Rhizosphere Soil Enzyme Activities Research Articles

Dynamic interplay between soil microbial communities, enzyme activities, and pear quality across planting years

Few studies have been reported on the effect of planting years on fruit quality and soil of pear trees. In this study, four planting years (T5, T20, T30, and T40) of Cuiguan pears were used to analyze fruit quality, rhizosphere soil enzymes, and microbial diversity of pear trees, and their correlations. The results showed that the content of sucrose, reducing sugar and ascorbic acid in Cuiguan Pear showed a tendency of increasing and then decreasing with the increase of planting years, in which the highest content was found in 20- and 30-year-old fruits, and the highest content of total acid was found in 5-year-old fruits. Rhizosphere soil enzyme activities varied with planting year, with the highest protease activity in 20-year-old soil, phosphatase and urease in 30-year-old soil, polyphenol oxidase in 5-year-old soil, and sucrase in 40-year-old soil. The microbial diversity index and the number of OTUs showed an increasing and decreasing trend with the increase of planting years. Among the top 11 bacteria in pear rhizosphere soil average relative abundance, with Bradyrhizobium decreasing in relative abundance at the peak pear fruiting stages (T20 and T30), while Acidothermus showed an increasing trend in relative abundance with increasing planting years. RDA analysis showed that there were differences in the microbial community structure of pear trees at different planting years, and that both sucrose and reducing sugar contents in pears were positively correlated with T20 and T30, ascorbic acid content was positively correlated with T40, whereas the total acid content was positively correlated with T5, and that T20 was positively correlated with soil protease and phosphate mono esterase activities, and that T30 was positively correlated with polyphenol oxidase and urease activities, whereas T40 was positively correlated with sucrase activity. In summary, with the increase of planting years, changes in soil microbial community structure and soil enzyme activity have a significant impact on pear quality formation, and the results of the study provide a theoretical basis for scientific management of pear orchards.

Synthetic consortia of four strains promote Schisandra chinensis growth by regulating soil microbial community and improving soil fertility.

Synthetic consortia performed better in promoting Schisandra chinensis growth than individual strains, and this result provides valuable information for the development of synthetic microbial fertilizers. Schisandra chinensis is an herbal medicine that can treat numerous diseases. However, the excessive reliance on chemical fertilizers during the plantation of S. chinensis has severely restricted the development of the S. chinensis planting industry. Plant growth-promoting rhizobacteria (PGPR) can promote the growth of a wide range of crops, and synthetic consortia of them are frequently superior to those of a single strain. In this study, we compared the effects of four PGPR and their synthetic consortia on S. chinensis growth. The pot experiment showed that compared with the control, synthetic consortia significantly increased the plant height, biomass, and total chlorophyll contents of S. chinensis, and their combined effects were better than those of individual strains. In addition, they improved the rhizosphere soil fertility (e.g., TC and TN contents) and enzyme activities (e.g., soil urease activity) and affected the composition and structure of soil microbial community significantly, including promoting the enrichment of beneficial microorganisms (e.g., Actinobacteria and Verrucomicrobiota) and increasing the relative abundance of Proteobacteria, a dominant bacterial phylum. They also enhanced the synergistic effect between the soil microorganisms. The correlation analysis between soil physicochemical properties and microbiome revealed that soil microorganisms participated in regulating soil fertility and promoting S. chinensis growth. This study may provide a theoretical basis for the development of synthetic microbial fertilizers for S. chinensis.

