Photosynthetic light and CO2 response curves
Photosynthetic response curves to light (A -PAR), CO2 (A -C i) were performed in completely expanded leaves from 45 day-old plants of all genotypes using a portable infrared gas exchange analyser (IRGA) (LiCor 6400XT, Lincoln, NE, USA). A -PAR curves were measured using 400 ppm CO2, block temperature at 28 °C and 10% of blue light, whilst A -C i were carried out using 1000 µmol photons m-2 s-1. A three component exponential rise to maximum equation was used to fit the photosynthetic curves: A = a (1 -e-bx ) + c , where A = photosynthetic rate, x = PAR or substomatal CO2concentration (C i), and a, b, c are parameters estimated by the non-linear regression (Watling, Press & Quick, 2000).