelon varieties and defenses at the leaf surface. For defenses at mesophyll cells, aphid infestation increased salicylic acid (SA) content at 48 h post-infestation (hpi) and ROS accumulation at 6 and 12 hpi in six watermelon varieties. For phloem defenses, aphid infestation increased callose content in JMD plants but decreased callose content in JX, TW, ZJ, MFL, and XN plants at 6, 12, 24, and 48 hpi. Moreover, callose deposition suppressed by 2-deoxy-d-glucose (2-DDG) neutralized the resistance of JMD plants and exacerbated the susceptibility of XN plants to aphids, which exhibited a higher population abundance and E2 phase time. Collectively, phloem defenses regulated by aphid-induced callose deposition were responsible for differences in aphid resistance among the watermelon varieties. [ABSTRACT FROM AUTHOR]

We have performed a lab-based hypergravity cultivation experiment using a centrifuge equipped with a lighting system and examined long-term effects of hypergravity on the development of the main axis of the Arabidopsis (Arabidopsis thaliana (L.) Heynh.) primary inflorescence, which comprises the rachis and peduncle, collectively referred to as the main stem for simplicity. Plants grown under 1 × g (gravitational acceleration on Earth) conditions for 20–23 days and having the first visible flower bud were exposed to hypergravity at 8 × g for 10 days. We analyzed the effect of prolonged hypergravity conditions on growth, lignin deposition, and tissue anatomy of the main stem. As a result, the length of the main stem decreased and cross-sectional area, dry mass per unit length, cell number, and lignin content of the main stem significantly increased under hypergravity. Lignin content in the rosette leaves also increased when they were exposed to hypergravity during their development. Except for interfascicular fibers, cross-sectional areas of the tissues composing the internode significantly increased under hypergravity in most types of the tissues in the basal part than the apical part of the main stem, indicating that the effect of hypergravity is more pronounced in the basal part than the apical part. The number of cells in the fascicular cambium and xylem significantly increased under hypergravity both in the apical and basal internodes of the main stem, indicating a possibility that hypergravity stimulates procambium activity to produce xylem element more than phloem element. The main stem was suggested to be strengthened through changes in its morphological characteristics as well as lignin deposition under prolonged hypergravity conditions. [ABSTRACT FROM AUTHOR]

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Fusarium head blight (FHB) of wheat, mainly caused by Fusarium graminearum, leads to severe economic losses worldwide. Effective management measures for controlling FHB are not available due to a lack of resistant cultivars. Currently, the utilization of biological control a promising approach that can be used to help manage FHB. Previous studies have confirmed that Streptomyces pratensis S\O harbors excellent inhibitory effects on E graminearum. However, there is no information regarding whether invasive hyphae of E graminearum are inhibited by SIO, Thus, we investigated the effects of 310 on E graininearum strain PH-1 hypha extension, toxisome formation, and TRI5 gene expression on wheat plants via microscopic observation. The results showed that 10 effectively inhibited the spread of K graminearum hyphae along the rachis, restricting the infection of neighboring florets via the phloem. In the presence of S 10, the hyphal growth is impeded by the formation of dense cell wall thickenings in the racllis internode surrounding the E graminearum infection site, avoiding cell plasmolysis and collapse. We further demonstrated that SIO largely prevented cell-to-cell invasion of fungal hyphae inside wheat coleoptiles using a constitutively green fluorescence protein-expressing E graminectrum strain, PH - 1. Importantly, S. pratensis S10 inhibited toxisome formation and TR/5 gene expression in wheat plants during infection. Collectively, these findings indicate that S. pratensis S\O prevents the spread of E graminearum invasive hyphae via the rachis. [ABSTRACT FROM AUTHOR]

Summary: Secondary xylem and phloem originate from a lateral meristem called the vascular cambium that consists of one to several layers of meristematic cells. Recent lineage tracing studies have shown that only one of the cambial cells in each radial cell file functions as the stem cell, capable of producing both secondary xylem and phloem. Here, we first review how phytohormones and signalling peptides regulate vascular cambium formation and activity. We then propose how the stem cell concept, familiar from apical meristems, could be applied to cambium studies. Finally, we discuss how this concept could set the basis for future research. [ABSTRACT FROM AUTHOR]

It is shown that the differences water-soluble and water-insoluble fractions of plant leaf biomass, as well as phloem, are evolutionarily determined. They are associated with metabolic reactions during assimilation and photorespiration and do not depend on the illumination mode or on the spectral ranges of photosynthetic active radiation (PAR) used in illumination. The above isotopic shifts are the cause of isotopic differences in assimilatory and photorespiratory carbon stocks that feed various metabolic processes. Due to the strict temporal and spatial organization of metabolism, carbon fluxes from the funds retain isotopic differences without complete mixing. The differences in the isotopic composition of carbon of the water-soluble fraction of the biomass and carbon of phloem juice from carbon of the water-insoluble fraction are small (1–3‰), but they are quite stable and easily fixed. The carbon of the water-soluble fraction is very close in isotopic composition to the carbon of the phloem and is noticeably enriched in isotope 13C relative to the water-insoluble fraction, which makes it possible to use it as a marker in the study of assimilate transport in plants, especially during budding and fruiting. It is shown that the reason for the enrichment of autotrophic organs and tissues with the isotope 12C relative to carbon of heterotrophic parts of the plant is the result of predominant participation in their formation of an isotopically light assimilation fund, whereas an isotopically heavy photorespiratory fund takes part in the formation of heterotrophic organs. It is shown that the manifestation of the formation of two isotopically different funds is the discovered relationship of the carbon isotope composition of leaves with their age. [ABSTRACT FROM AUTHOR]

In forests, a significant proportion of the carbon fixed by trees during photosynthesis is transported belowground along the conducting phloem, so variations in phloem anatomy can lead to variations in transport capacity. Phloem conductance at tree level (Ktree) is also affected by tree height. Both the phloem anatomy and the tree size change during ontogeny, and also differ under different environmental conditions. The goal of our work was to identify the main drivers of variation in Ktree in Scots pine trees growing in natural boreal forests. We conducted a phloem anatomical study and calculated Ktree in trees of three age groups growing in different climatic conditions along a latitudinal gradient from south to north. We found that Ktree was maintained at the same level in actively growing pine trees (25–80-years-old) but increased in old-aged trees (180–190-years-old), possibly reflecting the shift in source-sink relationships of aboveground and belowground parts of trees. Trees of the same age group growing in different climatic conditions demonstrated similar values of Ktree due to coordinated changes in the phloem anatomy and the tree height. In general, the negative influence of tree height on Ktree is offset by the positive influence of phloem width (or trunk diameter) and sieve cell diameter. The exception was young trees growing in the transition zone of the northern taiga subzone to the tundra, where Ktree was the highest in its age group and even exceeded Ktree of middle-aged trees. [ABSTRACT FROM AUTHOR]

