Effects of intermittent exposure to high atmospheric CO2 on vegetative growth in soybean

Abstract

Short‐term exposure to high CO2 increases rates of photosynthesis and growth in soybeans, but with prolonged high CO2 exposure, these high rates are sometimes not maintained. Growth of soybean (Glycine max (L.) Merrill cv. Fiskeby V) seedlings kept for 25 days at atmospheres of 350 or 1000 μ/l CO2 was compared with growth of plants given 2, 4 or 6 day alternating exposure to high and low CO2 levels (13 days of total exposure to each level). Final dry weight of plants increased with number of days in high CO2 but leaf areas were not greatly affected. Thus dry weight gains per unit leaf area (net assimilation rates) were higher in high CO2 than in low CO2 throughout the entire period of the experiment and the pattern of exposure to high CO2 did not affect the rate of dry weight gain in high CO2.