Abstract: The study with pot experiment and simulation test showed that after planted hyperaccumulator Sedum alfredii Hance on mining soil, the water soluble Zn and NH₄OAc extractable Zn in rhizosphere were decreased obviously, while the available Zn in nonrhizosphere had less change. The pH value of rhizosphere soil was decreased by 0.3 units, whereas the organic matter and dissolved organic matter (DOM) contents were increased by 13.6% and 20.9%, respectively, compared with the soil without S. alfredii. The effects of DOM from S. alfredii rhizosphere on Zn absorption and desorption varied with the kinds of test soils. After the addition of rhizosphere DOM, the maximal absorption capacity (X_m) of mining soil, quaternary red clay soil, and fluaviomarine yellow loamy soil was reduced by 17.8%, 21.9% and 27.7%, respectively, whereas the addition of nonrhizosphere DOM had no effects on Zn absorption. The Zn desorption in the three soils, especially in fluavio-marine yellow loamy soil, was promoted by the addition of rhizosphere DOM. It was indicated that the DOM from S. alfredii rhizosphere could reduce the maximal absorption capacity and accelerate the desorption of adsorbed Zn, and thus, increase the Zn mobility and bioavailability.

Key words: drought stress, exogenous plant hormones, endogenous hormone, sweet potato, yield