Root Environment Research Articles

Residual Effect of Silicate Agromineral Application on Soil Acidity, Mineral Availability, and Soybean Anatomy

Silicate agrominerals (SA) may be sustainable soil amendments that can minimize dependence on conventional fertilizers (CF). We evaluated the residual effects of SA application as a source of Si and as a soil remineralizer, using soils with contrasting chemical-physical features cultivated with soybean. The experiment was conducted under greenhouse conditions and treatments were arranged in a 5 × 2 + 2 factorial scheme: five rates of SA, two soils in addition to CF. The soil was incubated before cultivation, followed by the sequential sowing of corn and soybean. At the R4 phenological stage, when the pods were fully developed, soybean plants were harvested for anatomical leaf tissue analysis and P, Ca, Mg, and Si accumulation. After harvest, the soil was analyzed. Application of SA rates reduced potential acidity (H + Al) and exchangeable acidity (Al3+) and increased soil pH, sum of bases (SB), cation-exchange capacity (CEC), and base saturation (BS), in addition to promoting the nutrient’s availability and Si. Stomatal density was higher on the adaxial face of plants cultivated in the medium-textured soil. Silicate agrominerals can be used as a soil acidity corrector and remineralizer, improving the root environment and increasing the availability of nutrients and silicon.

Electrogenesis in the Root Environment of Various Lettuce Varieties

Electrogenesis in the Root Environment of Various Lettuce Varieties

Design of a device for improving the root environment of fruit trees

Design of a device for improving the root environment of fruit trees

Enhancing carrot (Daucus carota var. sativa Hoffm.) plant productivity with combined rhizosphere microbial consortium.

Plant growth-promoting rhizobacteria (PGPR) are an integral part of agricultural practices due to their roles in promoting plant growth, improving soil conditions, and suppressing diseases. However, researches on the PGPR in the rhizosphere of carrots, an important vegetable crop, is relative limited. Therefore, this study aimed to isolate and characterize PGPR strains from the rhizosphere soil of greenhouse-grown carrots, with a focus on their potential to stimulate carrot growth. Through a screening process, 12 high-efficiency phosphorus-solubilizing bacteria, one nitrogen-fixing strain, and two potassium-solubilizing strains were screened. Prominent among these were Bacillus firmus MN3 for nitrogen fixation ability, Acinetobacter pittii MP41 for phosphate solubilization, and Bacillus subtilis PK9 for potassium-solubilization. These strains were used to formulate a combined microbial consortium, N3P41K9, for inoculation and further analysis. The application of N3P41K9, significantly enhanced carrot growth, with an increase in plant height by 17.1% and root length by 54.5% in a pot experiment, compared to the control group. This treatment also elevated alkaline-hydrolyzable nitrogen levels by 72.4%, available phosphorus by 48.2%, and available potassium by 23.7%. Subsequent field trials confirmed the efficacy of N3P41K9, with a notable 12.5% increase in carrot yields. The N3P41K9 treatment had a minimal disturbance on soil bacterial diversity and abundance, but significantly increased the prevalence of beneficial genera such as Gemmatimonas and Nitrospira. Genus-level redundancy analysis indicated that the pH and alkali-hydrolyzable nitrogen content were pivotal in shaping the bacterial community composition. The findings of this study highlight the feasibility of combined microbial consortium in promoting carrot growth, increasing yield, and enriching the root environment with beneficial microbes. Furthermore, these results suggest the potential of the N3P41K9 consortium for soil amelioration, offering a promising strategy for sustainable agricultural practices.

