Root System Research Articles

How root-grafted trees form networks: Modeling network dynamics with pyNET

Natural root grafting is a widespread phenomenon in woody plants. While previous studies have focused on the effects of reduced growth and resource exchange at the individual level, we lack an understanding of the collective behavior of groups of grafted trees and the networks they form. Here, we present pyNET, a mechanistic agent-based model designed to explore the emergence of root graft networks. We performed simulation experiments with different scenarios involving water scarcity and different cost-benefit dynamics. Costs denote the resources required to form root grafts, while benefits denote the water redistributed among trees. Our model successfully replicates observed patterns linking structural variables to network characteristics. Specifically, we were able to reproduce observed characteristics such as grafting frequency and mean group size. In particular, we find that while the network structure is naturally strongly influenced by the size of the root system, the time and resources allocated to grafting are also critical factors. pyNET serves as a valuable tool for exploring the formation of root grafting networks under diverse environmental conditions and understanding their impact on resource competition. Our study supports theory development on the subject and hopefully stimulates further empirical studies.

Effects of Different Straw Returning Periods and Nitrogen Fertilizer Combinations on Rice Roots and Yield in Saline–Sodic Soil

Straw return is an effective management practice for improving physical and chemical properties of saline–sodic soil in Northeast China. Straw decomposition and nutrient release are deeply influenced by soil and climatic factors. In Northeast China, straw decomposes slowly due to the long winter with low temperatures. Therefore, the season of straw return may be a key issue affecting rice. However, the impact of returning straw in different seasons on rice is disregarded and not commonly researched. We conducted a 2-year field experiment, including two residue management treatments: spring straw return treatment (SR) and autumn straw return treatment (AR), each containing five different N rates (0, 90, 180, 270, and 360 kg ha−1) as sub-treatments. The results reveal that, compared with the spring straw returning treatment, the autumn straw returning treatment significantly improved root morphology and root vigor and increased the number of spikes per unit area, which directly increased rice yield by 4.76% (2020) and 6.62% (2021). In addition, rice yield showed an increasing and then decreasing trend with the increase in N fertilizer application, and it was at its maximum when the N application rate was 270 kg ha−1. Compared to the spring straw return treatment, the autumn straw return treatment was able to reduce 31.46% (2020) and 38.48% (2021) of N fertilizer application without decreasing rice yield. Our findings demonstrate that straw return combined with nitrogen fertilization may be a promising management practice for improving rice root systems and yield in saline–sodic soils, and under the conditions of the autumn straw returning treatment, the best nitrogen fertilizer application rate was 270 kg ha−1.

AtZAT10/STZ1 improves drought tolerance and increases fiber yield in cotton

Drought poses a significant challenge to global crop productivity, necessitating innovative approaches to bolster plant resilience. Leveraging transgenic technology to bolster drought tolerance in crops emerges as a promising strategy for addressing the demands of a rapidly growing global populace. AtZAT10/STZ1, a C2H2-type zinc finger protein transcription factor has shown to significantly improve Arabidopsis’ tolerance to various abiotic stresses. In this study, we reports that AtSTZ1 confers notable drought resistance in upland cotton (Gossypium hirsutum), amplifying cotton fiber yield under varying conditions, including irrigated and water-limited environments, in field trials. Notably, AtSTZ1-overexpressing transgenic cotton showcases enhanced drought resilience across critical growth stages, including seed germination, seedling establishment, and reproductive phases. Morphological analysis reveals an expanded root system characterized by an elongated taproot system, increased lateral roots, augmented root biomass, and enlarged cell dimensions from transgenic cotton plants. Additionally, higher contents of proline, chlorophyll, soluble sugars, and enhanced ROS-scavenging enzyme activities are observed in leaves of transgenic plants subjected to drought, underscoring improved physiological adaptations. Furthermore, transgenic lines exhibit heightened photosynthetic rate, increased water use efficiency, and larger stomatal and epidermal cell sizes, coupled with a decline in leaf stomatal conductance and density, as well as diminished transpiration rates compared to the wild type counterparts. Transcriptome profiling unveils 106 differentially expressed genes in transgenic cotton leaves post-drought treatment, including protein kinases, transcription factors, aquaporins, and heat shock proteins, indicative of an orchestrated stress response. Collectively, these findings underscore the capacity of AtSTZ1 to augment the expression of abiotic stress-related genes in cotton following drought conditions, thus presenting a compelling candidate for genetic manipulation aimed at enhancing crop resilience.

