摘要 : Tropical forests are experiencing unprecedented high-temperature conditions due to climate change that could limit their photosynthetic functions. We studied the high-temperature sensitivity of photosynthesis in a rainforest site ... 展开 Tropical forests are experiencing unprecedented high-temperature conditions due to climate change that could limit their photosynthetic functions. We studied the high-temperature sensitivity of photosynthesis in a rainforest site in southern Amazonia, where some of the highest temperatures and most rapid warming in the Tropics have been recorded. The quantum yield (F- v/F- m) of photosystem II was measured in seven dominant tree species using leaf discs exposed to varying levels of heat stress. T-50 was calculated as the temperature at which F- v/F- m was half the maximum value. T-5 is defined as the breakpoint temperature, at which F- v/F- m decline was initiated. Leaf thermotolerance in the rapidly warming southern Amazonia was the highest recorded for forest tree species globally. T-50 and T-5 varied between species, with one mid-storey species, Amaioua guianensis, exhibiting particularly high T-50 and T-5 values. While the T-50 values of the species sampled were several degrees above the maximum air temperatures experienced in southern Amazonia, the T-5 values of several species are now exceeded under present-day maximum air temperatures. 收起