Effects of Antimony Stress on Growth and Physiology of 10 Genotypes of Catalpa bungei

Increasing levels of antimony (Sb) pollution have been recognized as an emerging environmental problem. Phytoremediation of Sb-contaminated soil is a green, economical, and effective method for restoring polluted soils. Here, we studied differences in Sb tolerance, accumulation, and transport by different genotypes of Catalpa bungei C. A. Mey, with the goal of identifying genotypes that are suitable for remediating Sb-contaminated soil. Different concentrations of Sb were applied to soil, and we analyzed variation in growth, biomass, Sb content in different organs, Sb transport capacity, oxidizing substances, antioxidants, and antioxidant enzyme activities in 10 C. bungei genotypes. Marked differences were found in plant height, ground diameter, and biomass among different genotypes at given Sb concentrations. The Sb concentration in different plant organs also varied between genotypes. The content of Sb in each genotype was proportional to the exposure. At 600 mg Sb/kg soil, the highest concentration of Sb in roots and leaves was found in Genotype 63, and that in stems was found in Genotype 8402. The lowest concentration of Sb in roots, stems, and leaves was found in Genotypes 8402, 2-8, and 20-01, respectively. At 1200 mg Sb/kg soil, Genotype 5-2 had the highest concentration of Sb in roots, and Genotype 1-1 had the highest concentration in stems and leaves. The lowest concentration of Sb in roots was in Genotype 72, and that in stems and leaves was found in Genotype 20-01. At 2000 mg Sb/kg soil, the highest concentration of Sb in roots was found in Genotype 5-8, in stems in Genotype 8402, and in leaves in Genotype 72. The lowest concentration of Sb in roots was observed in Genotype 72 and in stems and leaves in Genotype 2-8. After absorption by C. bungei, Sb mainly accumulated in the roots, and upward transfer ability was poor. The Sb biological concentration factor of roots of all genotypes was >1 at each tested Sb concentration. Our results demonstrate that all 10 C. bungei genotypes could be used for plant stabilization of Sb-contaminated soil. However, the different genotypes of C. bungei had different responses to different Sb concentrations. Based on root Sb accumulation values, at soil Sb concentrations around 600 mg/kg, Genotypes 1, 63, and 5-8 are suited to phytoremediation; Genotypes 5-8, 1, and 5-2 are suited to phytoremediation at soil Sb concentrations around 1200 mg/kg; and Genotypes 5-8, 1, and 8402 are suited to phytoremediation at soil Sb concentrations around 2000 mg/kg. We demonstrate for the first time that Sb-contaminated soil can be improved by using specific plant genotypes tailored to different levels of Sb pollution.