Optimal Water and Nitrogen Regimes Increased Fruit Yield and Water Use Efficiency by Improving Root Characteristics of Drip-Fertigated Greenhouse Tomato (Solanum lycopersicum L.)

The growth of root system directly affects the absorption and utilization of soil water and nitrogen, and understanding the responses of root characteristics to water and nitrogen regimes is thus crucial for optimizing water and nitrogen management. The root characteristics of each soil layer, i.e., root length, root surface area, and root volume, as well as fruit yield and water use efficiency of greenhouse tomato under drip fertigation in response to different irrigation levels and nitrogen rates were explored in northwest China. There were four irrigation levels, i.e., 50% ETC (W1), 75% ETC (W2), 100% ETC (W3), and 125% ETC (W4), where ETC is the crop evapotranspiration, and four nitrogen rates, i.e., 0 kg ha−1 (N1), 150 kg ha−1 (N2), 250 kg ha−1 (N3), and 350 kg ha−1 (N4). The results showed that reasonable irrigation and nitrogen regimes (W3N3) significantly increased fruit yield by 31.64% and root length, root surface area, and root volume by 45.03%, 61.24%, and 148.21% compare to W3N1, respectively. The promoting effect of increasing irrigation level on root characteristics increased with soil depth and had the greatest increases in root volume by 27.07%, 123.43%, and 211.47% for the 0–10, 10–20, and 20–30 cm soil layers, respectively. In addition, reducing irrigation level significantly increased the percentages of roots in the top soil by 29.71%, 26.77%, and 18.53% for root length, root surface area, and root volume, respectively. The reasonable nitrogen rate (N3) significantly increased fruit yield by 41.11%, water use efficiency by 34.42%, and root length, root surface area, and root volume by 40.42%, 41.44%, and 112.76%, respectively. The over-application of nitrogen (N4) reduced root characteristics of all soil layers, fruit yield, and water use efficiency. The promoting effect of increasing nitrogen rate on root length of each soil layer decreased with soil depth, by 71.01%, 48.96%, and 15.71% for 0–10, 10–20, and 20–30 cm soil layers, respectively. Irrigation level was the main factor dominating the root growth of each soil layer. The correlation analysis showed that fruit yield had significantly positive correlations with root characteristics in all soil layers, while water use efficiency had significantly positive correlations with the percentages of root length and root surface area in the 0–10 cm soil layer. In conclusion, rational water and nitrogen regimes achieved better fruit yield by promoting root growth of greenhouse tomato, and the water use efficiency of greenhouse tomato was improved by increasing the root percentage in the topsoil layer to alleviate the adverse effects under water stress conditions. This study reveals how irrigation volume and nitrogen application can enhance tomato yield and water use efficiency by regulating root characteristics and vertical root distribution, providing support for understanding the response of root systems to changes in soil water and nitrogen conditions.

Migration of Plutonium, Micro- and Macroelements in the “Soil–Plant” System at Different Soil Moisture

In the vegetation experiment, the plutonium, micro- and macroelements migration in the “soil–agricultural plant” system depending on soil moisture in the range from 15 to 40٪ of absolute soil moisture were studied. The content of 239Pu was analyzed by α-spectrometry with preliminary radiochemical isolation. The elemental composition was analyzed by the ICP-MS and ICP-AES methods. Beans (Fabaceae) variety “Amber” were used as a test culture. The plutonium transfer factor obtained in the vegetation experiments are in the range of of 5.3×10–4–1.5×10–2, with an average value of 5.4×10–3 for the aboveground part of bean and range of 4.5×10–2–2.7×10–1, with an average of 1.6×10–1 for bean roots. It was determined that the distribution of plutonium, micro and macro elements in the vegetative organs of plants is not equally, the transfer factor of plutonium for the aboveground part of plants is lower than for the root part. It has been established that the accumulation of plutonium, micro- and macroelements, depending on soil moisture, is different for the organs of beans. The dependence of plutonium accumulation by plants on soil moisture is significantly higher than for other considered elements. A decrease in the coefficient of accumulation of plutonium in the aerial part of the beans is recorded with an increase in soil moisture up to two orders of magnitude. There is a trend towards a slight decrease in the accumulation coefficients of Fe, Mg, Mn, Cr, Mo, Ni, Co, Cu. For the root system of beans, a clear dependence of the accumulation of the considered elements on soil moisture is not observed.

