• 作者： 高景輝
• 作者服務機構： 國立臺灣大學農藝學系
• 中文摘要： 本試驗主要之目的是瞭解荷爾蒙，尤其cytokinins對水稻切離葉片老化之影響。引起葉片老化之原因亦為本試驗之研究重點。臺中在來一號水稻幼苗種植於人工氣候室(日溫為30°C、夜溫25°C，光照為自然光照)九天，此時幼苗之第三葉片(即第三完全葉)之生長已完全，而第四葉片剛開始長出。本試驗之材料即用此生長九天之第三葉片。 六種供試之荷爾蒙中，cytokinins與gibberellic acid顯著的延緩水稻葉片老化。但是cytokinins之效果大於gibberellic acid，indoleacetic acid對葉片老化無影響。 abscisic acid、Ethrel與naphthaleneacetic acid可顯著的促進葉片老化。不論是以葉綠素、氨基態氮或蛋白質含量為葉片老化指標，在五種供試之cytokinins中benzyladenine都是延緩葉片老化最有效之cytokinins。不論是植物體內自然產生的或者人工合成之cytokinins均可有效的延緩葉片老化。 葉片老化過程中，細胞質內蛋白質之分解要早於葉綠體內葉綠素之分解。Cycloheximide(一種細胞質內蛋白質合成抑制劑)顯著的延緩葉片老化，但chloramphenicol(一種葉綠體內蛋白質合成之抑制劑)則無此效應。因此細胞質內某種蛋白質之連續合成(很可能是蛋白質分解酵素)似乎是引起葉片老化之原因。benzyladenine與cycloheximide延緩葉片老化之效應很近似，但benzyladenine之效果要小於cycloheximide，因此benzyladenine之所以能延緩葉片老化很可能是其能抑制蛋白質分解酵素合成。
• 英文摘要： Action of hormones, especially cytokinins, in regulating rice leaf segments was studied. Among the six hormones studied, cytokinins and gibberellic acid significantly retard senescence, though the latter is less effective. Indoleacetic acid has no influence on senescence. Abscisic acid, Ethrel, and naphthaleneacetic acid promote senescence. Of the five cytokinins tested, benzyladenine is the most active in retarding senescence. Both natural and synthetic cytokinins are effective in delaying senescence. During rice leaf senescence, proteolysis is observed early in the cytoplasm, preceding the breakdown of chlorophyll. Cycloheximide strongly retards senescence, whereas chloramphenicol exerts no effect on senescence. Continuous protein synthesis in the cytoplasm, most probably the formation of proteolytic enzymes, seems to be of prime importance in initiation of senescence process. The effect of benzyladenine in retarding senescence is similar to that of cycloheximide, though the former is less effective. It suggests, but does not prove, that benzyladenine possibly retards rice leaf senescence by inhibiting the synthesis of proteolytic enzymes.
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