Impacts of AlaAT3 transgenic poplar on rhizosphere soil chemical properties, enzyme activity, bacterial community, and metabolites under two nitrogen conditions

ABSTRACT Poplar stands as one of the primary afforestation trees globally. We successfully generated transgenic poplar trees characterized by enhanced biomass under identical nutrient conditions, through the overexpression of the pivotal nitrogen assimilation gene, pxAlaAT3. An environmental risk assessment was conducted for investigate the potential changes in rhizosphere soil associated with these overexpressing lines (OL). The results show that acid phosphatase activity was significantly altered under ammonium in OL compared to the wild-type control (WT), and a similar difference was observed for protease under nitrate. 16SrDNA sequencing indicated no significant divergence in rhizosphere soil microbial community diversity between WT and OL. Metabolomics analysis revealed that the OL caused minimal alterations in the metabolites of the rhizosphere soil, posing no potential harm to the environment. With these findings in mind, we anticipate that overexpressed plants will not adversely impact the surrounding soil environment.

Effects of Marquandomyces Marquandii SGSF043 on Maize Growth Promotion and Soil Enzyme Activity

In order to further clarify the growth-promoting effect of the non-core Metarhizium sp. Marquandomyces marquandii on plants, M. marquandii SGSF043, which was obtained via pre-screening in the laboratory, was selected as a test strain and the seed soaking method was adopted. The effects of a fermentation broth obtained from this strain on the seed germination, seedling growth, and rhizosphere soil enzyme activity of maize were studied. The results were as follows: In seed germination tests, M. marquandii SGSF043 fermentation liquid had a certain inhibitory effect on corn seed germination, and the germination rate was only 15%. When the fermentation solution was diluted 10 times, the germination rate reached 97%. After the germination test, the growth of maize plumules was promoted in the groups treated with 10-times and 1000-times dilutions. In the field community experiment, based on the comprehensive evaluation of seedling biomass indicators, the solution diluted 100 times had the best growth-promoting effect. The aboveground fresh weight was increased by 127.13% compared with the control group. The results show that M. marquandii SGSF043 has the potential to promote the growth of maize and improve the soil environment, which provides a theoretical basis for the research on and the application of M. marquandii in farmland.

The effect of white grub (Maladera Verticalis) larvae feeding on rhizosphere microbial characterization of aerobic rice (Oryza sativa L.) in Puer City, Yunnan Province, China

BackgroundRhizosphere microorganisms are vital in plants’ growth and development and these beneficial microbes are recruited to the root-zone soil when experiencing various environmental stresses. However, the effect of white grub (Maladera verticalis) larvae feeding on the structure and function of rhizosphere microbial communities of aerobic rice (Oryza sativa L.) is unclear.ResultsIn this study, we compared physicochemical properties, enzyme activities, and microbial communities using 18 samples under healthy and M. verticalis larvae-feeding aerobic rice rhizosphere soils at the Yunnan of China. 16 S rRNA and ITS amplicons were sequenced using Illumina high throughput sequencing. M. verticalis larvae feeding on aerobic rice can influence rhizosphere soil physicochemical properties and enzyme activities, which also change rhizosphere microbial communities. The healthy and M. verticalis larvae-feeding aerobic rice rhizosphere soil microorganisms had distinct genus signatures, such as possible_genus_04 and Knoellia genera in healthy aerobic rice rhizosphere soils and norank_f__SC − I−84 and norank_f__Roseiflexaceae genera in M. verticalis larvae-feeding aerobic rice rhizosphere soils. The pathway of the metabolism of terpenoids and polyketides and carbohydrate metabolism in rhizosphere bacteria were significantly decreased after M. verticalis larvae feeding. Fungal parasite–wood saprotroph and fungal parasites were significantly decreased after M. verticalis larvae feeding, and plant pathogen–wood saprotroph and animal pathogen–undefined saprotroph were increased after larvae feeding. Additionally, the relative abundance of Bradyrhizobium and Talaromyces genera gradually increased with the elevation of the larvae density. Bacterial and fungal communities significantly correlated with soil physicochemical properties and enzyme activities, respectively.ConclusionsBased on the results we provide new insight for understanding the adaptation of aerobic rice to M. verticalis larvae feeding via regulating the rhizosphere environment, which would allow us to facilitate translation to more effective measures.

