INTERACTION OF TEMPERATURE AND CO2 ENRICHMENT ON SOYBEAN: PHOTOSYNTHESIS AND SEED YIELD

Abstract

Seed yield and photosynthetic responses of soybean (Glycine max L. Merr. ’Ransom’) were studied in growth chambers at day/night temperatures of 18/12, 22/16, and 26/20 °C and atmospheric CO 2 concentrations of 350, 675 and 1000 μL L −1 . No seeds were produced at 18/12 °C within any of the CO 2 concentrations. Numbers of pods and seeds increased with increasing temperature and CO 2 levels. Carbon dioxide enrichment increased seed yield of soybean grown at moderately cool temperatures. This increase was associated with an increase in net photosynthetic rate. Leaf photosynthesis in response to CO 2 enrichment increased more at 22/16 °C than at 26/20 °C. Increases in temperature and CO 2 levels enhanced total growth of plants but hastened senescence of leaves. The extended photosynthetic capacity at cool temperatures did not result in allocating more dry matter to developing pods. CO 2 enrichment at 26/20 °C resulted in greater seed yield increases than CO 2 enrichment at lower temperatures.Key words: Soybean yield, low temperature, CO 2 × temperature