EFFECTS OF CARBON-DIOXIDE AND LIGHT ON PH OTOSYNTHESIS OF PRIMROSE (PRIMULA-OBCONICA HANCE)

Net CO2 exchange rates were measured on a 1 m2 crop of Primula obconic a placed in a closed loop growing chamber as a function of irradiation and CO2 concentration. Greenhouse cultivation with CO2 enrichment (70 0 ppm) or without (350 ppm) had only very little effect on dry weight or on flowering rate and did not modify photosynthetic capacity of pri mrose. Productivity differences between horticultural techniques, such as supplemental lighting and/or CO, enrichment, can be partly explain ed by study of photosynthesis curves: light increase is more efficient than carbon dioxide increase, the latter giving the best results with young primroses under strong irradiation.