Effect of Higher CO2 Concentration on Photosynthesis in Codiaeum Variegatum under Different Sky Conditions

The objective of this study was to evaluate the effect of different CO2concentrations that influences photosynthesis of Codiaeum variegatum under different sky conditions. Accordingly, diurnal changes in photosynthetic responses among plants grown at ambient concentration (AC) and elevated concentration (EC) of CO2 were studied under contrasting sky conditions. EC stimulated the daily sum of fixed CO2 and light use efficiency under clear sky. Both these parameters were reduced under cloudy sky compared with AC treatment. Photosynthesis rate was reduced under cloudy sky particularly associated with EC-stimulated, xanthophylls dependent thermal dissipation of absorbed light energy. Anoticeable depression of CO2 assimilation rate was found in sun-adapted leaves under EC compared with AC conditions in case of clear sky condition, in the afternoon.