Effects of Klebsiella michiganensis LDS17 on Codonopsis pilosula growth, rhizosphere soil enzyme activities, and microflora, and genome-wide analysis of plant growth-promoting genes.

We comprehensively evaluated the plant growth-promoting characteristics and heavy metal (HM) resistance ability of the LDS17 strain, as well as the effects of strain LDS17 inoculation on the Codonopsis pilosula seedling growth and the soil qualities in the Codonopsis pilosula rhizosphere. We conducted whole-genome analysis and identified lots of genes and gene clusters contributing to plant-beneficial functions and HM resistance, which is critical for further elucidating the plant growth-promoting mechanism of strain LDS17 and expanding its application in the development of plant growth-promoting agents used in the environment under HM stress.

The effect of modifier and a water-soluble fertilizer on two forages grown in saline-alkaline soil.

Saline-alkali soil significantly impairs crop growth. This research employs the impacts of the modifier and water-soluble fertilizer, as well as their interaction, on the root systems of alfalfa and leymus chinensis in saline-alkali soil. The results exhibit that the hydrochar source modifier effectively enhances the root growth of both forage species. There are certain improvements in the root growth indicators of both crops at a dosage of 20 g/kg. Root enzyme activity and rhizosphere soil enzyme activity are enhanced in alfalfa, showing significant improvements in the first planting compared to the second planting. The application of water-soluble fertilizers also promotes root growth and root dehydrogenase activity. The root dehydrogenase activity of alfalfa and leymus chinensis are enhanced 62.18% and 10.15% in first planting than that of blank, respectively. Additionally, the two-factor variance analysis revealed a correlation between rhizosphere soil enzyme activity and changes in root traits. Higher rhizosphere soil enzyme activity is observed in conjunction with better root growth. The combined application of a modifier and water-soluble fertilizer has demonstrated a significant interaction effect on various aspects of the first planting of alfalfa and leymus chinensis. Moreover, the combined application of the modifier and water-soluble fertilizer has yielded superior results when compared to the individual application of either the modifier or the water-soluble fertilizer alone. This combined approach has proven effective in improving saline-alkali soil conditions and promoting crop growth in such challenging environments.

Biochar amendments improve soil functionalities, microbial community and reduce Pokkah boeng disease of sugarcane

BackgroundBiochar is mainly used to enhance soil fertility, microbial activity, improve plant performance and reduce disease incidence.MethodsA greenhouse experiment was designed to investigate the response of biochar on rhizosphere soil chemical properties, enzyme activity, microbial communities, and sugarcane Pokkah boeng disease (PB). Two sugarcane varieties Zhongzhe 9 (Z9) and ROC22, susceptible/resistant to PB, were cultivated and treated with: no biochar, 15 t ha−1 biochar, and 30 t ha−1 biochar.ResultsThe amendment of 30 t ha−1 of biochar (B2) significantly improve soil pH by 1.50% and 9.61% compared with that of B1 and B0, followed by 0.51% increase by 15 t ha−1 of biochar (B1) compared with that of control (B0). The application of 15 t ha−1 biochar significantly increased available phosphorus (AP) and ammonium nitrogen (NH4+–N) by 209.93 mg kg−1 and 12.1 mg kg−1, while the application of 30 t ha−1 of biochar significantly increased 241.04 mg kg−1 of available potassium (AK) (P < 0.05). Furthermore, biochar application increased the activities of soil acid phosphatase (S-ACP), urease (S-UE), and sucrase (S-SC). Alpha diversity analysis showed that the addition of biochar significantly altered the variety and abundance of rhizosphere microorganisms (P < 0.01) and increased the relative abundance of beneficial microorganisms Rhodanobacteraceae, Stachybotryaceae, Agaricacea, Talaromyces, Nectriaceae, Sistotrema, and Bacillus (P < 0.01). There was a significant decrease in the relative abundance of the soil pathogen Fusarium (P < 0.01).ConclusionThese findings suggested that the application of 15 t ha−1 biochar could bring desirable variations in soil functionalities, modulate soil microbial community by increasing soil health and reduce the disease index of PB.Graphical

