Plants growing under elevated atmospheric CO2 concentrations often have reduced stomatal conductance and subsequently increased leaf temperature.
Šigut et al. find that this is indeed the case for broadleaved Fagus sylvatica and coniferous Picea abies saplings growing under elevated CO2, but that the higher leaf temperatures do not lead to an increased heat stress tolerance of primary photochemical reactions. The increases in temperature optima of photosynthetic CO2 uptake observed under elevated CO2 are instantaneous and are caused by reduced photorespiration and limitation of photosynthesis by RuBP regeneration. However, the increases disappear when plants are exposed to identical CO2 concentrations. The results therefore do not support the hypothesis that elevated CO2 leads to temperature acclimation of photosynthesis in the species studied.
This article appears in the special issue Plants and Climate Change.