Photosynthetic Rate During Steady-State Growth as Influenced by Carbon- Dioxide Concentration

Abstract

Cultivars of burley and flue-cured tobacco (Nicotiana tabacum L.) were allowed to attain steady-state exponential growth at 2 nitrate levels and in 400 or 1000 .mu.l/l CO2 in the ambient atmosphere. The unit leaf area rates of net CO2 exchange were measured at the same CO2 concentrations at which the plants were grown. The NCER [net CO2 exchange rate] were greater at 400 than at 1000 .mu.l/l CO2 in both cultivars and at both nitrate levels. The NCER were also greater in the flue-cured than in the burley cultivar and at the high nitrate level.