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《Journal of Agro-environmental Science》 2005-02
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Effects of Heavy Metals on the Respiratory Rate and Expression of Related Isozymes in Rice

GE Cai lin, LUO Jian feng, LIU Chong, YIN Chao zhen, WANG Ze gang, MAFei, LUO Shi shi (Agriculture Institute, Yangzhou University, Yangzhou 225009, China)  
The ions Cu2+, Cd2+and Hg2+were selected to determine theeffects of heavy metals on respiratory metabolism of rice plants. Rice plants from the indica variety Yangdao No.6 and the japonica variety Wuyungen No.8 were cultivated with the modified Kimura B nutrient solution, and were treated for 7 days starting from the eight day after flowering with 0.025, 0.05, 0.1, 0.5, 1.0and 2.0 mmol·L-1 of Cu2+, Cd2+and Hg2, respectively. The respiratory rate in the leaves of the indica variety (measured with an oxygen electrode method) was enhanced at lower concentrations (0.025~0.1 mmol·L-1) and inhibitedat higher concentrations (0.1mmol·L-1) of these ions, respectively, while,the respiratory rate of leaves in the japonica variety was inhibited by 0.025~1.0 mmol·L-1 of these ions. The root respiratory rate was strongly inhibited by 0.025~1.0 mmol·L-1 of the three ions in the two varieties. The activities of isozymes related to respiration were analyzed using a polyacrylamide concentration gradient gel electrophoresis technique. The expression of amylase isozymes in the leaves of the two varieties was inhibited by a high concentration (0.1 and 0.5mmol·L-1) of the ions. The expression of malate dehydrogenase(MDH) isozymes in the leaves of the two varieties were induced by 0.05 mmol·L-1 Cu2+and 0.05~0.5 mmol·L-1 Cd2+and Hg2+, but that in the roots was induced by 0.05 mmol·L-1, and inhibited by 0.1 and 0.5 mmol·L-1 of the three ions. The expression of cytochrome oxidase(COD) isozymes in leaves was inhibited by 0.05 mmol·L-1 Cu2+in Yangdao No.6, and by 0.05~0.5 mmol·L-1 of the three ions in Wuyungen No.8; the COD expression in roots was also strongly inhibited by 0.1 and 0.5 mmol·L-1 Cu2+and Cd2+and 0.05~0.5 mmol·L-1 Hg2+in the two varieties. These results indicated that the effects of heavy metals on respiration varied with organs, genotypes and the concentrations of the ions in the rice plants, and suggested that changes of respiration rate in the leaves and/or roots might arise from the changes of expression levels of the isozymes under the stress.
【Fund】: 国家自然科学基金资助项目(30300026)
【CateGory Index】: X173
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