Stem Vascular Bundles Research Articles

Biogas slurry: A potential substance that synergistically enhances rapeseed yield and lodging resistance

Biogas slurry (BS) plays a vital role in improving the efficiency of crop production. On the flip side, the impact of BS on plant lodging factors and yield related traits is still obscure. Hence, we aimed to study the effects of pig and cow BS applications on yield formation, morpho-anatomical, mechanical, physiological properties and transcript expression patterns. The results showed that the yield and lodging resistance of rapeseed were synergistically improved via applying full BS dosage versus nitrogen fertilizer (CK). In addition, the seed yield was significantly increased by 23.9 % by promoting the dry matter accumulation and transport-ability, increasing number of pods by 8.4 % and 1000-seed weight by 5.1 %, respectively. Moreover, BS developed the stem mechanical strength by decreasing lodging index by 34.2 %, which was manifested by an increase in stem thickness and stiffness and a reduction in plant height. Besides, it enhanced the photosynthesis through promoting chlorophyll synthesis, delaying plant senescence, and accumulating N and K concentration. Anatomical observations revealed that BS increased greater number and area of stem vascular bundles, vessels, and maintained a dense microstructure than CK. Also, it boosted pectin, Ca2+ and K+ contents, which were significantly positively correlated with stem mechanical strength and reduced cellulose, lignin and hemicellulose contents. Meanwhile, correlation and structural equation modeling analysis validated the above results. Additionally, the differentially expressed genes were enriched in cell wall formation pathway, especially about the biosynthesis of pectin (PME, PG and PL), cellulose (CesA and CSL), lignin (PAL, POD, CCR, LAC and COMT) and hemicellulose (XTH and Xyl) were identified under BS. The above-mentioned results indicated that BS simultaneously affected lodging behavior by altering structural carbohydrates and modified yield composition by regulating dry-matter accumulation and allocation. This is the first comprehensive strategy on synchronizing rapeseed yield increase and lodging resistance under optimized BS management.

Phenotype identification and genome-wide association study of ear-internode vascular bundles in maize (Zea mays).

The vascular bundle in the ear-internode of maize is a key conduit for transporting photosynthetic materials between "source" and "sink", making it critically important to examine its micro-phenotypes and genetic architecture to identify advantageous characteristics and cultivate high-yielding and high-quality varieties. Unfortunately, the limited observation methods and scope of study precludes any comprehensive and systematic investigations into the microscopic phenotypes and genetic mechanisms of vascular bundle in maize ear-internode. In this study, 47 phenotypic traits were extracted in 495 maize inbred lines using micro computed tomography (Micro-CT) scanning technology and a deep learning-based phenotype acquisition method for stem vascular bundle, which included stem slice-related, epidermis zone-related, periphery zone-related, inner zone-related and vascular bundles-related traits. Phenotypic analysis indicated that there was extensive phenotypic variation of vascular bundle traits in ear-internode, especially that in the inner zone. Of these, 30 phenotypic traits with heritability greater than 0.70 were conducted for GWAS, and a total of 4,225 significant SNPs and 416 candidate genes with detailed functional annotations were identified. Furthermore, 20 genes were highly expressed in stem-related tissues, especially in maize internodes. Functional analysis of candidate genes indicated that the pathways obtained for candidate genes of different trait groups were distinct, mainly involved in vitamin synthesis and metabolism, transport of substances, carbohydrate derivative catabolic process, protein transport and localization, and anatomical structure development. The results of this study will help to further understand the phenotypic traits of stem vascular bundles and provide a reference for revealing the genetic mechanism of maize ear-internode vascular bundles.

How do novel plant growth regulators and cultivation models strategies affect mechanical strength, lodging resistance and maize productivity in semi-arid regions?

