土施和喷施锌肥对镉低积累油菜吸收镉的影响

Effects of soil application and foliar spray of zinc fertilizer on cadmium uptake in a pakchoi cultivar with low cadmium accumulation

采用盆栽试验,研究了土施和喷施不同用量Zn SO4对镉（Cd）低积累油菜生长、Cd吸收及微量元素含量的影响,并通过分析Cd在油菜体内的累积分配规律及土壤Cd有效性变化来揭示其作用机理.结果表明,土施锌（Zn）肥可以显著提高Cd低积累油菜的地上部生物量,最大可使其比对照处理增加71.4%;而喷施Zn肥对Cd低积累油菜地上部生物量没有显著影响.土施和喷施Zn肥都可显著降低Cd低积累油菜的地上部Cd含量,最大降幅为41.4%;在Zn肥用量相差8-10倍的情况下,二者降低油菜地上部Cd含量的效果无显著差异.土施Zn肥可使Cd低积累油菜地上部Cu和Fe含量显著升高,而喷施Zn肥对其没有显著影响,土施和喷施Zn肥都使Cd低积累油菜地上部Mn含量显著降低.土施Zn肥可显著提高土壤有效态Zn含量,但对土壤有效Cd含量没有显著影响;土施和喷施Zn肥可以显著降低油菜根部Cd净吸收量和Cd转运系数,油菜地上部Cd含量与根部Cd净吸收量呈显著的正相关关系（p〈0.01）,而与Cd转运系数无显著的相关性,这表明施用Zn肥降低油菜地上部Cd含量主要是由于抑制根部Cd吸收引起的.总之,喷施Zn肥是调控Cd低积累油菜安全生产的较好措施.

A pot experiment was conducted to study the effects of soil and foliar application of Zn SO4 with different dosages on growth and concentrations of cadmium（ Cd） and other trace elements in a low cadmium accumulating cultivar of Brassica chinensis. The regulating mechanism was elucidated through analyses of Cd uptake and transport in the low cadmium accumulating cultivar and soil available Cd concentrations. Results show that soil zinc（ Zn） application significantly increased shoot biomass of the tested low cadmium accumulating cultivar,with a maximal increase of 71. 4% compared to the control. Meanwhile,foliar Zn treatments had insignificant effect on shoot biomass of the low cadmium accumulating cultivar. Soil and foliar Zn applications significantly decreased shoot Cd concentrations of the low cadmium accumulating cultivar,with a maximal reduction of 41. 4% compared to the control. Although the difference between the Zn dosages of soil application and foliar spray were 8 to 10 folds,the reduction of shoot Cd concentration due to foliar Zn application was not significantly different from that due to soil Zn application. Soil Zn application increased significantly shoots copper and ferrum concentrations of the low cadmium accumulating cultivar,and foliar Zn application had insignificant effect on shoots copper and ferrum concentrations. However,soil and foliar Zn applications decreased significantly shoots manganese concentrations of the low cadmium accumulating cultivar. Soil Zn application increased the soil available Zn concentrations and had insignificant effect on the soil available Cd concentrations. Soil andfoliar Zn applications reduced significantly Cd net uptake via roots and Cd translocation factor of Brassica chinensis. The shoot Cd concentration was positively correlated with Cd net uptake via roots,and not significantly correlated with Cd translocation factor,which indicated that inhibition of Cd uptake by root resulted in decrease in shoot Cd concentration of Brassica chinensis under soil and foliar Zn treatments. In summary,foliar spray of Zn SO4 is suitable for safe production of the low cadmium accumulating cultivar of Brassica chinensis in Cd polluted soils.