Response of Thai rice varieties under elevated CO2 concentrations

At maximum tillering until heading stage, net photosynthesis, stomatal conductance and transpiration will be measured in the flag leaf using an infrared gas analyzer system (LI-6400, Li-Cor Inc., USA). The steady-state fluorescence yield (Fs) will be measured after registering the gas-exchange parameters. A saturating light pulse will be applied to achieve the light-adapted maximum fluorescence (Fm'). The operating PSII photochemical efficiency (φPSII) will be determined as φPSII = (Fm' – Fs)/Fm'.