Plant growth regulators are synthetic compounds that have become a significant and technical guarantee for agricultural productivity. In China, "Jindeli", which contains active elements of ethephon and cycocel (EC), has been proven to prevent maize stem elongation, improve maize stem thickness, stem morphology and mechanical strength, root growth, lodging resistance, and yield under various cultivation models. Diethyl aminoethyl hexanoate (DA-6) can promote cell division and growth. From 2020–2021, four growth regulators sprays were used to conduct a field experiment; G1: water spraying; G2: EC spraying; G3: DA-6 spraying; G4: EC+DA-6 spraying under two cultivation models; R: ridge covered with plastic film mulching and T: traditional flat planting without plastic mulching. The results indicated that RG4 treatment considerably decreased plant height, internode length, ear height, lodging rate, and center of gravity height, while improved the internode bending strength, cross-sectional area, cortical thickness, and stem vascular bundles as compared with rest of all other treatments. RG4 treatment considerably improved internode diameter, stem mechanical strength, filling degree, root growth, mean tilt angle, and lignin content, while significantly reducing LAI. In addition, RG4 considerably enhanced the quality of corn stems, such as increasing mechanical properties and enhancing the compressive strength of corn stalks that content of hemicellulose, cellulose, and lignin has been increased. Furthermore, RG4 treatment significantly improved grain yield by optimizing leaf layer structure and increasing bleeding saps levels, increasing the grains per row and ear. Thus, under the RG4 treatment maize lodging rate was decreased 72.1%, and increased WUE (52.8%), and grain yield (46.6%). In conclusion, the results clearly demonstrate that in the semi-arid regions risk of lodging can be avoided by spraying EC+DA-6 with ridge covered plastic film mulching to the enriched stalk quality, shaping plant morphological characteristics, and proving a stable cultivation model to improving maize productivity.

Genome-wide analysis of AhCN genes reveals the AhCN34 involved in bacterial wilt resistance in peanut

Peanut (Arachis hypogaea L.) bacterial wilt (BW), caused by Ralstonia solanacearum (RS), is a devastating soil-borne disease that poses a significant threat to peanut yield and quality. Nucleotide-binding leucine-rich repeat (NBS-LRR) proteins are a class of plant-specific immune receptors that recognize pathogen-secreted effector molecules and activate immune responses to resist pathogen infections. However, the precise functions of AhCN genes (CN is a class of NLR genes lacking LRR structural domains) in peanut plants are not fully understood. In this study, a total of 150 AhCN genes were identified and classified into nine subfamilies based on a systematic phylogenetic analysis. The AhCN genes showed highly conserved structural features; promoter cis-elements indicated involvement in plant hormone signaling and defense responses. Following inoculation with RS, the highly resistant peanut variety ‘H108’ significantly outperformed the susceptible variety ‘H107’ in physiological indicators such as plant height, main stem diameter, and fresh weight, likely due to inhibition of bacterial proliferation and diffusion in the stem vascular bundle. AhCN34 was found to be significantly upregulated in H108 compared to H107 during plant infection and in response to treatment with each of three plant hormones. Importantly, AhCN34 overexpression in peanut leaves enhanced their resistance to BW. These findings demonstrate the great potential of AhCN34 for applications in peanut resistance breeding. Our identification and characterization of AhCN genes provide insights into the mechanisms underlying peanut BW resistance and inform future research into genetic methods of improving peanut BW resistance.

Drought stress-induced modification of morpho-anatomical and yield attributes of mung bean associated with the application of silicon and Moringa leaf extract

Mung bean (Vigna radiata) is the rich source of fiber and essential nutrients. They play a vital role in sustainable agriculture due to their ability to fix nitrogen in the soil and enhance soil fertility. Drought is characterized by limited water resources and severe arid climatic conditions, notably impair crop growth and yield. In the current experiment, two genotypes, Azri-M 2006 and NM-92, were studied against drought stress that was applied as 2 days and 4 days irrigation gap per week. Foliar application of magnesium-silicate (20 ppm and 30 ppm concentrations) and Moringa leaf extract (30% v/v solution) was applied as treatments. The results from the experiment morphology anatomical and yield components were recorded according to the prescribed methods. The result revealed that drought stress reduced the growth of plant. Foliar application of 30 ppm silicon against drought stress showed a highly significant (p<0.001) result compared with control group. Morphology parameters, including shoot and root length, shoot and root fresh weight, root dry weight, leaf area, leaf number, the anatomical structure included (stem epidermis, cortex, and stem vascular bundles,) and also yield components (pod length, and seed numbers). In contrast, MLE (30%) showed a significant impact (p<0.01) on leaf lamina thickness (Leaf anatomical parameters; midrib xylem and phloem, number of stomata on the adaxial and abaxial surface) and yield components included (100-grain weight, grains weight per plant, and numbers of pods,). The overall impact of 30 ppm Si was 39.9% more positive on Azri-M2006 than the NM-92 against the drought stress. The 30-ppm silicon and 30% MLE showed 90% similar results in all studied parameters. This study confirms that 30% MLE could be recommended to farmers to improve productivity under arid conditions than the silicon.