The ecological niche of aphids is largely defined by the phloem sap of plants, which they consume. Previous studies revealed that aphids may change the phloem sap metabolome and that a previous aphid infestation may benefit them. As aphids reproduce parthenogenetically, the performance and preference of aphids of the same monoclonal aphid lineage can be compared between previously uninfested and previously aphid‐infested plants.Wheat (Triticum aestivum) leaves were infested by clonal lineages of Sitobion avenae aphids for 9–10 days. Leaf phloem exudates were analysed using amino acid profiling and metabolic fingerprinting, capturing mainly specialised metabolites. It was investigated whether aphid colony sizes differ between leaves that were previously uninfested or infested by aphids of a different clonal lineage or by aphids of the same clonal lineage and whether aphids show a preference for any of these leaves.The relative concentrations of metabolites in the phloem exudates were not affected by aphid infestation. Aphid colonies were partly larger on previously aphid‐infested leaves than on control leaves. However, this effect was transient and finally colonies had similar sizes. Given a choice between previously aphid‐infested and uninfested leaves, S. avenae nymphs showed no preferences.The findings that positive effects of previous aphid infestation on aphid performance are transient and that the performance but not the preference of the aphids was affected by previous aphid infestation highlight the temporal dynamics and complexity of aphid–plant interactions. Niche alteration processes may be partly involved in these interactions. [ABSTRACT FROM AUTHOR]

Cork, the outermost tissue of bark, plays an important role in protecting trees from the surrounding environment and is used for various purposes, including flooring and insulation materials for buildings. This study focused on the amount and distribution of hydrophobic substances such as suberin and lignin in cork, as well as moisture conditions, to understand the mechanical properties of Cerasus jamasakura cork. Strips of cork were subjected to tensile tests after exposure to various moisture conditions (water-saturated, air-dried and oven-dried), and also after the desuberinisation and delignification of specimens. Cork with a high moisture content showed significant strain to the tensile load, whereas oven-dried specimens showed little toughness. The increased toughness of cork at higher moisture contents was due to the continued elongation in the plastic region, especially in the inner cork. The fibre length of the highly deformed cork differed significantly before and after the tensile test. Tensile tests of cork after desuberinisation and delignification indicated that the removal of suberin caused an earlier reduction in tensile properties than the removal of lignin. The presence of suberin in cork, distributed mainly in the inner cork, is believed to affect the tensile properties of cork. [ABSTRACT FROM AUTHOR]

Abstract Adventitious root (AR) formation is a genetically complex trait with high genotypic variability. Therefore, only a limited range of cultivars are currently propagated by cuttings in rose. In this study, we analysed the anatomy of in vitro shoots, the early formation of root primordia (RP) and the formation of ARs in a diverse set of 106 rose genotypes. Correlation analysis indicated that the growth in shoot diameter and the vasculature dimensions after 1 week of rooting contributed to successful AR formation. Using phenotypic data for genome-wide association studies (GWAS) analyses, nine significantly associated single nucleotide polymorphisms (SNPs) and genomic regions contributing to various RP and AR formation traits were identified. The contribution of genomic regions to trait variation was notably greater for traits associated with earlier processes than for traits associated with later developmental stages. The combination of RP and AR data allowed the detection of regions by GWAS that contain factors that potentially limit RP emergence. Homologues of 47 genes known to be involved in AR formation from the literature could be assigned to the identified peaks. Further studies are needed to investigate the suitability of SNPs exhibiting strong effects as allele-specific PCR markers for use in breeding.

Xuan paper is a classic Chinese handmade paper with long history and has been listed as a national intangible cultural heritage since 2009, which is mainly composed of wingceltis (Pteroceltis tatarinowii) phloem fibers and straw fibers. Due to the unique properties of wingceltis phloem fibers, Xuan paper is spotless, flexible, stable, and durable, and is widely used by calligraphers, painters, or museums for restoration. Uncovering the variation of phloem fiber properties throughout the traditional pulping process is essential for a comprehensive understanding of the special performance of Xuan paper. In this study, chemical, structural, and mechanical characterization was conducted on the raw bark (phloem fiber), treated phloem fiber, and pulp fiber at different steps of the traditional pulping process for making Xuan paper. The compositional and morphological analysis revealed the effective removal of the matrix polymers, while the phloem fiber almost retained the original fiber structure during the traditional process. Wide-angle X-ray scattering results indicated that the relative crystallinity of cellulose increased and crystals expanded after the lime cooking and exposure to sun and rain. Compared to the raw phloem fibers, the ultimate stress and tensile stiffness of pulp fibers decreased by 24.35% and 9.79%, respectively. However, the fracture strain and fracture toughness of pulp fibers showed a drastic promotion, which might be attributed to the energy dissipation caused by the cell wall structure, the breaking and reforming of hydrogen bonds, and the slipping and rearrangement of cellulose microfibrils. [ABSTRACT FROM AUTHOR]

Emerald ash borer (EAB, Agrilus planipennis) is an invasive killer of ash trees (Fraxinus spp.) in North America and Europe. Ash species co‐evolved with EAB in their native range in Asia are mostly resistant, although the precise mechanism(s) remain unclear. Very little is also known about EAB or ash tree microbiomes. We performed the first joint comparison of phloem mycobiome and metabolites between a native and a nonnative ash species, infested and uninfested with EAB, in conjunction with investigation of larval mycobiome. Phloem mycobiome communities differed between the tree species, but both were unaffected by EAB infestation. Several indicator taxa in the larval gut shared a similarly high relative abundance only with the native host trees. Widely targeted metabolomics revealed 24 distinct metabolites in native trees and 53 metabolites in nonnative trees, respectively, that differed in relative content between infested and uninfested trees only in one species. Interestingly, four metabolites shared a strong relationship with the phloem mycobiomes, majority of which affected only the native trees. Collectively, our results demonstrate a complex interplay between host tree chemistry and mycobiome, and suggest the shared relationships between the mycobiomes of the native host tree and EAB may reflect their shared co‐evolution. Summary statement: Joint analysis of metabolome and mycobiota of native and nonnative Fraxinus species to emerald ash borer infestation identified four metabolites affecting phloem mycobiomes. Indicator taxa of the larval gut shared a high abundance with the insect's native host, suggesting possible co‐evolution. [ABSTRACT FROM AUTHOR]

Some species of the genus Passiflora have leaf morphological adaptations that grow to influence the development of the plant in producing areas. Hence, the objective of this work is to quantify and characterize the leaf anatomy of passion fruit species distributed in the South American region, which can become an important strategy in the selection of species more adapted to the environment where they will be grown. This work evaluates the abaxial and adaxial cuticle thickness (ABCT and ADCT), abaxial and adaxial epidermis thickness (ABET and ADET), xylem diameter (XD), phloem diameter (PD), and thickness of the palisade parenchyma (TPP), of the species Passiflora quadrangularis L., Passiflora foetida L., Passiflora edulis Sims, Passiflora gibertii N.E Brown, Passiflora coccinea Aubl, Passiflora alata Curtis, Passiflora tenuifila Killip, Passiflora caerulea L., and Passiflora cincinnata Mast. Passion fruit species present differences in leaf anatomy, which may influence the plant’s development. The species Passiflora quadrangularis L. showed a greater thickness of cuticles, epidermis, conducting vessels, and palisade parenchyma. The species Passiflora edulis has higher density and stomatal functionality. All Passiflora species formed druses on their leaves.

