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標題: | 水稻幼苗鎘逆境生理之研究:硫或熱休克之效應 Studies on the Cd Stress of Rice Seedlings: Effect of Sulfur or Heat Shock |
作者: | Chun-Ling Kuo 郭俊伶 |
指導教授: | 高景輝(Ching–Huei Kao) |
關鍵字: | 水稻,鎘,缺硫,熱休克,銨離子, rice,cadmium,sulfur deficiency,heat shock,NH4+, |
出版年 : | 2008 |
學位: | 碩士 |
摘要: | 本論文係以水稻品種台中在來1號 (Oryza sativa L. cv. Taichung Native 1, TN1) 為材料,探討 (一) 水稻在缺硫與鎘之雙重逆境對鎘毒害之影響與 (二) 水稻幼苗熱休克前處理對鎘逆境所誘導之銨離子累積與 PAL 活性增加之影響。
幼苗在缺硫下生長,至第三片葉片完全展開後進行鎘處理。試驗結果顯示,缺硫處理降低水稻幼苗地上部株高、鮮重和乾重,但不影響根長、根鮮重與根乾重。缺硫處理也降低水稻幼苗葉片蛋白質和葉綠素含量。不論以 3,3'–diamino–benzidine 染色觀察或化學分析都發現,缺硫會導致幼苗葉片與根部 H2O2 累積。但分析水稻幼苗第二片葉片與根中 ABA 含量,發現對照與缺硫處理間沒有顯著差異。缺硫處理亦可降低水稻幼苗含硫化合物,如: non–protein thiols、cysteine (Cys) 與 reduced 型式 glutathione (GSH) 之含量,與降低 ascorbate peroxidase (APX)、glutathione reductase (GR)、catalase (CAT) 之活性,然而缺硫處理增加 superoxide dismutase (SOD) 活性。試驗結果也顯示,缺硫之水稻幼苗會使後續之鎘毒害加重。外加 GSH、Cys 處理可降低缺硫幼苗所表現之鎘毒害。試驗結果似乎說明缺硫之水稻幼苗由於抗氧化物 (cysteine 與 glutathione) 含量與抗氧化酵素 (APX、GR、CAT) 活性之降低,是造成後續鎘毒害加劇的可能原因。 鎘逆境會誘導幼苗第二片葉片中 NH4+ 含量與 phenylalanine ammonia–lyase (PAL) 比活性增加,而熱休克前處理 (HS,黑暗下 45℃) 則降低鎘所誘導 NH4+ 含量與 PAL 比活性增加。在 30℃ 黑暗下 (non–HS) 進行 H2O2 (0.5 mM) 與 GSH (1 mM) 前處理亦可降低鎘所誘導 NH4+ 累積與 PAL 比活性之增加。在 HS 狀況下處理 GSH 合成抑制劑 buthionine sulfoxinine 與 NADPH oxidase 合成抑制劑 imidazole 可促進 NH4+ 累積與 PAL 比活性之增加。在 non–HS 狀況下,外加 ascorbate 及其合成前驅物 galactono–1,4–lactone 可降低鎘所誘導 NH4+ 累積與 PAL 比活性之增加。 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. Length, dry weight and fresh weight of shoot and the contents of chlorophyll and protein content were reduced under sulfur–deficient conditions. Moreover, sulfur– deficient 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. Cd 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. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/9700 |
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