Space Biology Laboratory, Brain Research Institute, University of California, Los Angeles, California 90024.
Plant Physiol. 1974 Feb;53(2):176-9. doi: 10.1104/pp.53.2.176.
We have shown Xanthium strumarium exhibit two distinct leaf movement rhythms with one occurring in continuous light and presumably related to an endogenous rhythm initiated by the "light-on" signal and the other occurring in continuous dark and presumably related to an endogenous rhythm initiated by the "light-off" signal. Characteristic of the light-on rhythm is a sudden and rapid downward movement of the leaf occurring about 16 hours after the light-on signal. Characteristic of the light-off rhythm is an immediate and sudden upward movement following the light-off signal. Under certain photoperiodic treatments, the two movements seem to be in conflict.The characteristic light-on downward movement was predominant in the light-dark 14: 10 and 16: 8 treatments while the light-off upward movement was predominant in light-dark 8: 16 and 10: 14 treatments. In the light-dark 12: 12 treatment, one movement was predominant in about half of the cases and vice versa. Thus leaf movements of X. strumarium plants given these light-dark treatments were found to fit a hypothesis based on the participation of both a light-on and a light-off rhythm. The over-all leaf movement rhythm may be controlled by what might be called two clocks. Both of these clocks may have essentially the same basic mechanism with one important distinction. One is rephased by the light-on signal and the other by the light-off signal. Furthermore, the leaf movements related to each clock are distinctive.The hypothesis of the participation of a light-on and a light-off rhythm was also found to be applicable to published data (M. Holdsworth, 1959. Effects of day length on the movements of pulvinate leaves. New Phytol. 58: 29-45). Interpretation of the Bauhinia leaf movements along this line is also presented.
我们已经表明，苍耳表现出两种截然不同的叶片运动节律，一种发生在连续光照下，可能与由“光开启”信号引发的内源性节律有关，另一种发生在连续黑暗中，可能与由“光关闭”信号引发的内源性节律有关。光开启节律的特征是，在光开启信号后大约 16 小时，叶片会突然快速向下运动。光关闭节律的特征是，在光关闭信号后立即出现突然向上运动。在某些光周期处理下，这两种运动似乎存在冲突。特征性的光开启向下运动在光暗 14:10 和 16:8 处理中占主导地位，而光关闭向上运动在光暗 8:16 和 10:14 处理中占主导地位。在光暗 12:12 处理中，一种运动在大约一半的情况下占主导地位，反之亦然。因此，给予这些光暗处理的苍耳植株的叶片运动被发现符合基于光开启和光关闭节律参与的假设。整体叶片运动节律可能由两个时钟控制。这两个时钟可能具有基本相同的基本机制，但有一个重要区别。一个由光开启信号重新同步，另一个由光关闭信号重新同步。此外，与每个时钟相关的叶片运动是独特的。光开启和光关闭节律参与的假设也被发现适用于已发表的数据（M. Holdsworth，1959. 日长对卷须叶运动的影响。新植物学。58: 29-45）。还提出了沿此思路解释羊蹄甲叶片运动的方法。
