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

将8年生水杉幼苗以45°的角度倾斜2周，以诱导茎下部形成压缩木材。在取样分析形成层区乙烯释放和内源吲哚-3-乙酸(IAA)含量后，将剩余的幼苗向相反方向倾斜，上下两边互换，并保持2周以上，直到取样。用气相色谱-火焰离子化检测法测定形成层释放的乙烯，用气相色谱-质谱法测定内源IAA，用显微镜测定管胞产量和压缩木材的形成。结果表明，无论是在原始倾斜期还是在随后的反向倾斜期，都促进了管胞的产生，压缩木管胞总是在茎的重力较低侧发育。伴随着内源IAA浓度的增加和形成层区域乙烯释放速率的加快。倾斜方向的反转改变了内源IAA和乙烯的分布，而内源IAA和乙烯的分布与压缩材在横切面上的分布有关。对这两种激素在压缩木材形成中的作用进行了比较研究。此外，还研究了茉莉酸甲酯对日本花樱桃幼苗伸长的影响，赤霉素A1、吲哚-3-乙酸和脱落酸在垂直型日本樱桃中的分布，日本落叶松茎形成层在春季开始形成层活动时内源植物激素水平的变化，以及东北红豆杉形成层中梭形细胞的变化。

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.