Effect of Higher CO2 Concentration on Photosynthesis in Codiaeumvariegatum Under Different Sky Conditions

The objective of this study was to evaluate the effect of different CO₂ concentrations that influences photosynthesis of Codiaeumvariegatumunder different sky conditions. Accordingly, diurnal changes in photosynthetic responses among plants grown at ambient concentration (AC) and elevatedconcentration (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, xanthophyllsdependent 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.