Smithsonian Tropical Research Institute, P.O. Box 0843-03092, Balboa, Ancón, Republic of Panama.
J Plant Physiol. 2013 Jun 15;170(9):822-7. doi: 10.1016/j.jplph.2013.01.005. Epub 2013 Feb 8.
Global warming and associated increases in the frequency and amplitude of extreme weather events, such as heat waves, may adversely affect tropical rainforest plants via significantly increased tissue temperatures. In this study, the response to two temperature regimes was assessed in seedlings of the neotropical pioneer tree species, Ficus insipida. Plants were cultivated in growth chambers at strongly elevated daytime temperature (39°C), combined with either close to natural (22°C) or elevated (32°C) nighttime temperatures. Under both growth regimes, the critical temperature for irreversible leaf damage, determined by changes in chlorophyll a fluorescence, was approximately 51°C. This is comparable to values found in F. insipida growing under natural ambient conditions and indicates a limited potential for heat tolerance acclimation of this tropical forest tree species. Yet, under high nighttime temperature, growth was strongly enhanced, accompanied by increased rates of net photosynthetic CO2 uptake and diminished temperature dependence of leaf-level dark respiration, consistent with thermal acclimation of these key physiological parameters.
全球变暖以及极端天气事件（如热浪）频率和幅度的增加，可能会通过显著升高组织温度对热带雨林植物产生不利影响。在这项研究中，评估了两种温度条件对新热带先锋树种榕属植物幼苗的影响。在生长室中，将植物在白天强烈升高的温度（39°C）下进行培养，同时夜间温度接近自然温度（22°C）或升高（32°C）。在这两种生长条件下，由叶绿素 a 荧光变化确定的不可逆叶片损伤的临界温度约为 51°C。这与在自然环境条件下生长的榕属植物的值相当，表明该热带森林树种对热胁迫的适应能力有限。然而，在高温夜间条件下，生长得到了极大的促进，伴随着净光合 CO2 吸收速率的增加和叶片暗呼吸对温度依赖性的降低，这些关键生理参数的热适应作用得到了证实。