Bioenergy sorghum nodal root bud development: morphometric, transcriptomic and gene regulatory network analysis

Bioenergy sorghum’s large and deep nodal root system and associated microbiome enables uptake of water and nutrients from and deposition of soil organic carbon into soil profiles, key contributors to the crop’s resilience and sustainability. The goal of this study was to increase our understanding of bioenergy sorghum nodal root bud development. Sorghum nodal root bud initiation was first observed on the stem node of the 7th phytomer below the shoot apex. Buds were initiated near the upper end of the stem node pulvinus on the side of the stem opposite the tiller bud, then additional buds were added over the next 6-8 days forming a ring of 10-15 nascent nodal root buds around the stem. Later in plant development, a second ring of nodal root buds began forming on the 17th stem node immediately above the first ring of buds. Overall, nodal root bud development can take ~40 days from initiation to onset of nodal root outgrowth. Nodal root buds were initiated in close association with vascular bundles in the rind of the pulvinus. Stem tissue forming nascent nodal root buds expressed sorghum homologs of genes associated with root initiation (WOX4), auxin transport (LAX2, PIN4), meristem activation (NGAL2), and genes involved in cell proliferation. Expression of WOX11 and WOX5, genes involved in root stem niche formation, increased early in nodal root bud development followed by genes encoding PLTs, LBDs (LBD29), LRP1, SMB, RGF1 and root cap LEAs later in development. A nodal root bud gene regulatory network module expressed during nodal root bud initiation predicted connections linking PFA5, SPL9 and WOX4 to genes involved in hormone signaling, meristem activation, and cell proliferation. A network module expressed later in development predicted connections among SOMBRERO, a gene involved in root cap formation, and GATA19, BBM, LBD29 and RITF1/RGF1 signaling. Overall, this study provides a detailed description of bioenergy sorghum nodal root bud development and transcriptome information useful for understanding the regulation of sorghum nodal root bud formation and development.

Performance of different wheat varieties and their associated microbiome under contrasting tillage and fertilization intensities: Insights from a Swiss long-term field experiment

Winter wheat is an important global cereal crop. However, conventional farming practices, characterised by intensive tillage and high fertilizer inputs, pose significant threats to the environment. In response, more conservative management practices are being applied aiming to maintain wheat production while promoting a beneficial microbiome. Here, we evaluated the suitability of three different wheat varieties for less intensive agricultural systems, focusing on reduced tillage and fertilizer intensity. The study was conducted over two consecutive years in a Swiss long-term field experiment comparing conventional versus reduced tillage and full fertilization versus half fertilization. In addition, we investigated the composition of plant-associated microbial communities using amplicon sequencing of phylogenetic marker genes, specifically targeting bacteria and fungi in rhizosphere samples and fungi in root samples. Our results revealed that in our study wheat variety most strongly predicted grain yield and quality, independent of tillage and fertilization intensity. Specifically, wheat varieties demonstrated higher yields and N uptake in plots subjected to conventional ploughing and full fertilization compared to those under reduced tillage and half fertilization. We found no significant effect of wheat variety on the composition of microbial communities. However, tillage emerged as the primary factor influencing microbial community composition in the rhizosphere, while fertilization intensity significantly impacted fungal communities in the root system. These findings underscore the complex interplay between agronomic practices, plant genetics, and microbial dynamics in agroecosystems, emphasizing the need for holistic and adaptive approaches and their further development to ensure sustainable crop production.