Soil quality index to access the impacts of long‐term vinasse application in sugarcane areas

AbstractSoil quality index (SQI) helps quantify management practices impacts on the soil, providing information for producers in decision‐making. Through evaluation in sugarcane areas, soil indicators were used to develop SQI to access and quantify the impacts of long‐term vinasse application on the soil. The treatments consisted of two soil types: clayey (490 g kg−1 clay) and sandy (80 g kg−1 clay) and two conditions: with (70 m3 ha−1 year−1) and without vinasse application for 10 years. Soil samples were collected in the 0‐ to 10‐cm, 10‐ to 20‐cm, and 20‐ to 30‐cm layers in each treatment. Four soil functions were developed to calculate SQI: root environment quality (REQ), air/water ratio (AWR), soil chemical quality (SCQ), and soil tolerance to erosion (STE). Twelve soil indicators related to soil fertility and aggregation/structure were used. The long‐term vinasse application increased water storage (32%–58% of soil porosity), sum of bases (11–19 mmolc dm−3) and aggregate stability index (41% vs. 78%) compared to without vinasse treatment in sandy soil. In the clayey soil, vinasse increased (p < 0.05) the REQ, SCQ, and STE functions by 10%, 14%, and 13%, respectively, besides not affecting AWR. The long‐term application of vinasse promoted greater benefits, proportionally, in the sandy soil, with increments (p < 0.05) of 30% in AWR, 25% in SCQ, and 27% in STE. According to the SQI, long‐term vinasse application increased the capacity of the clay soil to perform its functions by 8%, while it increased to the sandy soil was 22%.

Response of Wheat to Static and Dynamic Non-Uniform Distribution of Salt in the Root Environment

Response of Wheat to Static and Dynamic Non-Uniform Distribution of Salt in the Root Environment

Rust Disease Changes the Abundance and Composition of Bacterial Community in Iris lactea Rhizosphere

The microbial community plays a vital role in root–environment interactions, which affect plant performance under biotic stress. Rust disease significantly affects plant growth, which may also affect rhizosphere microbial community. However, there is a scarcity of studies investigating the microbial community of rhizosphere under rust disease stress. Iris lactea is a widely utilized plant in gardening and landscaping due to its versatility and ornamental value, but it is often susceptible to rust disease in landscape settings. In this study, we compared the bacterial communities between bulk soil (non-cultivated control), rhizosphere soil of healthy Iris lactea plants, and rhizosphere soil of Iris lactea plants infected with rust disease (rhizosphere-R). Results revealed significant alterations in the abundance and composition of bacterial communities associated with rust disease infection. Specifically, the rhizosphere-R samples exhibited a decreased Shannon index at 1.9% compared to bulk soil and the relative abundance of Proteobacteria was increased at 31.65%. Moreover, distinct changes in β-diversity were shown between bulk soil and rhizosphere samples. Notably, potentially pathogenic bacteria increased in abundance under rust disease stress, while beneficial bacterial taxa decreased. Overall, our results show that rust disease affects the rhizosphere microbial community, which emphasizes the ecological implications of plant–microbe interactions under biotic stress and implications for developing targeted rhizobacterial-based biocontrol strategies.

Effects of Trichoderma harzianum and Bacillus subtilis on the root and soil microbiomes of the soybean plant INTACTA RR2 PRO™.

Soybean is a significant export product for several countries, including the United States and Brazil. There are numerous varieties of soybean. Among them, a genetically modified type known as INTACTA RR2 PRO™ has been designed to demonstrate resistance to glyphosate and to produce toxins that are lethal to several species of caterpillars. Limited information is available on the use of Trichoderma harzianum and Bacillus subtilis to promote plant growth and their impact on the plant microbiome. This study aimed to evaluate the effects of these microorganisms on this soybean cultivar by analyzing parameters, such as root and shoot dry matter, nutritional status, and root and soil microbial diversity. The results indicated that treatments with B. subtilis alone or in combination with T. harzianum as seed or seed and soil applications significantly enhanced plant height and biomass compared to the other treatments and the control. No significant differences in phosphorus and nitrogen concentrations were detected across treatments, although some treatments showed close correlations with these nutrients. Microbial inoculations slightly influenced the soil and root microbiomes, with significant beta diversity differences between soil and root environments, but had a limited overall impact on community composition. The combined application of B. subtilis and T. harzianum particularly enhanced plant growth and promoted plant-associated microbial groups, such as Rhizobiaceae, optimizing plant-microbe interactions. Furthermore, the treatments resulted in a slight reduction in fungal richness and diversity.

