铅在小麦和玉米中活性形态和分布的比较研究

以小麦和玉米的根和叶为对象，采用分级离心和逐级提取方法研究了铅的形态和迁移积累状况。结果表明，铅在小麦根中的含量高于玉米根，玉米和小麦吸收铅主要集中于根部，而且主要分布在根部的细胞壁与残渣态（F1），其所占比例为70％～92％；从重金属形态分级提取来看，主要集中在活性较低的醋酸态、盐酸态和氯化钠态。

Comparisons on Active Chemical Form and Distribution of Lead in Wheat and Corn

Based on analysis of lead distribution in parts of wheat and corn soaked by lead solution, the content of lead in cell wall and residual state is very high. The ratios of lead in foliage and rootstalk are 1:5.7 and 1:10.05 in corn and wheat, indicating the larger amount of heavy metal element and higher migrating ability in young plants than that in old plants. The migration ability of lead in different plants depends on their physiological structure. The lead distribution in rootstalk of corn and wheat is 93% and 92.1%, respectively. The distribution in foliage is 71% and 82.8%, respectively. The distribution of lead in cell wall and residual state (F1) is over 70% and the proportion of the rest is very small, with the order the cell core state (F2)>the mitochondrion state (F3) > the nucleoprotein state (F4). The order of proportion of corn foliage is the mitochondrion state (F3)>the nucleoprotein state (F4) > the cell core state (F2). From the distribution of cell component in rootstalk and foliage, the lead are absorbed and deposited by cell wall. Lead is prevented to be entered protoplasm in cell and keep away from toxicity, which explains why the proportion of the cell wall and residual state (F1) in roots is more than that in leaves both wheat and corn. Sequential extraction shows the chemical lead extracted by Acetic (FHAC), HCl (FHCl) and NaCl (FNaCl) is gradually reduced in the rootstalk of wheat and corn, and the total of three is over 80%, especially the proportion of lead extracted by HAC over 45% in rootstalk, and that of extracted by HCl over 50% in foliage. The content of FHAC in the foliage of corn is higher than that in wheat, and the content of FHCl in wheat foliage is higher than that in corn. The lead extracted by water (FW) and alcohol (FE) provided with less active chemical form in foliage than that in rootstalk. The young foliage of corn is more easily poisoned than old foliage of wheat.