Photosynthèse de la primevère (Primula obconica Hance): Effets du gaz carbonique et de l’éclairement

Abstract

Net CO2 exchange rates were measured on a 1 m2 crop of Primula obconica placed in a closed loop growing chamber as a function of irradiation and CO2 concentration. Greenhouse cultivation with CO2 enrichment (700 ppm) or without (350 ppm) had only very little effect on dry weight or on flowering rate and did not modify photosynthetic capacity of primrose. Productivity differences between horticultural techniques, such as supplemental lighting and/of CO2 enrichment, can be partly explained 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. Key words: Primula obconica, net assimilation, carbon dioxide air concentration, light intensity, carbon fertilization

Characteristics of leaf photosynthesis and simulated individual carbon budget in Primula nutans under contrasting light and temperature conditions

“…The leaf carbon gain might thus be underestimated if the actual photosynthetic rate decreased with leaf aging. Other Primula species tend to exhibit large seasonal variation in photosynthetic capacity (Whale 1983;Combe et al 1993). However, since P. nutans can be considered as a simultaneous species, which all the leaves open as a flush during a short period, the carbon gain of individual ramets may not change so much because simultaneous leaf-open species tend to have a slow decrease of canopy photosynthesis during leaf aging (Kikuzawa 2003).…”

“…Even for the genus Primula there are only a few reported studies dealing with photosynthesis (Whale 1983;Combe et al 1993;Noda et al 2004Noda et al , 2007. Whale (1983) reported that the maximum photosynthetic rate of three Primula species declined steadily as the growing season advanced; this suggests the importance of early spring in the carbon economy of these species.…”