Plant synaptotagmins structurally resemble animal synaptotagmins and extended-synaptotagmins. Animal synaptotagmins are well-characterized calcium sensors in membrane trafficking, and extended-synaptotagmins mediate lipid transfer at the endoplasmic reticulum--plasma membrane contact sites. Here, we characterize SYNAPTOTAGMIN 4 (SYT4), which belongs to the six-member family in Arabidopsis. Fluorometric GUS assay showed that the SYT4 promoter was strongest in roots and the least active in rosettes and cauline leaves, which was confirmed by qPCR. In seedlings, promoter activity was influenced by several factors, such as plant growth regulators, mannitol, sucrose, polyethylene glycol and cold. GUS histochemistry revealed SYT4 promoter activity in the phloem of all organs and even almost exclusively in sieve element precursors and differentiating sieve elements. Accordingly, the SYTGFP fusion protein also accumulated in these cells with maximal abundance in sieve element precursors. The protein formed a network in the cytoplasm, but during sieve tube differentiation, it deposited at the cell periphery and disappeared from mature tubes. Using photoconvertible fluorescence technology, we showed that a high abundance of SYT4 protein in meristematic protophloem cells was due to its extensive synthesis. SYT4 protein synthesis was interrupted in differentiating sieve elements, but protein degradation was also reduced. In addition to phloem, the fusion protein was detected in shoot and root stem cell niche as early as the late heart stage of the embryo. We isolated and molecularly and biologically characterized five syt4 T-DNA insertion alleles and subjected them to phenotype analysis. The allele with the C2B domain interrupted by an T-DNA insertion exhibits increased sensitivity to factors such as auxins, osmotics, salicylic acid, sodium chloride, and the absence of sucrose in the root growth test. [ABSTRACT FROM AUTHOR]

Girdling is often used as an experimental method to study source/sink controls of cambial growth. However, the phloem responses to girdling have not been well investigated. The aim of this research was to characterize the anatomical changes in the phloem and xylem of different species following trunk girdling. Different species of gymnosperm (Abies sibirica, Pinus sylvestris) and angiosperm (Alnus incana, Populus tremula) woody plants were selected. We girdled trunks during active growth and sampled tissues at two levels (1 cm and 35 cm) above the girdle at the end of the growing season. General responses to girdling were recorded for the studied species, such as increased phloem increments, parenchymatization of conducting tissues, reduction in the size of conducting elements, and an increase in the size of axial parenchyma cells in the phloem and xylem. We observed the suppression of xylogenesis in 3 out of 4 species. Differences in the structure of conducting tissues were found, which are due to species differences in the initial tissue structure. In gymnosperms, noticeable differences in the number of resin ducts in the xylem were observed between control and girdled trees. In angiosperms, we found the formation of cells with thickened cell walls in girdled trees (i.e., the formation of phloem and xylem fibers with thickened cell walls in aspen and sclereids in the phloem of alder). Based on the literature data, the observed responses may be due to both the wounding effect and the influence of the high sugar content above the girdle. [ABSTRACT FROM AUTHOR]

The electrical penetration graph (EPG) allows researchers to obtain information on the feeding behavior of herbivorous piercing–sucking insects, mostly Hemiptera. Guidelines are proposed for designing and conducting EPG experiments on insect–plant interactions, and for analyzing and interpreting the data. Several statistical issues common in EPG experiments are discussed. Pre‐recording insect handling, wiring, and being tethered can affect feeding behavior and recommendations are made to minimize such stresses. Recording duration can have a large effect on some variables and interpretation of the data. The pros and cons of long vs. short recording duration are discussed, and suggestions are made for reconciling these conflicting concerns. Replicates lacking a specific waveform pose problems for analyzing variables associated with that waveform. Proper ways for handling these replicates when analyzing data are discussed. The waveform in progress when the recording ends will be terminated before it would naturally end; consequently, its duration will be artificially short (truncated). This creates a problem for calculating mean or median duration of waveform periods (a waveform period is a single occurrence of the waveform), especially for waveforms that tend to occur relatively few times during a recording and in long periods, such as waveforms E2 and G (phloem and xylem sap ingestion for aphids) or Xi (xylem sap ingestion for xylem feeders). Based on a detailed analysis (see the supporting information), guidance is given on how to calculate mean and median duration of waveform periods when the last period is truncated. A modified experimental design is suggested to avoid the problem of truncated waveform periods. Most EPG variables are interdependent, and their values can affect one another. This interdependence should be considered when drawing conclusions from the data. In studies on plant resistance against vascular sap‐feeders, variables that are associated with resistance encountered during the penetration route to the vascular tissue and those encountered in the vascular tissue are discussed. [ABSTRACT FROM AUTHOR]

Summary: Daphniphyllum macropodum produces alkaloids that are structurally complex with polycyclic, stereochemically rich carbon skeletons. Understanding how these compounds are formed by the plant may enable exploration of their biological function and bioactivities.We employed multiple metabolomics techniques, including a workflow to annotate compounds in the absence of standards, to compare alkaloid content across plants and tissues.Different alkaloid structural types were found to have distinct distributions between genotypes, between tissues and within tissues. Alkaloid structural types also showed different isotope labelling enrichments that matched their biosynthetic relationships.The work suggests that mevalonate derived 30‐carbon alkaloids are formed in the phloem region before their conversion to 22‐carbon alkaloids which accumulate in the epidermis. This sets the stage for further investigation into the biosynthetic pathway. [ABSTRACT FROM AUTHOR]

Sucrose transporters (SUTs) play vital roles in phloem sucrose unloading and transportation in wheat grains. However, the genomic information regarding the SUT gene family and their expression patterns in response to heat stress in grains of male-sterile wheat (Triticum aestivum L.) lines has not been systematically studied. In this study, a thorough examination of the wheat SUT gene family was conducted, focusing on their expression patterns in male-sterile lines under heat stress conditions in grain tissues. A total of 19 SUT genes were identified, with phylogenetic analysis indicating their classification into five distinct groups. Polyploidization was identified as a substantial factor in the expansion of SUT genes, with segmental duplication being the predominant mechanism driving the evolutionary expansion of the SUT gene family in wheat. Transcriptome data indicate that the expression levels of TaSUT1 and TaSUT2 were higher than other SUT genes in grains of male-sterile lines. The TaSUT1 expression showed a gradual decreasing trend, while TaSUT2 showed a reverse trend with the process of grain filling. After heat stress, the TaSUT1 expression in grains of male-sterile lines was first significantly increased and then significantly decreased with the filling stage extension, aligning with the observed trend of sucrose levels, indicating that heat stress may decrease the grain weight by reducing sucrose unloading and transportation process in grains. These results provide a systematic analysis of the SUT gene family and lay a theoretical foundation for us to study the grain filling of male-sterile lines in response to abiotic stress. [ABSTRACT FROM AUTHOR]

