Root Tips Research Articles

Sweet specificities of the root extracellular trap of perennial ryegrass (Lolium perenne), a fructan accumulating plant

Perennial ryegrass (Lolium perenne) is a fructan-accumulating plant constituting one of the most important grassland species with high herbage production, nutritive value and digestibility for grazing cattle. Although fructans were reported to be involved in plant defense acting as antioxidants or stress signals, their contribution in root protection is still to be explored. In roots, atypical defense is provided by the “Root Extracellular Trap” or “RET” at the root-soil interface. The molecular composition and structural organization of the RET are essential to provide root defense against pathogen attacks and abiotic stresses. The RET was reported to be mainly composed of polysaccharides (homogalacturonan, xylogalacturonan, xyloglucan) and proteoglycans such as arabinogalactan proteins (AGPs). Our aim is to characterize the RET composition of L. perenne using cell imaging techniques and a wide range of monoclonal antibodies directed against epitopes from cell wall glycomolecules and to investigate the potential presence of fructans. Interestingly, we found that both mucilage and cell wall surface of border cells were enriched in AGP epitopes. An increased amount of the AGP-containing mucilage was produced by L. perenne root tip in response to both elicitor and osmotic stress. Fructan epitopes were also detected in root cap cells and appeared to be released in the RET under stress conditions. Taken together our findings suggest that AGPs together with fructans are involved in root response of L. perenne to environmental stresses.

Mycorrhization, root tip vitality and biomass of Fagus sylvatica, Picea abies and Pseudotsuga menziesii in monospecific and mixed combinations under water reduction and nitrogen addition

Key messageIn mixed combinations, the negative impact of water reduction and N addition is mitigated for F. sylvatica, but not for conifers.Insight into the responses of trees in mixed and monospecific cultivation to water scarcity and nitrogen (N) excess is necessary to recommend suitable tree mixtures for future European forests. Our aim was to investigate the impact of water reduction, N addition or water reduction + N addition in comparison with control (well-watered, no excess N) on mycorrhizal roots and biomass of three temperate forest species (Fagus sylvatica Fs, Picea abies Pa, and Pseudotsuga menziesii Pm) grown in monospecific (FsFs, PaPa, PmPm) and mixed combinations (PaFs, PmFs). We predicted the probability of the responses with a Bayesian approach. Mycorrhizal colonization declined marginally for P. menziesii in PmFs under water reduction. Under water reduction and N addition combined, we found a decline in root tip vitality of F. sylvatica in PaFs and of P. abies in PaPa. F. sylvatica shoot biomass declined under water reduction + N addition in the monospecific combination. P. abies and P. menziesii had lower root biomass in mixture with F. sylvatica under water reduction + N addition and under water reduction as single factor, respectively. With water reduction and N addition, P. menziesii performed better than P. abies in terms of biomass production. F. sylvatica had a growth advantage in mixture with conifers instead of conspecifics. These findings suggest that young trees show rapid and interspecific responses to species mixing and water + N availability. The selection of suitable tree species should, therefore, consider their interactive responses to changing abiotic factors.

Heterodimerization domains in MAP4 KINASEs determine subcellular localization and activity in Arabidopsis.

Signal transduction relies largely on the activity of kinases and phosphatases that control protein phosphorylation. However, we still know very little about phosphorylation-mediated signaling networks. Plant MITOGEN-ACTIVATED PROTEIN KINASE KINASE KINASE KINASEs (MAP4Ks) have recently gained more attention, given their role in a wide range of processes, including developmental processes and stress signaling. We analyzed MAP4K expression patterns and mapped protein-MAP4K interactions in Arabidopsis (Arabidopsis thaliana), revealing extensive co-expression and heterodimerization. This heterodimerization is regulated by the C-terminal, intrinsically disordered half of the MAP4K, and specifically by the coiled coil motif. The ability to heterodimerize is required for proper activity and localization of the MAP4Ks. Taken together, our results identify MAP4K-interacting proteins and emphasize the functional importance of MAP4K heterodimerization. Furthermore, we identified MAP4K4/TARGET OF TEMPERATURE3 (TOT3) and MAP4K5/TOT3-INTERACTING PROTEIN 5 (TOI5) as key regulators of the transition from cell division to elongation zones in the primary root tip.

