Stomatal conductance (gs) and water use efficiency (WUE)
The CO2 assimilation rate, measured at 400 µmol photons m-2 s-1, was 14% and 19% higher in CAx3 and CAx5 than in the VC (Fig. 6c ). It is important to note that increases in photosynthetic rates were associated with decreases in stomatal conductance and transpiration rates in the transgenic lines. Stomatal conductance decreased by 7% - 13% in the transgenics, as compared to VC plants (Fig. 6d ). Consequently, the transpiration rate decreased by 7% -10% in FbβCA overexpressor plants (Fig. 6e ). Therefore, the water use efficiency, which is the ratio of the CO2 assimilation rate to the transpiration rate (μmol CO2 m-2s-1/mmol H2O m-2s-1) was higher by 22% and 26% in CAx3 and CAx5, respectively, than that in VC (Fig. 6f ).