Quantification of nanoplastic uptake and distribution in the root, stem and leaves of the edible herb Lepidum sativum

This study confirms the uptake, translocation and bioaccumulation of 100 nm polystyrene nanoplastics in the root, stem and leaves of the plant Lepidum sativum at exposure concentrations ranging from environmentally realistic 10 μg/L up to a high of 100 mg/L. Accumulation in plant tissues was characterised by aggregation in the intercellular spaces and heterogeneous distribution. Nanoplastic presence was confirmed in the root tips, root surface and stele, lateral roots, root hairs, stem vascular bundles, leaf veins and mesophyll, as well as leaf epidermis including stomatal sites. Quantification results show that majority of the particles were retained in the root and accumulation in stem and leaves was only 13 to 18 % of the median value in roots. There was a reduction of 38.89 ± 9.62 % in the germination rate, 55 % in plant fresh weight, as well as in root weight (> 80 %), root length (> 60 %), shoot weight (51 to 78 %) and number of lateral roots (> 28 %) at exposure concentrations at and above 50 mg/L. However, lower, environmentally probable exposure concentrations did not affect the plant health significantly. Our results highlight the urgent need for further exploration of this issue from the point of view of food safety and security. Statement of environmental implicationMicro and nanoplastics have been reported in agricultural environments across the globe and reports regarding their hazardous effects over agricultural and plant health call for an urgent exploration of this issue. This work demonstrates the uptake, bioaccumulation and distribution of nanoplastics in an edible plant at an environmentally realistic concentration and raises serious concerns regarding the possible implications for food safety and security. It presents a novel approach which addresses the quantification of nanoplastic accumulation in plant tissues and helps identify the mechanism and trends behind this phenomenon which has been a challenge up until now.

MICROMORPHOLOGICAL AND ANATOMICAL RESPONSES OF NATIVE DICOTS TO INDUSTRIAL EFFLUENTS RELEASED FROM CONTAMINATED REGION OF THE CHENAB RIVER IN PAKISTAN

Faisalabad industrial units discharge effluents and associated toxic chemicals into the environment, deteriorating ecological conditions and ecosystem health. Morphoanatomical changes in some medicinally important native species (Calotropis procera, Eclipta alba, Phyla nodiflora, and Ranunculus sceleratus) exposed to heavy industrial pollution gained evaluation. These species of choice were due to their widespread distribution in the area. Ten sites selected in the River Chenab, Chiniot, had three near point source pollution of Faisalabad industries within the 500-m radius (polluted) at three drains and two sites inside the river after each drain point source with the control site at 14 km after from the first industrial drain point source. The general response of all plants to effluents was growth retardation. Plant height increased significantly in all species from river sites. An increase in tallness was more prominent in species like C. procera and P. nodiflora. An increase in stem sclerification in C. procera and E. alba from polluted sites occurred, which indicated a better ability to tolerate industrial pollution. Remarkable increases in stem and leaf epidermis, intensive stem sclerenchyma, and closely packed stem vascular bundles in C. procera appeared, which could increase resistance to industrial pollution. Most of the morphoanatomical parameters notably attained a decrease in E. alba, the most vulnerable species. Plant survival depends on particular structural changes in dermal, mechanical, parenchymatous, and vascular tissues. Overall, industrial pollution adversely impacts plant morphological and micromorphological features, although the reaction of specific species to industrial contamination varies. The study determined that stem and leaf anatomical features, such as, epidermis size and storage tissue thickness, are suitable morphoanatomical markers for industrial pollution biomonitoring. Internal modifications of plants vegetating different industrial contaminated sites played a significant role in high tolerance levels.