Dicranopteris dichotoma rhizosphere-derived Bacillus sp. MQB12 acts as an enhancer of plant growth via increasing phosphorus utilization, hormone synthesis, and rhizosphere microbial abundance

In recent years, microbial inoculants have showed a great potential to replace chemical fertilizers as a new generation of soil amendment agents, however, the understanding of their effects on nutrient cycling within plants and rhizosphere microbial diversity are still limited. In this study, the rhizosphere growth-promoting bacteria MQB12 was used to inoculate Vigna radiata to evaluate the effects of external inoculants on plant transcriptomics and rhizosphere soil microbial diversity. Enrichment analysis using GO and KEGG revealed significant enrichment in DNA-binding transcription factor activity, transcriptional regulatory factor activity, and phenylpropanoid biosynthesis among the differentially expressed genes. MQB12 inoculation positively responded to phosphorus starvation response, increased the expression of phosphorus starvation response genes (PHT/PAP), enhanced the synthesis of ethylene and salicylic acid to cope with external stress, and improved the expression of plant disease resistance genes to strengthen the disease resistance of plants to pathogens. At the same time, microbial diversity analysis further revealed the positive effect of MQB12 inoculum. MQB12 inoculum enriched beneficial flora, improved flora abundance, changed the structure and diversity of V. radiata rhizosphere microbial community, enhanced the interconnections between the flora, and positively promoted growth. MQB12 was found to adjust the microflora of the rhizosphere, which subsequently changed the environment for plant colonization. This change led to the enrichment of beneficial bacteria and removal of pathogenic bacteria, which positively affected the internal pathways of plants. Additionally, changes in gene expression levels of plants resulted in the formation of different phenotypes and various metabolites, further influencing the formation of rhizosphere microbial communities through close contact between roots and soil. This study provides new insights into the effects of microbial agents on plant growth and root environment construction and is conducive to the further development and application of microbial agents.Graphical

Effect of Humic Acids on the Generation of Potential Differences in a Bioelectrochemical System

The possibility of increasing the electrogenic properties of the root environment through the use of potential electron carriers, humic acids (HA), was studied. For this purpose, a bioelectrochemical cell has been created, including electrode systems introduced into the planters to remove the potential difference formed during the development of plants. Using the example of Typhoon lettuce, it was determined that an increase in the concentration of HA in the root environment by 2 times allowed to increase the voltage by 7–16% of the control variant, depending on the place of their introduction. The best result – a more stable generation of a high potential difference from the early periods of vegetation was typical for the variant with addition of HA to the upper electrode area – the average voltage value for it was 418 ± 29 mV and a specific power of 0.2 MW/m2. A number of physicochemical parameters of near-electrode regions in plant bioelectrochemical systems have been studied: electrical conductivity, pH, concentration of humic acids at the end of the growing season. The potential electroactivity of microorganisms in the root environment of lettuce has been revealed. It is shown that the ability of humic acids to play the role of a redox mediator in a bioelectrochemical system largely depends on the place of their concentration.

Effects of peanut shell biochar and fermented cow manure on plant growth and metabolism of tomato

BackgroundThis experimental study used peanut shell biochar and fermented cow manure as the main raw materials forming a substrate for tomato plants.ResultsSubstrates were created from peanut shell biochar, fermented cow manure, slag, and vermiculite mixed in volume ratios of 6:0:1:2, 5:1:1:2, 4:2:1:2, and 3:3:1:2, respectively. Comparisons were made to a control substrate composed of peat, slag, and vermiculite in a volume ratio of 6:1:2, respectively. As the proportion of biochar in the substrate increased, the bulk density showed a downward trend while the total porosity, aeration porosity, and water holding capacity showed upward trends. As the proportion of cow manure increased, the total N, available K, Ca, and Mg in the substrate increased. Tomatoes demonstrated similar or better growth than the control at experimental substrate composition ratios of 6:0:1:2 and 5:1:1:2. This was reflected in seedling strength index, seedling growth, chlorophyll content, root growth, plant carbohydrates, purine metabolism, caffeine metabolism, galactose metabolism, and starch and sucrose metabolism. The results of this study indicate the experimental substrate composition ratios of 6:0:1:2 and 5:1:1:2 were the most beneficial in terms of supporting the growth of tomato plants.ConclusionsThe study confirms biochar in composite substrate promotes plant growth by improving the root environment and plant metabolism. This investigation provides new information to moderate the use of peat and support efforts to achieve carbon neutrality through the creative utilization of agricultural waste.Graphical abstract

