Abstract: Effects of 4PU-30, N-phenyl-N'-(2-chloro-4-pyridyl) urea, on contents of protein and nucleic acid and specific activity of hemoglobin-digesting protinase and ribonuclease were studied during leaf senescence in vitro and in vivo in hybrid rice shanyou 63. In vitro leaf sections of about 5 cm in length were floated on the solution of 4PU-30 at the concentration of 10-3, 10-2, 10-1 and 100 mg/L respectively and placed in darkness at 30℃. The result showed that all 4PU-30 concentration significantly retarded the process of leaf senescence. At 6th day incubation, contents of chlorophyll, protein, RNA and DNA were 791. 8%, 44. 4%, 32. 2 % and 33. 7% more than in control, and at the contrary specific activity of hemoglobin-digesting proteinase and ribonuclease were 73. 9%,44. 7% less in 4PU-30 (10-1mg/L) solution than in control solution. In vivo, rice plants were sprayed with 115 mL/m² 4PU-30 (100 mg/L) solution 10 days after heading at one week intervals for 3 times. 4PU-30 also retarded the process of senescence of intact leaves. For instance, at 28th day after spraying, contents of chlorophyll, protein, RNA and DNA were 60. 3%. 17. 3 %, 15. 7% .and 28. 3 % higher and specific activity of hemoglobin-digesting proteinase and ribonuclease were 51. 5% and 24. 7% lower in 4PU-30 treatment than in control respectively. It was proposed that the physiological basis of 4PU-30 in delaying the degradation of protein and nucleic acids during leaf senescence was to decrease the increasing of specific activity of hemoglobin-digesting proteinase and ribonuclease.

Key words: N-phenyl-N’-(2-chloro-4-pyridyl) urea, hemoglobin-digesting proteinase, leaf senescence, nucleic acids, protein, ribonuclease

摘要： 以汕优63连体和离体叶片为材料，研究了4PU-30对水稻叶片衰老进程及叶片内蛋白质、核酸含量和相关酶活力的调控效应。4PU-30能显著地延缓水稻叶片衰老，保绿效果明显。叶片中蛋白质和核酸含量及相关酶活力的变化表明，4PU-30控制叶片衰老过程中蛋白质水解酶和核糖核酸酶比活上升，减缓蛋白质和核酸的降解，是其延缓杂交水稻叶片衰老的主要生理基础之一。

关键词: 4PU-30, 蛋白质, 核酸, 血红蛋白水解酶, 核糖核酸酶