Studies on the Cd Stress of Rice Seedlings: Effect of Sulfur or Heat Shock
Date Issued
2008
Date
2008
Author(s)
Kuo, Chun-Ling
Abstract
In this thesis, rice (Oryza sativa L. cv. Taichung Native 1, TN1) seedlings were cultivated hydroponically in green house and were used to study Cd toxicity of rice seedlings under sulfur deficienct conditions. Also included this thesis is the effect of heat shock on Cd–induced accumulation of ammonium ion and increase specific activity in leaves of rice seedlings.ength, dry weight and fresh weight of shoot and the contents of chlorophyll and protein content were reduced under sulfur–deficient conditions. Moreover, sulfur–eficient treatment resulted in accumulation of H2O2 in roots and leaves. However, sulfur deficiency had no effect on abscisic acid content. Sulfur containing compounds, such as non–protein thiols, cysteine and glutathione, were reduced in leaves of rice seedlings grown under sulfur–deficient conditions. Sulfur–deficient seedlings had lower activity of APX, GR and CAT, but higher activity of SOD than sulfur-sufficient seedlings. Exogenous application of glutathione, cysteine to sulfur–deficient rice seedlings reduced cadmium toxicity of rice seedlings. Results suggest that decrease in the contents of cysteine and glutathione and activities of APX, GR and CAT is the possible reasons of increase in cadmium toxicity in of rice seedlings under sulfur deficient conditions. d treatment resulted in an accumulation of NH4+ and increase in PAL activity in leaves of rice seedlings. Rice seedlings were pretreated with heat shock (HS, 45℃, dark) at the time when the third leaves were fully expanded and then treated with CdCl2. The results indicated that CdCl2 induced NH4+ accumulation and increased PAL activities in leaves of rice seedlings. HS pretreatment decreased Cd–induced NH4+ accumulation and PAL specific activity. H2O2 (0.5 mM) and GSH (1 mM) pretreatments under non–HS conditions also had the same effects as HS pretreatment. Pretreatments with GSH inhibitor, buthionine sulfoxinine, or NADPH oxidase inhibitor, imidazole, under HS condition resulted in enhancing Cd–induced NH4+ accumulation and PAL specific activity. Under non–HS condition, pretreatments with ascorbate and its precursor galactono–1,4–lactone reduced Cd–induced NH4+ accumulation and decrease PAL specific activity.
Subjects
rice
cadmium
sulfur deficiency
heat shock
NH4+
Type
thesis
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