Photosynthetic Gas Exchange, Photoassimilate Partitioning, and Development in Tomato under CO2 Enrichment

Interest in CO2 enrichment has focussed primarily on its application in horticultural greenhouse production (1). CO2 may be added to the greenhouse atmosphere to maintain a level of approximately 330ul/L or enriched to higher levels (eg. 700–1500 μ1/L) to further stimulate growth. Elevated CO2 levels are also experienced by crops in some outdoor production situations. Recently Wallis and Grodzinski (2) reported that sweet pepper plants grown inside polyethylene tunnels on mulched soil experienced CO2 levels exceeding 3000 μ1/L due to soil respiration and restricted gas exchange. Potential global increases in CO2 concentration have also stimulated interest in plant responses to altered CO2 levels (3). Growth and development of plants is associated with photosynthetic activity and partitioning of carbon (4) as well as with the action and integration of plant growth regulators (5). In this study determinate tomato plants were grown as transplant stock at CO2 concentrations of 300, 1000, and 3000 μ1/L. Their growth and photosynthetic metabolism was studied during the period of early vegetative development. Leaf ethylene metabolism was examined as it relates to leaf photosynthetic activity and potential growth regulation.