热带落叶树降香黄檀次生韧皮部薄壁组织细胞超微结构的季节变化

Seasonal Ultrastructural Changes of Secondary Phloem Parenchyma Cells in a Tropical Tree, Dalbergia odorifera

利用透射电子显微镜技术研究了热带落叶树降香黄檀 (DalbergiaodoriferaT .Chen)末端小枝次生韧皮部韧皮和射线薄壁组织细胞的季节变化。这些变化主要表现为细胞内贮藏物质(其中包括中央液泡中的贮藏蛋白质 ,质体中的淀粉粒、类脂球和铁蛋白 ,以及圆球体中的类脂等 )的周期性的积累和消耗。降香黄檀在冬季落叶期不出现在温带落叶树木中看到的与抗寒有关的若干细胞学改变。降香黄檀也象温带树木一样 ,薄壁细胞在落叶期形成高度折叠的质膜 ,并由此形成无数的小泡。有人认为 ,温带树木中的这些结构与抗寒有关 ,但我们认为 ,它们在热带树木中的作用可能是实现细胞间物质的转运。

The seasonal changes of the ray and phloem parenchyma cells of secondary phloem in terminal branchlets of Dalbergia odorifera T. Chen (Papilionaceae), a tropical deciduous tree, were studied by using transmission electron microscopy. The changes were mainly the cyclic alternation of accumulation and exhaustion of the storage materials including proteins in the central vacuole, the starch grains, lipoid globules and phytoferritin in the plastids, and lipoids in the spherosomes. D. odorifera did not undergo some of the cytological changes which were found in the temperate trees studied and believed to be related with the hardiness. Like the stuctures found in temperate trees, in D. odorifera the highly folded plasmalemma and numerous small vesicles pinched of by the plasmalemma appeared in the actively reserve-accumulating cells during the leaf-fall period. It was suggested that the structures play a role in translocation of the materials between the cells, while in the temperat trees the structures were considered involving in frost resistance. The differences in seasonal ultrastructural changes between D. odorifera and the temperate tree can be explained by adaptation of the trees to climatic conditions in their habitats.