Infrared gas analyzer measurements (IRGA)
The gas exchange rate of 4week-old plants was measured using a LI-6400XT portable photosynthesis system (Li-Cor Biosciences Inc.). Five individual plants, grown under short-day conditions (8-h light provided by cool white fluorescent bulbs, 100 µM m-2s-1, 22 °C; 16-h dark, 20 °C) were used for each experiment. For the light-dependent tests, the whole-plant chamber was set up with the following parameters: 200 µmol/sec flow rate, 20◦C block temperature, 50–70% relative humidity, and 400 µmol/mol [CO2]. For differential light conditions, the plants were dark-exposed (0 PAR) for 30 min and then light-exposed (400 PAR) for 30 min followed by another dark (0 PAR) phase for 30 min. The data was logged every 30 sec. The LI-6400XT portable photosynthesis system (Li-Cor Biosciences Inc.) generates the raw data for the rate of transpiration over time with a default value for the area of the plants. Following the gas exchange rate measurement, ImageJ was used to determine the plant’s area (Schindelin et al., 2012). The rate of transpiration measurement was automatically standardized on the plant area by adding this value to the raw data from the LI-6400XT device. Furthermore, the time scale was modified in accordance with the experiment. For instance, the graph’s x-axis can be modified to show 30 minutes on the negative scale and 60 minutes on the positive scale once the time point 0 is set at 400 PAR light. Data presented are means of at least three leaves from individual plants for each experiment. Experiments were repeated at least three times.