Metagenomic Analysis of Rhizospheric Bacterial Community of Citrus Trees Expressing Phloem-Directed Antimicrobials

Huanglongbing, also known as citrus greening, is currently the most devastating citrus disease with limited success in prevention and mitigation. A promising strategy for Huanglongbing control is the use of antimicrobials fused to a carrier protein (phloem protein of 16 kDa or PP16) that targets vascular tissues. This study investigated the effects of genetically modified citrus trees expressing Citrus sinensis PP16 (CsPP16) fused to human lysozyme and β-defensin-2 on the soil microbiome diversity using 16S amplicon analysis. The results indicated that there were no significant alterations in alpha diversity, beta diversity, phylogenetic diversity, differential abundance, or functional prediction between the antimicrobial phloem-overexpressing plants and the control group, suggesting minimal impact on microbial community structure. However, microbiota diversity analysis revealed distinct bacterial assemblages between the rhizosphere soil and root environments. This study helps to understand the ecological implications of crops expressing phloem-targeted antimicrobials for vascular disease management, with minimal impact on soil microbiota.

Response of wheat (Triticum aestivum L. cv.) to the coexistence of micro-/nanoplastics and phthalate esters alters its growth environment

Micro- and nano-plastics (MPs/NPs) have emerged as a global pollutant, yet their impact on the root environment of plants remains scarcely explored. Given the widespread pollution of phthalate esters (PAEs) in the environment due to the application of plastic products, the co-occurrence of MPs/NPs and PAEs could potentially threaten the growth medium of plants. This study examined the combined effects of polystyrene (PS) MPs/NPs and PAEs, specifically dibutyl phthalate and di-(2-ethylhexyl) phthalate, on the chemical properties and microbial communities in a wheat growth medium. It was observed that the co-pollution with MPs/NPs and PAEs significantly increased the levels of oxalic acid, formic acid, and total organic carbon (TOC), enhanced microbial activity, and promoted the indigenous input and humification of dissolved organic matter, while slightly reducing the pH of the medium solution. Although changes in chemical indices were primarily attributed to the addition of PAEs, no interaction between PS MPs/NPs and PAEs was detected. High-throughput sequencing revealed no significant change in microbial diversity within the media containing both PS MPs/NPs and PAEs compared to the media with PS MPs/NPs alone. However, alterations in energy and carbohydrate metabolism were noted. Proteobacteria dominated the bacterial communities in the medium solution across all treatment groups, followed by Bacteroidetes and Verrucomicrobia. The composition and structure of these microbial communities varied with the particle size of the PS in both single and combined treatments. Moreover, variations in TOC, oxalic acid, and formic acid significantly influenced the bacterial community composition in the medium, suggesting they could modulate the abundance of dominant bacteria to counteract the stress from exogenous pollutants. This research provides new insights into the combined effects of different sizes of PS particles and another abiotic stressor in the wheat root environment, providing a critical foundation for understanding plant adaptation in complex environmental conditions.