Spatial variations of fungal community assembly and soil enzyme activity in rhizosphere of zonal Stipa species in inner Mongolia grassland

Rhizosphere soil fungal and enzyme activities affect the nutrient cycling of terrestrial ecosystems, and rhizosphere fungi are also important participants in the ecological process of vegetation succession, responding to changes in plant communities. Stipa is an excellent forage grass with important ecological and economic value, and has the spatial distribution pattern of floristic geographical substitution. In order to systematically investigate the synergistic response strategies of fungal communities and enzyme activities in the rhizosphere under the vegetation succession. Here we explored the turnover and assembly mechanisms of Stipa rhizosphere fungal communities and the spatial variation of metabolic activity under the succession of seven Stipa communities in northern China grassland under large scale gradients. The results indicated that the composition, abundance and diversity of fungal communities and microbial enzyme activities in rhizosphere soil differed among different Stipa species and were strikingly varied along the Stipa community changes over the geographic gradient. As the geographical distribution of Stipa community changed from east to west in grassland transect, Mortierellomycetes tended to be gradually replaced by Dothideomycetes. The null models showed that the rhizosphere fungal communities were governed primarily by the dispersal limitation of stochastic assembly processes, which showed decreased relative importance from S. grandis to S. gobica. Moreover, the MAT and MAP were the most important factors influencing the changes in the fungal community (richness, β-diversity and composition) and fungal community assembly, while SC and NP also mediated fungal community assembly processes. These findings deepen our understanding of the responses of the microbial functions and fungal community assembly processes in the rhizosphere to vegetation succession.

Responses of the maize rhizosphere soil environment to drought-flood abrupt alternation stress.

Changes in the soil environment in the root zone will affect the growth, development and resistance of plants. The mechanism underlying the effect of drought and flood stress on rhizosphere bacterial diversity, soil metabolites and soil enzyme activity is not clear and needs further study. To analyze the dynamic changes in bacteria, metabolites and enzyme activities in the rhizosphere soil of maize under different drought-flood abrupt alternation (DFAA) stresses, the barrel test method was used to set up the 'sporadic light rain' to flooding (referring to trace rainfall to heavy rain) (DFAA1) group, 'continuous drought' to flooding (DFAA2) group and normal irrigation (CK) group from the jointing to the tassel flowering stage of maize. The results showed that Actinobacteria was the most dominant phylum in the two DFAA groups during the drought period and the rewatering period, and Proteobacteria was the most dominant phylum during the flooding period and the harvest period. The alpha diversity index of rhizosphere bacteria in the DFAA2 group during the flooding period was significantly lower than that in other stages, and the relative abundance of Chloroflexi was higher. The correlation analysis between the differential genera and soil metabolites of the two DFAA groups showed that the relative abundance of Paenibacillus in the DFAA1 group was higher during the drought period, and it was significantly positively correlated with the bioactive lipid metabolites. The differential SJA-15 bacterium was enriched in the DFAA2 group during the flooding period and were strongly correlated with biogenic amine metabolites. The relative abundances of Arthrobacter, Alphaproteobacteria and Brevibacillus in the DFAA2 group were higher compared with DFAA1 group from rewatering to harvest and were significantly positively correlated with hydrocarbon compounds and steroid hormone metabolites. The acid phosphatase activity of the DFAA1 group was significantly higher than that of the DFAA2 group during the flooding period. The study suggests that there is a yield compensation phenomenon in the conversion of 'continuous drought' to flooding compared with 'sporadic light rain', which is related to the improvement in the flooding tolerance of maize by the dominant bacteria Chloroflexi, bacterium SJA-15 and biogenic amine metabolites. These rhizosphere bacteria and soil metabolites may have the potential function of helping plants adapt to the DFAA environment. The study revealed the response of the maize rhizosphere soil environment to DFAA stress and provided new ideas for exploring the potential mechanism of crop yield compensation under DFAA.

