Plant thermal tolerance is a crucial research area as the climate warms and extreme weather events become more frequent. Leaves exposed to temperature extremes have inhibited photosynthesis and will accumulate damage to PSII if tolerance thresholds are exceeded. Temperature-dependent changes in basal chlorophyll fluorescence (T-F₀) can be used to identify the critical temperature at which PSII is inhibited. We developed and tested a high-throughput method for measuring the critical temperatures for PSII at low (CT_MIN) and high (CT_MAX) temperatures using a Maxi-Imaging fluorimeter and a thermoelectric Peltier plate heating/cooling system. We examined how experimental conditions of wet vs dry surfaces for leaves and heating/cooling rate, affect CT_MIN and CT_MAX across four species. CT_MAX estimates were not different whether measured on wet or dry surfaces, but leaves were apparently less cold tolerant when on wet surfaces. Heating/cooling rate had a strong effect on both CT_MAX and CT_MIN that was species-specific. We discuss potential mechanisms for these results and recommend settings for researchers to use when measuring T-F₀. The approach that we demonstrated here allows the high-throughput measurement of a valuable ecophysiological parameter that estimates the critical temperature thresholds of leaf photosynthetic performance in response to thermal extremes.

随着气候变暖和极端天气事件变得越来越频繁，植物的耐热性是一个至关重要的研究领域。暴露于极端温度下的叶片会抑制光合作用，如果超过耐受阈值，则会对PSII造成损害。基底叶绿素荧光的温度依赖性变化（T - F ₀）可用于鉴定PSII被抑制的临界温度。我们开发并测试了一种高通量方法，用于在低温（CT _MIN）和高温（CT _MAX）下测量PSII的临界温度）的温度使用Maxi-Imaging荧光计和热电珀尔帖板加热/冷却系统。我们检查了湿和干表面的叶片和加热/冷却速率的实验条件如何影响四种物种的CT _MIN和CT _MAX。无论在潮湿表面还是干燥表面上，CT _MAX估计值均无差异，但在潮湿表面上，叶片的耐寒性显然较弱。加热/冷却速率对CT _MAX和CT _MIN都有很强的影响，这是特定于物种的。我们讨论了产生这些结果的潜在机制，并建议研究人员在测量T - F时要使用的设置₀。我们在这里演示的方法可以对有价值的生态生理参数进行高通量测量，该参数可估计叶片对光热响应的极限温度阈值，以应对极端温度。