Re-Evaluation of Vascular Histogenesis in the Root Tips of Selected Species in the Poaceae Using New Methods: Analysis of the Plerome, Vascular Initials, Pericycle and Late-Maturing Metaxylem Vessels

Serial sectioning and 3D image reconstruction methods were applied to elucidate the structures of the apices of root vascular cylinders (VCs) in taxa of the Poaceae: Zea mays “Honey Bantam”, Z. mays ssp. mexicana, Hordeum vulgare and Oryza sativa. The primary and nodal roots were investigated. Observations were performed using high-quality sectioning and 3D image-processing techniques improved and developed by the authors. We found that a quiescent uniseriate plerome was located at the most distal part of each VC. Vascular initials were located immediately basipetally to the plerome as a specific uniseriate layer that could be classified into central and peripheral initials that produced all the cells in the VC. No supplying of cells from the plerome to the vascular initials was observed. Numerical analysis revealed a “boundary point” along the root axis where the rate of increase of the vascular cell number markedly declined, and the VC diameter, number of vascular cells, and number of late-maturing metaxylem vessels (LMXs) at that point showed a similar relationship among the taxa and the types of roots examined (primary vs. nodal). The plerome and vascular initials layer can be considered independent after seed germination in these taxa. A boundary point at which procambial cell proliferation sharply declined was identified. The diameters of the VCs, number of LMXs, and number of vascular cells at the boundary point were found to be strongly related to each other.

Influence of GA3 (gibberellic acid) and Ca(calcium) on root trait variation and osmotic potential of linseed (Linum usitatissimum L.) under chloride-dominated salinity

Linseed (Linum usitatissimum) is a versatile crop cultivated for its seeds, which are valuable source of ω-3 fatty acids. It adversely affected by soil salinity, as high salt levels can hinder their growth and reduce yields. To assess the potential for mitigating the adverse effects of high salinity concentrations, enhancing the resilience of three genotypes (Shekhar, Sheela, and Kartika) of linseed plants, this research aimed to find out the impact of Gibberellic acid (GA3) and Calcium (Ca) on various aspects of root morphology, osmotic potential of linseed, under varying levels of Cl- dominated salinity. The study employed three salinity levels (0, 5, and 10 dSm-1) and exogenous application of 10−6 M GA3 and/or 10 mg CaCl2 kg-1 in potted plants.The findings indicated that increasing salinity stress significantly (p≤0.05) affected root parameters, including total surface area(43.45%), average diameter(42.06%), total projected area(44.45%), length per volume (66.23%), root length, total root volume (73.23%), tips, forks,fine roots, and osmotic potential(66.67%). Correlations among linseed genotypes were observed between various root morphology and osmotic potential parameters. The application of GA3 and Ca effectively ameliorated the impact of salinity stress at its highest level (10 dSm-1), resulting in increased root parameters while decreasing the osmotic potential (Ψs). Both GA3 and Ca treatments significantly influenced root architecture and maintained optimal osmotic potential. The chloride-dominated salinity exerted inhibitory effects on all three genotypes’ (Shekhar, Sheela, and Kartika) root growth parameters while applying GA3 and Ca successfully mitigated these effects, enhancing root growth.

Flow physics during durge of an axial-centrifugal compressor

Aerodynamic instability design is one of the crucial elements when designing a compressor. Unstable phenomenon such as surge harms the compressor in both performance and structure integrity. The complex unsteady flow process during instability strongly relates to the compressor design. This paper investigates the transient instability process using URANS on a three-stage-axial and one-stage-centrifugal combined compressor under its off-design conditions. Results show that the compressor suffers two surge patterns. The mild surge happens first, with a higher frequency than the traditional mild surge. Then, with the decrease of valve opening, the deep surge is initiated, and the axial stages work at the peak pressure ratio because the mass flow rate is limited by the choked radial diffuser. Moreover, analysis of aerodynamic loads reveals that IGV and the first rotor have the largest unsteady force among all blade rows. According to the flow field, the rotor root and stator tip suffer the most serious impulse caused by reversed flow during surge conditions.

Presenting Eco-Anatomical Data for Saponaria jagelii, a Species on the Edge of the Blade.

