Abstract

Roots were the major site of Cd accumulation. Cd accumulation in stems was three folds higher than that of leaves, and each internode contained more Cd than that in each pair of leaves. The accumulation of Cd in plants was affected not only by external Cd concentration but also by the plants’ age and organ development stages. The Cd accumulation ability of young leaves was much higher than that of older ones. Kinetic study on the time course of Cd absorption showed that the saturation time for different plant parts was slightly different, ranging from 8 to 14 days. Cd-treated plants could release the absorbed or adsorbed Cd from their plant body, and they also showed conspicuous redistribution of Cd in different plant parts after transferring to regular Hoagland’s solution for 6 days. The redistribution patterns of Cd in plants were also affected by the concentrations of Cd in pretreatment. The lower the pretreatment Cd concentration, the lower the Cd redistribution. The loss of Cd from roots was tremendous. The time course study of Cd release showed that primary extrication of Cd occurred in the first two days, and lessened afterwards. A reduction in the dry weights of whole plants, roots and shoots was observed in Cd-treated plants. Dose response curves for different organs were quite different.

中文摘要

植物吸收鎘離子主要存在於根部。將地上部區分節間與對葉一一對應時檢測各區的鎘分布情形﹐莖部的總鎘累積量約為葉部的三倍﹐同時各節間的鎘累積量也比各對葉多。鎘在植物體內的累積量與處理外界鎘濃度和植物生長發育時期有關﹐幼葉的鎘累積量比老葉高。鎘吸收的動力學研究顯示不同的區位其飽和時間約在 8 至14 天之間。鎘處理的植株移置無鎘的營養液後六天﹐植物體內的鎘有重分布的現象﹐其中以根部的鎘流失嚴重；鎘的流失量與植物的先鎘處理處理有相關；植株內鎘的重分布以移置後兩天內最多﹐而後急速減少。植物各部對鎘毒害的反應曲線不一致﹐有關鎘在莖部的橫向運輸與其意義須待進一部的探討。

Keyword: Accumulation, Cadmium, Growth retardation, Redistribution, Release, Zinnia elegans.