Interactions of Elevated CO2 Concentration and Drought Stress on Photosynthesis in Eucalyptus Cladocalyx F. Muell

Response of net photosynthetic rate (P _N), stomatal conductance (g _s), intercellular CO₂ concentration (c _i), and photosynthetic efficiency (F_v/F_m) of photosystem 2 (PS2) was assessed in Eucalyptus cladocalyx grown for long duration at 800 (C₈₀₀) or 380 (C₃₈₀) µmol mol^-1 CO₂ concentration under sufficient water supply or under water stress. The well-watered plants at C₈₀₀ showed a 2.2 fold enhancement of P _N without any change in g _s. Under both C₈₀₀ and C₃₈₀, water stress decreased P _N and g _s significantly without any substantial reduction of c _i, suggesting that both stomatal and non-stomatal factors regulated P _N. However, the photosynthetic efficiency of PS2 was not altered.