Summary: Pteroceltis tatarinowii , a tertiary relic plant, has a long and fascinating history in China due to its irreplaceable role in traditional papermaking. In this study, the anatomical differences between young and old bark were analysed by light microscopy (LM), fluorescence microscopy (FM), and polarized light microscopy (PLM). Both the young and old bark contain periderm, cortex, and phloem. In the non-conducting phloem, the curved radial phloem rays were perpendicular to bands of sieve-tube elements and axial parenchyma cells, forming a net-like pattern. Primary phloem fibres only occurred in young bark, and both primary and secondary phloem fibres contained a gelatinous layer (G-layer). Transmission electron microscopy (TEM) showed that the thickness of the G-layer in the primary phloem fibres was about 1.5–4 times higher than that of the secondary phloem fibres. The thick G-layer might be an important potential reason for the absorption of ink by paper made from P. tatarinowii phloem fibres, due to the good water absorption of the gelatinous layer. [ABSTRACT FROM AUTHOR]

[Objectives] Peach shoot blight (PSB) greatly influenced the development of peach industry, Phomopsis amygdali which caused PSB was the most prevalent pathogens in peach orchard at south China. However, the infection process and pathogenic influencing factors remain unclear. Therefore, this study aimed to explore the infection process of P.amygdali and its pathogenic influencing factors. [Methods]In this work, conidial germination of P.amygdali and infection sites were observed through scanning electron microscopy (SEM) . Different environmental conditions were used to explore pathogenic influencing factors of P.amgdali. Commercial fusicoccin was used to measured its virulence effect. [Results] The germination rate of α-conidia of P.amygdali was 66.4% at 3 hours post inoculation, 97.6% at 9 h, then, single long germ tube produced at 24 h, septum formed at 30 h, and branching mycelium formed at 36 h. SEM observation showed that infective hyphae might mainly infect xylem and pith part of peach twigs, that destroyed the structure of xylem, and there were no infective hyphae at the phloem. Further, the study found that temperature and relative humidity (RH) were the main factors affecting the pathogenicity of P.amygdali. Among them, 30 ℃ and 98% RH were the best optimum temperature and relative humidity for the disease. Fusicoccin, one toxin produced by P.amygdali, was also one of pathogenic factors of P.amygdali. [Conclusions] In this work, the infection process of P.amygdali was investigated for the first time and the main environmental factors affecting its pathogenicity were temperature and RH. [ABSTRACT FROM AUTHOR]

Simple Summary: The emerald ash borer (EAB, Agrilus planipennis Fairmaire) is currently a highly destructive forest pest, causing substantial economic losses. Ash species (Fraxinus spp.) are economically invaluable components of natural forests and urban environments. However, these trees have been severely damaged by EAB. Endophytes, which are prevalent in plants, are hypothesized to contribute to the complex relationships between insects and plants. However, research on the effect of EAB infestation on the community changes in endophytic fungi and bacteria in phloem of Fraxinus is scarce. To bridge this gap, we compare changes in fungi and bacteria diversity, community makeup, and the potential roles of various endophytic fungi and bacteria in both EAB-infested and uninfected Fraxinus bungeana trees. We observed an elevation in bacterial richness, without notable changes in diversity, whereas fungal richness and diversity remained unaffected. Furthermore, we identified four key microbial genera undergoing substantial shifts post-infestation. The functional roles of endophytic fungi and bacteria also exhibited changes, with a decline in beneficial activities and an emergence of potentially detrimental functions. Network analyses have shown elevated negative correlations and core genera shift in EAB-infected phloem. The findings of our study contribute to a better understanding of the complex interactions between plants, insects, and endophytic microorganisms. Endophytes, prevalent in plants, mediate plant–insect interactions. Nevertheless, our understanding of the key members of endophyte communities involved in inhibiting or assisting EAB infestation remains limited. Employing ITS and 16S rRNA high-throughput sequencing, along with network analysis techniques, we conducted a comprehensive investigation into the reaction of endophytic fungi and bacteria within F. bungeana phloem by comparing EAB-infested and uninfected samples. Our findings reveal that EAB infestation significantly impacts the endophytic communities, altering both their diversity and overall structure. Interestingly, both endophytic fungi and bacteria exhibited distinct patterns in response to the infestation. For instance, in the EAB-infested phloem, the fungi abundance remained unchanged, but diversity decreased significantly. Conversely, bacterial abundance increased, without significant diversity changes. The fungi community structure altered significantly, which was not observed in bacteria. The bacterial composition in the infested phloem underwent significant changes, characterized by a substantial decrease in beneficial species abundance, whereas the fungal composition remained largely unaffected. In network analysis, the endophytes in infested phloem exhibited a modular topology, demonstrating greater complexity due to an augmented number of network nodes, elevated negative correlations, and a core genera shift compared to those observed in healthy phloem. Our findings increase understanding of plant–insect–microorganism relationships, crucial for pest control, considering endophytic roles in plant defense. [ABSTRACT FROM AUTHOR]

Our study explores the impact of sudden gap formation on the bark volatile and internal chemical profiles of Norway spruce trees during the initial dry year of research plot 2018 following gap formation. We investigated the annual variation in two main physiological traits of Norway spruce trees at the forest edge (FE) and in the forest interior (FI): bark monoterpene (MT) emission spectra and internal phloem MT composition. Given that gap formation increases the solar radiation dose and temperature for trees at the forest edge, we hypothesized that the concentrations of airborne terpenes released from the tree bark and internal phloem terpenes will increase as a consequence of induced tree defenses. Our findings demonstrate significant increases in both airborne terpene concentrations and internal terpene composition in trees at the forest edge compared to the control trees in the forest interior. This study provides novel insights into the annual dynamics of bark monoterpenes following forest edge establishment and underscores the physiological changes experienced by trees in response to the gap formation. [ABSTRACT FROM AUTHOR]