The seeds, roots, leaves, flowers and fruits of the critically endangered (CR) species Saponaria jagelii Phitos & Greuter (Caryophyllaceae) were studied. The morphology of the seeds was investigated with scanning electron microscopy. The seeds were imbibed, germinated and developed into young plants. These plants, along with strictly selected wild-growing plants, were used for optical microscopic observations. The leaves and flowers were observed with scanning electron microscopy as well. At least two types of active glandular trichomes were detected on both the leaves and the calyxes of the flowers. The structures of the primary and secondary roots were also investigated. The roots turned into secondary structures very quickly and very close to the root tip. Light microscopy and histochemical reagents were employed to detect secondary metabolites of interest in the leaves. All the metabolites detected were already reported to be synthesized in stressed plants. Distribution data are presented. Conservation actions based on the habitat morphology and the human activities within it, such as the limitation of beach access during the seed-dispersing period and the prohibition of vehicle usage, are recommended in order to protect this tolerant yet severely stressed plant species.

The colonization of Penicillium oxalicum SL2 on rice root surface increased Pb interception capacity of iron plaque and decreased Pb uptake by roots

The exploration of microbial resources to reduce Pb accumulation in rice attracted great attention. In this study, we found Penicillium oxalicum SL2, a Pb-tolerant strain with good capability of dissolving phosphorus and stabilizing Pb in soil, was able to colonize on the root surface of rice seedlings without additional carbon sources, and promoted the secretion of metabolites related to amino acid metabolism, organic acid metabolism, signal transduction and other pathways in rhizosphere exudates, in which the secretion of oxalate increased by 47.7 %. However, P. oxalicum SL2 increased Fe(II) proportion and Fe availability on the root surface, resulting in iron plaque content decrease. Moreover, by converting root surface Pb from Pb-Fe state to PbC2O4 and Pb-P compounds, P. oxalicum SL2 increased Pb intercept capacity of iron plaque by 118.0 %. Furthermore, P. oxalicum SL2 regulated element distribution on the root surface, and reduced the relative content of Pb on the maturation zone of root tip, which was conducive to reducing Pb uptake by apoplastic pathway and the risk of Pb accumulation in root system. Our findings further revealed the interaction between P. oxalicum SL2 and rice root, providing a theoretical basis for the development and application of microbial agents in Pb-contaminated farmland.

Evaluation of Genotoxic and Cytotoxic Activities of Leaf and Seed Extracts of Telfairia occidentalis

Telfairia occidentalis Hook (cucurbitaceae) leaves and seeds, which are used as vegetable in the preparation of soups and as medicine traditionally to treat various diseases by the Ibibios were investigated for genotoxic and cytotoxic effects using Allium cepa test. The effects of the leaves and seeds extracts on the root meristem cells of Allium cepa were investigated using onion bulbs exposed to 2.5 mg/mL, 5 mg/mL, and 10 mg/mL concentrations of the extracts for macroscopic and microscopic analysis. Tap water was used as a negative control and Methotrexate (0.1 mg/ml) was used as a positive control. There was statistically significant (p< 0.05) inhibition of root growth depending on concentration by the extracts when compared with the negative control group. All the tested extracts were observed to have cytotoxic effects on cell division in A. cepa. The extracts-induced chromosomal aberrations and micronuclei (MNC) formations in A. cepa root tip cells were significant (p<0.05) when compared with control group. The extracts treatment further induced cell death, ghost cells, cells membrane damage, and binucleated cells. The seed extract was found to have a higher cytotoxic and genotoxic effects than the leaf extract. These results suggest that the leaf and seeds extract of Telfairia occidentalis possess cytotoxic and genotoxic effects on A. cepa.

Cytogenotoxic effect of trichothecene T2 toxin on Allium sativum root tip meristematic cells

Trichothecene T2 is a mycotoxin from the Fusarium species. This research aims to test the effect of the Trichothecene T2 toxin on mitotic index% (M.I.%) and induction of mitotic aberrations by using the Allium sativum (garlic) test system. The toxin concentrations in ppm were 0.00, 0.30, 0.60, 0.90, and 1.20 for 12 hours. The garlic roots were then cut, and mitotic slides were prepared using squash and examined under a light microscope. The results revealed that the mycotoxin has a significant mitodepressive effect at all concentrations compared to the control, and the MI% reduction was proportional to increasing toxin concentration. The highest reduction in mitotic index was observed in the 1.2 ppm treatment. Moreover, this mycotoxin induced and increased the rate of mitotic abnormalities% (MA%) with increasing the mycotoxin concentration. The observed mitotic abnormalities were star-shaped anaphase, sticky metaphase, C-mitosis, sticky anaphase, depolarization, micronuclei, laggard chromosomes, anaphase bridges, and chromosome loss. The least frequently observed abnormality was micronuclei compared to the most frequent aberration, laggard chromosomes. The total mitotic abnormalities significantly increased with increasing the toxin dose concentration. These results suggest that this mycotoxin can inhibit the mitotic activity of the meristematic cells; it is mutagenic and can disrupt the spindle fibers' activity of the dividing cells at all concentrations, especially at higher doses in food. Therefore, the foods must be tested for fungi producing this mycotoxin. Keywords: Mycotoxin; mitodepressive; root tip; spindle fibers; mutagenic

