Sieve tubes in action
Sieve tubes in action
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DOI：
10.1105/tpc.10.1.35
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发表时间：
1998-01-01
期刊：
影响因子：
11.6
通讯作者：
van Bel, AJE
中科院分区：
文献类型：
--
作者：
Knoblauch, M;van Bel, AJE
设计了一种用激光共聚焦扫描显微镜观察筛元/伴生物的方法。将一片附着在完整蚕豆植株上的叶子倒挂在共聚焦显微镜的台上。在大静脉处做了两个浅皮层旁切口。基底皮质窗口使我们能够观察到韧皮部的完整。利用距观察点3cm的根尖窗口，应用韧皮部-流动荧光染料对观察点的活筛元素进行鉴定。在完整的筛管中，筛板不会对质量流动形成障碍，因为荧光染料的易位似乎不受阻碍。区分了两种主要的闭塞机制。在强烈的激光的作用下，壁蛋白从质膜上分离出来，形成一个由微小的链和聚集的物质组成的网络，这些物质聚集并压在筛板上。由于受到机械损伤，均匀分布的P质体发生爆炸，在筛板上形成一个巨大的塞子。在机械损伤的情况下，壁蛋白转变成弹性线（股），延伸到整个筛元腔。我们的观察涵盖了在以前的显微镜和电子显微镜研究中遇到的现象，并提供了时间上的解开，这些事件导致了迄今为止观察到的令人困惑的大量结构。
A method was designed for in vivo observation of sieve element/companion complexes by using confocal laser scanning microscopy. A leaf attached to an intact fava bean plant was mounted upside down on the stage of a confocal microscope. Two shallow paradermal cortical cuts were made in the major vein. The basal cortical window allowed us to observe the phloem intact. The apical window at 3 cm from the site of observation was used to apply phloem-mobile fluorochromes, which identified living sieve elements at the observation site. In intact sieve tubes, the sieve plates did not present a barrier to mass flow, because the translocation of fluorochromes appeared to be unhindered. Two major occlusion mechanisms were distinguished. In response to intense laser light, the parietal proteins detached from the plasma membrane and formed a network of minute strands and clustered material that aggregated and pressed against the sieve plate. In response to mechanical damage, the evenly distributed P plastids exploded, giving rise to the formation of a massive plug against the sieve plate. In case of mechanical damage, the parietal proteins transformed into elastic threads (strands) that extended throughout the sieve element lumen. Our observations cover the phenomena encountered in previous microscopic and electron microscopic studies and provide a temporal disentanglement of the events giving rise to the confusing mass of structures observed thus far.