Can leaf net photosynthesis acclimate to rising and more variable temperatures?

Under future climates, leaf temperature (Tl) will be higher and more variable. This will affect plant carbon (C) balance because photosynthesis and respiration both respond to short‐term (subdaily) fluctuations in Tl and acclimate in the longer term (days to months). This study asks the question: To what extent can the potential and speed of photosynthetic acclimation buffer leaf C gain from rising and increasing variable Tl? We quantified how increases in the mean and variability of growth temperature affect leaf performance (mean net CO2 assimilation rates, Anet; its variability; and time under near‐optimal photosynthetic conditions), as mediated by thermal acclimation. To this aim, the probability distribution of Anet was obtained by combining a probabilistic description of short‐ and long‐term changes in Tl with data on Anet responses to these changes, encompassing 75 genera and 111 species, including both C3 and C4 species. Our results show that (a) expected increases in Tl variability will decrease mean Anet and increase its variability, whereas the effects of higher mean Tl depend on species and initial Tl, and (b) acclimation reduces the effects of leaf warming, maintaining Anet at >80% of its maximum under most thermal regimes. Under future climates, leaf temperatures will be higher and more variable, with effects on the plant carbon balance. This study asks the question: To what extent can leaf net photosynthesis acclimate to buffer leaf carbon gains from rising and increasingly variable leaf temperatures? A probabilistic description of short‐ and long‐term changes in leaf temperature is parameterized by means of a dataset on net photosynthetic responses to these changes, encompassing 75 genera and 111 species. Our results show that (a) the expected increases in leaf temperature variability have always detrimental effects on leaf performance, whereas the effects of higher mean leaf temperatures depend on the species and initial temperature, and (b) acclimation greatly reduces the consequences of leaf warming. [ABSTRACT FROM AUTHOR]