Response of tomato plants to saline water as affected by carbon dioxide supplementation. I. Growth, yield and fruit quality

Tomato plants (Lycopersicon esculentum (L.) Mill. cv. F144) were irrigated with low concentrations of mixed salts; the highest level (E.C. 7 dS m^-1) simulated conditions used to produce quality tomatoes in the Negev highlands. CO₂ enrichment (to 1200 μmol mol^-1, given during the daytime) increased plant growth at the early stage of development. However, later growth enhancement was maintained only when combined with salt stress. In the absence of CO₂ supplementation, overall growth decreased with salt (7 dS m^-1) to 58% and fresh biomass yields to 53% of the controls. However, under elevated CO₂ concentrations total plant dry biomass was not reduced by salt stress. CO₂ enrichment of plants grown with 7 dS m^-1 salt increased total fresh fruit yields by 48% and maintained fruit quality in terms of total soluble salts, glucose and acidity. Fruit ripening was about 10 d earlier under CO₂ enrichment, regardless of salinity treatment. It is suggested that a combined utilization of brackish water and CO₂ supplementation may enable the production of high-quality fruits without incurring all the inevitable loss in yields associated with salt treatment.