Role of calcium in abscission of citrus

为了研究钙在柑橘落叶中的作用，1)油菜素内酯(BR)与三氟拉嗪(TFP)的相互作用。2)叶片外植体衰老和脱落过程中钙的亚细胞定位。BR是一种新型的植物生长调节内酯，它能显著延缓卡拉蒙丁(CitrusMaduretisis Lour.)叶片外植体的脱落。BR在浓度低至0.021µM时有效，且比IAA表现出更强的作用，IAA也延缓脱落。钙调素-钙复合体的抑制剂TFP加速了细胞的脱落，这种加速作用可被同时加入IAA或BR所抵消，IAA的作用更强。这表明BR延缓落叶的机制可能与IAA不同。BR和IAA对…幼果外植体脱落有明显的延缓和促进作用用扫描电子显微镜和扫描电子显微镜观察了钙在离层细胞和邻近侧生组织中的定位。采用Calamondin叶片外植体的Roux锑盐沉淀法。通过对比加或不加锑酸钾固定剂固定的标本，发现钙是电子致密的小颗粒，被认为是游离钙离子。在新鲜或IAA处理的外植体中，离层细胞中只有少量颗粒存在，主要沿质膜排列。在稍有衰老的外植体中，这些细胞沿细胞膜、细胞质和细胞壁中层均有较多的颗粒。用三氟拉嗪(TFP)处理的脓肿外植体，退化的中叶中含有丰富的颗粒。这些结果表明，离层细胞中钙的数量、类型和亚细胞定位与离层密切相关。较少

To study the role of calcium in abscission of citrus, 1) interaction of brassinolide (BR) and trifluoperazine (TFP), an. initiator of calamondin- calcium complex in abscission, 2) subcellular localization of calcium during senescence and abscission of leaf explants, were investigated. BR, a novel plant growth-regulating steroidal lactone, markedly retarded the abscission of leaf explants of Calamondin (Citrus maduretisis Lour.), when dissolved in itiator and fed through the petiole. BR was effective at concentrations as low as 0.021muM, and showed a stronger effect than IAA which also retarded abscission. TFP, an inhibitor of the calmodulin-calcium complex, accelerated abscission, and this acceleration could be counteracted by a simultaneous addition of IAA or BR, the effect of IAA being stronger. This suggests the mechanism of retardation of abscission by BR may be different from that of IAA. BR and IAA also markedly retarded and TFP accelerated the abscission of fruitlet explants of … More Calamondin.Subcellular localization of calcium in the cells of abscission layer and adjacent parencliyma tissue was investigated electronmicroscopically by Slocum and. Roux's antimonate precipitation method using leaf explants of Calamondin. By comparing the specimens which were fixed with fixatives with or without potassium antimonate, calcium was detected as electron-dense small particles and that was thought to be free calcium ion. In fresh or IAA-treated explants only a few particles were present in the cells of abscission layer maiixly along plasmalemma. In the explants which uiiderwetit some senescence, more particies were present in these cells along pasmalemma but also in, cytoplasm and middle lamella of tile cell wall. In abscising explants which were treated with trifluoperazine(TFP), abundant particles were present in the degenerated middle lamella. These results show that the amount, type and subcellular localization of calcium present in the cells of abscission layer closely related to the abscission. Less