| As a result of human activities, such as mining, water treatment, waste water irrigation and sludge application etc., more and more heavy metals like Cd, Zn etc. enter into soil environment. Cadmium, as a dangerous heavy metal, decomposes slowly in ecological environment, is easily absorbed by crops and accumulates in soil and crops, poisons human beings and animals through food chains. Zinc is not only an essential element for plant growth and human health, but also is a source of environmental pollution as a heavy metal. Cd and Zn always co-exist in the nature environment. The effects of Cd and Zn combined pollution have much difference from the effects caused by single Cd or Zn due to the interaction between Cd and Zn. Ryegrass (Lolium perenne L.) is a monocotyledon plant of grass family and planted in the Yangtze valley extensively. Some reasearches suggested that ryegrass can accumulate high Cd, but little is known about resistance of ryegrass on Cd, Zn and rhizosphere character of Cd, Zn stress. A root-bag experiment was conducted to study the influence of zinc, cadmium stress on the growth of ryegrass, activities of peroxidase (POD) and superoxide dismutase (SOD), concentration of glutathione (GSH) and proline, root tolerance index (RTI), Zinc, Cadmium uptake and accumulation, root exudates under Zinc, Cadmium stressl. The results showed that:1. The growth of ryegrass was inhibited by cadmium and zinc combined pollution. The order of inhibition was Cd and Zn>Cd>Zn.The stem length, shoot and root dry weights decreased by 50.6%, 42.1%, 43.7% under cadmium and zinc combined pollution, while them decreased by 2.4%, 5.0%, 3.2% under zinc pollution.2. The activity of POD and SOD, proline concentration were significantly increased by zinc, cadmium single and combined pollution, the effect of increase was in an order of Cd and Zn>Cd>Zn. Root system vigor and concentration of chlorophyll significantly reduced by zinc, cadmium single and combined pollution, the effect of decrease was in an order of Cd and Zn>Cd>Zn.3. The concentrations of N, P and K in plant of ryegrass were significantly decreased by zinc pollution, cadmium pollution and the combined pollution of cadmium and zinc. The combined pollution of cadmium and zinc had largest inhibitation. The Cd concentration of ryegrass in... |
