Study Of The Sensitivity To Cadmium Of Different Vegetable Seedlings

Excessive accumulation of cadmium (Cd) in agricultural soil can influence the growth of vegetables. Based on the amount of Cd uptake and accumulation, this paper evaluated the sensitivity of vegetable seedlings to Cd. The higher cumulative amount of Cd in the vegetable seedlings, the more sensitivity of vegetables to Cd. And this will help a lot to safe production of agricultural products and adjustment of planting structure .A hydroponic experiment was carried out to study the sensitivity to cadmium (Cd) of different vegetable seedlings. Leafy vegetables(Chinese cabbage and cabbage), fruit vegetables ( tomato, cucumber and cowpea) and root vegetables(lettuce and radish) were chosen as experiment materials. The effects of Cd on vegetable seedlings growth were studied by testing the germination rate, emergent seedling rate, root length,shoot height and biomass(fresh weitht). The absorbing and accumulating characters of different types of vegetables were studied by determined Cd contents in the root and shoot,through which the sensitivity sequence to Cd of vegetable seedlings was inferred. Furthermore,the effects of Cd on root activity,chlorophyll and catalase (CAT)were also studied. The results showed that: Vegetable seedling root length and biomass significantly decreased (P<0.05) with the increasing concentration of Cd. And 5.0mg·L-1 Cd significantly decreased emergent seedling rate of cowpea (P<0.05),which indicated that Cd (0.1mg·L-1) inhibited the growth of vegetables,especially the root.The impact on vegetables in increasing order was cowpea> Chinese cabbage> cucumber> cabbage >tomato>radish>lettuce.However,Cd contents in all vegetable seeding root and shoot significantly increased (P<0.05)with the increasing of Cd concentration,which showed that Cd was much easy to be absorbed and accumulated by vegetable seedlings and it was easier in root than in shoot.But the effects varied significantly with different concentrations of Cd and different types of vegetables .Took Cd concentrations 1.0mg·L-1 as an example, the uptake capacity of root for Cd was cabbage >Chinese cabbage > tomato >radish>cucumber>lettuce >cowpea.And the uptake capacity of shoot for Cd was radish>cabbage>Chinese cabbage>tomato>cucumber>lettuce>cowpea.Radish had the best root activity among all vegetables tested and it increased with the increasing concentration of Cd.The root activity of cabbage and tomato decreased when Cd concentration was more than 0.01mg·L-1. The chlorophyll of lettuce and radish increased with the increasing concentration of Cd,but that of cowpea and Chinese cabbage decreased at Cd concentration more than 1.0mg·L-1.The CAT contents of Chinese cabbage, cabbage and tomato increased with the increasing concentration of Cd.But it increased only when Cd concentration was more than 1.0mg·L-1 for cowpea and lettuce.And the CAT contents of cucumber significantly decreased at Cd10.0mg·L-1.