Thermal acclimation of photosynthetic activity and RuBisCO content in two hybrid poplar clones
2019
Benomar, Lahcen | Zwiazek, Janusz J. | Moutaoufik, Mohamed Taha | Elferjani, Raed | Isabel, Nathalie | DesRochers, Annie | El Guellab, Ahmed | Khlifa, Rim | Idrissi Hassania, Lala Amina
The mechanistic bases of thermal acclimation of net photosynthetic rate (A n ) are still difficult to discern, and the data sets available are scarce, particularly for hybrid poplar. In the present study, we examined the contribution of a number of biochemical and biophysical traits on thermal acclimation of A n 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 ten weeks, we measured leaf RuBisCO (RAR) and RuBisCO activase (RARCA) amounts and the temperature response of A n , dark respiration (R d ), stomatal conductance, (g s ), apparent maximum carboxylation rate of CO 2 (V cmax ) and apparent photosynthetic electron transport rate (J). Results showed that a 10°C increase in growth temperature resulted in a shift in thermal optimum (T opt ) of A n of 6.2±1.6 °C and 8.0±1.2 °C for clone M×B and M×N respectively, and an increased A n and g s 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 RARCA amount and the ratio of its short to long isoform was stimulated by the warm condition for clone M×N and at low N for clone M×B. The activation energy of apparent V cmax and apparent J decreased under the warm condition for clone M×B and remained unchanged for clone M×N. Our study demonstrated the involvement of both RARCA, the activation energy of apparent V cmax and stomatal conductance in thermal acclimation of A n.
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