Photosynthetic rate (An) and stomatal conductance (gs) were
measured twice (70 and 90 days after sowing) from the upper
canopy fully expanded leaves (two leaves per plant and four
leaves per treatments) between 11:00 and 14:00 h with a portable
photosynthetic system (CIRAS-2, PP Systems, Hitchin, UK). Measurements
were performed on 1.7 cm2 of leaf area at 400 mol ml−1
of CO2 and 1000 mol m−2 s−1 of photosynthetic active radiation
(PAR). Chlorophyll content index (CCI) was measured with portable
CCM-200 (Opti-Science, Tyngsboro, MA, USA) on the same leaves
used for gas exchange measurement.