Nakamura T, Yoshida M
Faculty of Science, Japan Women's Univ, Tokyo.
Biol Sci Space. 2000 Oct;14(3):123-31. doi: 10.2187/bss.14.123.
In this review, we attempted to summarize the effect of gravity on growth of woody plants, broad leaved trees, on earth. It is well known that in tilted broad leaved trees, tension wood formed in the secondary xylem causes negative gravitropism. Gibberellin has been shown to induce tension wood in weeping branch, causing its upright growth. Recent study has shown that seedling of Japanese cherry tree grown on three dimensional clinostat, a device that simulates microgravity, grew at random angles, and that the formation of secondary xylem, as supporting tissue for upright growth, decreased. In the decreased xylem formation, the inhibition of the differentiation and development of fiber cell was clearly observed. These results suggest that in attitude control and morphogenesis of stem in woody plant, secondary xylem formation seriously relates to gravity on earth. In woody plant, the mechanism of gravity perception and the following signal transduction have not yet been elucidated, although the recent study reported the possibility that endodermal starch sheath cells and plant hormones may play some role in the mechanism. Space experiment for woody plant is expected to study these problem.
在本综述中，我们试图总结重力对地球上木本植物、阔叶树生长的影响。众所周知，在倾斜的阔叶树中，次生木质部中形成的拉力木会导致负向地性。赤霉素已被证明能在下垂枝条中诱导产生拉力木，使其直立生长。最近的研究表明，在三维回转器（一种模拟微重力的装置）上生长的日本樱花树幼苗以随机角度生长，并且作为直立生长支撑组织的次生木质部的形成减少。在木质部形成减少的情况下，明显观察到纤维细胞的分化和发育受到抑制。这些结果表明，在木本植物茎的姿态控制和形态发生中，次生木质部的形成与地球上的重力密切相关。在木本植物中，重力感知机制及随后的信号转导尚未阐明，尽管最近的研究报道了内皮层淀粉鞘细胞和植物激素可能在该机制中发挥某些作用的可能性。木本植物的空间实验有望研究这些问题。
