Low antimony concentration promoted growth, glucosinolates metabolism and biological activity of two Brassica species

Abstract

Antimony (Sb), a common rare heavy metal, is found naturally in soils at low concentrations. This study aimed to understand the effect of low Sb concentrations on plant growth and metabolism. To this end, canola (Brassica napus L. var. napus) and turnip roots (Brassica rapa L. var. rapa) were treated with Sb at low concentrations (8 mg/kg soil) to explore the effect Sb on their growth, photosynthesis, glucosinolate metabolism, redox status, and biological activity. Our results revealed that Sb significantly promoted growth by 1.34 and 1.14-fold in B. napus and B. rapa compared to control conditions. This increase can be explained by the observed increase in photosynthesis as indicated by increased chlorophyll content. Low Sb concentration significantly improved total glucosinolate accumulation, through improved amino acid production, namely alanine, leucine, isoleucine, valine, methionine, phenylalanine, tyrosine, and tryptophan. There were increases in myrosinase activity, which stimulated glucosinolate hydrolysis to yield health-promoting sulforaphane. In contrast, a low level of ineffective sulforaphane nitrile was detected. Sb also improved antioxidant metabolites (tocopherol) and enzymes (CAT, POX, SOD) in both species but to a bigger extent in B. napus by 1.98, 2.77, 2.46, and 2.05 fold, respectively. In conclusion, although high Sb concentrations are toxic, low Sb concentrations can promote biomass and bioactive compound accumulation in Brassica spp.