To investigate the low-temperature adaptability of different provenances of Ziziphus jujuba var. spinosa, we used 21 clones from seven provenances as experimental materials and observed the changes in physiological and biochemical indicators and the characteristics of anatomical structures under low-temperature stress. A comprehensive evaluation of their cold resistance was conducted using the membership function method. As the temperature decreased, the relative electrical conductivity (REC) of clone 89 became stable and had the lowest LT50 value (−44.04 °C). The cold-resistant Z. jujuba var. spinosa had a higher bound water/free water (BW/FW) ratio and antioxidant enzyme activity and accumulated large quantities of osmotic regulatory substances. Higher xylem, phloem, and xylem–cortex ratios and greater conduit density enhanced the cold resistance of Z. jujuba var. spinosa. The membership function values of clones 89, 90, 91, 604, and 612 were greater than 0.6, indicating that they could be evaluated as resources with the potential for low-temperature resistance. The cold resistance rankings for the different provenances were as follows: Kazuo, Liaoning > Jiaxian, Shaanxi > Fuxing, Heibei > Changqing, Shandong > Neiqiu, Heibei > Yanchuan, Shaanxi > Xiaxian, Shanxi. These results provide a scientific basis for the rapid and accurate identification of cold resistance in Z. jujuba var. spinosa resources and the breeding and cultivation of new cold-resistant varieties of this subspecies. [ABSTRACT FROM AUTHOR]

Detailed anatomical features of bark are used and interpreted in plant taxonomy, phylogenetics, and other areas of plant science. However, the delicate nature of bark cells, combined with the difficulty of obtaining high-quality sections and reliable data, limits the potential for utilizing and processing bark. In this study, the anatomical structure of the bark of 10 Quercus species growing in Yunnan Province, China, was characterized in detail. The results indicate that the anatomical features of the barks of 10 Quercus spp. show a certain degree of consistency. Specifically, sieve tubes are distributed in solitary elements or in small groups, mostly as compound sieve plates containing 2–8 sieve areas, suggesting that Quercus spp. may occupy a conservative evolutionary position. Additionally, for the first time, this study reports the presence of simple sieve plates in the sieve tube elements of Quercus phloem. Each sieve tube element has a companion cell on one side. The companion cell strands contain 2–7 cells. Axial parenchyma is diffuse, with parenchyma strands typically consisting of 4–7 cells; druses are present within chambered crystalliferous cells. Phloem rays are of two distinct sizes and often exhibit dilatation and sclerification, and the ray composition consists of procumbent cells. Sclerenchyma is composed of fibers and sclereids, both of which contain prismatic crystals. Most of the fibers are gelatinous fibers, which are distributed in discontinuous tangential bands of about five cells in width. Sclereids appear in clusters. The presence of sclerenchyma provides mechanical support to the bark, reducing the collapse of the phloem. Periderm usually consists of around 10–30 layers of phellem, and Quercus acutissima and Q. variabilis can reach dozens or hundreds layers. The phelloderm typically consists of from two to five layers, with Q. variabilis having up to ten or more layers. The filling tissue of lenticels in all Quercus species is nonstratified (homogeneous) and largely nonsuberized. Overall, this study enriches our comprehension of Quercus bark anatomy, elucidating evolutionary patterns, functional adaptations, and ecological ramifications within this significant botanical genus. [ABSTRACT FROM AUTHOR]

Leaf wounding triggers rapid long-range electrical signaling that initiates systemic defense responses to protect the plants from further attack. In Arabidopsis, this process largely depends on clade three GLUTAMATE RECEPTOR-LIKE (GLR) genes GLR3.3 and GLR3.6. In the cellular context, phloem sieve elements and xylem contact cells where GLRs were mostly present are implicated in the signaling events. In spite of that, the spatial requirements of different leaf cell types for leaf-to-leaf signaling remain poorly investigated. In this study, we dissected cell-type-specific long-distance wound signaling mediated by GLR3s and showed that phloem companion cells are critical in shaping the functions of GLR3.3 and GLR3.6 in the signaling pathway. GLR3.3-mediated response is phloem-specific, during which, GLR3.3 has to be renewed from companion cells to allow its function in sieve elements. GLR3.6 functions dually in ectopic phloem companion cells, in addition to xylem contact cells. Furthermore, the action of GLR3.6 in phloem is independent of its paralog GLR3.3 and probably requires synthesis of GLR3.6 from xylem contact cells. Overall, our work highlights that the phloem companion cell is crucial for both GLRs in controlling leaf-to-leaf electrical signaling. [ABSTRACT FROM AUTHOR]

The present study investigates the stem anatomy and development of cambial variants in 10 species of Merremia and related genera (Convolvulaceae) were compared histologically. Among them, Camonea kingii, C. umbellata, Distimake aegyptius, D. quinquefolius, D. vitifolius and M. hederacea increased their stem diameter by initiating successive cambia. In contrast, remaining species showed regular secondary growth. These species also demonstrated inversely oriented vascular elements, phloem wedges, intraxylary cambia, parenchyma proliferation and development of radial vascular cylinders in the large rays of xylem. Phloem wedges developed by the differential activity of regular cambium in small segments by depositing only unlignified parenchyma internally whereas nearby sectors of the cambium behaved regularly. After the development of intraxylary protophloem from procambial derivatives, additional phloem was formed from the pith cells and by initiating intraxylary cambium. Initially, intraxylary cambium was unifacial in all species, but eventually became bifacial (except M. emarginata) and deposited both xylem and phloem. In conclusion, Merremia species use all feasible methods to generate new vascular elements to compensate for the supply of water, nutrients and photosynthate. Inter-and intraxylary phloem development appears to provide an additional and safe conduit for long-distance vertical conduction, whereas radial vascular cylinders facilitate radial conduction. [ABSTRACT FROM AUTHOR]

The anatomy of climbing plants shows a fascinating arrangement of vascular tissues, which may vary from species to species. In the present study, stem anatomy of Gymnema cuspidatum, G. latifolium, G. montanum and G. sylvestre (Apocynaceae) and the occurrence of vascular variants are described here for the first time. They were compared histologically to understand the structural variations in the secondary xylem and ontogeny of vascular variants if any within the species. All four species increase their stem diameter by a single ring of vascular cambium like most of the eudicots. In thick stems, periderm forms distinct ridges and furrows in all the species except G. sylvestre, in which it was minimal. Differential activity of the cambium resulted in the formation of distinct and deep phloem wedges in G. latifolium and G. sylvestre while in other species they were either shallow or almost absent. The secondary xylem was diffuse-porous with distinct growth rings in G. cuspidatum and G. montanum while they were indistinct in G. latifolium and G. sylvestre. Besides regular xylem elements, the presence of perforated ray cells and radially oriented laticifers in the xylem rays was observed frequently in all the investigated samples. The formation of the intraxylary primary phloem was observed concomitant to the regular protoxylem and protophloem at the pith margin. Subsequently, an additional intraxylary phloem was developed from the adjacent pith cells and by the activity of intraxylary/medullary cambium at the pith margin. In thick stems, parenchymatous cells situated between the protoxylem and intraxylary protophloem led to the initiation of intraxylary cambium. In conclusion, three species showed distinct ridges and furrows due to the formation of periderm except G. sylvestre, phloem ray parenchyma showed the formation of sclerenchyma only in the thick stems of G. sylvestre. The formation of intraxylary phloem in all four species may serve as an additional way for the transport of organic nutrients. [ABSTRACT FROM AUTHOR]

