Rivera G, Borchert R
Instituto Multidisciplinario de Biología Vegetal, Universidad Nacional de Córdoba, Argentina.
Tree Physiol. 2001 Mar;21(4):201-12. doi: 10.1093/treephys/21.4.201.
During the late rainy season in October 1997 we observed. over a range of >100 km, the highly synchronous emergence of flower buds in several deciduous tree species of the semi-deciduous tropical forest in Guanacaste, Costa Rica. Synchronous flowering soon after the rapid decline in day length around the September equinox and in the absence of any notable climatic cues suggested flower induction by declining photoperiod. By combining field observations and the analysis of flowering herbarium collections, we established highly synchronous flowering periods with low interannual and latitudinal variation predicted for photoperiodic flower induction for more than 25 tree species and a few herbs. We describe morphogenetic changes at the shoot apex of three species during flower induction and the suppression and induction of flowering in several herbaceous species by experimental daylight extension. The combined observations provide strong, mainly indirect evidence for photoperiodic induction of flowering in many tropical tree species. At low latitudes with annual variation in day length of 1 hour, flower induction must be caused by a decline in photoperiod of 30 min or less. This is the first report of photoperiodic control of flowering in trees.
1997年10月雨季后期，我们在哥斯达黎加瓜纳卡斯特半落叶热带森林中，观察到在超过100公里的范围内，几种落叶树种的花芽高度同步出现。在9月秋分前后白昼长度迅速缩短之后，且没有任何明显气候线索的情况下，同步开花表明光周期缩短诱导了开花。通过结合实地观察和对开花植物标本馆收藏的分析，我们确定了25种以上树木和一些草本植物的高度同步开花期，其年际和纬度变化较小，这是光周期诱导开花所预测的。我们描述了三种植物在花诱导期间茎尖的形态发生变化，以及通过实验性延长日照对几种草本植物开花的抑制和诱导。综合观察结果为许多热带树种的光周期诱导开花提供了有力的、主要是间接的证据。在低纬度地区，白昼长度年变化为1小时，花诱导必定是由光周期缩短30分钟或更少引起的。这是树木开花光周期控制的首次报道。
