Thermal acclimation of photosynthetic activity and Rubisco content in two hybrid poplar clones

Abstract

The mechanistic bases of thermal acclimation of net photosynthetic rate (An) are still difficult to discern and empirical research remains limited, particularly for hybrid poplar. In the present study, we examined the contribution of a number of biochemical and biophysical traits on thermal acclimation of An for two hybrid poplar clones. We grew cuttings of Populus maximowiczii × Populus nigra (M×N) and Populus maximowiczii × Populus balsamifera (M×B) clones under two day/night temperature of 23°C/18°C and 33°C /27°C and under low and high soil nitrogen level. After 10 weeks, we measured leaf RuBisCO and RuBisCO activase (RCA) amounts and the temperature response of An, dark respiration (Rd), stomatal conductance, (gs), maximum carboxylation rate of CO2 (Vcmax) and photosynthetic electron transport rate (J). Results showed that a 10°C increase in growth temperature resulted in a shift in thermal optimum (Topt) of An of 6.2±1.6 °C and 8.0±1.2 °C for clone M×B and M×N respectively, and an increased An and gs at the growth temperature for clone M×B but not M×N. RuBisCO amount was increased by N level but was insensitive to growth temperature while RCA amount and the ratio of its short to long isoform was stimulated by warm condition for clone M×N and at low N for clone M×B. The activation energy of Vcmax and J decreased under warm condition for clone M×B and remain unchanged for clone M×N. Our study demonstrated the involvement of both RCA, activation energy of Vcmax and stomatal conductance in thermal acclimation of An.

Pfam domain adaptation profiles reflect plant species’ evolutionary history

“…Unlike both Arabidopsis and poplar, maize is a C4 grass species adapted to grow in hot environments, and maize net photosynthesis is maximized between 30-35℃ [56]. In contrast, net photosynthesis reaches a maximum in poplar between 25-30℃ [57] and Arabidopsis maximum photosynthetic rate occurs around 25℃ [58]. We hypothesize that the observed difference in leaf and root protein temperature profiles in maize reflects the higher temperatures in which this species is photosynthetically active.…”