Effect of CO sub 2 enriched air on the kinetics of leaf expansion. [Pisum sativa; Glycine max]

Vegetative plants of Pisum sativum (pea) and Glycine max (soybean) were transferred from 350 to 1,200 ppm CO{sub 2} when they had one (pea) or two (soybean) mature leaves and several developing leaves. Controls were kept at 350 ppm. For pea, high CO{sub 2} for 8 days increased dry mass of root, stem, and leaf fractions by 30-50%. Leaf dry mass increase was due primarily to carbohydrate, particularly starch. Dawn levels of starch increased 10-fold within 1 day at high CO{sub 2} and 20-fold at 2 days. At 2 days after transfer leaf starch levels were 1.0 mg cm{sup {minus}2} of leaf area or nearly 30% of leaf dry weight. Soybean data are less complete, but 10 days at high CO{sub 2} increased leaf + stem dry mass by 50% and leaf weight per unit area increased by 14 and 48% at dawn within 1 and 2 days, respectively, at high CO{sub 2}. However 8-10 days at high CO{sub 2} increased total leaf area only slightly (about 15%) for both species, with all the leaf area increase occurring at nodes that were nearly microscopic at the time of transfer. For soybean, most of the increased leaf area due to highmore » CO{sub 2} was from lateral bud break despite a high CO{sub 2} did not stimulated more leaves per plant. Apparently, extra photosynthate had a delayed effect on leaf expansion and did not increase nodes along the main axis. Leaf expansion under high CO{sub 2} was not limited by photosynthate.« less