Studies on the Senescence of Rice Leaves: Effects of Abscisic Acid and Methyl Jasmonate
Date Issued
2004
Date
2004
Author(s)
Hung, Kuo Tung
DOI
zh-TW
Abstract
In this dissertation, we studied the possible mechanism of abscisic acid (ABA)- and methyl jasmonate (MJ)-promoted senescence of detached rice leaves. The main results are outlined as follows:
1. Nitric oxide (NO) donors prevented paraquat (PQ)-induced toxicity, PQ-increased MDA content and PQ-decreased antioxidative enzyme activities in detached rice leaves in the light. NO donors were also effective in reducing hydrogen peroxide-induced senescence, hydrogen peroxide-induced lipid peroxidation, hydrogen peroxide-decreased antioxidant [ascorbic acid (AsA) and reduced glutathione (GSH)] contents, and hydrogen peroxide-increased antioxidative enzyme specific activities in rice leaves under dark condition. The protective effect of NO donors on PQ- and hydrogen peroxide-induced responses was reversed by carboxy-2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, indicating that the protection effect of NO donors is attributable to NO released. The effect of NO donors is mediated through its ability to scavenge reactive oxygen species.
2. Free radical scavengers (sodium benzoate and GSH) and NO donors reduced ABA- and MJ-induced senescence, ABA- and MJ-increased malondialdehyde (MDA) and hydrogen peroxide contents, antioxidative enzyme specific activities, and ABA- and MJ-decreased antioxidant contents of detached rice leaves. It seems ABA- and MJ-promoted senescence of detached rice leaves is mediated through oxidative stress.
3. NADPH oxidase, which is sensitive to diphenyleneiodonium (DPI) and imidazole (IMD), and peroxidase (POD), which is sensitive to KCN and NaN3, are two enzymes responsible for hydrogen peroxide production in rice leaves treated with ABA and MJ.
4. Phosphatidylinositol 3-kinase inhibitors LY 294002 (LY) and wortmannin (WM) inhibited ABA- or MJ-induced hydrogen peroxide production and senescence of rice leaves, suggesting that phosphatidylinositol 3-phosphate is required for NADPH oxidase activation.
5. Inhibitors of hydrogen peroxide production (DPI, IMD, KCN, NaN3, LY, and WM) and chemical trap for hydrogen peroxide (dimethylthiourea) were able to reduce ABA- and MJ-promoted senescence and accumulation of ammonium ions and anthocyanins, suggesting that hydrogen peroxide is involved in ABA- and MJ-promoted senescence and accumulation of ammonium ions and anthocyanins of rice leaves.
6. CaCl2 and A23187, calcium ionophore, were effective in preventing ABA-, MJ- and hydrogen peroxide-promoted senescence and accumulation of ammonium ions and anthocyanins of rice leaves, suggesting the effect of ABA, MJ, and hydrogen peroxide is mediated through blocking the entrance of Ca2+ into cytosol.
Subjects
脫落酸
甲基茉莉酸鹽
水稻
老化
methyl jasmonate
rice
senescence
abscisic acid
Type
thesis
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