Allelochemicals extract of star fruit (Averrhoa carambola L.) modulates wheat growth through alterations in anatomical architecture

Context Allelopathy is recognised as a potential technology to control weeds, and could also be a suitable approach for enhancement of crop yield. Aims The study was conducted to investigate the allelopathic role of Averrhoa carambola leaf extract on growth, anatomical and physiological features of three wheat lines, namely 3094, 7076 and A2011. Methods Three dilutions i.e. 0% (control), 15% and 30% of the leaf aqueous extract were applied at 15 day intervals (total five applications) on wheat lines until maturity. Key results All wheat lines showed differential behaviour to allelochemicals of A. carambola leaf extract. Increased root area was accompanied by a high proportion of storage parenchyma tissues and enlarged vascular bundles in line 3094. Disintegration of root cortical parenchyma and complete transformation of chlorenchyma into sclerenchyma in stem was recorded in all wheat lines, particularly at the highest concentration of leaf extract. Line 7076 showed very different behaviour, as it possessed a proportionally enlarged root cortex, enlarged stem vascular bundles and increased leaf thickness, primarily at the highest concentration of leaf extract. Line A2011 was relatively more sensitive, indicating a significant reduction (P < 0.05) in root and stem area and deformed leaves. Conclusions A low concentration (15%) of leaf extract promoted growth and development, whereas a higher concentration caused significant reduction in growth and anatomical attributes. Implications A lower dose of Averrhoa leaf extract promoted growth and development in all wheat lines, and hence can be used as a growth promoter. A higher concentration is important for eradicating unwanted plants.

First Report of Cockscomb Root Rot Caused by Fusarium solani in Iraq

Cockscomb ( Celosia argentea L.) is one of the most important ornamental plants in Iraq. In August 2021, severe root rot of cockscomb plants was observed, with an incidence of 30%, in all of the nurseries surveyed in the Karbala and Babylon provinces, Iraq. The symptoms appeared as severe leaf chlorosis and wilting with brown discoloration of the stem vascular bundle associated with dark brown lesions on the root that extended to the root collar and became extensive rot. The morphological features of 50% of the fungal colonies were identical and similar to those of Fusarium spp. The internal transcribed spacer, translation elongation factor, RNA polymerase I and II, beta-tubulin 1, and mitochondrial small-subunit ribosomal RNA genes were amplified and sequenced. BLASTn analysis of these genetic markers’ sequences found 99.84 to 100% similarity with the corresponding global sequences of Fusarium solani (Mart.). This identification was confirmed by phylogenetic analysis of the concatenated sequences of the genetic markers. Although F. solani has caused economic damage to a broad range of commercially important plants in Iraq, to our knowledge, this is the first report of F. solani causing root rot of cockscomb ( C. argentea) in Iraq.

Low night temperature-induced feedback inhibition of photosynthesis through sucrose accumulation in sugar beet (Beta vulgaris L.) leaves

Sugar beet ( Beta vulgaris L.) is a globally important sugar crop that is mainly used to produce sucrose. However, its cultivation is limited by poor growth and seedling necrosis under low night temperatures (LNT). The aim of this study was to investigate the effects of LNT on growth, photosynthetic characteristics, and sucrose accumulation in sugar beet. LNT stress reduced growth, photosynthesis, membrane stability, and dark respiration. Following LNT stress, we observed thicker leaves and a reduction in diameter of the stem vascular bundle. LNT stress also decreased sucrose synthase, resulting in decreased sucrose decomposition. Under low night temperature, the reduction of sucrose decomposition, nocturnal respiratory consumption, and sucrose output from leaves to roots resulted in significant sucrose accumulation in leaves, which in turn inhibited photosynthesis and sucrose phosphate synthase. The sucrose accumulation in leaves subjected to lower night temperature (4 ℃) was higher than that in leaves at 12 ℃, resulting in stronger inhibition of photosynthetic feedback. The results of this study confirmed that LNT stress can decrease photosynthesis via feedback inhibition of sucrose in leaves, providing a theoretical basis for the improvement and cultivation of sugar beet. • A mechanism of feedback inhibition of leaf sucrose on photosynthesis was proposed. • Low night temperature led to significant sucrose accumulation in sugar beet leaves. • Low night temperature reduced sucrose output from leaves to roots. • Low night temperature reduced nocturnal respiratory consumption.

