Cd对叶菜生长和产量的影响及其在叶菜体内的积累

选取广东省菜薹、芥菜、叶用莴苣、蕹菜和苋菜等几种主要的叶类蔬菜,在水培条件下进行Cd在不同浓度下对叶菜生长、产量及其在叶菜体内积累的影响研究。结果表明,培养液中Cd的添加浓度为0.01、0.1、0.5mg·kg-1时,其对叶菜生长、产量及其在叶菜体内积累都有明显的影响,且因Cd浓度和叶菜种类的不同而有很大差异。随着培养液中Cd浓度的增大,各种类叶菜的受害症状加重,减产幅度增大,可食用部位Cd含量和Cd累积量都极显著增加,且它们分别与培养液中的Cd浓度呈显著或极显著的正相关(前者r=0.987￣0.999,P<0.01,N=4;后者r=0.967￣0.999,P<0.05,N=4)。各叶菜产量受影响程度的顺序为:叶用莴苣>苋菜、芥菜>菜薹>蕹菜。可食用部位富集Cd量的顺序为:苋菜>菜薹>叶用莴苣>芥菜、蕹菜。

Effects of Cadmium on the Growths and Yields of Leaf Vegetables and Accumulation of Cadmium

In many places in China, sewage effluent is widely used for agricultural irrigation due to water deficiency. Many literatures reported that sewage irrigation largely brought about heavy metal pollution of farmland and deterioration of agricultural eco-environment. A great deal of sewage containing cadmium (Cd), including untreated water and treated water not up to the standard, is directly used to irrigate crops, thus leading to Cd contamination of soil and posing the risk of phytotoxicity. However, the direct effect of Cd in wastewater on leaf vegetables under the condition of irrigation with sewage effluent was little known. Five main leaf vegetable cultivars of Guangdong Province were chosen and grown in culture solution with several levels of Cd to evaluate the effects of Cd on the growths and yields of leaf vegetables and accumulation of Cd. The results showed that the effects varied significantly with different levels of Cd. The yields of leaf vegetables decreased and the Cd contents in edible parts of plants increased significantly with increased concentration levels of Cd. The positive correlation coefficients (r) of Cd concentration in culture solution with Cd accumulation amount per plant and Cd content in different leaf vegetables were significant or very significant (r = 0.987 ~ 0.999, P < 0.01, N=4; r = 0.967 ~ 0.999, P < 0.05, N = 4), respectively. The yield of leaf lettuce decreased most, followed by edible amaranth, leaf mustard, flowering Chinese cabbage, and water spinach (swamp cabbage). The amounts of residual Cd in edible parts of leaf vegetables were found to follow the sequence: edible amaranth > flowering Chinese cabbage > leaf lettuce > leaf mustard and water spinach (swamp cabbage). The content of Cd in different leaf vegetables depended on its biomass in some cases. Carefully selecting plants that have more biomass and lower Cd-accumulating ability for use on Cd-contaminated soils should be a possible practical method to control the accumulation of Cd.