Measurements were carried out under white fluorescence lamps in the climate chamber adopting standardized settings : CO2 concentration 350±5 ppm,light intensity 100±5 molm−2 s−1 PAR, a boundary layer resistance(Rb)of 0.27m2 s mol−1 and a leaf chamber air flow rate of 200 mlmin−1. Net photosynthetic rate(Pn)was measured on the same leaf used for the chlorophyll fluorescence measurements(10 plants per treatment, one measurement per plant).