Optimization of Potato Cultivation Through the Use of Biostimulator Supporter

Seed potato treatment is vital for plant protection, yield enhancement, and product quality. In the conducted research, the plant biostimulator Supporter was applied to evaluate its impact on potato yields and its structure. Supporter contains both synthetic and SL amino acids, which promote plant growth by enhancing nutrient utilization and fostering the development of a more effective root system. Such a formulation allows to maintain better resistance to environmental stresses, which may include drought or nutrient deficiency, among others. The field study was conducted in 2015–2017 in four towns located in different regions of Poland (Barankowo, Głubczyce, Kędrzyno, and Ryn) using a randomized complete block design with a split-plot design. Varieties (‘Innovator’, ‘Lilly’, ‘Lady Claire’, and ‘Verdi’) were tested. The experiment compared the cultivation technology using Supporter biostimulator with which seed potatoes were treated compared to conventional cultivation (control object) by soaking the tubers in distilled water before planting. The total yield of potato tubers after Supporter application was higher by 13.3%, while the commercial yield increased by 21.1% compared to the traditional cultivation method. The most productive, regardless of cultivation technology and years of research, in terms of total tuber yield was the ‘Lilly’ variety with an average yield of 47.95 t∙ha−1, while the least productive variety was the ‘Innovator’ variety with an average yield of 29.93 t∙ha−1. The ‘Lady Claire’ variety had the highest commercial tuber yield, while the ‘Innovator’ variety had the lowest.

Potential Identification of Root System Architecture Using GPR for Tree Translocation as a Sustainable Forestry Task: A Case Study of the Wild Service Tree

Sustainable economic development serves society but requires taking over space, often at the expense of areas occupied by single trees or even parts of forest areas. Techniques for transplanting adult trees used in various conflict situations at the interface of economy and nature work as a tool for sustainable management of urbanized and industrial areas, as well as, in certain circumstances, forest or naturally valuable areas. This study aimed to evaluate the effectiveness of ground-penetrating radar (GPR) in determining the horizontal and vertical extent of tree root systems before transplantation. Employing this non-invasive method to map root system architecture aids in the appropriate equipment selection and helps define the dimensions and depth of trenches to minimize root damage during excavation. This study specifically focused on the root systems of wild service trees (Sorbus torminalis (L.) Crantz) found in a limestone mine area, where some specimens were planned to be transplanted, as the species is protected under law in Poland. The root systems were scanned with a ground-penetrating radar equipped with a 750 MHz antenna. Then, the root balls were dug out, and the root parameters and other dendrometric parameters were measured. The GPR survey and manual root analyses provided rich comparative graphic material. The number of the main roots detected by the GPR was comparable to those inventoried after extracting the stump. The research was carried out in problematic soil, causing non-standard deformations of the root systems. Especially in such conditions, identifying unusually arranged roots using the GPR method is valuable because it helps in a detailed planning of the transplanting process, minimizing root breakage during the activities carried out, which increases the survival chances of the transplanted tree in a new location.

Plastic mulching enhances maize yield and water productivity by improving root characteristics, green leaf area, and photosynthesis for different cultivars in dryland regions

Uneven precipitation during the growing season and frequent seasonal droughts on the Loess Plateau in Northwest China adversely affect crop production and water use efficiency. While plastic mulching (PM) has been used to alleviate water stress, few studies have examined the traits maize cultivars need to adapt to the altered water environment under PM and achieve high yields. A two-year field experiment was conducted to assess the root characteristics and aboveground growth traits of three widely used high-yielding maize cultivars—Zhengdan 958 (ZD), Huanong 138 (HN), Heboshi 122 (HBS)—under no mulching (NM) and PM conditions. Among the three cultivars, HBS had the highest root system indices—root length density (RLD), root surface area density (RSD), and root biomass—in the topsoil (0–40 cm), followed by ZD and HN under both NM and PM conditions. Under NM, HBS_NM treatment exhibited strong water absorption, improving photosynthesis and yield, making it suitable for drought conditions. Under PM, topsoil moisture increased significantly, with root system indices increasing by 22.5–36.1 % for RLD, 30.2–36.1 % for RSD, and 25.2–36.5 % for root biomass across the cultivars compared to NM. While ZD_PM did not have the highest root system indices under PM, it exhibited higher green leaf area index (4.5–7.5 %), chlorophyll content (2.8–8.6 %), and photosynthetic rate (6.0–14.5 %), resulting in the highest aboveground biomass and yield among the treatments. These findings suggest ZD is better adapted to the enhanced soil moisture under PM. Future research should focus on breeding genotypes that thrive under PM conditions, emphasizing traits such as larger leaf areas and higher photosynthetic rates to boost crop productivity in rainfed areas.

