Foliar application of anthocyanin extract regulates cadmium accumulation and distribution in rice (Oryza sativa L.) at tillering and booting stages

Abstract

Anthocyanin extract has been applied in agricultural production and enhanced tolerance of plants to adverse effects of Cd stress. Rice was subjected to different concentration of Cd and blueberry anthocyanin, and the effects on rice growth, antioxidative defense, Cd distribution in rice tissues, FTIR and TEM characterization of rice leaves were examined to explain the Cd reductions in rice grains and the protective mechanisms by blueberry anthocyanin. Foliar spray of blueberry anthocyanin at tillering and booting stages was effective for reducing Cd concentration in rice grains and increasing the rice yield, anthocyanin and Cd concentration of rice leaves under 1.0 and 10.0 mg/kg Cd stress. The Cd concentration in rice grains was less than the China national standard of Cd for rice grains (0.2 mg/kg) after surface spraying by 5.0–12.5 g/L blueberry anthocyanin under 1.0 mg/kg Cd stress, while 7.5 g/L spray concentration was the best choice. Blueberry anthocyanin spraying prevents Cd from being transferred from leaves to rice grains mainly by fixation of Cd in soluble and organelle fractions at the tillering and booting stages, and reduces H2O2 and MDA accumulation in rice leaves to decrease Cd toxicity. Combined with FTIR and TEM characterization of rice leaves, the results indicated that surface spraying of 7.5 g/L blueberry anthocyanin under 1.0 mg/kg Cd stress could effectively relieve Cd oxidative damage, and form chelates with Cd ions to immobilize Cd in rice leaves. Hence, blueberry anthocyanin could be used as a foliar resistance control agent to reduce Cd accumulation in rice grains through chelate compound synthesis and decrease Cd toxicity by preventing membrane lipid peroxidation and H2O2 accumulation.