On the Relationships of Net CO2 Assimilation and Leaf Expansion to Vegetative Growth in Lycospersicum esculentum, var Jubilee

Relationships between net plant CO(2) exchange rate (CER) and canopy development were examined in ;jubilee' tomato over the initial 4 weeks of vegetative growth. A comparison was made between two plant groups that were alternatively exposed to 200 or 800 microeinsteins per square meter per second midday irradiation to establish a differential in net CER. Plants exposed to higher irradiation demonstrated a 2- to 4-fold greater net photosynthetic rate per leaf area and 100% average higher net CO(2) assimilation rate/plant. day. However, leaf-stem growth differed by <50% suggesting a poor relationship to CER. Leaf area growth rate (LAGR) of individual leaves appeared closely related to CER during initial leaf expansion but a greater function of order of emergence in successive leaf growth. LAGR on a per plant basis increased linearly with leaf dry weight but appeared more limited by factors determining maximum leaf enlargement and rate of new leaf development. Net CO(2) assimilation/leaf area and leaf starch consistently declined with time while net CO(2) assimilation plant/day approached a constant rate following 2 to 3 weeks growth. Composite results suggested a simple relationship for sucessive growth where accumulated leaf carbohydrate in excess of 200 milligrams/plant.day could be expected to be partitioned to other plant segments.