Root traits of soybeans exposed to polyethylene films, polypropylene fragments, and biosolids

Biosolid use imports microplastics into the rhizosphere where they may interfere with root-soil-microbial interactions and cause morphological adaptations in crop root systems. Few studies have examined the response of crop roots to microplastics at documented soil concentrations, and many studies collect root traits using destructive techniques. Hence, there is little information on when and how microplastics effect the physical structure of root systems. Using the rhizobox method, soybeans (Glycine max) were grown in soil amended with biosolid microplastic mimics (polyethylene film or polypropylene fragments at 2,000 and 15,000 particles/kg dry soil) or biosolids and imaged weekly until maturity (11 weeks) using a custom scanner system. Plant biomass increased in the polyethylene treatments and decreased in the high concentration polypropylene treatment. Relative to the Control, polyethylene treatments had larger root length, reduced root diameters, reached maturity faster, had deeper root systems, and had a greater number of lateral roots. In contrast, polypropylene treatments had a mixed response, with high concentrations eliciting a lower root length, fewer laterals, and a more vertical root orientation. Segmented linear regression revealed that root growth in the Control and Biosolid treatments continued through the course of the experiment, while the microplastic treatments reached maturity up to two weeks earlier. Imagery revealed that microplastics elicited deeper rooting depth within the first week and differences in all root traits were evident by the development of the first trifoliate leaflets. Microplastic effects on root traits at early life stages suggest soil physiological drivers, while increased branching frequency and lower lateral elongation are suggestive of changes in soil nitrogen availability. The minimal difference in root traits in the biosolid treatment may be attributable to differences in microplastic properties or counteractive effects by other biosolid constituents.

Impact of saflufenacil and glyphosate-based herbicides on the morphoanatomical and development of Enterolobium contortisiliquum (Vell.) Morong (Fabaceae): new insights into a non-target tropical tree species.

The unregulated use and improper management of herbicides can cause negative effects on non-target species and promote changes in biological communities. Therefore, the current study is aimed at understanding morphoanatomical responses and effects on seedling development induced by the herbicides glyphosate and saflufenacil in Enterolobium contortisiliquum, a non-target tropical species. The plants were cultivated in a greenhouse and subjected to herbicides at doses of 0, 160, 480, and 1440g a.e ha-1 for glyphosate, and 0, 25, 50, and 100g a.i ha-1 for saflufenacil. We conducted visual and morphological assessments over 90days post-application. Leaf samples were collected 12days after the application for anatomical analysis, and we also performed a micromorphometric analysis of the leaf tissues. Biomarkers of phytotoxicity were identified in plants exposed to both herbicides, even at the lowest doses, including in leaves without visual symptoms. The main morphological alterations were the decrease in growth, stem diameter, and dry mass. Furthermore, the leaves and stems visually exhibited chlorosis and necrosis. Both herbicides triggered anatomical modifications such as significant changes (p < 0.05) in the thickness of leaf tissues, hypertrophy, cell collapse, and changes in epicuticular waxes. However, the alterations induced by glyphosate were more widespread compared to saflufenacil, encompassing alterations in the root system. We confirmed that the different mechanisms of action of each herbicide and the existence of an underground reserve system in this species are intrinsically linked to the morphological and developmental responses described. Our findings suggest that E. contortisiliquum could be a potential bioindicator species for these herbicides in the environment, even at concentrations lower than those typically recommended for field application.

A Treasure Trove of Urban Microbial Diversity: Community and Diversity Characteristics of Urban Ancient Ginkgo biloba Rhizosphere Microorganisms in Shanghai.

