Synergistic effect of antioxidant systems enhance cadmium phytoextraction and translocation in Amaranthus hypochondriacus under rutin application

Abstract

Amaranthus hypochondriacus (A. hypochondriacus) is a good cadmium (Cd) accumulating plant with characterized by fast growth, large biomass and strong adaptability. However, Cd stress leads to overaccumulation of reactive oxygen species (ROS), which affects its growth and limits Cd extraction performance. Rutin is a natural flavonoid compound with a strong ability to scavenge free radicals and resist environmental stress. So far, the effect of rutin on plant tolerance under Cd stress is not clear. In present study, we explored the effect of exogenous rutin on plant growth and Cd uptake in A. hypochondriacus, and further analyzed the Cd-resistance mechanisms based on antioxidant systems. The results showed that rutin had a positive effect on plant biomass and Cd uptake. Under 10, 50 and 100 mg/kg Cd treatments, 5 mg/mL rutin stimulation increased the total amount of Cd in A. hypochondriacus by 2.97 times, 2.9 times and 2.67 times, respectively. Meanwhile, rutin enhanced the plant tolerance, and showed different Cd resistance mechanisms under different Cd concentrations. At lower concentrations of Cd (10 mg/kg), the flavonoids synthesis was activated by rutin in response to oxidative stress. At higher concentrations of soil Cd (50 and 100 mg/kg), rutin comprehensively increased the levels of flavonoids, glutathione (GSH) and antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT)), activated more stress resistance pathways to improve the Cd tolerance. In addition, the metabolic activity of flavonoids in leaves was highly correlated with the Cd concentration and had a significant effect on Cd tolerance. These results indicated that rutin could alleviate Cd toxicity by inducing flavonoid metabolism and enhancing the antioxidant system, effectively improving the repair efficiency of A. hypochondriacus.