The heat tolerance of photosystem II (PSII) may promote carbon assimilation at higher temperatures and help explain plant responses to climate change. Higher PSII heat tolerance could lead to (a) increases in the high-temperature compensation point (T_max); (b) increases in the thermal breadth of photosynthesis (i.e. the photosynthetic parameter Ω) to promote a thermal generalist strategy of carbon assimilation; (c) increases in the optimum rate of carbon assimilation P_opt and faster carbon assimilation and/or (d) increases in the optimum temperature for photosynthesis (T_opt). To address these hypotheses, we tested if the T_crit, T₅₀ and T₉₅ PSII heat tolerances were correlated with carbon assimilation parameters for 21 plant species. Our results did not support Hypothesis 1, but we observed that T₅₀ may be used to estimate the upper thermal limit for T_max at the species level, and that community mean T_crit may be useful for approximating T_max. The T₅₀ and T₉₅ heat tolerance metrics were positively correlated with Ω in support of Hypothesis 2. We found no support for Hypotheses 3 or 4. Our study shows that high PSII heat tolerance is unlikely to improve carbon assimilation at higher temperatures but may characterize thermal generalists with slow resource acquisition strategies.

中文翻译：

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光系统 II 耐热性表征热通才和碳同化的上限

光系统 II (PSII) 的耐热性可能会促进更高温度下的碳同化，并有助于解释植物对气候变化的反应。较高的 PSII 耐热性可能导致 (a) 高温补偿点 (T _max ) 增加；(b) 增加光合作用的热广度（即光合参数Ω）以促进碳同化的热通才策略；(c) 增加碳同化的最佳速率 P _opt和更快的碳同化和/或 (d) 增加光合作用的最佳温度 (T _opt )。为了解决这些假设，我们测试了 T _crit、T ₅₀和 T ₉₅PSII 耐热性与 21 种植物的碳同化参数相关。我们的结果不支持假设 1，但我们观察到 T ₅₀可用于估计物种水平上 T _{max 的}热上限，并且群落平均 T _crit可能有助于近似 T _max。T ₅₀和 T ₉₅耐热性指标与 Ω 正相关，支持假设 2。我们发现没有支持假设 3 或 4。我们的研究表明，高 PSII 耐热性不太可能在较高温度下改善碳同化，但可以表征具有缓慢资源获取策略的热学通才。