Can leaf net photosynthesis acclimate to rising and more variable temperatures?
Plant Cell Environ. 2019 Feb 1 [Epub ahead of print]
Vico G, Way DA, Hurry V, Manzoni S

Abstract
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 (sub-daily) 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 increasingly 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: i) 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 ii) acclimation reduces the effects of leaf warming, maintaining Anet at >80% of its maximum under most thermal regimes.

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