The content of heavy metals in the soil in Guizhou Province, which is a high-risk area for heavy metal exposure, is significantly higher than that in other areas in China. Therefore, the objective of this study was to evaluate the ability of CaCO3 and clay to accumulate heavy metals in topsoil sample collected from Lixisol using the method of indoor simulation. The results showed that the contents of Cu, Zn, Cd, Cr, Pb, Hg and As in the soil sample were 10.8 mg/kg, 125 mg/kg, 0.489 mg/kg, 23.5 mg/kg, 22.7 mg/kg, 58.3 mg/kg and 45.4 mg/kg, respectively. The soil pH values increased with the CaCO3 concentration in the soil, and the fluctuation of the soil pH values was weak after the CaCO3 concentrations reached 100 g/kg. The adsorption capacity of lime soil increased by approximately 10 mg/kg on average, and the desorption capacity decreased by approximately 300 mg/kg on average. The desorption of all heavy metals in this study did not change with increasing clay content. Pseudo-second-order kinetics were more suitable for describing the adsorption kinetics of heavy metals on the soil material, as evidenced by the higher R2 value. The Freundlich model can better describe the adsorption process of As on lime soil. The process of As, Cr, Cd and Hg adsorption on the soil sample was spontaneous and entropy-driven. Additionally, the process of Cu and Pb adsorption on the soil materials was spontaneous and enthalpy-driven. Generally, the adsorption and desorption of heavy metals in polluted soil increased and decreased, respectively, with increasing CaCO3 content. The effect of calcium carbonate on the accumulation of heavy metals in soil was greater than that of clay. In summary, CaCO3 and pH values in soil can be appropriately added in several areas polluted by heavy metals to enhance the crop yield and reduce the adsorption of heavy metals in soils.
Plants have evolved a number of defense and adaptation responses to protect themselves against challenging environmental stresses. Genes containing a heavy metal associated (HMA) domain are required for the spatiotemporal transportation of metal ions that bind with various enzymes and co-factors within the cell. To uncover the underlying mechanisms mediated by StHMA genes, we identified 36 gene members in the StHMA family and divided them into six subfamilies by phylogenetic analysis. The StHMAs had high collinearity and were segmentally duplicated. Structurally, most StHMAs had one HMA domain, StHIPPc and StRNA1 subfamilies had two, and 13 StHMAs may be genetically variable. The StHMA gene structures and motifs varied considerably among the various classifications, this suggests the StHMA family is diverse in genetic functions. The promoter analysis showed that the StHMAs had six main cis-acting elements with abiotic stress. An expression pattern analysis revealed that the StHMAs were expressed tissue specifically, and a variety of abiotic stresses may induce the expression of StHMA family genes. The HMA transporter family may be regulated and expressed by a series of complex signal networks under abiotic stress. The results of this study may help to establish a theoretical foundation for further research investigating the functions of HMA genes in S. tuberosum to elucidate their regulatory role in the mechanism governing the response of plants to abiotic stress.
Plants can alter microbial communities through root exudates, and change the characteristics of the soil. However, the relationship between soil microbial communities and environmental factors is not well understood. Here, we studied bacterial and fungal communities and their relationships with environmental factors. We integrated data of environmental factors, microbial composition, diversity, functional prediction, and co-occurrence network from uncultivated, maize, cabbage, and cocozelle soils in a karst area of Southwest China. Soil bacterial and fungal community composition differed with plant types. Maize soil had more taxa and greater alpha diversity of bacteria and fungi than other soils. In maize soil, the relative abundance of Actinobacteria and Ascomycota was significantly lower than that in uncultivated soil, while its contents of soil organic matter (OM), alkali-hydrolyzable nitrogen, and total nitrogen (TN) showed the opposite trend. These indicators were not significantly different between cabbage and cocozelle soils. The results of the Mantel test and the RDA analysis indicated that TN and OM were important drivers of bacterial and fungal communities. Functional prediction and network analysis showed that maize soil had a high nitrogen fixation capacity and a complex and stable network. To summarize, maize soil not had a low relative abundance of Ascomycota and high content of TN and OM, nitrogen fixation ability, and a rich microbial community. Therefore, cultivating maize is suitable for improving soil microbial community. These findings might help in formulating a reasonable cultivation management program to prevent land degradation in the karst areas.
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