Yeang Hoong-Yeet
57-1 Jalan Medang Serai, Bukit Bandar Raya, Kuala Lumpur, Malaysia.
New Phytol. 2007;175(2):283-289. doi: 10.1111/j.1469-8137.2007.02089.x.
How tropical trees flower synchronously near the equator in the absence of significant day length variation or other meteorological cues has long been a puzzle. The rubber tree (Hevea brasiliensis) is used as a model to investigate this phenomenon. The annual cycle of solar radiation intensity is shown to correspond closely with the flowering of the rubber tree planted near the equator and in the subtropics. Unlike in temperate regions, where incoming solar radiation (insolation) is dependent on both day length and radiation intensity, insolation at the equator is due entirely to the latter. Insolation at the upper atmosphere peaks twice a year during the spring and autumn equinoxes, but the actual solar radiation that reaches the ground is attenuated to varying extents in different localities. The rubber tree shows one or two flowering seasons a year (with major and minor seasons in the latter) in accordance with the solar radiation intensity received. High solar radiation intensity, and in particular bright sunshine (as distinct from prolonged diffuse radiation), induces synchronous anthesis and blooming in Hevea around the time of the equinoxes. The same mechanism may be operational in other tropical tree species.
在赤道附近，热带树木在没有明显的日长变化或其他气象线索的情况下如何同步开花，长期以来一直是个谜。橡胶树（巴西橡胶树）被用作研究这一现象的模型。结果表明，太阳辐射强度的年周期与种植在赤道附近和亚热带地区的橡胶树的开花密切相关。与温带地区不同，在温带地区，入射太阳辐射（日照）取决于日长和辐射强度，而赤道地区的日照完全取决于后者。在春秋分时，高层大气中的日照每年达到峰值两次，但到达地面的实际太阳辐射在不同地区会有不同程度的衰减。根据接收到的太阳辐射强度，橡胶树一年有一个或两个开花季节（后者有主要和次要季节）。高太阳辐射强度，特别是明亮的阳光（与长时间的漫射辐射不同），会在春分和秋分前后诱导橡胶树同步开花和绽放。相同的机制可能在其他热带树种中也起作用。
