Water deficit also reduced Pn of
390 WS plants, while plants growing under elevated CO2 had offset
the effect of moderate water deficit, resulting in Pn rates in 750 WS
plants being similar to those of well-watered plants (390 WW
and 750 WW). Elevated CO2 concentrations have often been found
to reduce stomatal conductance and increase transpiration effi-
ciency, especially under water deficit conditions, conserving water
and thus maintaining photosynthetic capacity