Analysis of exogenous lactic acid bacteria on growth and development of different herbaceous peony varieties and rhizosphere soil nutrients

There are replanting problems in the production of herbaceous peony. If ramet seedlings are replanted in the original planting hole, they weaken year-by-year until their death, which reduces the land utilisation rate and increases the production costs. In this study, exogenous lactic acid bacteria (LAB, the main component is Lactobacillus plantarum) were applied to improve the planting soil of herbaceous peony for the first time to alleviate the replanting problems, to reduce the production costs, and to provide a new way to promote the of the herbaceous peony industry. In this study, herbaceous peony main cultivars varieties ‘Dafugui’ ‘Hongxiuqiu’ and ‘Zifengyu’ were selected, and experiments were conducted using exogenous LAB. Morphological, rhizosphere soil, and root physiology indexes were measured by sampling at the end of the high-growth periods of herbaceous peony. The results showed that after LAB treatment, the plant height, flowering rate, other morphological indexes and root vitality of ‘Hongxiuqiu’ were increased, with a better promoting effect than that of ‘Dafugui’ and ‘Zifengyu’. The ‘Dafugui’ rhizosphere soil nutrient content and enzyme activity were improved, followed by ‘Hongxiuqiu’ and ‘Zifengyu’. The rhizosphere soil free salicylic acid content and root abscisic acid content decreased, whereas the soil bacterial abundance, root antioxidant enzyme activity, proline and paeoniflorin content increased in all varieties. This study found that LAB application can improve soil fertility and enzyme activity, promote the growth and development of herbaceous peony, increase the flowering rate and improve the ornamental value. However, the influence of LAB on different herbaceous peony varieties varied. Therefore, it is necessary to further expand the number of varieties, optimise the application concentration and frequency of LAB application, alleviate the replanting problems in herbaceous peony production, improve the utilisation rate of land, promote excellent varieties of herbaceous peony, and provide a new methods and references.Graphical abstract

Effects of polyethylene microplastics and heavy metals on soil-plant microbial dynamics

Polyethylene (PE) microplastics are emerging pollutants that pose a significant threat to the environment and human health. However, little is known about the effects of PEs on soil‒plant interactions, especially in heavy metal (HM)-contaminated soil. In this study, the effects of PE on rhizosphere soil enzyme activities, microbial interactions and nutrient cycling processes were analyzed from ecological network and functional gene perspectives for the first time. The results indicated that PE-MP addition significantly reduced the biomass of Bidens pilosa L. In addition, the partial increase in carbon, nitrogen, and phosphorus enzyme activities suggested that the effects of PE as a carbon source on microbial functions in HM-contaminated soil should not be ignored. The average path length of bacterial network nodes was found to be higher than that of fungal network nodes, demonstrating that the bacterial ecological network in PE-MP and HM cocontaminated environments has good buffering capacity against changes in external environmental conditions. Furthermore, structural equation modeling demonstrated that particle size and dosage affect soil nutrient cycling processes and that cycling processes are acutely aware of changes in any factor, such as soil moisture, soil pH and soil nitrogen nutrients. Hence, PE-MP addition in HM-contaminated soil has the potential to alter soil ecological functions and nutrient cycles.