Volatile oil serves as a traditional antipyretic component of Bupleuri Radix. Bupleurum marginatum var. stenophyllum (Wolff) Shan et Y. Li belongs to the genus Bupleurum and is distinguished for its high level of saikosaponins and volatile oils; nonetheless, prevailing evidence remains inconclusive regarding its viability as an alternative resource of other official species. This study aims to systematically compare the volatile oil components of both dried and fresh roots of B. marginatum var. stenophyllum and the four legally available Bupleurum species across their chemical, molecular, bionics, and anatomical structures. A total of 962 compounds were determined via GC-MS from the dried roots; B. marginatum var. stenophyllum showed the greatest differences from other species in terms of hydrocarbons, esters, and ketones, which was consistent with the results of fresh roots and the e-nose analysis. A large number of DEGs were identified from the key enzyme family of the monoterpene synthesis pathway in B. marginatum var. stenophyllum via transcriptome analysis. The microscopic observation results, using different staining methods, further showed the distinctive high proportion of phloem in B. marginatum var. stenophyllum, the structure which produces volatile oils. Together, these pieces of evidence hold substantial significance in guiding the judicious development and utilization of Bupleurum genus resources. [ABSTRACT FROM AUTHOR]

A Cucurbita phloem exudate lectin (CPL) from summer squash (Cucurbita pepo) fruits was isolated and its sugar-binding properties and biological activities were studied. The lectin was purified by affinity chromatography and the hemagglutination assay method was used to determine its pH, heat stability, metal-dependency and sugar specificity. Antimicrobial and anticancer activities were also studied by disc diffusion assays and in vivo and in vitro methods. The molecular weight of CPL was 30 ± 1 KDa and it was stable at different pH (5.0 to 9.0) and temperatures (30 to 60 °C). CPL recovered its hemagglutination activity in the presence of Ca2+. 4-nitrophenyl-α-D-glucopyranoside, lactose, rhamnose and N-acetyl-D-glucosamine strongly inhibited the activity. With an LC50 value of 265 µg/mL, CPL was moderately toxic and exhibited bacteriostatic, bactericidal and antibiofilm activities against different pathogenic bacteria. It also exhibited marked antifungal activity against Aspergillus niger and agglutinated A. flavus spores. In vivo antiproliferative activity against Ehrlich ascites carcinoma (EAC) cells in Swiss albino mice was observed when CPL exerted 36.44% and 66.66% growth inhibition at doses of 3.0 mg/kg/day and 6.0 mg/kg/day, respectively. A 12-day treatment by CPL could reverse their RBC and WBC counts as well as restore the hemoglobin percentage to normal levels. The MTT assay of CPL performed against human breast (MCF-7) and lung (A-549) cancer cell lines showed 29.53% and 18.30% of inhibitory activity at concentrations of 128 and 256 µg/mL, respectively. [ABSTRACT FROM AUTHOR]

During plant development, woody plants progress from a juvenile phase to the reproductive mature phase. This process is marked by morphological, physiological, and biochemical changes, including loss of competence to vegetative reproduction. During in vitro stabilisation, mature tissues undergo rejuvenation, however, the exact degree of juvenility attained is not known and differing regeneration capabilities are observed between genotypes. Markers indicating juvenility state would assist the in vitro rejuvenation process and increase the efficiency of successful micropropagation. Several leaf and stem morphological and anatomical traits were analysed as possible juvenility markers in mature and rejuvenated silver birch in vitro shoots. The results showed that juvenility state of birch in vitro shoots varies between different genotypes and between plants from the same genotype. Mature birch in vitro shoots had approximately two times larger and thicker leaves compared to rejuvenated and juvenile shoots. Stem radius, including cortex, phloem, xylem and pith width as well as phloem width : stem radius and phloem width : xylem width ratio was significantly larger in mature shoots. Periderm development and loss of rooting ability were observed in mature shoots. These anatomical and morphological traits could be used as possible juvenility/maturation markers. [ABSTRACT FROM AUTHOR]

Thaumatin-like proteins (TLPs) in plants are involved in diverse biotic and abiotic stresses, including antifungal activity, low temperature, drought, and high salinity. However, the roles of the TLP genes are rarely reported in early flowering. Here, the TLP gene family was identified in P. trichocarpa. The 49 PtTLP genes were classified into 10 clusters, and gene structures, conserved motifs, and expression patterns were analyzed in these PtTLP genes. Among 49 PtTLP genes, the PtTLP6 transcription level is preferentially high in stems, and GUS staining signals were mainly detected in the phloem tissues of the PtTLP6pro::GUS transgenic poplars. We generated transgenic Arabidopsis plants overexpressing the PtTLP6 gene, and its overexpression lines showed early flowering phenotypes. However, the expression levels of main flowering regulating genes were not significantly altered in these PtTLP6-overexpressing plants. Our data further showed that overexpression of the PtTLP6 gene led to a reactive oxygen species (ROS) burst in Arabidopsis, which might advance the development process of transgenic plants. In addition, subcellular localization of PtTLP6-fused green fluorescent protein (GFP) was in peroxisome, as suggested by tobacco leaf transient transformation. Overall, this work provides a comprehensive analysis of the TLP gene family in Populus and an insight into the role of TLPs in woody plants. [ABSTRACT FROM AUTHOR]

