Carbon Dioxide Enrichment in `Virosa' Tomato Plant: Responses to Enrichment Duration and to Temperature

Responses of the tomato ( Lycopersicon esculentum Mill. cv. Virosa) plant to elevated CO 2 concentrations applied throughout the photoperiod or part of it were studied under two temperature regimes. Plants were exposed to CO 2 at 340 (control), 700, and 1000 μl·liter –1 . The highest concentration was applied only at 22/16C (day/night) and 700 μl·liter –1 at 22/16C and 25/16C. Transpiration rates were lower and photosynthetic rates were higher under elevated CO 2 than at the ambient level. Biomass production was higher only for plants grown at 700 μl·liter –1 and 25/16C. Concentrations of macronutrients were lower in plants exposed to 1000 μl CO 2 /liter than in the control plants. Intermittent CO 2 was applied using two timing methods. In method 1, plants were exposed to 4- or 8-hour high-CO 2 concentrations during their 12-hour photoperiod. In method 2, plants were exposed for 3.5 days of each week to 700 μl CO 2 /liter. Only two of the 8-hour exposures resulted in greater growth than the controls. The lack of higher growth for CO 2 -enriched plants at 22/16C was attributed to a higher dark respiration rate and to a lack of efficient transport of photosynthates out of leaves.