水稻幼苗鎘逆境生理之研究：氮或熱休克之效應

Studies on the Cd stress of Rice Seedlings: Effects of Nitrogen or Heat Shock

林雅琳(Ya-Lin Lin)

指導教授 ： 高景輝

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00450

摘要

本論文係以水稻台中在來一號（Oryza sativa L. cv. Taichung Native 1，TN1）為試驗材料，探討：（一）缺氮狀態下鎘對水稻幼苗之影響；（二）熱休克處理（HS）幼苗對鎘所誘導glutamine synthetase（GS）與protease活性改變之影響。
缺氮處理之水稻幼苗，地上部生長受抑制、鮮乾重減少，但不影響根長與根之鮮乾重。缺氮處理亦造成葉綠素、蛋白質及硝酸根離子含量降低，並出現明顯葉片黃化現象。水稻幼苗經缺氮處理誘導葉片累積H2O2，降低抗氧化物ascorbate（ASC）含量與抗氧化酵素ascorbate peroxidase、glutathione reductase、catalase活性，但增加superoxide dismutase活性。逆境荷爾蒙脫落酸累積於缺氮水稻幼苗葉片，可能與造成缺氮植株之矮化有關。與正常幼苗相比較，缺氮幼苗經氯化鎘處理，葉片、地上部與根部會顯著地累積較多鎘，而水稻幼苗鎘毒害加劇。以ASC處理缺氮幼苗可減緩氯化鎘之毒害。因此推測缺氮幼苗加劇鎘毒害之可能機制與缺氮造成抗氧化能力下降及鎘之吸收增加有關。
鎘處理導致水稻幼苗葉片內GS活性下降，protease比活性上升。HS（45℃黑暗下3小時）會抑制鎘所誘導GS與protease活性變化。HS對鎘所誘導GS與protease活性變化之效應可因NADPH oxidase抑制劑imidazole處理而抵消。Buthionine sulfoximine（BSO）為還原態glutathione（GSH）合成抑制劑。BSO處理可去除HS對鎘所誘導GS與protease活性改變之效果，而BSO作用又可被外加GSH抵消。在無熱休克處理（non-HS）下外加H2O2或GSH，可抑制因鎘誘導GS或protease活性之改變。L-galactono-1,4-lactone（GalL）為合成ASC之前趨物。non-HS下外加ASC或GalL亦可部份恢復鎘所導致之GS與protease活性改變。說明HS可有效抑制鎘誘導水稻幼苗葉片GS與protease活性之變化，係經由抗氧化系統作用所造成。

關鍵字

鎘 ； 氮 ； 熱休克 ； 水稻 ； 多重逆境

並列摘要

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.
The 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.
CdCl2 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.

並列關鍵字

cadmium ； nitrogen ； heat shock ； rice ； stress combination

參考文獻

張尊國（2002）台灣地區土壤污染現況與整治政策分析。財團法人國家政策研究基金會

Kuo MC, Kao CH (2004) Antioxidant enzyme activities are upregulated in response to cadmium in sensitive, but not in tolerant, rice (Oryza sativa L.) seedlings. Botanical Bulletin of Academia Sinica 45: 291-299

Alcantara E, Romera FJ, Canete M, Delaguardia MD (1994) Effects of heavy metals on both induction and function of root Fe(III) reductase in Fe-deficient cucumber (Cucumis sativus L.) plants. Journal of Experimental Botany 45: 1893-1898

Allan AC, Maddumage R, Simons JL, Neill SO, Ferguson IB (2006) Heat-induced oxidative activity protects suspension-cultured plant cells from low temperature damage. Functional Plant Biology 33: 67-76

Apel K, Hirt H (2004) Reactive oxygen species: Metabolism, oxidative stress, and signal transduction. Annual Review of Plant Biology 55: 373-399