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.

Alyssum strigosum s.l. (Brassicaceae)’un Morfolojik, Anatomik ve Palinolojik Özellikleri

Alyssum strigosum Banks & Sol. subsp. strigosum and A. strigosum Banks & Sol. subsp. cedrorum (Schott & Kotschy) Dudley, which are two subspecies of Alyssum strigosum with their morphological, anatomical, palynological traits, were presented in detail with this study. The anatomical analysis has been carried out using handmade sections. The transverse sections of roots showed that two subspecies have similar anatomical characters as with primer structure. The sections of stem were reflected the typical dicotyledonous stem anatomical structure and were determined that species have oval shaped cortex parenchyma. The vascular bundles in stem were arranged in one row both examined species. The mesophyll type was detected as equifacial. The examined species have monad, isopolar, prolate and tricolpate pollen grains. For two examined species, exine sculpture were observed as reticulate. As a conclusion, the characteristics of anatomical and palynological in Alyssum strigosum have been showed the supporting the separation of subspecies.

A mechanistic view on lodging resistance in rye and wheat: a multiscale comparative study.

SummaryThe development of crop varieties that are resistant to lodging is a top priority for breeding programmes. Herein, we characterize the rye mutant ´Stabilstroh’ (‘stable straw’) possessing an exceptional combination of high lodging resistance, tall posture and high biomass production. Nuclear magnetic resonance imaging displayed the 3‐dimensional assembly of vascular bundles in stem. A higher number of vascular bundles and a higher degree of their incline were the features of lodging‐resistant versus lodging‐prone lines. Histology and electron microscopy revealed that stems are fortified by a higher proportion of sclerenchyma and thickened cell walls, as well as some epidermal invaginations. Biochemical analysis using Fourier‐transform infrared spectroscopy and inductively coupled plasma‐optical emission spectrometry further identified elevated levels of lignin, xylan, zinc and silicon as features associated with high lodging resistance. Combined effects of above features caused superior culm stability. A simplistic mathematical model showed how mechanical forces distribute within the stem under stress. Main traits of the lodging‐resistant parental line were heritable and could be traced back to the genetic structure of the mutant. Evaluation of lodging‐resistant wheat ‘Babax’ (‘Baviacora’) versus contrasting, lodging‐prone, genotype ´Pastor´ agreed with above findings on rye. Our findings on mechanical stability and extraordinary culm properties may be important for breeders for the improvement of lodging resistance of tall posture cereal crops.

Tissue-specific systemic responses of the wild tobacco Nicotiana attenuata against stem-boring herbivore attack

