Data from: Photosynthetic acclimation to warming in tropical forest tree seedlings

Tropical forests have a mitigating effect on man-made climate change by acting as a carbon sink. For that effect to continue, tropical trees will have to acclimate to rising temperatures, but it is currently unknown whether they have this capacity. We grew seedlings of three tropical tree species over a range of temperature regimes (TGrowth = 25, 30, 35 °C) and measured the temperature response of photosynthetic CO2 uptake. All species showed signs of acclimation: the temperature-response curves shifted, such that the temperature at which photosynthesis peaked (TOpt) increased with increasing TGrowth. However, although TOpt shifted, it did not reach TGrowth at high temperature, and this difference between TOpt and TGrowth increased with increasing TGrowth, indicating that plants were operating at supra-optimal temperatures for photosynthesis when grown at high temperatures. The high-temperature CO2 compensation point did not increase with TGrowth. Hence, temperature-response curves narrowed with increasing TGrowth. TOpt correlated with the ratio of the RuBP regeneration capacity over the RuBP carboxylation capacity, suggesting that at high TGrowth photosynthetic electron transport rate associated with RuBP regeneration had greater control over net photosynthesis. The results show that although photosynthesis of tropical trees can acclimate to moderate warming, carbon gain decreases with more severe warming.热带森林通过充当碳汇（carbon sink），对人为气候变化发挥着重要的缓解作用。若要维持这一效应，热带树木必须适应不断升高的气温，但目前尚不清楚它们是否具备该适应能力。本研究在一系列生长温度（TGrowth = 25、30、35 ℃）条件下培育了三种热带树种的幼苗，并测定了光合CO₂吸收的温度响应特性。所有供试树种均表现出温度适应迹象：其温度响应曲线发生偏移，光合速率峰值对应的温度（TOpt）随生长温度升高而上升。不过，尽管TOpt发生了偏移，但在高温条件下其并未达到TGrowth水平，且TOpt与TGrowth的差值随TGrowth升高而增大，这表明植株在高温环境下培育时，光合作用处于超适温运行状态。高温下的CO₂补偿点并未随TGrowth升高而上升，因此温度响应曲线的宽度随TGrowth升高而变窄。TOpt与RuBP（核酮糖-1,5-二磷酸）再生能力和RuBP羧化能力的比值呈显著相关，这表明在高生长温度条件下，与RuBP再生相关的光合电子传递速率对净光合速率具有更强的调控作用。研究结果显示，尽管热带树木的光合作用能够适应适度升温，但随着变暖程度加剧，其碳增益能力会出现下降。