Reduced photosynthetic thermal acclimation capacity under elevated ozone in poplar (Populus tremula) saplings

Abstract

The sensitivity of photosynthesis to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial carbon cycle response to future climate change. Although thermal acclimation of photosynthesis under rising temperature has been reported in many tree species, whether tropospheric ozone (O3) affects the acclimation capacity remains unknown. In this study, temperature responses of photosynthesis (light‐saturated rate of photosynthesis (Asat), maximum rates of RuBP carboxylation (Vcmax), and electron transport (Jmax) and dark respiration (Rdark) of Populus tremula exposed to ambient O3 (AO3, maximum of 30 ppb) or elevated O3 (EO3, maximum of 110 ppb) and ambient or elevated temperature (ambient +5°C) were investigated in solardomes. We found that the optimum temperature of Asat (ToptA) significantly increased in response to warming. However, the thermal acclimation capacity was reduced by O3 exposure, as indicated by decreased ToptA, and temperature optima of Vcmax (ToptV) and Jmax (ToptJ) under EO3. Changes in both stomatal conductance (gs) and photosynthetic capacity (Vcmax and Jmax) contributed to the shift of ToptA by warming and EO3. Neither Rdark measured at 25°C (Rdark25) nor the temperature response of Rdark was affected by warming, EO3, or their combination. The responses of Asat, Vcmax, and Jmax to warming and EO3 were closely correlated with changes in leaf nitrogen (N) content and N use efficiency. Overall, warming stimulated growth (leaf biomass and tree height), whereas EO3 reduced growth (leaf and woody biomass). The findings indicate that thermal acclimation of Asat may be overestimated if the impact of O3 pollution is not taken into account.

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

“…However, once the optimal temperature threshold of photosynthesis is exceeded, exposure to heat stress could cause the separation of the light‐harvesting complexes from the photosystem II (PSII) reaction center or the denaturation of proteins (Gounaris et al ., 1984 ; Yamane et al ., 1997 ). The consequences are reduced A sat, V c max, and J max with high temperatures (Medlyn et al ., 2002 ; Dai et al ., 2021 ; Dusenge et al ., 2021 ), a reduction of the maximum photochemical efficiency ( F v / F m ) and decreasing chlorophyll (Chl) concentrations. Variation in these responses largely depends on the species' temperature range.…”

High Temperature Acclimation of Leaf Gas Exchange, Photochemistry, and Metabolomic Profiles in Populus trichocarpa

“…Our observations directly support H1 and are largely consistent with the results of previous studies on temperature acclimation in poplar. 20,50,51 Hybrid poplar clones (P. maximowiczii x P. nigra and P. maximowiczii x P. balsamifera) 50 and P. tremula saplings 51 grown at an elevated temperature showed an increase in T Opt and acclimation of R d . 50 Equally, P. euramericana saplings at the same growth temperatures used in the present study (HGT, 35 °C and LGT, 25 °C) showed a considerable downward acclimation of P n , g s , and both dark (R d ) and light respiration (R l ).…”

Direct and Indirect Effects of Long-Term Field Warming Methods on the Physical Environment and Biological Responses in a Subtropical Forest

“…A sat for M. breviflora in CBMF and MEBF were mainly reduced by the direct effect of higher T soil , subsequently leading to lower water uptake from the soil, and lower g s . Higher T air directly increased g s of S. rehderianum in MEBF, leading to increasing A sat and growth (Dai et al, 2021). However, growth of S. rehderianum in CBMF was lower due to translocation warming.…”