BackgroundPlants are able to optimize defense responses induced by various herbivores, which have different feeding strategies. Local and systemic responses within a plant after herbivory are essential to modulate herbivore-specific plant responses. For instance, leaf-chewing herbivores elicit jasmonic acid signaling, which result in the inductions of toxic chemicals in the attacked leaf (tissue-specific responses) and also in the other unattacked parts of the plant (systemic responses). Root herbivory induces toxic metabolites in the attacked root and alters the levels of transcripts and metabolites in the unattacked shoot. However, we have little knowledge of the local and systemic responses against stem-boring herbivores. In this study, we examined the systemic changes in metabolites in the wild tobacco Nicotiana attenuata, when the stem-boring herbivore Trichobaris mucorea attacks.ResultsTo investigate the systemic responses of T. mucorea attacks, we measured the levels of jasmonic acid (JA), JA-dependent secondary metabolites, soluble sugars, and free amino acids in 7 distinct tissues of N. attenuata: leaf lamina with epidermis (LLE), leaf midrib (LM), stem epidermis (SE), stem pith (SP), stem vascular bundle (SV), root cortex with epidermis (RCE), and root vascular bundle (RV). The levels of JA were increased in all root tissues and in LM by T. mucorea attacks. The levels of chlorogenic acids (CGAs) and nicotine were increased in all stem tissues by T. mucorea. However, CGA was systematically induced in LM, and nicotine was systematically induced in LM and RCE. We further tested the resource allocation by measuring soluble sugars and free amino acids in plant tissues. T. mucorea attacks increased the level of free amino acids in all tissues except in LLE. The levels of soluble sugars were significantly decreased in SE and SP, but increased in RV.ConclusionsThe results reveal that plants have local- and systemic-specific responses in response to attack from a stem-boring herbivore. Interestingly, the level of induced secondary metabolites was not consistent with the systemic inductions of JA. Spatiotemporal resolution of plant defense responses against stem herbivory will be required to understand how a plant copes with attack from herbivores from different feeding guilds.

Bacterial wilt biocontrol by the endophytic bacteria Gluconacetobacter diazotrophicus in Río Grande tomato cultivar

Bacterial wilt disease caused by Ralstonia solanacearum affects a wide variety of crops, including tomatoes. Novel natural products and organisms offer opportunities for innovation in agroindustry as an alternative way to pest and pathogen controls. Gluconacetobacter diazotrophicus Pal5 (Gd) belongs to PGPBEs (Plant-Growth-Promoting Bacterial Endophytes), which facilitate plant growth via phytostimulation, biofertilization and biocontrol. In this study Río Grande tomato seedlings were inoculated with Gd to test its ability to colonize them and its protective potential against the phytopathogen Ralstonia solanacearum A21 (Rso). Gd root and stem colonization of tomato seedlings were determined. Stem height was markedly affected by the inoculation with Gd after 80 dpi and a set of biochemical and anatomical structural changes in root, stem and leaves were triggered. The resistance mechanisms elicited in the plant after inoculation with the endophytic bacteria involved reinforcement of the cell walls in the root vascular cylinder and stem vascular bundles, with the presence of an augmented number of contact cells with dense cellular content, probably pectins, lignin and tannins. Roots and stems presented thicker and more lignified xylem vessel walls. These plants showed statistically significant differences with mock inoculated plants in several quantitative variables, such as area of the xylem vessels in root and stem. Biocontrol assays without Gd showed wilting at 9 dpi with Rso. Histological analysis showed bacteria cells filled xylem vessels and dispersal through tissue degradation. In contrast, plants with Gd remained asymptomatic and phytopathogen colonization was observed to a lesser extent in the stem and root. Anatomical changes primed by Gd were enhanced upon Rso infection and the tyloses process appeared. Therefore, Gd primes the resistance mechanism in Río Grande tomato plants significantly reducing bacterial wilt caused by Rso.

Uptake and translocation of nano/microplastics by rice seedlings: Evidence from a hydroponic experiment

Microplastics (MPs) are emerging contaminants in terrestrial systems that cause diverse impacts on plants. However, little is known about whether MPs especially micro-sized MPs can be accumulated and translocated in plants particularly food crops. Hereby, a hydroponic experiment was conducted to verify whether nano-sized (80 nm) and micro-sized (1 µm) fluorescently labeled polystyrene (PS) microspheres can enter rice roots and translocate to aerial parts. Plant samples were taken for detection of PS after 14 days and 40 days exposure, respectively. Both nano- and micro-sized PS microspheres were detected in roots, stems, and leaves of rice seedlings by using confocal laser scanning microscopy. Both 80 nm and 1 µm PS microspheres accumulated in the vascular systems of plant tissues, especially root stele, stem vascular bundles and leaf veins, and mostly aggregated on cell walls and in the intercellular regions. These findings imply that both nano- and micro-sized MPs could be absorbed by rice roots and subsequently translocated to aerial parts, and apoplastic transport may be the main pathway. In conclusion, rice seedlings can accumulate nano/microplastics in their roots and translocate them to aboveground tissues, thereby possibly transferring the accumulated nano/microplastics to higher trophic levels through the food chain.

