Comparative responses of container- versus ground-grown soybean to elevated carbon dioxide and ozone

Abstract

In studies of CO2-enrichment effects on plants, the applicability of results derived from experiments using container-grown plants for predictions of future crop performance in a CO2-enriched atmosphere has been questioned. Concerns also have been expressed about plant growth studies with the air pollutant O3 in pot-grown plants. Further, since elevated CO2 and O3 co-occur, studies are required with the combination of gases. In this 2-yr experiment, soybean [Glycine max (L.) Merr.] plants grown in large pots (15 and 21 L) and in the ground were exposed to mixtures of CO2 and O3 in open-top chambers. The CO2 treatments were ambient and CO2 enrichment of approximately 337 μmol mol-1 added 24 h d -1. Ozone treatments were charcoal-filtered (CF) air (23 nmol mol-1) and approximately 1.5 times ambient O3 levels (71 nmol mol-1) given 12 h d-1. Relative effects of elevated CO2 and O3 on ahoveground hiomass and seed yield were quite similar for plants grown in pots compared with plants grown in the ground. Elevated CO2 increased total seed mass and O3 suppressed it to similar magnitudes in both rooting environments. Elevated CO2 also reduced the toxic effects of O3. Net photosynthesis (A) was similar while stomatal conductance (gs) was higher in pot-grown compared with ground-grown plants, possibly due to better soil moisture status. The results indicated that planting density and rooting environment affected plant morphology, but relative responses of seed yield to elevated CO 2 and O3 were not fundamentally different between soybean plants grown in large pots and in the ground in open-top chambers. © Crop Science Society of America.