Assessment of the resistance of wild grasses in the northwestern region of the Russian Arctic to chloride salinization

Wild grasses are prevalent across various types of vegetation, playing a significant role in both natural ecosystems and human economic endeavors. The potential of using grasses to restore areas affected by tidal erosion and saline soils has not been fully investigated. A study was conducted to examine the impact of different levels of NaCl salinity (ranging from 20 to 200 mM) on seed germination and early growth of Agrostis capillaris L., Deschampsia cespitosa (L.) P. Beauv., Phalaris arundinacea L., and Phleum pratense L. These plants are commonly found in the Arctic region within the Belomorsky district of the Republic of Karelia. Through research, a direct connection was discovered between the germination of seeds and the growth of seedlings based on the salt levels in the root environment and the type of grass species present. In summary, all species successfully germinated at NaCl concentrations of 20–80 mM. However, germination rates decreased at 100 and 200 mM in most cases. When exposed to NaCl concentrations of 60 mM and higher, the growth of root and shoot in the grasses was slowed down to some extent (depending on the species), but not completely inhibited. Due to the resilience of wild grasses to cold temperatures, it is proposed that they could be used in the phytoremediation of Arctic areas with a salinity level of up to 100 mM (0.6 % salinity). An analysis of the data resulted in a ranking of grass species based on their salt resistance: P. pratense ˃A. capillaris ˃P. arundinacea ˃D. cespitosa.

Genome-Wide Identification and Expression Analysis of BrBASS Genes in Brassica rapa Reveals Their Potential Roles in Abiotic Stress Tolerance.

The bile acid sodium symporter (BASS) family plays an important role in transporting substances and coordinating plants' salt tolerance. However, the function of BASS in Brassica rapa has not yet been elucidated. In this study, eight BrBASS genes distributed on five chromosomes were identified that belonged to four subfamilies. Expression profile analysis showed that BrBASS7 was highly expressed in roots, whereas BrBASS4 was highly expressed in flowers. The promoter element analysis also identified several typical homeopathic elements involved in abiotic stress tolerance and stress-related hormonal responses. Notably, under salt stress, the expression of BrBASS2 was significantly upregulated; under osmotic stress, that of BrBASS4 increased and then decreased; and under cold stress, that of BrBASS7 generally declined. The protein-protein interaction analysis revealed that the BrBASS2 homologous gene AtBASS2 interacted with Nhd1 (N-mediated heading date-1) to alleviate salt stress in plants, while the BrBASS4 homologous gene AtBASS3 interacted with BLOS1 (biogenesis of lysosome-related organelles complex 1 subunit 1) via co-regulation with SNX1 (sorting nexin 1) to mitigate an unfavorable growing environment for roots. Further, Bra-miR396 (Bra-microRNA396) targeting BrBASS4 and BrBASS7 played a role in the plant response to osmotic and cold stress conditions, respectively. This research demonstrates that BrBASS2, BrBASS4, and BrBASS7 harbor great potential for regulating abiotic stresses. The findings will help advance the study of the functions of the BrBASS gene family.

The Great Banyan Tree (<i>Ficus benghalenszs</i> L.), Indian Botanic Garden, Howrah-The Periodical Variation in its Soil Fertility Status

Under the present investigation, for preserving the Great Banyan Tree (Ficus benghalensis L.) of religious, tourism and botanical significance,-its root environment has thoroughly been investigated which was not yet been explored. From the results it is clear that the entire soil which is supporting nearly 95-98% soil-proproot system is quite low in organic carbon content and consequently resulting into its unfavourable physico-chemical properties. A few important physico-chemical properties have been tabulated and at the end some valuable suggestions are given.

Influence of Soil Additives (Gypsum and Dolomite) on Peanuts Productivity and Soil Properties: A Review

Although India is steadily progressing in oilseeds production, but the average yields of most of the oilseeds like groundnut are still extremely low when compared to those prevailing in other countries of the world. This is because oilseeds are cultivated mostly in marginal and sub-marginal land of semi-arid areas with very less management, hence remain vulnerable to vagaries of nature. Among oilseed crops groundnut is an important source of vegetable oil and protein. Lack of appropriate management practices leads to decreased yields of the crop. Applications of amendments like gypsum and dolomite based on soil pH is necessary to provide a better environment for roots and plant growth.

