| Sichuan is a major grain production province, and the rice(Oryza sativa L.) production in Chengdu plain plays an important role in the whole province. According to the research information, the city soil in Chengdu was polluted by heavy metals, such as Hg, Cd, As, Cr, Pb, Cu and Zn. In addition, the soil was also polluted badly by the sewage and garbage of towns and villages. However, the studies on effects of heavy metals on rice growth focused on the single element, or established on the nutrient solution as the basis of culture, and the research of eco-physiology of rice were limited to a certain period. Because of the complexity in the agro-ecological environment and the stress resistance of rice, the effects of heavy metals on eco-physiology of rice is especially complex. The effects of heavy metals on eco-physiology of rice at different growth stages have not been reported. Thus, according to rice production conditions in Chengdu plain, taking rice production in the field as the basic and combining the soil pot experiment, the effects of compound of Zn and Cr on roots eco-physiology at different growth stages, yield and quality of rice were investigated. And then, the changes of eco-physiology of rice under Zn and Cr stress would be revealed. Those could be expected to provide a theoretical basis to study the safety of rice production. The main results showed as follows:1. The effects of compound pollution of Zn and Cr on the soil enzyme activities were different at different growth stages of rice. With the heavy metals(Zn and Cr) concentration in soil increased, the soil urease enzyme activity and the soil invertase activity had a falling trend at tillering stage of rice, and increased at booting and filling stages. Differing from the soil urease enzyme activity and the soil invertase activity, the soil catalase activity had a trend to falling at three different growth stages(tillering stage, booting stage and filling stage) with the increase of heavy metals' concentration in soil. 2. The superoxide dismutase(SOD) activity, the peroxidase(POD) activity, and the catalase(CAT) activity of rice roots did not simply increase or reduced with the increase of heavy metals' concentration in the soil. At tillering stage, SOD activity increased after reduced with the increase of Cr concentration, and with Zn concentration increasing, SOD activity had an increased trend. With the concentration of heavy metals increasing, SOD activity was increased after reduced and then dropped at booting stage, and reduced at filling stage. Differing from SOD activity of rice roots, with the concentration of heavy metals increasing, POD activity increased at tillering stage, reduced at booting stage and filling stage, and CAT activity reduced at different growth stages of rice.3. Under the compound pollution of Zn and Cr, the soluble carbohydrate content of rice roots increased at different growth stages with the concentration of heavy metals increasing. The changes of total nitrogen content and soluble protein content of rice roots were not obvious with the increase of Cr concentration, but obvious with the increase of Zn concentration. The nitrogen content was increased at first and then reduced with the increase of Zn concentration, and the turn concentration was 250 mg·kg-1. At the same time, the soluble protein content increased at tillering stage with the increase of Zn concentration. The changes of soluble protein content at booting stage and filling stage, with the increase of Zn concentration, were the same as the changes of total nitrogen content.4. With Zn concentration increasing in the soil, the Zn content of rice roots at different growth stages increased at first and then reduced, and the turn of the concentration was 250 mg·kg-1. With Cr concentrations increasing in the soil, the Cr content of rice roots at different stages increased. The order of Zn content in the entire growth period of rice roots was: tillering stage>filling stage>booting stage, and the order of Cr content was: booting stage>filling stage>tillering stage. The concentrations of Zn and Cr in the soil did not have compound effect to Zn content or Cr content of rice roots.5. With the increase of heavy metals' concentration, the roots dry weight and the shoots dry weight both showed a decreasing trend, but the root/shoot ratio showed a rising trend. The 1000-grain weight and the individual yield of rice had a downward trend. Meanwhile, the concentrations of Zn and Cr in soil had synergy effect of inhibiting to individual yield of rice, and had a highly significant linear relationship. As far as the role of Zn and Cr was concerned, the effect of Zn on the individual yield of rice was stronger than Cr.6. The effects of compound pollution of Zn and Cr on the brown rice rate, the milled rice rate, the head milled rice rate, the grain length, the grain width and the length to width ratio were not obvious with the increase of heavy metals' concentration, but the chalky rice rate increased. With the increase of heavy metals' concentration in the soil, the amylose content of grains decreased, but the protein content of grains showed a tendency to increase. The Zn content of grains increased with the increase of Zn concentration in the soil, but the change of law was not obvious with the increase of Cr concentrations in the soil. However, with the increase of Zn and Cr concentrations in the soil, the Cr content of grains increased. At meanwhile, the concentrations of Zn and Cr had synergy effect of promoting to the Cr content of grains, but did not have compound effect to the Zn content of grains.
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