镉与豆磺隆复合胁迫下小麦根-土界面镉形态的变化

通过根际箱试验，研究了Cd与豆磺隆复合胁迫下小麦根 土界面Cd形态变化的空间和时间效应.在空间上将根－土界面(0～5 mm)细化到1 mm，在时间上将取样时间分为14、21、28、35和42 d，并将小麦体吸收的Cd与根 土界面各形态Cd作相关分析，从而得出影响小麦体生长的Cd形态.结果表明，在小麦不同的生长时间内，可交换态Cd表现出的空间效应明显不同.在小麦生长的第14天，根－土界面可交换态Cd大体上由根中心区(6.186 mg·kg^-1)向根外区(6.482 mg·kg^-1)逐渐增加；从小麦生长第21天到42天，根-土界面可交换态Cd呈现出由根中心区到某一层升高，之后又由该层到土体下降的趋势.根-土界面各层碳酸盐和铁锰结合态Cd向可交换态Cd转化的趋势由根中心区向根外区逐渐减弱，而向残留态Cd转化的趋势逐渐加强，有机结合态Cd浓度变化在近根区较大.碳酸盐结合态Cd、铁锰结合态Cd、有机结合态Cd浓度随时间而逐渐下降；残留态Cd浓度则表现出明显的上升趋势.相关分析表明，近根层的可交换态Cd和有机结合态Cd是小麦能直接利用的两种Cd形态.豆磺隆对可交换态Cd含量变化以及碳酸盐和铁锰结合态Cd的转化有明显影响.

Changes of Cd forms on wheat root-soil interface under stress of combined Cd and chlorimuron-ethyl.

With rhizobox experiment, this paper studied the changes of Cd forms on wheat root-soil interface under the stress of combined cadmium (Cd) and chlorimuron-ethyl. The root-soil interface (0-5 mm) was separated into 6 parts every other 1 mm, and the sampling time was 14, 21, 28, 35 and 42 days after treatment. The correlativity between Cd forms and Cd absorption by wheat was made to assess the availability of each Cd form. The results showed that exchangeable Cd showed different spatial effect during various growth periods. The trend of carbonate-bound Cd and Fe-Mn oxide-bound Cd transforming to exchangeable Cd was weaken, but the trend of the two Cd forms transforming to residual Cd was strengthened from root-center zone to non-rhizosphere. The concentration of organic-bound Cd varied significantly in neighboring root zone. During the whole experiment period, the concentrations of carbonate-bound Cd, Fe-Mn oxide-bound Cd and organic-bound Cd decreased, while that of residual Cd increased. Correlation analysis suggested that exchangeable Cd and organic-bound Cd nearby the root were the main Cd forms that could be absorbed by wheat. It could be concluded that the transformation of carbonate-bound Cd and Fe-Mn oxide-bound Cd and the concentration of exchangeable Cd were affected by chlorimuron-ethyl significantly.