The Tomato Chlorosis Criniviruses (ToCV) and Tomato yellow leaf curl Geminivirus (TYLCV), which naturally infecting and limited to the phloem, have caused a drastic reduction in tomato yield. The current study aimsto determine the incidence of single and mixed viruses using biological, serological and molecular PCR methods in natural tomato plants. The incidence of mixed infection was found more frequently, followed by ToCV and TYLCV (42.3, 28.8, 17.8 in 2020 and 49.1, 29.7 and 19.1% in 2021, respectively). ToCV causes chlorosis, TYLCV causes leaf curl and yellowing, while mixed ToCV & TYLCV cause progress symptoms. By using the heat shock protein 70 (HSP70) and coat protein (CP) genes, ToCV and TYLCV isolates could be identified. These isolates were recorded in GenBank under accession codes "ON951644.1" and "OP265136.1" respectively. Host plants responded differently to severe and common disease density between ToCV and TYLCV. The transmitted whitefly could distinguish between ToCV and TYLCV within 15-20 minutes of the acquisition period. ToCV increases in fields with high whitefly populations, requiring further research to understand effects and reduce harm. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB) is a severe citrus disease worldwide. Wild Australian limes like Citrus australasica, C. inodora, and C. glauca possess beneficial HLB resistance traits. Individual trees of the three taxa were extensively used in a breeding program for over a decade to introgress resistance traits into commercial-quality citrus germplasm. We generated high-quality, phased, de novo genome assemblies of the three Australian limes using PacBio long-read sequencing. The genome assembly sizes of the primary and alternate haplotypes were determined for C. australasica (337 Mb/335 Mb), C. inodora (304 Mb/299 Mb), and C. glauca (376 Mb/379 Mb). The nine chromosome-scale scaffolds included 86–91% of the genome sequences generated. The integrity and completeness of the assembled genomes were estimated to be at 97.2–98.8%. Gene annotation studies identified 25,461 genes in C. australasica, 27,665 in C. inodora, and 30,067 in C. glauca. Genes belonging to 118 orthogroups were specific to Australian lime genomes compared to other citrus genomes analyzed. Significantly fewer canonical resistance (R) genes were found in C. inodora and C. glauca (319 and 449, respectively) compared to C. australasica (576), C. clementina (579), and C. sinensis (651). Similar patterns were observed for other gene families associated with potential HLB resistance, including Phloem protein 2 (PP2) and Callose synthase (CalS) genes predicted in the Australian lime genomes. The genomic information on Australian limes developed in the present study will help understand the genetic basis of HLB resistance. [ABSTRACT FROM AUTHOR]

There is an urgent need to stimulate agricultural output in many tropical and subtropical countries of the world to combat hunger and malnutrition. The starchy crop cassava (Manihot esculenta), growing even under sub-optimal conditions, is a key staple food in these regions, providing millions of people with food. Cassava biotechnology is an important technique benefiting agricultural progress, but successful implementation of many biotechnological concepts depends on the availability of the right spatiotemporal expression tools. Yet, well-characterized cassava promoters are scarce in the public domain. In this study, we investigate the promoter activity and tissue specificity of 24 different promoter elements in stably transformed cassava plants. We show that many of the investigated promoters, especially from other species, have surprisingly low activity and/or tissue specificity, but feature several promoter sequences that can drive tissue-specific expression in either autotrophic-, transport- or storage tissues. We especially highlight pAtCAB1, pMePsbR, and pSlRBCS2 as strong and specific source promoters, pAtSUC2, pMeSWEET1-like, and pMeSUS1 as valuable tools for phloem and phloem parenchyma expression, and pStB33, pMeGPT, pStGBSS1, as well as pStPatatin Class I, as strong and specific promoters for heterotrophic storage tissues. We hope that the provided information and sequences prove valuable to the cassava community by contributing to the successful implementation of biotechnological concepts aimed at the improvement of cassava nutritional value and productivity. [ABSTRACT FROM AUTHOR]

Summary: Stable oxygen isotope ratio of tree‐ring α‐cellulose (δ18Ocel) yields valuable information on many aspects of tree–climate interactions. However, our current understanding of the mechanistic controls on δ18Ocel is incomplete, with a knowledge gap existent regarding the fractionation effect characterizing carbonyl‐water oxygen exchange during sucrose translocation from leaf to phloem.To address this insufficiency, we set up an experimental system integrating a vapor 18O‐labeling feature to manipulate leaf‐level isotopic signatures in tree saplings enclosed within whole‐canopy gas‐exchange cuvettes. We applied this experimental system to three different tree species to determine their respective relationships between 18O enrichment of sucrose in leaf lamina (Δ18Ol_suc) and petiole phloem (Δ18Ophl_suc) under environmentally/physiologically stable conditions.Based on the determined Δ18Ophl_suc‐Δ18Ol_suc relationships, we estimated that on average, at least 25% of the oxygen atoms in sucrose undergo isotopic exchange with water along the leaf‐to‐phloem translocation path and that the biochemical fractionation factor accounting for such exchange is c. 34‰, markedly higher than the conventionally assumed value of 27‰.Our study represents a significant step toward quantitative elucidation of the oxygen isotope dynamics during sucrose translocation in trees. This has important implications with respect to improving the δ18Ocel model and its related applications in paleoclimatic and ecophysiological contexts. [ABSTRACT FROM AUTHOR]

The properties of bark and xylem contribute to tree growth and survival under drought and other types of stress conditions. However, little is known about the functional coordination of the xylem and bark despite the influence of selection on both structures in response to drought. To this end, we examined relationships between proportions of bark components (i.e. thicknesses of tissues outside the vascular cambium) and xylem transport properties in juvenile branches of five Cupressaceae species, focusing on transport efficiency and safety from hydraulic failure via drought‐induced embolism. Both xylem efficiency and safety were correlated with multiple bark traits, suggesting that xylem transport and bark properties are coordinated. Specifically, xylem transport efficiency was greater in species with thicker secondary phloem, greater phloem‐to‐xylem thickness ratio and phloem‐to‐xylem cell number ratio. In contrast, species with thicker bark, living cortex and dead bark tissues were more resistant to embolism. Thicker phellem layers were associated with lower embolism resistance. Results of this study point to an important connection between xylem transport efficiency and phloem characteristics, which are shaped by the activity of vascular cambium. The link between bark and embolism resistance affirms the importance of both tissues to drought tolerance. Summary statement: The study highlights the functional coordination between xylem transport properties and bark structure of Cupressaceae. We found xylem transport efficiency strongly related to phloem characteristics, while xylem safety is associated with both dead and living cell content. [ABSTRACT FROM AUTHOR]

SUMMARY: Phosphate (Pi) is essential for plant growth and development. One strategy to improve Pi use efficiency is to enhance Pi remobilization among leaves. Using transcriptome analysis with first (top) and fourth (down) leaf blades from rice (Oryza sativa) in Pi‐sufficient and deficient conditions, we identified 1384 genes differentially expressed among these leaf blades. These genes were involved in physiological processes, metabolism, transport, and photosynthesis. Moreover, we identified the Pi efflux transporter gene, OsPHO1;3, responding to Pi‐supplied conditions among these leaf blades. OsPHO1;3 is highly expressed in companion cells of phloem, but not xylem, in leaf blades and induced by Pi starvation. Mutation of OsPHO1;3 led to Pi accumulation in second to fourth leaves under Pi‐sufficient conditions, but enhanced Pi levels in first leaves under Pi‐deficient conditions. These Pi accumulations in leaves of Ospho1;3 mutants resulted from induction of OsPHT1;2 and OsPHT1;8 in root and reduction of Pi remobilization in leaf blades, revealed by the decreased Pi in phloem of leaves. Importantly, lack of OsPHO1;3 caused growth defects under a range of Pi‐supplied conditions. These results demonstrate that Pi remobilization is essential for Pi homeostasis and plant growth irrespective of Pi‐supplied conditions, and OsPHO1;3 plays an essential role in Pi remobilization for normal plant growth. Significance Statement: By using transcriptome analysis with young and old leaf blades from rice in Pi‐sufficient and deficient conditions, we identified that OsPHO1;3 played an essential role in Pi remobilization in rice. Thus, we provide a powerful method to identify candidates involved in the mobilization of nutrient elements in plants. [ABSTRACT FROM AUTHOR]