Anatomy of Carlina corymbosa L., Carthamus dentatus Vahl. and Picnomon acarna (L.) Cass. (Asteraceae)

Species of Carlina corymbosa L.,Carthamus dentatus Vahl. and Picnomon acarna (L.) Cass. are belonging to Asteraceae family. The purpose of the study is to determine the anatomical structures of these species in the same tribe and to compare the features. Samples of root, stem and leaf of e-ach species were collected, fixed and examined using a light micros-cope. In addition, some anatomical features were measured. Secondary growth was observed in the root cross section of each species. Secretory ducts were determined in all species. While the pith is filled with xylem elements in C. corymbosa and C .dentatus, the pith of P. acarna consists of different shaped parenchyma cells. Periderm was observed in the stem in all species. All species contain bicollateral vascular bundles in stem. In all species, glandular and non-glandular trichomes were observed on the leaf cross section, on the surface of the adaxial and abaxial epidermis. While C. corymbosa has dorsiventral mesophyll, unifacial mesophyll is observed in other species. There is bicollateral vascular bundle in C. corymbosa whereas collateral vascular bundle was identified in C.dentatus and P.acarna. Also, C. corymbosa and C.dentatus have only one vascular bundle in the midrib but P.acarna has three vascular bundles.

First Report of Pectobacterium polaris Causing Soft Rot and Black Leg of Potato in Russia.

Blackleg and soft rot of potato (Solanum tuberosum) were monitored in the Central European part of Russia within a period of 2012- 2019. Symptoms included decay of tubers, blackening of stem vascular bundles, and partial yellowing of leaves. The disease causes serious potato yield losses in the field and storage. Pectobacterium parmentieri, P. brasiliense, P. versatile (syn. Ca. Pectobacterium maceratum), P. carotovorum, P. atrosepticum, Dickeya dianthicola, and D. solani are considered as main causal agents of soft rot and blackleg disease in Russia (Voronina et al. 2019, Ngoc Ha et al., 2019, Shirshikov et al. 2018, Kornev et al. 2012). Potato plant samples collected in commercial fields in routine plant health assay were used for bacteria isolation on crystal violet pectate agar (CVP) (Helias et al. 2012) as described previously (Voronina et al. 2019). Bacterial colonies producing pitting on CVP were re-isolated and purified on nutrient broth yeast extract medium. DNA of bacterial isolates was extracted, and polymerase chain reaction (PCR) amplifications were performed using gapA primers (Cigna et al. 2017) followed by sequencing. DNA sequence alignment showed that the isolates F099, F100, F106, F109, and F118 were identical (deposited as part of NCBI Ref.Seq. for F109 NZ_RRYS01000004.1, locus KHDHEBDM_RS06360) and grouped together with the type strain Pectobacterium polaris NIBIO1006T (CP017481), a new species described as a potato pathogen (Dees et al. 2017). These strains were negative in diagnostic PCR assays using specific primers Y45/Y46 for the detection of P. atrosepticum, Br1f and L1r for P. brasiliense (Duarte et al. 2004), and ADE1/ADE2 for Dickeya sp. (Nassar et al. 1996). To further validate the identification, strain F109 of P. polaris was selected for genome sequencing. The genome of P. polaris strain F109, (NCBI Reference Sequence NZ_RRYS00000000.1) reveals >99% sequence similarity with type strain P. polaris IPO_1606 (GenBank accession GCA_902143345.1). The strain F109 was deposited to All-Russian Collection of Microorganisms under number VKM V-3420. Thus, the characterization of five isolates provided evidence that a previously unreported pathogen was present in the surveyed fields. The isolates were uniform in genetic and physiological properties; they were gram negative, facultative anaerobes with pectinolytic activity, negative for oxidase, urease, indole production, gelatin liquefaction. All isolates were catalase positive, produced acid from lactose, rhamnose, saccharose, xylose, and trehalose, and were tolerant to 5% NaCl, unable to utilize malonate and citrate. All the isolates grew at 37°C. All isolates caused soft rot symptoms on 10 inoculated potato tubers. They produced typical black leg rot symptoms in young potato plants inoculated with 107 CFU/ml of the pathogen by stem injection and incubated at 25°C for 48 h. The bacteria were re-isolated successfully from symptomatic potato and pathogen confirmed by gapA sequencing to complete Koch's postulates. To our knowledge, this is the first report of blackleg and soft rot caused by P. polaris on potato in the Russian Federation. According to the data of commercial diagnostic laboratory "PhytoEngineering" (Moscow region), P. polaris occurred in 5% potato seed stocks harvested in 2017-2019 in the Moscow region. This finding may indicate that new Pectobacterium strains have adapted to a diverse environment, which is consistent with widespread distribution of commercial seed potatoes. The author(s) declare no conflict of interest. Funding: This work was supported by Russian Science Foundation grant #16-16-00073.