Tillage Methods Change Nitrogen Distribution and Enzyme Activities in Maize Rhizosphere and Non-Rhizosphere Chernozem in Jilin Province of China

The tillage method in farming systems is essential to develop strategies to increase fertilizer uptake by plant roots and to avoid environmental pollution. The field study aimed to investigate the characteristics of nitrogen and enzyme activities in rhizosphere soil with different tillage methods. Four treatment plots applied with fertilizers were established: continuous rotary tillage (CR), plowing-rotary tillage (PR), continuous no-till (CN) and ploughing-no-till (PN). The total content of nitrogen in chernozem was high during early stages of plant growth, and then it decreased with the maize growth. In the rhizosphere soil, the total N accounted 1314.45, 1265.96, 1120.47, 1120.47, 1204.05 mg·kg−1 of CR, PR, CN, and PN, respectively, which were markedly greater than that of non-rhizosphere soil (1237.52, 1168.40, 984.51, 1106.49 mg·kg−1 of CR, PR, CN, and PN, respectively). At first growth stages, content of NH4+-N and NO3−-N in two soil regions was low, then increased gradually, which followed the order of CR &lt; PR &lt; PN &lt; CN. The rhizosphere soil showed slightly higher concentration of NH4+-N and NO3−-N than non-rhizosphere. The soil enzymes were more active in the rhizosphere soil than that of non-rhizosphere during the whole maize growth stages. Due to minimal damage to the soil environment and optimal soil moisture and temperature, the urease and catalase activities were greatest in the rhizosphere for CN treatment. Therefore, CN was recommended to be used by farmers for the improvement of macronutrient availability and soil enzyme activities in the soil.

Control effect of root exudates from mycorrhizal watermelon seedlings on Fusarium wilt and the bacterial community in continuously cropped soil.

Watermelon (Citrullus lanatus) is susceptible to wilt disease caused by Fusarium oxysporum f. sp niveum (FON). AMF colonization alleviates watermelon wilt and regulates the composition of root exudates, but the effects of mycorrhizal watermelon root exudates on watermelon Fusarium wilt is not well understood. Root exudates of watermelon inoculated with AMF (Funeliformis mosseae or Glomus versiformme) were collected in this study. Then the root exudates of control plants and mycorrhizal plants were used to irrigate watermelon in continuous cropping soil, respectively. Meanwhile, the watermelon growth, antioxidant enzyme activity, rhizosphere soil enzyme activities and bacterial community composition, as well as the control effect on FON were analyzed. The results indicated that mycorrhizal watermelon root exudates promoted the growth of watermelon seedlings and increased soil enzyme activities, actinomyces, and the quantity of bacteria in rhizosphere soil. The proportion of Proteobacteria and Bacteroides was decreased, and the proportion of Actinobacteria, Firmicutes, and Chloroflexi in rhizosphere soil was increased when the seedlings were watered with high concentrations of mycorrhizal root exudates. The dominant bacterial genera in rhizosphere soil were Kaistobacter, Rhodanobacter, Thermomonas, Devosia, and Bacillus. The root exudates of mycorrhizal watermelon could reduce the disease index of Fusarium wilt by 6.7-30%, and five ml/L of watermelon root exudates inoculated with F. mosseae had the strongest inhibitory effect on watermelon Fusarium wilt. Our results suggest mycorrhizal watermelon root exudates changed the composition of bacteria and soil enzyme activities in rhizosphere soil, which increase the resistance of watermelon to Fusarium wilt and promoted the growth of plants in continuous cropping soil.

Effects of a compound Trichoderma agent on Coptis chinensis growth, nutrients, enzyme activity, and microbial community of rhizosphere soil.