Rapid urbanization has exerted immense pressure on urban environments, severely constraining the growth of ancient trees. The growth of ancient trees is closely linked to the microbial communities in their rhizospheres, and studying their community characteristics may provide new insights into promoting the growth and rejuvenation of ancient trees. In this study, the rhizosphere soil and root systems of ancient Ginkgo biloba trees (approximately 200 years old) and adult G. biloba trees (approximately 50 years old) in Shanghai were selected as research subjects. Phospholipid fatty acid (PLFA) analysis and high-throughput sequencing were employed to investigate the diversity of microbial communities in the G. biloba rhizosphere. The results indicated that the 19 PLFA species selected to characterize the soil microbial community structure and biomass were present in the rhizosphere soil of both ancient and adult G. biloba trees. However, the total microbial biomass and the microbial biomass in the rhizosphere soil of ancient G. biloba were lower than the microbial biomass in the rhizosphere soil of adult G. biloba. The biomasses of Gram-negative bacteria (G-), arbuscular mycorrhizal fungi (AMF), and protozoans (P) were significantly different. Total phosphorus, organic matter, and pH may be the key factors influencing the soil microbial community in the rhizosphere zone of ancient G. biloba. An in-depth study of AMF showed that the roots and rhizosphere soil of G. biloba contained abundant AMF resources, which were assigned to 224 virtual taxa using the MaarjAM reference database, belonging to four orders, ten families, and nineteen genera. The first and second most dominant genera were Glomus and Paraglomus, respectively. Archaeospora and Ambispora were more dominant in the rhizosphere than the roots. Furthermore, the abundance of live AMF was significantly higher in ancient G. biloba than in adult G. biloba. Therefore, future research should focus on the improvement of soil environmental characteristics and the identification and cultivation of indigenous dominant AMF in the rhizosphere of ancient G. biloba, aiming for their effective application in the rejuvenation of ancient trees.

Three-dimensional numerical modeling of soil-roots system based on X-ray computed tomography: Hydraulic effects study

Vegetation roots enhance soil stability by influencing saturation and pore structure, playing a pivotal role in stabilizing slopes, reducing erosion, and enhancing soil structure. However, current research on the hydraulic effects of roots on soil remains relatively limited. The micro-mechanisms of vegetation's impact on soil and the macro-level connections are not yet fully understood, which poses a challenge to the modeling of root-soil system. This study develops a three-dimensional (3D) finite element model of root-soil composites based on root computed tomography (CT) images and experimental results. Four different groups are modeled, including the rootless group, and those with Festuca arundinacea (FA) roots at various growth stages. The simulation results show that the saturation in the shallow layers significantly decreases in root-soil composite groups, and the rhizosphere water content is lower than that away from the roots, resulting in a net water flux toward the roots. The influence range of roots on suction is gradually amplified with increasing root growth process and root water uptake time. Higher levels of root development result in a stronger overall water uptake effect, leading to a more pronounced decrease in saturation. Closer proximity to the surface roots results in a more rapid increase in soil suction. Compared with one-dimensional root water uptake models, this model considers the effects of spatial heterogeneity of root structures on soil, which provides a comprehensive modeling basis for studying the effect of root system on soil.

Combined cellular phenotyping and high-throughput sequencing analysis reveals the symbiotic relationships between different types of macadamia root systems and arbuscular mycorrhizal fungi

Macadamia nuts, scientifically designated as Macadamia integrifolia, are a highly valuable crop that originated in Australia. This study provides a comprehensive examination of the symbiotic relationships between various macadamia root systems and arbuscular mycorrhizal fungi (AMF). The four principal macadamia-producing regions in Yunnan Province were selected for investigation on the basis of meticulous criteria. To determine the AMF infection rate, the roots were stained. Furthermore, high-throughput sequencing was employed to conduct a comprehensive analysis of the fungal diversity in the rhizosphere soil. The findings were definitive, indicating that both normal and cluster roots are capable of establishing a symbiotic relationship with AMF. Secondary forests exhibited significantly elevated fungal diversity relative to normal roots, while cluster roots demonstrated the lowest diversity and notable regional variation, indicating that the environment exerts a considerable influence on inter-root fungi and AMF. The analysis of the fungal community composition revealed that the predominant groups were Ascomycetes and Basidiomycetes. The FUNGuild function prediction clearly indicated distinct differences in the fungal functions of secondary forests, cluster roots, and normal roots. This study provides a scientific foundation for the sustainable development of macadamia nuts and significantly contributes to a deeper comprehension of the intricate interactions between macadamia and AMF, thereby fostering the long-term stable and healthy growth of the macadamia nut industry.