Acropetally developing vascular bundles coexisting with basipetally developing and basally blindly ended vascular bundles in scapes of Eriocaulon taquetii (Eriocaulaceae, monocotyledons).

In various monocotyledons, there are basally blindly ended stem vascular bundles, which never connect to the vascular bundles of roots. These blindly ended vascular bundles seem to be unsuitable for transferring water in terrestrial plants. In the present study, we aim to clarify the trace of the blindly ended stem vascular bundles in whole plants, and consider the evolutional process for holding such vascular bundles in the stem. We examined a whole stem vasculature of Eriocaulon taquetii (Eriocaulaceae, monocotyledons) by observation of serial transverse sections, cut by a manual rotary microtome, and viewed under an epifluorescence microscope. Our investigation revealed a threedimensional reconfiguration of the scape vasculature and detected basipetally developing and basally blindly ended vascular bundles, originated from involucral bracts and arranged with acropetally developing vascular bundles alternately in the scape internode. The basipetally developing and basally blindly ended vascular bundles, which originate from the primodia of foliar organs, have been reported in various commelinids. The characteristic vascular bundles would be homologous and presumed to be a synapomorphy of commelinids. These vascular bundles are considered to be a relic characteristic from ancestral semiaquatic plants of monocotyledons.

Exogenous application of Mn significantly increased Cd accumulation in the Cd/Zn hyperaccumulator Sedum alfredii.

Sedum alfredii is a Cd/Zn hyperaccumulator native to China, which was collected from a mined area where Mn content in soil was extremely high, together with Zn and Cd content. We investigated the tolerance and accumulation ability of Mn and its possible association with Cd hyperaccumulation in this plant species by using MP-AES, SR-μ-XRF, and RT-PCR. The results showed that the hyperaccumulating ecotype (HE) S.alfredii exhibited high tolerance to Mn and accumulating around 10,000 and 12,000mgkg-1 Mn in roots and shoots, respectively, without exhibiting toxicity under 5000mgkg-1 Mn treatment for 4 weeks. Exposure to Cd significantly reduced plant uptake of Mn. In contrast, exogenous Mn application significantly improved root uptake and root-to-shoot translocation of Cd, resulting in the increased Cd accumulation in the shoots of HE S.alfredii. SR-μ-XRF analysis demonstrated that high Mn (20μM) exposure resulted in higher intensities of Cd localized in both stem vascular bundles and cortex, as well as leaf mesophyll cells, than in those treated with low Mn levels (0.2μM or 2.0μM). RT-PCR analysis of several genes possibly involved in Mn/Cd transportation showed that expression of SaNramp3 in roots was significantly reduced under high Mn exposure. These results suggested a significant interaction between Cd and Mn in the HE S.alfredii plants, possibly through their competition for transporters and theoretically provided a strategy to improve the efficiency of Cd extraction from polluted soils by this plant species, after using appropriate nutrient management of Mn.