镉污染土壤施硒对植物生长及根际镉化学行为的影响

采用根箱培养的方式,研究了在不同镉污染水平(0.5 mg·kg-1、5 mg·kg-1土壤)的酸性黄棕壤中施用外源硒对小白菜生长、光合特性及根际土壤中镉的化学行为影响.结果表明:镉污染土壤中施硒可显著增加小白菜的生物量,增强小白菜叶片的光合速率和蒸腾速率;镉污染严重时,施硒还可提高小白菜的气孔导度;施用适量硒(0.25 mg·kg-1)可显著降低小白菜地上部镉含量,其中镉污染浓度较低(0.5 mg·kg-1)时,该效果达显著水平.在镉污染程度低(0.5 mg·kg-1)的土壤施用适量硒(0.25 mg·kg-1),可显著降低土壤交换态镉含量,其中,根际和非根际土壤交换态Cd含量分别降低了22.20%和43.79%.外源Se有效地降低了土壤Cd的生物有效性,这种作用在Se的施用浓度较低时表现更加明显;当Cd污染浓度较高时,土壤Cd形态分布相对稳定,外源Se对根际和非根际土壤Cd形态分布的影响不显著.研究结果为深入揭示Se对菜地Cd污染的调控机理提供理论参考.

Effect of selenium application to the cadmium-polluted rhizosphere on plant growth and chemical behavior of cadmium

To investigate the role of Selenium (Se) on the growth of cabbage and the chemical behavior of cadmium (Cd) in rhizosphere soil under the stress of Cd, root box training experiments were performed in this study. Acidic yellow-brown soil was treated with low (0.5 mg·kg^-1) or high (5 mg·kg^-1) concentrations of Cd. The growth of Chinese cabbage, photosynthesis characteristics and the chemical form and distribution of Cd in rhizosphere soil after cultivation were observed. Results showed that application of Se significantly increased the growth, leaf photosynthetic rate and transpiration rate in Chinese cabbage. Se application to the soil contaminated with high concentration of Cd would significantly improve the stomatal conductance. The content of Cd in shoot decreased with Se concentration of 0.25 mg·kg^-1, especially when soil was polluted with 0.5 mg·kg^-1 Cd. For lower Cd pollution, application of 0.25 mg·kg^-1 Se lowered the exchange form of Cd(ex-Cd) content in rhizosphere and non-rhizosphere soil by 22.20% and 43.7%, respectively. Se application, especially with lower concentration, effectively declined the bioavailability of Cd in soil. Meanwhile, for high concentration of Cd contamination, the distribution of different forms of Cd reached their balance while Se changed little in rhizosphere and non-rhizosphere. The results provided guidance on the regulation mechanism of Se to the contamination of Cd in agricultural environment.