Studies On The Injurous Mechanisms And Tolerance Of The Heavy Metal Stress In Rice

In this paper, the injuring mechanism and tolerance of different rice specie(Yangdao No.6, Wuyugen, Xieyou 818)were investigated by the different heavy metal concentration Cu2+, Cd2+, Hg2+. The results showed as follows:1. Effect of heavy metal stress on the growth and development (conformation guidelines) of riceUnder the condition of heavy metal stress, the spring ability and seeds power of rice, the height and fresh weight of rice seedling took on the decreasing tendency. The root growth of Yangdao No.6 was promoted by heavy metal stress of Cu2+ and Hg2+. However, the Cd2+ and Hg2+ stress in high concentration and Cu2+ stress inhibited the growth of rice root. When the rice grown as soil cultivation, the final height of rice was increased by Cu2+ stress or low concentration of Cd2+ and Hg2+ stress, but was inhibited by Cd2+ and Hg2+ stress in high concentration. The available development of rice was stimulated by Cu2+ stress in low concentration, but inhibited by Hg2+ stress and high concentration of Cu2+ and Cd2+ stress. The number of ear and ripe rate and the weight of thousand ear of rice were increased with the Cu2+ stress in a given concentration range. The Cd2+ and Hg2+ stress in low concentration range increased the number of ear and the ripe rate, whereas decreased the weight of thousand ear.2. Effect of heavy metal stress on the nitrogen metabolism in riceAs the rice seeds germinating, heavy metal stress of Cu2+, Cd2+, Hg2+ in low concentration encouraged the synthesis of protein, especially in the stimulation of protein synthesis in Wuyugen. With the concentration of Cu2+, Cd2+, Hg2+ increased, the synthesis of protein were inhibited by heavy metal stress. In rice seedling, the heavy metal stress in low concentration could promote the content of protein in leaf and root of rice, and difference was presented among three heavy metal. Under the condition of Cu2" stress, the protein of leaf and ear decreased. Xieyou 818 was sensitive to the heavy metal stress, and the protein content of leaf and ear of Xieyou 818 took on the negative relation with the concentration of heavy metal. As the rice furling, Yangdao No. 6 was more sensitive to the heavy metal stress than Wuyugen in the phase of protein synthesis, and sensitivity difference of the same rice in different organism was also showed. The Cu2+, Cd2+, Hg2+ stress with low concentration provoked the synthesis of protein in leaf and ear of Wuyugen increased obviously, however, it made the synthesis of protein in leaf and ear of Yangdao No.6 decreased evidently.3. Effect of heavy metal stress on the carbon metabolism in riceThe heavy metal stress of Cu2+, Cd2+, Hg2+ obviously reduced the leaf photosynthesis of rice. The chlorophyll content of rice and photosynthetic rate took on negative relation with the concentration of heavy metal. The low concentration of heavy metal stimulated the root respiration of rice seedling and promoted the respiratory rate. However, the heavy metal stress in high concentration inhibited the root respiration of rice seedling. With the concentration of heavy metal increased, the root respiration decreased continuously.With the concentration of Cu2+, Cd2+, Hg2+ stress increasing, the a-amylase activity in rice germinating increased when the concentration of Cu2+, Cd2+, Hg2+ was in low range, and decreased when the concentration of Cu2+, Cd2+, Hg2+ was in high range. The heavy metal stress strongly inhibited the activity of p-amylase of Yangdao No.6 and Xieyou 818 in germinating, but the low concentration of Cu2+, Cd2+, Hg2+ stress couldinduce the activity of P-amylase of Wuyugen in germinating. The low concentration of Cu2+, Cd2+, Hg2+ stress induced the expression of some amylase isozymes significantly, however, the high concentration of Cu2+, Cd2+, Hg2+ stress inhibited the expression of some amylase isozymes.. The COD activity of rice was induced by the Cu2+, Cd2+ stress with low concentration, and with the concentration of Cu2+, Cd2+ increasing, the COD activity decreased obviously. Th...