Cytogenotoxic effect of trichothecene T2 toxin on Allium sativum root tip meristematic cells

Trichothecene T2 is a mycotoxin from the Fusarium species. This research aims to test the effect of the Trichothecene T2 toxin on mitotic index% (M.I.%) and induction of mitotic aberrations by using the Allium sativum (garlic) test system. The toxin concentrations in ppm were: 0.00, 0.30, 0.60, 0.90, and 1.20 for 12 hours. The garlic roots were then cut and mitotic slides were prepared by the squash method and examined under a light microscope. The results revealed that the mycotoxin has a significant mitodepressive effect at all concentrations compared to the control and the MI% reduction was proportional to increasing toxin concentration. The highest reduction in mitotic index was observed in the 1.2 ppm treatment. Moreover, this mycotoxin induced and increased the rate of mitotic abnormalities% (MA%) with increasing the mycotoxin concentration. The observed mitotic abnormalities were star-shaped anaphase, sticky metaphase, C-mitosis, sticky anaphase, depolarization, micronuclei, laggard chromosomes, anaphase bridges, and chromosome loss. The least frequently observed abnormality was micronuclei compared to the most frequent aberration, laggard chromosomes. The total mitotic abnormalities significantly increased with increasing the toxin dose concentration. These results suggest that this mycotoxin can inhibit the mitotic activity of the meristematic cells, it is mutagenic and can disrupt the spindle fibers activity of the dividing cells at all concentrations, especially at its higher doses in food. Therefore, the foods must be tested for fungi producing this mycotoxin. Keywords: Mycotoxin; mitodepressive; root tip; spindle fibers; mutagenic

Biogenic carbonates (queras) in loess-palaeosol sequences of the Ebro Basin and their potential use as a palaeoenvironmental proxy

Secondary carbonate accumulations are very common in arid and semi-arid soils but are often poorly described and classified. This is the case for queras that are observed in several loess-palaeosol sequences of the Ebro Basin. Micromorphologically, queras are complex pedogenic features basically consisting of infillings of calcified root cells in channels, surrounded by decarbonated hypocoatings. They apparently result from biologically mediated calcification/decalcification processes at a microscale. The aim of this study is to systematically characterize biocalcifications found in dated loess-palaeosol sequences, to determine the main factors of formation, and to discuss their possible use as a palaeoenvironmental proxy. Different queras show a similar number of biosparite layers (four to five) around a central channel, and a decarbonated hypocoating around the queras. This supports the hypothesis that queras originate from the calcification of root tips and are related to the acidification of surrounding soil for nutrient absorption. Under cathodoluminescence microscopy, biosparite has a different behaviour than non-biological calcite crystals: the latter appears reddish while biosparite remains black. The queras, with ages corresponding to Marine Isotope Stages 1–3, are younger than that of the loess where they are found in. The stable isotope values likely correspond to C3 plants, and the estimated temperatures of formation reflect a Mediterranean temperate climate. This suggests that the biocalcifications developed during short moist seasons amidst arid periods of the Quaternary.

