Photosynthetic response to temperature
The responses of net photosynthesis (Asat) to temperature were measured about two weeks after commencing the water deficit treatment (i.e. 51 and 58 DAP for warm and cool grown plants, respectively). Five plants within each temperature × water treatment combination were randomly selected and were transferred to a vacant bay to manipulate the measurement temperature. Measurements were carried out between 0930 and 1400 h to ensure irradiance was not limiting. Temperature in the glasshouse bay was initially cooled down to 15oC, and then warmed up to 45oC at 5oC intervals. Once the desired temperature was achieved, plants were maintained at each targeted temperature for at least 30 min before measurements were taken to maximize the equilibrium between leaf and air temperature. Asat was then recorded at saturated PPFD (1200 µmol m-2s-1) and growth CO2 concentration (420 ppm) , with the temperature in the cuvette tracking the ambient air temperature. Photosynthesis temperature (AT) response curves were generated by plotting Asat against its corresponding leaf temperature.