Effects of Exogenous Abscisic Acid on Cadmium Accumulation in Two Ecotypes of Hyperaccumulator Bidens Pilosa

摘要

Abscisic acid (ABA) is an important plant hormone that enhances plants' tolerance to heavy metal stress. In this study, we applied ABA to two ecotypes (mining and farmland) of the cadmium (Cd) hyperaccumulator Bidens pilosa which grown under Cd-contaminated conditions. The effects of ABA on Cd accumulation in the two ecotypes of B. pilosa were evaluated. Exogenous ABA decreased the biomass and plant height of the two ecotypes of B. pilosa compared with their respective controls. The plants treated with 10 μmol L~(-1) ABA showed the minimum biomass and plant height. Exogenous ABA also decreased the chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents of two ecotypes ofB. pilosa compared with their controls, but increased the chlorophyll a/b ratio. For both two ecotypes of B. pilosa, application of ABA increased the Cd contents in the roots, stems, leaves, and shoots, compared with the controls, but only 40 μmol L~(-1) ABA increased the amount of Cd extracted by the two ecotypes (an increase of 30.26% in shoots of the farmland ecotype and 16.36% in shoots of the mining ecotype) of B. pilosa. These results show that ABA inhibits the growth of two ecotypes of B. pilosa, and the high concentration (40 nmol L~(-1)) of ABA can enhance Cd extraction from Cd-contaminated soil.