At 17 DAS, photosynthetic rate (Pn) and transpiration rate were determined on the second fully expanded leaf with an Arabidopsis leaf chamber (6400-15 Arabidopsis Chamber, 0.785 cm2, LI-COR, Lincoln, NE,USA)mountedonaninfraredCO2/H2O analyzer (LI-6400 Portable Photosynthesis System, LI-COR)