Studies on the Relationship between Calcium and Cadmium Stress of Rice Seedlings
Date Issued
2010
Date
2010
Author(s)
Cho, Shih-Chueh
Abstract
Rice (Oryza sativa L. cv. Taichung Native 1,TN1) seedlings were used to investigate (a) the role of hydrohen peroxide (H2O2) in cadmium (Cd) toxicity in rice seedling roots, (b) the effect of calcium (Ca) on Cd toxicity in rice seedling roots, and (c) the effect of calcium (Ca) deficiency on Cd toxicity of rice seedlings.
Measurements of root length, crown root number, root dry weight and cell death in roots were selected as Cd toxicity index in rice seedling roots. Catalase (CAT) activity and GSH content decreased in 3 h after Cd treatment. Cd-induced H¬2O2 accumulation occurred 6 h after Cd treatment. Pretreatment of GSH, which increased GSH content, resulted in alleviation of Cd toxicity. Pretreatment of diphenylene iodonium (DPI) NADHP oxidase inhibitor, not only decreased H2O2 level but also alleviated Cd-inhibited root length, root dry weight and Cd-increased cell death. Cd decreased crown root number is not related to H2O2. The results obtained indicated that Cd-decreased CAT activity resulted in H2O2 accumulation. The accumulation of H2O2 in turn decreased root length and dry weight, and increased cell death.
Exogenous addition of Ca was observed to reduce Cd toxicity, Cd uptake and Cd-induced H2O2 accumulation. Ca-reduced Cd toxicity can be revered by H2O2 appilication. These results suggest that Ca- reduced Cd toxicity is mediated through inhibition of Cd uptake, which in turn increased CAT activity and reduced H2O2 accumulation.
The Ca deficiency treatment caused reduction of Ca concnetration in rice seedling. Ca deficiency resuled in decrease in CAT activity and GSH content and increase in SOD activity. Ca deficiency increased the toxicity of leaves of rice seedlings to subsequent Cd treatment. Cd concentration was higher in Ca-deficient shoot amd roots than their respective control shoot and roots. Cd-induced activities of SOD, CAT, APX, and GR and Cd-decreased AsA content in Ca-deficient seedlings were pronounced than Ca-sufficient seedlings. HS-induced Oshsp17.3 expression and HS protection of Cd stress were odserved in Ca-sufficient but not in Ca-deficient rice seedlings. Thus, it can be concluded that Ca is involved in the HS-induced expression of Oshsp17.3.
Subjects
Calcium
Cadmium
H2O2
oxidative stress
rice
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