Growth and Antimony Bioconcentration Characteristics of Wild Ramie (Boehmeria nivea) under Sb Stress in Different Valence States

[Objectives] To explore the effects of antimony (Sb) in different valence states on the growth and Sb bioconcentration and transfer of wild ramie (Boehmeria nivea). [Methods] A pot experiment was conducted to study the effects of Sb (III) and Sb (V) stress on plant height, biomass, leaf SPAD value, Sb contents in various organs, Sb bioconcentration and transfer factors, and other indexes. [Results] Both kinds of Sb treatments showed a trend of "first increasing and then decreasing" in plant height as Sb concentration increased. The plant heights in Sb (III) treatments with a concentration lower than 1 000 mg/kg and Sb (V) treatments with concentrations lower than 4 000 mg/kg were significantly higher than that of the control check (CK); and the Sb (III) treatment of the high concentration (4 000 mg/kg) resulted in a significant decrease in plant height, while the 8 000 mg/kg Sb (V) treatment still showed an increase in plant height, indicating that the toxicity of Sb (V) to wild ramie was significantly lower than that of Sb (III). The Sb (III) treatments with a concentration lower than 2 000 mg/kg had little effect on the dry weight of the aboveground part, while the treatment with a higher concentration showed a significant decrease; and the dry weights in various concentrations of Sb (V) treatments showed no significant differences, but they were significantly higher than the CK and corresponding concentration of Sb (III) treatment. Both types of Sb stress could promote the increase of SPAD value in wild ramie leaves, and the performance was significantly higher than the CK. As the concentration of Sb treatment increased, the Sb content in both the aboveground and underground parts showed a significant increase; and the comparison of Sb content under corresponding concentrations of the two types of Sb treatments showed that in the aboveground part, Sb (III) was higher than Sb (V), while in the underground part, the opposite was true. The bioconcentration factor (BF) of Sb decreased with the increase of Sb treatment concentration overall, and the value of Sb (V) was smaller than that of Sb (III), but both kinds of Sb stress were significantly smaller than the CK. The transfer factor (TF) of Sb in wild ramie showed a trend of "increasing first and then decreasing" with the concentration of Sb treatment, and various treatments of Sb (III) were higher than the CK, with significant differences, while among various treatments of Sb (V), except treatment B3, the reduction of which was not significant, other Sb (V) treatments showed significant decreases. Comparing the two types of Sb treatments, the BF and TF values of Sb in wild ramie under Sb (III) treatments were higher than those under Sb (V) treatments, and the TF reached a significant level, indicating that the Sb transport ability of wild ramie under Sb (III) treatments was stronger. [Conclusions] This study provides a theoretical basis for the mining of wild ramie Sb restoration genes and the application of large-scale cultivation in ecological restoration.