Emeritus Professor, University of Edinburgh, 21 Leadervale Road, Edinburgh EH16 6PB, Scotland, UK.
J Insect Physiol. 2013 Jan;59(1):1-10. doi: 10.1016/j.jinsphys.2012.11.003. Epub 2012 Nov 23.
In studies of photoperiodic induction of over-wintering diapause, independent variation of the light (L) and dark (D) components of the daily (LD) cycle shows, with few exceptions, that the duration of the night (D) is more important than that of the day (L). Extensions of D to give cycle lengths up to 3 days or more in so-called Nanda-Hamner (NH) experiments suggest that night length is measured repeatedly in the extended night, with peaks of high diapause incidence occurring at intervals close to 24 h. This indicates a circadian involvement in night length measurement. The circadian oscillation revealed in NH experiments is shown to take its principal time cue from the beginning of the night - at a phase close to Circadian time, CT 12 - in series of such experiments with increasing light (L) components, in a manner comparable to other circadian oscillations such as that controlling the adult eclosion rhythm. It is considered that the photoperiodic circadian oscillation is causally involved in the discrimination between short (summer) and long (autumnal) nights, although further 'downstream' actions of the circadian system on the outcome of time measurement are also likely. Therefore Bünning's original hypothesis - or development of it - is considered to offer the most likely explanation for the photoperiodic mechanism.
在光周期诱导越冬休眠的研究中，每日（LD）周期的光（L）和暗（D）成分的独立变化表明，除了少数例外，夜间（D）的持续时间比白天（L）更为重要。在所谓的南达-哈默（NH）实验中，将 D 延长以达到长达 3 天或更长的周期长度表明，在延长的夜间中多次测量夜间长度，高休眠发生率的峰值出现在接近 24 小时的间隔内。这表明昼夜节律参与了夜间长度的测量。NH 实验中揭示的昼夜节律振荡被证明主要从夜间开始获得时间提示——在接近昼夜节律时间（CT）12 的相位处，在一系列增加光照（L）成分的此类实验中，以与其他昼夜节律振荡（如控制成虫羽化节律的振荡）相类似的方式。虽然昼夜节律系统对时间测量结果的进一步“下游”作用也可能起作用，但人们认为光周期昼夜节律振荡与短（夏季）和长（秋季）夜间的区分有关。因此，布宁的原始假设——或其发展——被认为是对光周期机制最可能的解释。
