United States Department of Agriculture, State University Station, Fargo, North Dakota 58105.
Plant Physiol. 1985 Jun;78(2):272-6. doi: 10.1104/pp.78.2.272.
The effect of the defoliant thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea) on endogenous ethylene evolution and the role of endogenous ethylene in thidiazuron-mediated leaf abscission were examined in cotton (Gossypium hirsutum L. cv Stoneville 519) seedlings. Treatment of 20- to 30-day-old seedlings with thidiazuron at concentrations equal to or greater than 10 micromolar resulted in leaf abscission. At a treatment concentration of 100 micromolar, nearly total abscission of the youngest leaves was observed. Following treatment, abscission of the younger leaves commenced within 48 hours and was complete by 120 hours. A large increase in ethylene evolution from leaf blades and abscission zone explants was readily detectable within 24 hours of treatment and persisted until leaf fall. Ethylene evolution from treated leaf blades was greatest 1 day posttreatment and reached levels in excess of 600 nanoliters per gram fresh weight per hour (26.7 nanomoles per gram fresh weight per hour). The increase in ethylene evolution occurred in the absence of increased ethane evolution, altered leaf water potential, or decreased chlorophyll levels. Treatment of seedlings with inhibitors of ethylene action (silver thiosulfate, hypobaric pressure) or ethylene synthesis (aminoethoxyvinylglycine) resulted in an inhibition of thidiazuron-induced defoliation. Application of exogenous ethylene or 1-aminocyclopropane-1-carboxylic acid largely restored the thidiazuron response. The results indicate that thidiazuron-induced leaf abscission is mediated, at least in part, by an increase in endogenous ethylene evolution. However, alterations of other phytohormone systems thought to be involved in regulating leaf abscission are not excluded by these studies.
脱落酸噻二唑脲（N- 苯基 -N'-1,2,3-噻二唑-5-基脲）对内源乙烯释放的影响以及内源乙烯在噻二唑脲介导的叶片脱落中的作用，在棉花（Gossypium hirsutum L. cv Stoneville 519）幼苗中进行了研究。用浓度等于或大于 10 微米的噻二唑脲处理 20-30 天大的幼苗会导致叶片脱落。在 100 微米的处理浓度下，观察到最年轻叶片几乎完全脱落。处理后，较年轻叶片的脱落在 48 小时内开始，并在 120 小时内完全完成。在处理后 24 小时内，很容易检测到叶片和脱落区外植体的乙烯释放量大幅增加，并持续到叶片脱落。处理叶片的乙烯释放量在处理后 1 天达到最大，并达到每克鲜重每小时超过 600 纳升（26.7 纳摩尔每克鲜重每小时）的水平。乙烯释放的增加发生在没有增加乙烷释放、改变叶片水势或降低叶绿素水平的情况下。用乙烯作用抑制剂（硫酸银、低压）或乙烯合成抑制剂（氨基乙氧基乙烯基甘氨酸）处理幼苗会抑制噻二唑脲诱导的脱叶。外源乙烯或 1- 氨基环丙烷-1- 羧酸的应用在很大程度上恢复了噻二唑脲的反应。结果表明，噻二唑脲诱导的叶片脱落至少部分是由内源乙烯释放的增加介导的。然而，这些研究并没有排除其他被认为参与调节叶片脱落的植物激素系统的改变。
