Growth under elevated CO2 concentration affects the temperature response of photosynthetic rate

Abstract

In this study, we tested the hypothesis that an elevated CO2 concentration leads to a shift of the temperature optimum of the photosynthetic rate in trees. Since the elevated CO2 treatment usually leads to a significant decrease in stomatal conductance and consequently to decrease in transpiration followed by an increase in leaf temperature, we hypothesized that elevated CO2 results in the acclimation of photosynthetic apparatus to the higher temperature.We studied the two most common species in the Czech Republic – European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karsten). The eight-year-old trees were grown in glass domes at the experimental research site Bílý Kříž in the Beskydy Mts. and they were exposed to ambient (AC; 385 µmol CO2 mol-1) and elevated CO2 concentrations (EC; 700 µmol CO2 mol-1). Based on the gas-exchange and fluorescence techniques we determined the basic photosynthetic characteristics in the range of leaf temperatures from 10 to 45 °C. The changes in temperature acclimation of tree species studied were evaluated on the basis of the shift of temperature optima. EC treatment led indeed to an increase of leaf temperature up to 3.5 °C in both species studied. The temperature optimum of the light-saturated rate of CO2 assimilation, measured at the growth CO2 concentration (i.e. 385 for AC and 700 µmol CO2 mol-1 for EC trees), was higher by 3 °C in both tree species of the EC variant. Although the shift in photosynthetic temperature optimum disappeared when the AC plants were exposed to an elevated CO2 concentration, an acclimation of Rubisco carboxylation and electron transport to higher temperature was observed.

Impact of warmer and drier conditions on tree photosynthetic properties and the role of species interactions

“…Moreover, Holišová et al . ( 2013 ) showed that beech has an optimal foliar temperature of about 24.5°C for A sat . We observed a mean air temperature of around 29°C between 09:00 and 16:00 h in the middle of the growing season (i.e.…”

“…S2 ), suggesting that trees grown at warmer temperatures tended to acclimate for the optimum temperature of J max and V c max (Kattge & Knorr, 2007 ). Overall, our findings suggest that beech will suffer from a warming atmosphere (Šimpraga et al ., 2011 ; Holišová et al ., 2013 ), while oak may benefit from temperature rise in temperate climates where heat stress is not yet limiting this species (Arend et al ., 2013 ; Kuster et al ., 2014 ). As shown in our study, photosynthetic responses to chronic warming are highly dependent of local climatic conditions and species' origin.…”

Chronic warming and dry soils limit carbon uptake and growth despite a longer growing season in beech and oak

“…Therefore, variations in these responses depend on species-specific sensitivity to temperature. Beech typically grows in a mild climate and has a T opt around 24.5 °C ( Holišová et al 2013 ) whereas downy oak ( Quercus pubescens Willd.) usually grows in Mediterranean areas with a T opt of about 26 °C ( Ilnitsky et al 2021 ).…”