Genetic and transcriptomic dissection of nitrate-independent function of Arabidopsis NRT1.1/NPF6.3/CHL1 under high ammonium condition

ABSTRACT The Arabidopsis nitrate transceptor NRT1.1/NPF6.3/CHL1 regulates physiological responses to nitrate. Several studies have reported that Arabidopsis plants lacking NRT1.1 show enhanced shoot growth under toxic levels of ammonium without nitrate, suggesting a nitrate-independent function for NRT1.1. To further investigate this nitrate-independent function and its impact on ammonium tolerance, we conducted genetic analysis, tissue-specific expression analysis, and transcriptome analysis using various NRT1.1-related lines. Transgenic plants expressing either nonphosphomimic or phosphomimic mutants of NRT1.1 exhibited similar ammonium tolerance to the wild-type. The chl1–9 mutant, in which NRT1.1 with the P492L substitution is localized intracellularly rather than at the plasma membrane and fails to transport nitrate, showed significantly improved ammonium tolerance. Confocal imaging revealed that the NRT1.1-GFP signal was detected in the plasma membrane of various tissues, including cotyledon pavement cells, hypocotyl epidermal cells, mesophyll cells, root cap cells, and epidermal cells near root tips. In early seedlings, the absence of functional NRT1.1 altered the expression of genes associated with aliphatic glucosinolate biosynthesis, ethylene signaling, and low pH stress. Genes predicted to encode products localized to the extracellular space were enriched among those differentially expressed due to NRT1.1 deficiency. Our data suggest that in the absence of nitrate, plasma membrane-targeted NRT1.1 reduces ammonium tolerance irrespective of its phosphorylation state with alterations of gene expression associated with stress and senescence.

Multilevel Modeling Analysis of Odontogenic Risk Factors and Nasal Septum Deviation Associated with Maxillary Sinus Mucosal Thickening: A Cone-Beam Computed Tomography Study.

(1) Background: In this study, the impact of odontogenic risk factors with nasal septum deviation on maxillary sinus mucosal thickening was assessed using Cone-beam computed tomography CBCT. (2) Methods: A total of 328 maxillary sinus regions from 164 patients (85 males and 79 females) were examined. Images were interpreted by dental specialists and Otolaryngologists. Coronal and sagittal sections were examined to assess the proximity of the root tips of posterior maxillary teeth (RPMT) to the maxillary sinus. The periodontal bone loss for all maxillary posterior teeth was also assessed. Consequently, maxillary sinus mucosal thickening (MT) was further classified into three gradings. Multilevel modeling regression analysis was used due to the hierarchical structuring of the data. Four models were developed, a null model with no factors, a model with tooth-level factors (RPMT, PBL, tooth condition, and root length), a model with patient-level factors (gender and nasal septum deviation), and a model with combined patient- and tooth-level factors. Regression estimates (AOR) and 95% confidence intervals (CIs) of individual and tooth factors were calculated. (3) Results: Multilevel regression analysis showed that RPMT was significantly associated with MT of maxillary sinus (p < 0.001), where patients who had RPMT > 0 had higher odds of MT of maxillary sinus. Tooth condition was also found to be significantly associated with MT of maxillary sinus, where teeth with failed RCT (p < 0.001) and teeth with restorations (p < 0.008) had higher odds of MT of maxillary sinus (AOR = 2.87, 95%CI 1.65, 4.42, AOR = 1.64, 95%CI 1.14, 2.36, respectively). (4) Conclusions: In order to plan preoperative treatment for maxillary posterior teeth, it is important to assess the anatomical relationship between the sinus floor and the root tips of the maxillary posterior teeth. Additionally, we establish a better understanding of the clinician before surgical intervention is conducted.

Cytotoxic and Genotoxic Potentials of Datura innoxia Leaves Aqueous Extract on Allium cepa Meristemic Cells

Medicinal plants are still vitally important in the preparation of pharmaceutical products. Plants have been used both for their prophylactic effects and for the treatment of illnesses and diseases. According to the World Health Organization (WHO) about 80% of developing countries use traditional folk medicines, 85% of which are plant extracts. Datura plant was used medicinally over the world in historical times for treatment of colds, nervous conditions, and as ointment for cuts or wounds and to relieve pain during the setting of bones. The present study aimed to investigate the mutagenic potential of Datura innoxia water extract using Allium cepa root tip cells as biological systems they were used to find out the effect of Datura extract on chromosomal structure and behavior during cell division. Therefore, the mitotic index and chromosome aberration in treated cells were recorded. The root meristem cells were treated with different concentrations of D. innoxia at different times, cytological analysis revealed significant depression in cell division, this was seen noticeably in all used concentrations especially at high ones. The interaction of D. innoxia extract with the genetic material led to DNA damage and decreased cell number depending concentration and time.