Diversity and Functional Roles of Root-Associated Endophytic Fungi in Two Dominant Pioneer Trees Reclaimed from a Metal Mine Slag Heap in Southwest China

The utilization of fast-growing, economically valuable woody plants with strong stress resistance, such as poplar and willow, to revegetate severely metal-contaminated mine tailings not only offers a productive and profitable use of abandoned polluted soil resources but also facilitates the phytoremediation of these polluted soils. This study examines the diversity and functional roles of endophytic fungi naturally colonizing the roots of an artificially established Populus yunnanensis forest and the naturally reclaimed pioneer species Coriaria sinica on an abandoned tailing dam in southwest China. Culture-independent analyses revealed that the root systems of both plant species were abundantly colonized by arbuscular mycorrhizal fungi and endophytic fungi, forming rich and diverse endophytic fungal communities predominantly represented by the genera Ilyonectria, Tetracladium, Auricularia, and unclassified members of Helotiales. However, the composition of root endophytic fungal communities differed significantly between the two plant species. Using a culture-dependent approach, a total of 192 culturable endophytic fungal strains were isolated from the roots. The dominant genera included Cadophora, Cladosporium, Cyphellophora, and Paraphoma, most of which were previously identified as dark septate endophytes (DSE). Six representative DSE strains were selected for further study, and significant cadmium tolerance and various plant growth-promoting traits were observed, including the solubilization of insoluble inorganic and organic phosphorus, indole-3-acetic acid (IAA) production, and siderophore synthesis. In greenhouse experiments, inoculating two DSE strains mitigated the inhibitory effects of metal-polluted tailing soil on the growth of P. yunnanensis. This was achieved by reducing heavy metal uptake in roots and limiting metal translocation to the above-ground tissues, thereby promoting plant growth and adaptability. Our findings suggest that as plants reclaim metal-polluted tailings, root-associated endophytic fungal communities also undergo natural succession, playing a critical role in enhancing the host plant’s tolerance to stress. Therefore, these restored root-associated fungi, particularly DSE, are essential functional components of the root systems in plants used for tailing reclamation.

MCTP controls nucleocytoplasmic partitioning of AUXIN RESPONSE FACTORs during lateral root development.

The plant hormone auxin orchestrates almost all aspects of plant growth and development. AUXIN RESPONSE FACTORs (ARFs) control the transcription of auxin-responsive genes, forming cytoplasmic condensates to modulate auxin sensitivity and diversify auxin response regulation. However, the dynamic control of ARF distribution across different subcellular compartments remains largely obscure. Here, we show that three MULTIPLE C2 DOMAIN AND TRANSMEMBRANE REGION PROTEINs (MCTPs), MCTP3, MCTP4, and MCTP6, control ARF nucleocytoplasmic partitioning and determine lateral root development. MCTP3/4/6 are highly expressed in lateral roots and specifically interact with ARF7 and ARF19 to dissolve their cytoplasmic condensates. This promotes ARF nuclear localization in lateral root primordia and enhances auxin signaling during lateral root formation. Our findings confer MCTP as a key switch to modulate auxin responses and outline an MCTP-ARF signaling cascade that is crucial for the establishment of the plant root system.

Characterization of Al3+-toxicity responses and molecular mechanisms underlying organic acid efflux in Vigna mungo (L.) Hepper.

