Moore P H, Reid H B, Hamner K C
Department of Botanical Sciences, University of California, Los Angeles, California 90024.
Plant Physiol. 1967 Apr;42(4):503-9. doi: 10.1104/pp.42.4.503.
The flowering of Xanthium pensylvanicum Wallr. was investigated using long dark periods. Attempts were made to ascertain evidence for the involvement of a flowering rhythm in Xanthium by use of variable-dark-length and light-interruption experiments.It was found that factors such as plant height (age), partial defoliation, and various pretreatments had little effect on the general nature of the flowering response. Maximum sensitivity to red light occurred at the eighth hour of 24-, 48-, and 72-hour dark periods. Temperature had little influence on this timing. The time of maximum sensitivity was delayed to the tenth hour by a pretreatment with 8 hours of darkness followed by 6 hours of light. These properties are similar to those of Pharbitis, which showed a clear rhythmic sensitivity to red light interruptions. The possible involvement of a rapidly damping rhythm of sensitivity to red light is discussed on the basis of this similarity. A distinct flowering rhythm similar to that of soybean and Chenopodium was not found. Although the results are inconclusive with respect to a rhythm, they do indicate similarities and differences to the responses of other short-day plants in which rhythms have been demonstrated.
利用长黑暗期对苍耳的开花情况进行了研究。通过可变暗期长度和光中断实验，试图确定苍耳开花节律参与其中的证据。结果发现，植株高度（年龄）、部分去叶以及各种预处理等因素对开花反应的总体性质影响不大。在24小时、48小时和72小时黑暗期的第8小时，对红光的敏感性最高。温度对这个时间点影响不大。经过8小时黑暗接着6小时光照的预处理后，最大敏感时间推迟到了第10小时。这些特性与牵牛相似，牵牛对红光中断表现出明显的节律敏感性。基于这种相似性，讨论了对红光敏感性的快速衰减节律可能参与其中的情况。未发现与大豆和藜相似的明显开花节律。尽管关于节律的结果尚无定论，但它们确实表明了与已证明有节律的其他短日植物反应的异同。
