A METHOD FOR THE STUDY OF CO-2 EXCHANGES IN INVITRO CULTURED VITIS-RUPESTRIS PLANTLETS

A CO2 assay circuit adapted to in vitro culture was designed to investigate CO2 exchanges in test tube-grown Vitis rupestris plantlets. The CO2 concentration of the air in culture tubes was measured by injection of samples in the open circuit. It was observed under the culture conditions used that the CO2 content stabilized during the light phase at 3 times the CO2 compensation point. Measurements of dark respiration under closed circuit conditions at every two-hour interval during the night did not reveal any limiting by lack of the substrate under mixotrophic culture conditions. A mathematical model of the influence of ambient CO2 concentration on net CO2 uptake rates under closed circuit conditions was devised and used to compare net photosynthesis at different lighting levels. Measurement of CO2 evolution into CO2-free air under open circuit conditions revealed a postillumination burst characteristic of photorespiration which increased with the temperature.