Studies on the Cd stress of Rice Seedlings: Effects of Nitrogen or Heat Shock
Date Issued
2008
Date
2008
Author(s)
Lin, Ya-Lin
Abstract
Rice (Oryza sativa L. cv. Taichung Native 1) seedlings were used to investigate (a) the effect of nitrogen deficiency on Cd toxicity and (b) the effect of heat shock (HS) on Cd-induced changes in GS activity and protease specific activity.he N-deficient treatment caused reduction in length, fresh weight and dry weight of shoot, but had no effect on root. Nitrogen deficiency also caused reduction in chlorophyll, protein, and nitrate contents, and chlorosis in leaves. Rice seedlings grown under nitrogen deficient conditions resulted in an increase in hydrogen peroxide content, decrease in ascorbate (ASC) content, ascorbate peroxidase, glutathione reductase, and catalase activites, as well as increase in superoxide dismutase activity in leaves. Abscisic acid accumulated in N-deficient leaves, this may leads to the reduction of shoot growth. The cadmium concentration was higher in the leaves, shoot, and root of N-deficient seedlings than that in leaves, shoot, and root of control seedlings. Addition of ascorbate to N-deficient rice seedlings alleviated cadmium toxicity. On treatment with cadmium chloride, N-deficient rice seedlings had more severe toxic symptoms than those of control, which is most likely related to low antioxidant ability and high cadmium concentration in leaves of rice seedlings grown under N-deficient conditions.dCl2 treatment resulted in a decrease in GS activity and an increase in protease specific activity. HS pretreatment (45℃ for 3 h in the dark) protected against Cd-induced changes in GS and protease in rice seedlings. Exogenous application of imidazole (NADPH oxidase inhibitor) under HS condition counteracts the effect of HS on the activity of GS and the specific activity of protease. Buthionine sulfoximine (BSO) is an inhibitor of reduced glutathione (GSH) synthesis. BSO pretreatment reduced HS effect on Cd-induced changes in GS and protease. The effect of BSO was reversed by the application of GSH. Exogenous application of H2O2 or GSH under non-HS condition was able to inhibit the changes of GS and protease induced by CdCl2. L-Galactono-1,4-lactone (GalL) is a precursor of ASC biosynthesis. Pretreatment of rice seedlings with ASC or GalL under non-HS condition protected against the Cd effect on the activity of GS and the specific activity of protease. In conclusion, HS-reduced the changes of GS and protease by CdCl2 is most likely mediated through antioxidant systems.
Subjects
cadmium
nitrogen
heat shock
rice
stress combination
Type
thesis
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