Response of two important tropical tree species of Meliaceae (Azadirachta indica -neem and Melia dubiamelia) to elevated levels of CO2 (600 and 900 ppm) under simulated temperature and moisture regimes in Automated Open Top Chambers was studied. Growth, biochemical changes, antioxidant property and gas exchange parameters were estimated. The results indicate that A. indica is expected to acclimatize under elevated CO2 concentrations whereas M. dubia was observed to be a species sensitive to elevated CO2 concentrations, affecting the photosynthetic machinery, stomatal conductance and transpiration and a subsequent decrease in carbohydrates, proteins, sugars, amino acids and phenolics. The short-term and long-term responses with respect to stomatal conductance and transpiration rates were higher in neem than melia. Thus, a positive response of neem to increased CO2 concentrations is a good indication for its future establishment in potentially changed climatic conditions.

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