Description:
<jats:title>Abstract</jats:title><jats:p>Under future climates, leaf temperature (<jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content>) 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 <jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content> 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 <jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content>? We quantified how increases in the mean and variability of growth temperature affect leaf performance (mean net CO<jats:sub>2</jats:sub> assimilation rates, <jats:styled-content><jats:italic>A</jats:italic><jats:sub>net</jats:sub></jats:styled-content>; its variability; and time under near‐optimal photosynthetic conditions), as mediated by thermal acclimation. To this aim, the probability distribution of <jats:styled-content><jats:italic>A</jats:italic><jats:sub>net</jats:sub></jats:styled-content> was obtained by combining a probabilistic description of short‐ and long‐term changes in <jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content> with data on <jats:styled-content><jats:italic>A</jats:italic><jats:sub>net</jats:sub></jats:styled-content> responses to these changes, encompassing 75 genera and 111 species, including both C3 and C4 species. Our results show that (a) expected increases in <jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content> variability will decrease mean <jats:styled-content><jats:italic>A</jats:italic><jats:sub>net</jats:sub></jats:styled-content> and increase its variability, whereas the effects of higher mean <jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content> depend on species and initial <jats:styled-content><jats:italic>T</jats:italic><jats:sub><jats:italic>l</jats:italic></jats:sub></jats:styled-content>, and (b) acclimation reduces the effects of leaf warming, maintaining <jats:styled-content><jats:italic>A</jats:italic><jats:sub>net</jats:sub></jats:styled-content> at >80% of its maximum under most thermal regimes.</jats:p>