Seeds treatment with salicylic acid increases gene expression and activity of antioxidant enzymes in wheat plants under zinc or copper deficiency

The effect of wheat seeds treatment with salicylic acid (SA) on the expression of the TaCu/ZnSOD, TaFeSOD and TaCAT2 genes and the activity of antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)) in leaves at the optimal content of zinc (2 µM) and copper (0.3 µM) in root environment or there deficiencies has been studied. It was shown for the first time that seeds treatment with SA leads to an increase of the number of genes transcripts compared to untreated plants, both under optimal conditions of mineral nutrition and under zinc or copper deficiency. The activity of enzymes, especially catalase, also increases. Judging by the MDA content, this allows one to avoid increasing the intensity of lipid peroxidation (LPO) and, accordingly, the development of oxidative stress. It is concluded that the discovered positive effect of seed treatment with SA on the activity of the main enzymes of antioxidant system may underlie the stimulating effect of this phytohormone on physiological processes in plants under microelements deficiency.

The Impact of Magnesium on the Growth, Physiology and Quality of Tea (Camellia sinensis L.) Plants under Acid Stress

Magnesium plays a crucial role in plant physiological processes. However, the specific mechanisms underlying the response of tea plants to altered magnesium nutrition under acid stress remain unclear. This study investigates how root environment acidification impacts tea seedlings and the role of magnesium (Mg) in mitigating these effects. We examine varying pH and Mg levels’ influence on tea seedlings’ resistance to abiotic stress, focusing on antioxidant capacity and nutritional content. In a hydroponic experiment, we varied root pH (3.5, 5.0, 6.5) and Mg concentrations (0.01, 0.4, 0.8 mM), assessing parameters like antioxidant capacity, peroxidative damage, and nutritional content at 1, 7, 15, and 30 days post treatment. Root environment acidification and Mg deficiency worsened peroxidative damage in tea plant leaves and roots. Increased Mg supplementation enhanced antioxidant enzyme activity, reducing malondialdehyde and mitigating oxidative damage from root environment acid stress. Under acid stress, 0.8 mM Mg significantly increased tea leaf polyphenols, amino acids, and water-soluble extracts. Mg notably boosted chlorophyll content, surpassing lower Mg levels at pH 5. Additionally, Mg reversed root vitality inhibition induced by acid stress, leading to increased nitrogen, potassium, and Mg concentrations in leaves, promoting balanced nutrient absorption. Mg supplementation is crucial for enhancing tea plant antioxidant capacity, alleviating growth inhibition from root-environment acid stress, and improving chlorophyll content and root vitality, highlighting Mg’s significance in tea cultivation and broader agricultural practices.

Effects of root-derived organic acids on sorption of pharmaceutically active compounds in sandy topsoil

The presence and fate of pharmaceutically active compounds (PhACs) in agricultural fields are rarely investigated. The present study highlights that root-derived low-molecular-weight organic acids (LMWOAs) affect the mobility of PhACs in cultivated humic Arenosol. Sorption experiments are conducted using three PhACs characterised by different physicochemical properties: carbamazepine (CBZ), 17α-ethinylestradiol (EE2), and diclofenac-sodium (DFC). The results suggest that the adsorption of EE2 is more intense than the other two PhACs, whereas DFC and CBZ are primarily dominated by desorption. LMWOAs mainly provide additional low-energy adsorption sites for the PhACs, and slight pH changes do not significantly affect the sorption mechanism. During competitive adsorption, the high-energy sites of the adsorbents are initially occupied by EE2 owing to its high adsorption energy (∼15 kJ/mol). The new low-energy binding sites enhance the adsorption of DFC (from 8.5 % to 72.0 %) and CBZ (from 31.0 % to 70.0 %) during multicomponent adsorption. LMWOAs not only affect adsorption by modifying the pH but also provide additional binding sites that allow the PhACs to remain in the root environment for a longer period. As the concentration of LMWOAs temporarily changes, so does the availability of PhACs in the root zone. Environmental changes in the humic horizon enhance the mobility of the adsorbed PhACs, which renders them continuously available for uptake by plants, thus increasing the possibility of PhACs entering the human food chain.