Influence of CO2 concentration, light intensity, and sucrose concentration on net photosynthesis of citrus plantlets during in vitro propagation

Light curves of the CO2 gas exchange of irt vitro plantlets of citrus (Citrus limonia Osb. (Rutaceae)) were measured continuously in an open system using different CO2 concentrations (350, 1000, and 2000 mu l l(-1) CO2). The plantlets were grown in media with sucrose concentrations from 0 to 5% under light intensities of 60, 100, and 260 mu mol m(-2) l(-1). Before starting the measurements the plantlets were pretreated with 1000 mu l l(-1) CO2 for several weeks. Control plantlets were grown for the same period in gas tight vessels. CO2 concentration of the gas atmosphere inside the plant vessels had a stronger influence on CO2 gas exchange of citrus plantlets than sucrose concentration of the medium. Net photosynthesis of plantlets grown under various light intensities differed only little when using the same CO2 concentration for measurement as used for growing. After pretreatment with 1000 mu l l(-1) CO2 during growth, net photosynthesis of plantlets measured under 350 Cll l(-1) CO2 was higher compared to control plantlets.