PGI1-mediated vascular oxidative pentose phosphate pathway modulates photosynthesis via long-distance cytokinin signaling

In Arabidopsis, the plastidial isoform of phosphoglucose isomerase, PGI1, mediates growth and photosynthesis, likely due to its involvement in the vascular production of cytokinins (CK). To examine this hypothesis, we characterized pgi1-2 knockout plants impaired in PGI1 and pgi1-2 plants specifically expressing PGI1 in root tips and vascular tissues. Moreover, to investigate whether the phenotype of pgi1-2 plants is due to impairments in the plastidial oxidative pentose phosphate pathway (OPPP) or the glycolytic pathway, we characterized pgl3-1 plants with reduced OPPP and pfk4pfk5 knockout plants impaired in plastidial glycolysis. Compared with wild-type (WT) leaves, pgi1-2 leaves exhibited weaker expression of photosynthesis- and 2-C-methyl-D-erythritol 4-P (MEP) pathway-related proteins, and stronger expression of oxidative stress protection-related enzymes. Consistently, pgi1-2 leaves accumulated lower levels of chlorophyll, and higher levels of tocopherols, flavonols and anthocyanins than the WT. Vascular- and root tip-specific PGI1 expression countered the reduced photosynthesis, low MEP pathway-derived CK content, dwarf phenotype and the metabolic characteristics of pgi1-2 plants, reverting them to WT-like levels. Moreover, pgl3-1, but not pfk4pfk5 plants phenocopied pgi1-2. Histochemical analyses of plants expressing GUS under the control of promoter regions of genes encoding plastidial OPPP enzymes exhibited strong GUS activity in root tips and vascular tissues. Overall, our findings show that root tip and vascular PGI1-mediated plastidial OPPP activity affects photosynthesis and growth through mechanisms involving long-distance modulation of the leaf proteome by MEP pathway-derived CKs.

Nitrogen Application Timing and Levels Affect the Fate and Budget of Fertilizer Nitrogen in the Apple-Soil System.

This study aimed to determine the effects of the nitrogen (N) application period and level on the fate of fertilizer N and the contribution of N absorption and translocation to apple organ N. Two N application periods (labeled by the 15N tracer technique in spring and summer, represented by SP and SU, respectively) and three N levels (N0, MN, and HN) were used to determine the physiological indexes and aboveground, root, and soil 15N content of 4-year-old dwarf ('Red Fuji'/M9T337) and arborized ('Red Fuji'/Malus hupehensis Rehd.) apple trees. The results showed that HN led to shoot overgrowth, which was not conducive to the growth of the apple root system (root length, root tips, root surface area, and root volume) or the improvement of root activity. The contribution of soil N to apple organ N accounted for more than 50%, and the contribution of N application in summer to fruit N was higher than that in spring. Under HN treatment, the proportion of soil N absorbed by trees decreased, while that of fertilizer N increased; however, the highest proportion was still less than 50%, so apple trees were highly dependent on soil N. Under MN treatment, fertilizer N residue was similar to soil N consumption, and soil N fertility maintained a basic balance. Under HN treatment, fertilizer N residue was significantly higher than soil N consumption, indicating that excessive N application increased fertilizer N residue in the soil. Overall, the 15N utilization rate of arborized trees (17.33-22.38%) was higher than that of dwarf trees (12.89-16.91%). A total of 12.89-22.38% of fertilizer 15N was absorbed by trees, 30.37-35.41% of fertilizer 15N remained in the soil, and 44.65-54.46% of fertilizer 15N was lost. The 15N utilization rate and 15N residual rate of summer N application were higher than those of spring N application, and the 15N loss rate was lower than that of spring N application. High microbial biomass N (MBN) may be one of the reasons for the high N utilization rate and the low loss rate of N application in summer.

Cytological assessments and a methodological approach to observe the apoptotic effect of nickel sulfate (NiSO4) on Allium cepa L. root germination using EB/AO fluorescence staining

Ethidium bromide–acridine orange (EB/AO) is one of the fastest, most economically valid methods for separating living and dead cells in plant root tips. The present study aimed to investigate the apoptotic effect, nuclear abnormalities and cell division index using an Allium cepa test assay with EB/AO staining and an ImageJ program. Nickel sulphate (NiSO4) concentrations (1.75, 3.5, 7 and 14 ppm) were exposed to the root germination of A. cepa for 48 and 72 h to observe mitotic abnormalities, cytotoxic effects and 5-day exposure to apoptotic effects. It was found that amorphous nuclei, vacuolisation and C-mitosis were the most observed abnormalities, which increased at 14 ppm NiSO4 exposure after 48 and 72 h. The total number of nuclear abnormalities significantly increased at all concentrations and exposure periods. The ImageJ program was used to determine apoptosis rates. The data obtained showed that high concentrations of NiSO4 caused significantly more cell death in root tips than in the control group, resulting in root growth inhibition and increased apoptosis with increased concentration and exposure period. NiSO4 caused toxic activity on root growth, identified as apoptosis, especially at the cortex and vascular region in the root tips. The study found affected damaged and apoptotic areas on the root tips using an EB/AO staining method, which can be used as a marker of damaged tissue areas.

