Search

It is important to understand the changes in microbial properties of plant rhizospheres to elucidate the interaction between heavy metals and plant communities. In this study, high throughput sequencing method was used to analyze the effects of heavy metals on rhizosphere microbial community structure of the autochthonous plant Salsola collina in the Jinchuan mining area. The operational taxonomic units (OTU) number and species diversity, and richness of the bacterial community in the rhizosphere of Salsola collina were higher than those of the bulk soil. Proteobacteria, Actinobacteria, and Firmicutes were the major bacterial phyla, and Salsola collina, Kaistobacter, Citrobacter, Acinetobacter and Pseudomonas were the main genera. Principal component analysis (PCA) and unweighted pair group method using arithmetic average (UPGMA) cluster analysis showed that there were significant differences in bacterial community structure between site and between rhizosphere and bulk soil. The moisture content, total nitrogen, phosphorus, magnesium, nickel, chromium, lead, and zinc contents, and pH had significant effects on species richness of the bacterial community, with total phosphorus content having a significant effect on species diversity. The finding of this study could be used as an important guideline for bioremediation of heavy metals in mining area. [ABSTRACT FROM AUTHOR]

Brassinosteroids (BRs) are well recognized for their defensive role in plants under abiotic stress conditions, but 28-homobrassinolide (HBR)-induced tolerance to drought stress has not been reported in soybean (Glycine max L.). The present study investigated the effect of HBR on soybean seedlings under drought stress. Drought stress suppressed growth and photosynthetic systems while increased the proline, glycine betaine (GB), anthocyanin, total phenolic (TP), and total flavonoid (TF) levels in soybean seedlings. HBR restricted reactive oxygen species (ROS) accumulation and decreased the hydrogen peroxide (H2O2) and malondialdehyde (MDA) content by triggering the antioxidant systems. HBR acts as a shield in soybean, protecting the plant against the harmful effects of methylglyoxal (MG) effects by upregulating the enzymes glyoxalase I, (Gly I;15%) and glyoxalase II (Gly II;29.1%) compared to the levels in drought stressed seedlings. Overall, HBR improved drought tolerance in soybean seedlings by modulating osmolytes, the AsA–GSH cycle, and enzyme activities. [ABSTRACT FROM AUTHOR]