Root rot diseases are prevalent in many Coptis chinensis Franch. production areas, perhaps partially due to the overuse of synthetic fertilizers. Synthetic fertilizers can also lead to soil degradation. Trichoderma is widely used in biofertilizers and biopesticides. This study applied a combination of four Trichoderma species (compound Trichoderma agent, CTA) to C. chinensis and evaluated its effects on growth, as well as rhizosphere soil nutrients, enzyme activities, and microbial community structure. The purpose of this study was to estimate the potential of using CTA as a biofertilizer for C. chinensis, and determine if it could, at least partially, replace synthetic fertilizers to control root rot disease and maintain soil fertility. CTA, compound fertilizer and sterile water were applied to C. chinensis plants. After 60 days, the soluble sugar, soluble protein, chlorophyll of leaves, and individual weight of each plant were measured. The rhizosphere soil nutrient content, enzymatic activity, and the microbial community were also determined. The results were analyzed to evaluate the effect of CTA on C. chinensis growth and soil fertility. CTA increased the soluble protein, chlorophyll, and individual weight of C. chinensis plants while compound fertilizer decreased chlorophyll. CTA increased the activities of urease and catalase in rhizosphere soil, whereas the compound fertilizer decreased urease, catalase, and alkaline phosphatase activities. CTA elevated soil pH, while compound fertilizer reduced it. CTA had no significant effects on soil nutrients and organic matter. CTA decreased the fungal number and alpha-diversity of fungi and bacteria, and both the fungal and bacterial communities were significantly different from the other two. CTA increased B/F value, which improved the rhizosphere microbial community. Both CTA and the compound fertilizer significantly altered the soil microbial community. The relative abundance of Ascomycota was higher and Basidiomycota was lower after CTA treatment than after the other two treatments, indicating that the soil treated with CTA was healthier than that of the other two treatments. CTA decreased harmful Ilyonectria mors-panacis and Corynebacterium sp. And increased beneficial Ralstonia picketti. Trichoderma spp. could exist in C. chinensis rhizosphere soil for a long time. The functional prediction results demonstrated that CTA reduced some rhizosphere phytopathogenic fungi. Correlation analysis showed that CTA elevated rhizosphere pH and enzyme activities. In summary, synthetic fertilizers damaged soil fertility, and the overuse of them might be responsible for root rot disease, while CTA could promote C. chinensis growth, improve soil and decrease the incidence and severity of C. chinensis root rot disease. Therefore, as a biofertilizer, CTA can, at least partially, replace synthetic fertilizers in C. chinensis production. Combining it with organic fertilizer will increase the potential of Trichoderma.

Ecoenzymatic Stoichiometry in the Rhizosphere and Bulk Soil of a Larix principis-rupprechtii Plantation in North China

Soil extracellular enzymes play an important role in ecosystem energy conversion and material cycling. Ecoenzymatic stoichiometry can reflect the relationship between the soil’s microbial nutrient cycle and nutrient limitation. However, there have been few studies on the differences in ecoenzymatic stoichiometry and nutrient limitation between rhizosphere soil and bulk soil. This study examined soil nutrients and enzyme activities in rhizosphere soil and bulk soil in a Larix principis-rupprechtii plantation in north China. The results showed that the levels of soil organic carbon (C), total nitrogen (N), and available nutrients in the rhizosphere soil were significantly higher than those in the bulk soil, whereas the total potassium (TK) level was significantly lower. The soil C:N, C:P, and N:P ratios of the rhizosphere soil also exceeded those of the bulk soil. The acid phosphatase (ACP), urease (UE), and β-glucosidase (β-GC) activities in the rhizosphere soil exceeded those in the bulk soil, whereas the activities of N-acetyl-β-D-glucosidase (NAG), aminopeptidase (LAP), and nitrogenase (NA) were lower. The ratios of C, N, and P acquisition activities changed from 1:1.7:1 in the rhizosphere soil to 1:2:1 in the bulk soil. Redundancy analysis showed that the available K and soil water content in the rhizosphere soil were the most important soil factors affecting soil enzyme activities and ecoenzymatic stoichiometry; those in the bulk soil were soil N:P and soil water content. These results suggest that not all soil enzyme activities present rhizosphere effects and that bulk soil is more susceptible to N limitation in Larix principis-rupprechtii plantations. Plant roots play an important role in regulating soil nutrients and soil activities, and future studies should examine the underlying mechanisms in more detail.

Temporal and spatial changes in rhizosphere bacterial diversity of mountain Rhododendron mucronulatum.

