Physiological analysis
Net CO2 assimilation (A) ,G s, and transpiration (E) and VPD were measured in the sixth to ninth leaves of WT and oxPtrWRKY75plants using an infrared gas analysis system (LI-COR 6400, Lincoln, NE, USA) as previously described (Wang et al. , 2016). Eighteen plants were analyzed (six per line). The LI-COR 6400 infrared gas analysis system was used to measure light and CO2 curves in fully expanded leaves of plants grown in a greenhouse for 2 months under normal conditions. Light curves were measured at photosynthetically active radiation intensities of 1800, 1500, 1200, 1000, 800, 600, 400, 200, 150, 100, 80, 50, 20, and 0 µmol/m2/s with 450 µmol/mol external CO2.
Chlorophylls were extracted from detached leaves of WT andoxPtrWRKY75 plants with 80% acetone. A UV/visible spectrophotometer (YHB-061; GE Healthcare, Little Chalfont, Buckinghamshire, UK) was used to measure absorbance at 663 and 645 nm, and then chlorophyll contents were calculated as described elsewhere (Lichtenthaler, 1987; Wanget al. , 2016).
Chlorophyll fluorescence parameters were measured using a Dual-PAM-100 measuring system (Walz Heinz GmbH, Effeltrich, Germany) after 15 min of dark adaptation for each plant.
To measure biomass, the aboveground parts of plants were collected, killed by heating at 105 °C for 15 min, and then dried at 65 °C to constant weight and weighed.