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Title: COMPARATIVE RESPONSES OF CONTAINER- VERSUS GROUND-GROWN SOYBEAN TO ELEVATED CARBON DIOXIDE AND OZONE

Author
item Booker, Fitzgerald
item MILLER, JOSEPH - RETIRED USDA
item Fiscus, Edwin
item PURSLEY, WALTER - NC STATE UNIVERSITY
item STEFANSKI, LEN - NC STATE UNIVERSITY

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2004
Publication Date: 3/28/2005
Citation: Booker, F.L., Miller, J.E., Fiscus, E.L., Pursley, W.A., Stefanski, L. 2005. Comparative responses of container- versus ground-grown soybean to elevated carbon dioxide and ozone. Crop Science 45:883-895.

Interpretive Summary: Agricultural crop production is likely to be influenced by rising atmospheric concentrations of CO2 and other greenhouse gases caused by emissions from power plants, vehicles, deforestation and industrial activities. Scientific experiments conducted to determine how agricultural production might be affected by these emissions have been done in various ways. Some experiments are done with potted plants and some are done with plants grown in the ground, but it's uncertain whether results from the two types of experiments are equally good predictors of future crop responses. However, in our two-year experiment, relative effects of elevated CO2 and air pollutant O3 on soybean growth and yield were remarkably similar for plants grown in pots compared to plants grown in the ground. In both pot-grown and ground-grown plants, elevated CO2 increased total seed mass and O3 suppressed it to similar magnitudes in both rooting environments. Elevated CO2 also prevented the toxic effects of O3. Our study showed that soybean experiments with CO2 and O3 can be done in large pots or in the ground, thus lending validity to previous experiments that used large containers in elevated CO2 and O3 effects research. Our experiment also showed that the effects of elevated CO2 on promoting growth and yield are partly due to reductions in injury from ambient O3, which is pervasive across the United States and damaging for many crops.

Technical 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. It has been suggested that growth responses to elevated CO2 are limited in pot-grown compared with ground-grown plants. Concerns also have been expressed about plant growth studies with the air pollutant O3 with pot-grown plants. Further, since elevated CO2 and O3 co-occur, studies are required with the combination of gases. In a two-year experiment, soybean [Glycine max (L.) Merr.] plants grown in large pots (14-l and 21-l) and in the ground were exposed to mixtures of CO2 and O3 concentrations in open-top chambers. The CO2 treatments were ambient and CO2 enrichment of approximately 337 µmol mol-1 added to ambient air 24 h d-1. Ozone treatments were charcoal-filtered air and approximately 1.5 times ambient O3 levels given for 12 h d-1. Relative effects of elevated CO2 and O3 on growth and yield were remarkably similar for plants grown in pots compared with plants grown in the ground. In both pot-grown and ground-grown plants, elevated CO2 increased total seed mass and O3 suppressed it to similar magnitudes in both rooting environments. Elevated CO2 also prevented the toxic effects of O3. These results indicated that planting density and rooting environment affected plant morphology, but responses to elevated CO2 and O3 were not fundamentally different between soybean plants grown in large pots and in the ground in open-top chambers.