Photosynthesis (A) was measured as a function of internal CO2 concentration
(Ci), A/Ci response curves, using a portable gas exchange
system (LI-COR 6400); leaf temperature was 25°C and leaf vapor pressure
deficitwas at;1.160.5 kPa. Leaveswere initially stabilized in the cuvette
at a saturating PPFD of 1200 mmol m22 s21 (provided by a red-blue light
source) and 400 mmol mol21 CO2 concentration. Measurements of A and
Ci were taken when A was stable. Subsequently, CO2 concentration was
decreased stepwise to 50 mol mol21 before returning to 400 mmol mol21
and then increased stepwise to 1600 mol mol21 CO2, and measurements
recorded when A was stabilized. Values of A and Ci were calculated using
the equations of (von Caemmerer and Farquhar, 1981).