Basic studies on responses of tree stems to gravitational stress and reaction wood formation

以8年生水杉幼苗为试材，以45 °倾斜2周诱导其茎下部产生压缩木。在取样用于分析形成层区乙烯释放和内源吲哚-3-乙酸（IAA）含量后，将剩余的幼苗倾斜到相反方向以使上下侧彼此相对，并保持2周以上直到取样。通过气相色谱-火焰离子化检测器测定形成层释放的乙烯，通过气相色谱-质谱（GC-MS）测定内源IAA，并通过显微镜测定管胞产生和压缩木材形成。结果表明，无论是在初始倾斜期还是在随后的反向倾斜期，都促进了管胞的产生，压缩材管胞始终在重力方向的下侧发育。与此同时，形成层区内源IAA含量增加，乙烯释放速率加快。倾斜方向的改变改变了内源IAA和乙烯的分布，并与压缩木在茎横截面上的分布相关。比较研究了这两种激素在压缩材形成中的作用。此外，茉莉酸甲酯对樱花幼苗伸长的影响，赤霉素A1、吲哚乙酸和脱落酸在垂枝型和直立型樱花中的分布，日本落叶松茎形成层在春季形成层活动开始时内源激素水平的变化，对刺楸形成层中的梭形细胞进行了研究。

Eight-year-old Metasequoia glyptostroboides seedlings were tilted at a 45^o angle for 2 weeks to induce compression wood formation on the lower side of the stems. After being sampled for analyses of cambial region ethylene emission and endogenous indole-3-acetic acid (IAA) content, the remaining seedlings were tilted to the opposite orientation to change the upper and lower sides to each other and kept for 2 more weeks till sampled. Cambium-emanated ethylene was measured by gas chromatography - flame ionization detection, endogenous IAA was measured by gas chromatography - mass spectrometry (GC-MS), and tracheid production and compression wood formation were determined by microscopy. The results showed that tracheid production was promoted and compression wood tracheids developed always on the gravitationally lower side of the stems either in the original tilting or the subsequent reversal tilting period. Those were companied by an increase in endogenous IAA concentration in and an accelerated ethylene emission rate from the cambial region of the side. Reversal of tilting orientation changed the distribution of endogenous IAA and ethylene, which were correlated with the distribution of compression wood on the transverse stem sections. The roles of both hormones in compression wood formation are comparatively studied. In addition, the methyl jasmonate effects on the elongation of seedlings in Japanese flowering cherry, distribution of gibberellin A1, indole-3-acetic acid and abscisic acid in weeping and upright types of Japanese cherry, Prunus spachiana, changes in levels of endogenous plant hormones in cambial regions of stems of Larix kaempferi at the onset of cambial activity in springtime, and fusiform cells in the cambium of Kalopanax pictus were studied.