Gas Exchange Measurements
Gas exchange measurements were performed in Pullman, WA, USA, with mean atmospheric pressure of 92.1 kPa. The mid portion of 3-5 uppermost, fully expanded leaves were used for gas exchange measurements using a LI-6400XT and a 2 x 3 cm leaf chamber with a red and blue light emitting diode light source (P/N 6400-02B, Li-Cor, Lincoln, NE, USA). Spot measurements were performed inside the growth chamber, and the light intensity, temperature, and relative humidity during gas exchange measurements were maintained similar to the growth chamber conditions under each treatment. Leaf-to-air vapor pressure deficit was kept at 1 kPa, flow rate maintained at 300 μmol air s-1, and oxygen partial pressure of 19.3 kPa (21 %).