Summary: Phloem sieve elements (PSE), the primary conduits collaborating with neighboring phloem pole pericycle (PPP) cells to facilitate unloading in Arabidopsis roots, undergo a series of developmental stages before achieving maturation and functionality. However, the mechanism that maintains the proper progression of these differentiation stages remains largely unknown.We identified a gain‐of‐function mutant altered phloem pole pericycle 1 Dominant (app1D), producing a truncated, nuclear‐localized active form of NAC with Transmembrane Motif 1‐like (NTL9). This mutation leads to ectopic expression of its downstream target CALLOSE SYNTHASE 8 (CalS8), thereby inducing callose accumulation, impeding SE differentiation, impairing phloem transport, and inhibiting root growth.The app1D phenotype could be reproduced by blocking the symplastic channels of cells within APP1 expression domain in wild‐type (WT) roots. The WT APP1 is primarily membrane‐tethered and dormant in the root meristem cells but entries into the nucleus in several cells in PPP near the unloading region, and this import is inhibited by blocking the symplastic intercellular transport in differentiating SE.Our results suggest a potential maintenance mechanism involving an APP1‐CalS8 module, which induces CalS8 expression and modulates symplastic communication, and the proper activation of this module is crucial for the successful differentiation of SE in the Arabidopsis root. [ABSTRACT FROM AUTHOR]

Using a unique 8‐year data set (2010–2017) of phloem data, we studied the effect of temperature and precipitation on the phloem anatomy (conduit area, widths of ring, early and late phloem) and xylem‐ring width in two coexisting temperate tree species, Picea abies and Fagus sylvatica, from three contrasting European temperate forest sites. Histometric analyses were performed on microcores taken from tree stems in autumn. We found high interannual variability and sensitivity of phloem anatomy and xylem‐ring widths to precipitation and temperature; however, the responses were species‐ and site‐specific. The contrasting response of xylem and phloem‐ring widths of the same tree species to weather conditions was found at the two Slovenian sites generally well supplied with precipitation, while at the driest Czech site, the influence of weather factors on xylem and phloem ring widths was synchronised. Since widths of mean annual xylem and phloem increments were narrowest at the Czech site, this site is suggested to be most restrictive for the radial growth of both species. By influencing the seasonal patterns of xylem and phloem development, water availability appears to be the most important determinant of tissue‐ and species‐specific responses to local weather conditions. Summary statement: A unique 8‐year data set of phloem and xylem anatomy datashows high sensitivity of phloem traits to precipitation and temperature. The species‐ and site‐specific response to weather factors indicates the ability of trees to adapt phloem structure to function optimally under local conditions. [ABSTRACT FROM AUTHOR]

Summary: Preliminary results of an investigation of the thinning effect on Norway spruce tree growth in terms of xylogenesis and phloemogenesis are presented. Three plots were selected where the stand densities were reduced by pre-commercial thinning to 1800 trees/ha (plot A; mild thinning) and 1300 trees/ha (plot C; heavy thinning) in February 2020. Plot B had no silvicultural intervention and represented a control variant (4500 trees/ha). Three dominant 14-year-old Norway spruce trees were sampled (micro-cored) for studying the xylem and phloem formation in the 2020 growing season. The total differentiation duration was determined to be around 169.7 ± 12.7–179.3 ± 4.0 days. The average number of xylem cells formed in control plot B was only 140 mature cells, plots C and A were determined to have 175 and 200 mature cells, respectively. Plot A had the fastest growth rate of all the plots studied. In all three plots (A, B, C), the beginning of the early phloem, late phloem sieve cells, and axial parenchyma cells coincided. Nonetheless, in terms of total phloem cell increase, plot C displayed the fastest growth rate among the three plots studied. The first results showed that the rate of total increment in both xylem and phloem cells, as well as the total number of produced tracheids and sieve cells, seem to be positively affected after the thinning application. [ABSTRACT FROM AUTHOR]

In northern temperate zones, peach trees are vulnerable to cold temperature injury in the fall, particularly as climate change prolongs warm weather in the fall and potentially delays the onset of cold acclimation. Four experiments evaluated how cold acclimation of flower buds and shoot phloem, cambium, and xylem is affected by exposure to varying temperatures in the fall. One-year-old peach shoots from trees grown in Maine, USA, were collected from October through November, exposed to 1, 3, or 6 days of low, high, and freezing temperatures, and subjected to stepwise controlled freezing to about −30 °C. Injury was visually quantified as oxidative browning of flower buds and shoot tissues. High temperature exposure, even of a single day, decreased cold tolerance of flower buds and shoot tissues until late November, when high temperatures only minimally decreased cold hardiness. In mid-November, increasing the duration of high temperature exposure from 1 to 3 days decreased cambium and phloem hardiness, but hardiness in flower buds was not further decreased by the longer duration of 3 days. By late November, hardiness in flower buds, cambium, and phloem was less responsive to high temperature, and was increased by prior exposure to 6 days of freezing. After high temperature, xylem lost hardiness to a small degree in mid-October and late November, but in mid-November this occurred in only one experiment. In this study, deacclimation during high temperature in the fall was greater in cambium and phloem than in flower buds and at times greater than in xylem. [ABSTRACT FROM AUTHOR]

To learn everything there is to know about the raw medicine, employ the straightforward and dependable tool known as Pharmacognosy. Being viewed as safe, environmentally friendly treatments, natural medicines are currently becoming more and more popular. Synthetic drugs are seen to be dangerous due to their unfavorable consequences because they may harm both people and the environment. Natural medicines cost less and, in certain cases, don't have any side effects. The current study was conducted to identify the various pharmacognostic characteristics, including microscopy, macroscopy, physicochemical parameters, extractive values, and preliminary phytochemical screening, in order to develop pharmacognostical standards. Phloem cells, sclereids, secondary phloem, outer periderm, the inner cortical zone, and the cortex were all visible in the stem's transverse section. Using powder microscopy, different types of fibres were found. The powdered stem's quantitative pharmacognostic analysis showed that it contained 0.31-0.37% moisture, 7.10-0.12 % total ash, 1.25-0.04 % acid insoluble ash, 3.91–0.08 % water soluble ash, 5.91-0.15 % sulphated ash, and 13.57-1.32 percent alcohol soluble extractive and 9.12-0.56 % water soluble extractive, respectively. Several secondary metabolites were discovered during phytochemical screening, which may open up new opportunities for the formulation of safe drugs in the future. For the first time, the Wagatea spicata stem's pharmacognostical profile was carried out; the information will be valuable for future research and biological activities. [ABSTRACT FROM AUTHOR]