Forestry Division, Japan International Research Centre for Agricultural Sciences, Ohwashi, Tsukuba, Ibaraki, 305-8686, Japan.
Forestry Biotechnology Division, Forest Research Institute Malaysia, Kepong, Selangor Darul Ehsan, Malaysia.
Am J Bot. 2020 Nov;107(11):1491-1503. doi: 10.1002/ajb2.1557. Epub 2020 Nov 14.
Leaf phenology is an essential developmental process in trees and an important component in understanding climate change. However, little is known about the regulation of leaf phenology in tropical trees.
To understand the regulation by temperature of leaf phenology in tropical trees, we performed daily observations of leaf production under rainfall-independent conditions using saplings of Shorea leprosula and Neobalanocarpus heimii, both species of Dipterocarpaceae, a dominant tree family of Southeast Asia. We analyzed the time-series data obtained using empirical dynamic modeling (EDM) and conducted growth chamber experiments.
Leaf production by dipterocarps fluctuated in the absence of fluctuation in rainfall, and the peaks of leaf production were more frequent than those of day length, suggesting that leaf production cannot be fully explained by these environmental factors, although they have been proposed as regulators of leaf phenology in dipterocarps. Instead, EDM suggested a causal relationship between temperature and leaf production in dipterocarps. Leaf production by N. heimii saplings in chambers significantly increased when temperature was increased after long-term low-temperature treatment. This increase in leaf production was observed even when only nighttime temperature was elevated, suggesting that the effect of temperature on development is not mediated by photosynthesis.
Because seasonal variation in temperature in the tropics is small, effects on leaf phenology have been overlooked. However, our results suggest that temperature is a regulator of leaf phenology in dipterocarps. This information will contribute to better understanding of the effects of climate change in the tropics.
叶片物候是树木发育的重要过程,也是理解气候变化的重要组成部分。然而,人们对热带树木叶片物候的调控机制知之甚少。
为了了解温度对热带树木叶片物候的调控作用,我们在无降雨影响的条件下,对龙脑香科两种树种——滇桐和望天树的幼树进行了为期一天的叶片生长观测。这两个树种都是东南亚优势树种龙脑香科的代表树种。我们利用经验动态建模(EDM)分析了获得的时间序列数据,并进行了生长室实验。
在没有降雨波动的情况下,龙脑香科植物的叶片生长出现波动,而且叶片生长的峰值比日照长度的峰值更为频繁,这表明尽管已有研究提出将这些环境因素作为龙脑香科植物叶片物候的调控因子,但它们并不能完全解释叶片的生长。相反,EDM 表明温度与龙脑香科植物叶片生长之间存在因果关系。经过长期低温处理后,当温度升高时,望天树幼苗在生长室内的叶片生长显著增加。即使仅提高夜间温度,也观察到了这种叶片生长的增加,这表明温度对发育的影响不是通过光合作用介导的。
由于热带地区温度的季节性变化较小,因此对叶片物候的影响一直被忽视。然而,我们的研究结果表明,温度是龙脑香科植物叶片物候的调控因子。这些信息将有助于更好地理解气候变化对热带地区的影响。