To better conserve the ecology of the wild Rhododendron mucronulatum range, we studied the rhizosphere microenvironment of R. mucronulatum in Beijing's Yunmeng Mountain National Forest Park. R. mucronulatum rhizosphere soil physicochemical properties and enzyme activities changed significantly with temporal and elevational gradients. The correlations between soil water content (SWC), electrical conductivity (EC), organic matter content (OM), total nitrogen content (TN), catalase activity (CAT), sucrose-converting enzyme activity (INV), and urease activity (URE) were significant and positive in the flowering and deciduous periods. The alpha diversity of the rhizosphere bacterial community was significantly higher in the flowering period than in the deciduous period, and the effect of elevation was insignificant. The diversity of the R. mucronulatum rhizosphere bacterial community changed significantly with the change in the growing period. A network analysis of the correlations revealed stronger linkages between the rhizosphere bacterial communities in the deciduous period than in the flowering period. Rhizomicrobium was the dominant genus in both periods, but its relative abundance decreased in the deciduous period. Changes in the relative abundance of Rhizomicrobium may be the main factor influencing the changes in the R. mucronulatum rhizosphere bacterial community. Moreover, the R. mucronulatum rhizosphere bacterial community and soil characteristics were significantly correlated. Additionally, the influence of soil physicochemical properties on the rhizosphere bacterial community was larger than that of enzyme activity on the bacterial community. We mainly analyzed the change patterns in the rhizosphere soil properties and rhizosphere bacterial diversity of R. mucronulatum during temporal and spatial variation, laying the foundation for further understanding of the ecology of wild R. mucronulatum.

Biofertilizer based on halotolerant microorganisms promotes the growth of rice plants and alleviates the effects of saline stress.

Long-term soil salinization easily contributes to soil hardness, soil nutrient imbalance, and soil microbial diversity reduction, resulting in low rice yields in the salinized fields, and microbial remediation is one of the important measures to improve salinized soil. To verify the effect of biofertilizer based on halotolerant microorganisms on promoting rice growth and alleviating saline stress, this study discussed the effects of biofertilizer on soil microbial diversity and community structure and analyzed the correlation between the formation of microbial community structure and soil nutrient factors in the salinized field. The result, in comparison with applying inorganic fertilizer (referred to as CK), showed that notably increased soil available nitrogen, available phosphorus, available potassium, and rice paddy yield (p < 0.05) and significantly decreased soil electrical conductivity (p < 0.05) were achieved via biofertilizer (referred to as G2). Additionally, the application of biofertilizer contributes to the increase in soil microbial diversity and reorganization of microbial community structure, and through the analysis of linear discriminant analysis effect size, a notable difference in relative abundance was found in 13 genera, 6 families, and 3 orders between the control group and experimental groups (p < 0.05), and by linear discriminant analysis, Desulfomonas was further identified as the differentiated indicator. The redundancy analysis showed that available phosphorus and cation exchange capacity were the key environmental factors that affected microbial community structure and composition. Through bacterial functional prediction, increased rhizosphere soil bacterial metabolism, enzyme activity, membrane transport, and other potential functions were achieved by applying biofertilizer. Therefore, the application of biofertilizer could significantly alleviate rice growth stress and increase nutrient supply capacity in saline soil. These findings provide theoretical support for soil microbial improvement technology in the salinized field.

Effect of Vermicompost on Fruit Quality, Growth, and Rhizosphere Soil Enzyme Activities of Blue Honeysuckle (Lonicera caerulea L.)

Effect of Vermicompost on Fruit Quality, Growth, and Rhizosphere Soil Enzyme Activities of Blue Honeysuckle (Lonicera caerulea L.)

Effect of Cd and Exogenous NO on the Physiological Response, Rhizosphere Soil Enzyme Activity, and Bacterial Community of WT and Transgenic SmZIP8 Tobacco

Effect of Cd and Exogenous NO on the Physiological Response, Rhizosphere Soil Enzyme Activity, and Bacterial Community of WT and Transgenic SmZIP8 Tobacco