A comparative study was carried out on the EM-cytochemical localization of calcium and Ca2+-ATPase activity in the suspension-cultured cells between the chilling-sensitive maize (Zea mays L. cv. Black Mexican Sweet) and chilling-insensitive Trititrigia (Triticum sect. Trititrigia mackey) at 4 ℃ chilling. When maize and Tyititrigia cells were cultured at 26 ℃, electron microscopic observations revealed that the electron-dense calcium antimonate deposits, an indication of the calcium localization, were localized mainly in the vacuoles, and few was found in the cytosol and nuclei. The electron-dense cerium phosphate deposits, an indication of Ca2+-ATPase activity, were abundantly distributed on the plasma membrane (PM). When the cells from both species were cultured at 4 ℃ for 1 and 3 h, an elevation of Ca2+ level in the cytosol and nuclei was observed, whereas the cerium phosphate deposits on the PM showed no quantitative difference from those of the 26 ℃-cultured cells, indicating that the enzymatic activities were not altered during these chilling periods. However, there was a distinct difference in the dynamics of the Ca2+ distribution and the PM Ca2+-ATPase activity between maize and Trititrigia when chilled at 4 ℃ for 12, 24 and 72 h. In maize cells, a large number of Ca2+ deposits still existed in the cytosol and nuclei, and the PM Ca2+-ATPase became less and less active, and even inactive at all. In Trititrigia cells, the increased cytosolic and nuclear Ca2+ ions decreased after 12 h chilling. By chilling up to 24 and 72 h, the intracellular Ca2+ concentration had been restored to a similar low level as those of the warm temperature-cultured cells, while the activity of the PM Ca2+-ATPase maintained high. The transient cytosolic and nuclear Ca2+ increase and the activities of PM Ca2+-ATPase during chilling are discussed in relation to plant cold hardiness.
杨树顶芽细胞内质网与其他膜系统的结构联系及其在休眠过程中的变化
简令成1* 李积宏1** 李本湘1*** 陈辉煌2
(1.Laboratory of Plant Hardiness,Department of Horticultyral Science, and Plant Biological Sciences Program, 2. Department of Horticulture, and Center for Gene Research and Biotechnology, Oregon State Unixersity,Corvallis,OR 97331, USA)
摘要：杨树 (Populusdeltoides Bartr.exMarsh)顶芽分生组织细胞经一种改良的高锰酸钾固定法固定后 ,显示出一种十分清晰的内膜结构 ,尤其展现了内质网与其他膜系统存在一种结构上的密切联系。一些与核膜相连接的内质网伸展到细胞质中与线粒体、质体及高尔基体发生联系 ,或延伸到质膜。还有些内质网的一端与一个细胞的核膜相连结 ,其另一端穿过胞间连丝与邻近的另一个细胞的核膜相连结 ,在两个相邻的细胞核之间形成一种结构上的“内质网桥”。这种“内质网桥”结构的揭示 ,进一步完善了共质体的概念。在植物细胞间 ,不仅通过胞间连丝造成细胞质的沟通 ;而且通过“内质网桥”形成核与核之间的联络。在短日照诱导的休眠过程中 ,内质网出现收缩现象 ,导致内质网与其他膜系统联系的中断 ,胞间连丝的中断 ,以及核与核之间“桥通道”的中断。在芽休眠被打破和复苏生长后 ,内质网的收缩现象消失 ,内质网与其他膜系统间联系 ,以及相邻细胞核之间重建“内质网桥”。这些结果揭示 ,内质网在沟通细胞核与各细胞器 ,以及核与核之间生命活动的关系上可能起着重要的作用。它的收缩作用可能导致生长的停止和休眠的发展
关键词： 内质网；内质网桥；内质网收缩；胞间连丝；休眠；杨树
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