Aluminium (Al3+) toxicity in acidic soils poses a significant challenge for crop cultivation and reduces crop productivity. The primary defense mechanism against Al3+ toxicity involves the activation of organic acid secretion. In this study, responses of 9 Vigna mungo cultivars to Al3+ toxicity were investigated, with a particular emphasis on the root system and crucial genes involved in Al3+ tolerance using molecular cloning and expression analysis. Sensitive blackgram-KM2 cultivars exposed to 100-µM Al3+ toxicity for 72h exhibited a root-growth inhibition of approximately 66.17%. Significant loss of membrane integrity and structural deformative roots were found to be the primary symptoms of Al3+ toxicity in blackgram. MATE (Multidrug and Toxic Compound Extrusion) and ALS3 (Aluminium Sensitive 3) genes were successfully cloned from a sensitive blackgram cv KM2 with phylogenetic analysis revealing their evolutionary relationship to Vigna radiata and Glycine max. The MATE gene is mainly localized in the plasma membrane, and highly expressed under Al3+, thus suggesting its role in transports of citrate-Al3+ complexes, and detoxifying Al3+ within plant cells. In addition, ALS3 was also induced under Al3+ toxicity, which codes the UDP-glucose transporter and is required for the maintenance of ions homeostasis. In summary, this study highlights the understanding of Al3+ toxicity and underlying molecular mechanisms linked to the efflux of organic acid in blackgram, ultimately aiding the framework for the development of strategies to enhance the resilience of blackgram and other pulse crops in Al-rich soils.

Physiological and biochemical responses in a cadmium accumulator of traditional Chinese medicine Ligusticum sinense cv. Chuanxiong under cadmium condition

Ligusticum sinense cv. Chuanxiong (L. Chuanxiong), one of the widely used traditional Chinese medicines (TCM), is currently facing the problem of excessive cadmium (Cd) content. This problem has significantly affected the quality and safety of L. Chuanxiong and become a vital factor restricting its clinical application and international trade development. Currently, to solve the problem of excessive Cd, it is essential to research the response mechanisms of L. Chuanxiong to Cd stress. However, there are few reports on its physiological and biochemical responses under Cd stress. In this study, we conducted the hydroponic experiment under 25 μM Cd stress, based on the Cd content of the genuine producing areas soil. The results showed that 25 μM Cd stress not only had no significant inhibitory effect on the growth of L. Chuanxiong seedlings but also significantly increased the chlorophyll a content (11.79%) and root activity (51.82%) compared with that of the control, which might be a hormesis effect. Further results showed that the absorption and assimilation of NH4+ increased in seedlings under 25 μM Cd stress, which was associated with high photosynthetic pigments. Here, we initially hypothesized and confirmed that Cd exceedance in the root system of L. Chuanxiong was due to the thickening of the root cell wall, changes in the content of the cell wall components, and chelation of Cd by GSH. There was an increase in cell wall thickness (57.64 %) and a significant increase in cellulose (25.48%) content of roots under 25 μM Cd stress. In addition, L. Chuanxiong reduced oxidative stress caused by 25 μM Cd stress mainly through the GSH/GSSG cycle. Among them, GSH-Px (48.26%) and GR (42.64%) activities were significantly increased, thereby maintaining a high GSH/GSSG ratio. This study preliminarily reveals the response of L. Chuanxiong to Cd stress and the mechanism of Cd enrichment. It provides a theoretical basis for solving the problem of Cd excessive in L. Chuanxiong.Graphical Physiological and biochemical mechanisms of L. Chuanxiong seedlings under Cd stress.

Rhizosheath Formation and Its Role in Plant Adaptation to Abiotic Stress

The rhizosheath, the layer of soil tightly attached to the roots, protects plants against abiotic stress and other adverse conditions by providing a bridge from the plant root system to the soil. It reduces the formation of air gaps between the root and soil and facilitates the transportation of water at the root–soil interface. It also serves as a favourable niche for plant-growth-promoting rhizobacteria in the surrounding soil, which facilitate the absorption of soil water and nutrients. This review compares the difference between the rhizosheath and rhizosphere, and summarises the molecular and physiological mechanisms of rhizosheath formation, and identifying the causes of rhizosheath formation/non-formation in plants. We summarise the chemical and physical factors (root hair, soil-related factors, root exudates, and microorganisms) that determine rhizosheath formation, and focus on the important functions of the rhizosheath in plants under abiotic stress, especially in drought stress, phosphorus deficiency, aluminium stress, and salinity stress. Understanding the roles played by the rhizosheath and the mechanisms of its formation provides new perspectives for improving plant stress tolerance in the field, which will mitigate the increasing environmental stress conditions associated with on-going global climate change.