INFLUENCE OF CO2 ENRICHMENT REGIME ON PHOTOSYNTHESIS AND YIELD OF A TOMATO CROP

Tomato plants var.
Melody were grown in two greenhouses at the Centre de Recherches d’Avignon, in the South of France, where two CO₂ enrichment regimes were compared:

• Standard regime with setpoint at 1000 ppm, 6 hours per day (treatment C₁₀₀₀)

• Simulation of a CO₂ enrichment technique using the smoke exhausts from the boiler used to heat the greenhouse (treatment C_s).

We measured in situ photosynthesis of leaves at different periods during the experiment, first before enrichment was applied, then during the CO₂ enrichment period.

These measurements were analyzed by fitting a leaf photosynthesis model to the data for each period; this curve fitting showed that when the amount of CO₂ feeded to the plants is low (setpoint at 1000–1500 ppm ; less than 2 hours per day) there is no acclimation effect on leaf assimilation ; but when the enrichment is stronger (6 hours per day at 1000 ppm or 2 hours at 2500–3500 ppm) the acclimation effect reduces significantly the assimilation during the non-enriched hours of the day.

The number and weight of fruits produced was measured for each of the three trusses ; the analysis of these results shows that the C₅ treatment can give the same yield as the standard regime C₁₀₀₀, provided the maximum CO₂ concentration in the greenhouse is maintained below a limit of 2000–2500 ppm.

IV International Symposium on CO2 in Protected Cultivation

J.J. Longuenesse

https://doi.org/10.17660/ActaHortic.1990.268.5