Rapid and chemically diverse C transfer from trees to mycorrhizal fruit bodies in the forest

Abstract Ectomycorrhizal fungi (EMF) are common belowground tree symbionts, supplying trees with water and nutrients. In return, large amounts of C assimilated by trees can be allocated into EMF. However, the chemical forms in which the C is transferred from trees to fungi under field conditions are mostly unknown. In this study, we aimed to unravel the fate of tree‐derived C in EMF. We conducted 13CO2 pulse labelling of Pinus halepensis trees in two forest sites with adjacent EMF sporocarps, combined with a non‐targeted metabolomics profiling of root and sporocarp tissues. 13C was measured in sporocarps of Tricholoma terreum and Suillus collinitus up to 3 m from pine stems. C was assimilated in the labelled trees' needles and transferred to their roots. Starting from Day 2 after labelling, the C was transferred to adjacent sporocarps, peaking on Day 5. We identified more than 100 different labelled metabolites of different chemical groups present in roots and sporocarps. Of them, 17 were common to pine roots and both EMF species, and additional eight common to roots and one of the two EMF. The major labelled metabolites in the root tips were amino acids and tricarboxylic acid intermediates. The major labelled metabolites in sporocarps were amino acids, nucleotides, and fatty acids. We also identified labelled carbohydrates in all tissues. Labelling patterns diverged across different tissues, which can hint at how the C was transferred. Considering the young tree as a sole C source for these sporocarps, and with a diurnal assimilation of 5.4 g C, the total monthly C source is ~165 g C. On average, there were 10 sporocarps around each tree, each requiring ~1 g C. Therefore, a 10 g C investment would make 6% of total tree C allocation, and about 12% of net primary productivity. Overall, we found that this significant and ubiquitous transfer of metabolites from tree roots to EMF sporocarps is more rapid and chemically diverse than once thought. Read the free Plain Language Summary for this article on the Journal blog.

Rhizosphere Ventilation Effects on Root Development and Bacterial Diversity of Peanut in Compacted Soil

Soil compaction is one of the crucial factors that restrains the root respiration, energy metabolism and growth of peanut (Arachis hypogaea L.) due to hypoxia, which can be alleviated by ventilation. We therefore carried out a pot experiment with three treatments: no ventilation control (CK), (2) ventilation volumes at 1.2 (T1), and 1.5 (T2) times of the standard ventilation volume (2.02 L/pot). Compared to no-ventilation in compacted soil, ventilation T1 significantly increased total root length, root surface area, root volume and tips at the peanut anthesis stage (62 days after sowing), while T2 showed a negative impact on the above-mentioned root morphological characteristics. At the podding stage (S2, 95 days after sowing), both ventilation treatments improved root morphology, especially under T1. Compared to CK, both ventilation T1 and T2 decreased the activities of enzymes involving the anaerobic respiration, including root lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase. The activities of antioxidant enzymes of root superoxide dismutase, peroxidase and catalase also decreased at S1, while superoxide dismutase and peroxidase significantly increased under T1 at S2. The ventilation of compacted soil changed soil nitrogen-fixing bacterial communities, with highest bacterial alpha diversity indices under T1. The Pearson correlation analyses indicated a positive relationship between the relative abundance of Bradyrhizobiaceae and root activity, and between unclassified_family of Rhizobiales and the root surface area, while Enterobacteriaceae had a negative impact on the root nodule number. The Pearson correlation test showed that the root surface, tips and activity positively correlated with root superoxide dismutase and peroxidase activities. These results demonstrate that soil ventilation could enhance plant root growth, the diversity and function of soil nitrogen-fixing bacterial communities. The generated results from this present study could serve as important evidence in alleviating soil hypoxia caused by compaction.