Plants have evolved the capability to respond to interspecific neighbors by changing morphological performance and reshaping belowground microbiota. However, whether neighboring plants influence the microbial colonization of the host’s root and further affect host performance is less understood. In this study, using 16S rRNA high-throughput sequencing of peanut (Arachis hypogaea L.) roots from over 5 years of mono- and intercropping field systems, we found that neighbor maize can alter the peanut root microbial composition and re-shape microbial community assembly. Interspecific maize coexistence increased the colonization of genera Bradyrhizobium and Streptomyces in intercropped peanut roots. Through endophytic bacterial isolation and isolate back inoculation experiments, we demonstrated that the functional potentials of available nutrient accumulation and phytohormones production from Bradyrhizobium and Streptomyces endowed them with the ability to act as keystones in the microbial network to benefit peanut growth and production with neighbor competition. Our results support the idea that plants establish a plant-endophytic microbial holobiont through root selective filtration to enhance host competitive dominance, and provide a promising direction to develop modern diversified planting for harnessing crop microbiomes for the promotion of crop growth and productivity in sustainable agriculture.
Aims: A cadmium (Cd)-tolerant Bacillus megaterium strain A14 was used to investigate the effects and mechanisms of bacterial inoculation on peanut growth, Cd accumulation in grains and Cd fixation in Cd-contaminated soil. Methods and Results: Spectroscopic analysis showed that A14 has many functional groups (-OH, -NH2 and -COO et al.) distributed on its surface. The pot experiment indicated that compared to the Cd-contaminated soil alone treatment, inoculation with strain A14 increased shoot and root biomass by 59Á93 and 58Á31% respectively. The accumulation of Cd in grains decreased by 48Á14%, while the proportion of exchangeable Cd in soil decreased from 40 to 26% in A14 inoculated soil. Conclusions: Inoculation with B. megaterium A14 improved peanut plant growth via (i) adsorbing Cd 2+ through functional groups on cell surface, (ii) immobilization of Cd in soil through extracellular secretions, (iii) scavenging the reactive oxygen species through production of antioxidant enzymes, and (iv) by reducing the phytoavailable Cd through regulation of Cd transport gene expression. Significance and Impact of the Study: This study provided a new sight on microbial approach for the chemical composition transformation of soil Cd and associated food safety production, which pointed out an efficient way to improve peanut cultivation.
Taking an office building in Jinan as an example, the simulation model of solar inter-seasonal soil heat storage was established by TRNSYS software, and the variation law of ground temperature in the heat storage period was analyzed. From the perspective of ground temperature change, the influence of the spacing, length, number of drilling wells and area of solar collector on the heat storage effect was analyzed. The results showed that the soil temperature increased rapidly at the beginning of heat storage, and then the temperature rise rate gradually slowed down. The ground heat exchanger spacing, length, number of drilling and collector area will have a great influence on the solar energy seasonal heat storage effect. Therefore, in practical engineering applications, for the solar inter-seasonal soil heat storage system, the parameters of buried pipes, collectors and other components are recommended to be reasonably determined by simulation to obtain the optimal heat storage effect.
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