Faculté de foresterie, de géographie et de géomatique, Université Laval, Québec, QC, Canada.
Department of Biochemistry, University of Regina, Regina, SK, Canada.
PLoS One. 2019 Feb 11;14(2):e0206021. doi: 10.1371/journal.pone.0206021. eCollection 2019.
The mechanistic bases of thermal acclimation of net photosynthetic rate (An) 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 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 ten weeks, we measured leaf RuBisCO (RAR) and RuBisCO activase (RARCA) amounts and the temperature response of An, dark respiration (Rd), stomatal conductance, (gs), apparent maximum carboxylation rate of CO2 (Vcmax) and apparent 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 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 Vcmax 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 Vcmax and stomatal conductance in thermal acclimation of An.
叶片净光合速率（An）对温度的驯化机制仍难以确定，而且可用的数据集很少，特别是对于杂交杨树。本研究以 2 个杂交杨树无性系为材料，在两种日/夜温度（23°C/18°C 和 33°C/27°C）和低氮、高氮土壤条件下，研究了若干生化和生物物理性状对叶片净光合速率温度驯化的贡献。10 周后，我们测定了叶片 RuBisCO（RAR）和 RuBisCO 激活酶（RARCA）含量以及 An、暗呼吸（Rd）、气孔导度（gs）、CO2 最大羧化速率（Vcmax）和表观光合电子传递速率（J）的温度响应。结果表明，生长温度升高 10°C，导致无性系 M×B 和 M×N 的 An 温度最适点（Topt）分别向高温移动 6.2±1.6°C和 8.0±1.2°C，无性系 M×B 的 An 和 gs 在生长温度下增加，但无性系 M×N 则不然。RuBisCO 含量随氮水平增加而增加，但对生长温度不敏感；而 RARCA 含量及其短/长同工型的比例则因温暖条件而增加，无性系 M×B 在低氮条件下亦是如此。无性系 M×B 的表观 Vcmax 和表观 J 的活化能在温暖条件下降低，而无性系 M×N 则保持不变。本研究表明，RARCA、表观 Vcmax 和气孔导度的活化能均参与了 An 的温度驯化。
