Measurements of gas exchange
Gas exchange was determined using flag leaves or the lastest expand leaves treated for 10 days by a gas exchange system (LI 6800). Air flow rate and CO2 concentration were maintained at 750 μmol s-1 and 400 μmol mol-1, respectively. Data including the area-based light-saturated net photosynthetic rate (A sat), stomatal conductance (g s), transpiration rate (E ), intercellular CO2concentration (C i) and ambient CO2 concentration (C a) were obtained as described previously (Li et al ., 2018).