Studies on the physiology of cadmium stress in rice seedlings:The role of glutathione, ascorbic acid and salicylic acid

• Main Authors: Chao-Yeh Chen, 陳炤曄
• Other Authors: Ching Huei Kao
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/91350177483456486265

碩士 === 國立臺灣大學 === 農藝學研究所 === 95 === In this thesis, two rice (Oryza sativa L.) cultivars (cv. Taichung Native 1 and cv. Tainung 67, TNG67) were used to study the regulatory role of glutathione (GSH) and ascorbic acid (AsA) in Cd induced toxicity. Also included in this thesis is the protective effect of salicylic acid (SA) against Cd toxicity of detached leaves of TN1 seedlings. Cd toxicity was judged by leaf chlorosis, the decrease in chlorophyll content and the increase in malondialdehyde (MDA) content. The results indicated that TNG67 rice seedlings are Cd tolerance and TN1 rice seedlings are Cd-sensitive. The different Cd sensitivities between those two cultivars seem to be regulated by GSH and AsA. This conclusion was based on the observations that (a) CdCl2 treatment resulted in a decrease in GSH and AsA contents of the leaves of TN1 seedlings, but not in those of TNG67 seedlings; (b) exogenous application of GSH, AsA and L-galactono- 1,4-lactone (a precursor of AsA) could decrease the subsequent Cd toxicity in TN1 seedlings; (c) buthionine sulphoximine ( an inhibitor of GSH synthesis, BSO) treatment reduced GSH content as well as Cd tolerance of TNG67 seedlings. Detached TN1 rice leaves pretreated with SA (3 mM) resulted in an increase in H2O2 content. Diphenyleneiodonium chloride (DPI) and imidazloe (IMD), both are NADPH oxidase inhibitor, inhibit SA-induced accumulation of H2O2. SA pretreatment also resulted in an increase in diamine oxidase (DAO) activity. These results suggest that NADPH oxidase and DAO are H2O2-generating enzymes in SA-pretreated detached leaves. On treatment with SA, the antioxidant enzymes activities (SOD, CAT, GR, APX) and GSH contents increased, but AsA contents decreased in detached leaves. Evidence was provided to show that SA protects detached rice leaves against paraquat and Cd toxicities.