Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 1996
Publication Date: N/A
Interpretive Summary: The ozone concentration during the summer growing season is increasing in a zone which extends from Atlanta, GA up the east coast. The ambient concentrations appear to be having adverse effects on both the quality and growth of ladino white clover. As CO2 increases it tends to compensate for the negative effect of ozone on both quality and dry matter yield. The data from this study indicate that white clover germplasm responds different to elevated ozone and CO2 levels. Consideration needs to be given to these responses in plant breeding programs and ozone concentrations need to be considered in growth models that are being developed for elevated CO2 concentrations.
Technical Abstract: Two studies were conducted to characterize the changes in nutritive value of ladino white clover chronically exposed to O3 and to determine potential O3 by CO2 interactions. In a field experiment, an O3 sensitive (NC-S) and an O3 resistant (NC-R) white clover clone were chronically exposed (40 d) to four levels (28, 50, 68 and 84 nL/L) of O3 at ambient CO2 (350 to 360 uL/L). In a greenhouse experiment, changes in clonal nutritive value were determined following chronic exposure (29 d) to three levels of O3 (17, 70, and 100 nL/L) at ambient CO2 (379 uL/L) and enriched CO2 (705 uL/L) concentrations. Charcoal-filtered air averaged 17 nL/L. In vitro dry matter disappearance (IVDMD) of laminae exposed in the field to charcoal filtered air (28 nL/L O3) was lower averaging 765 g/kg vs. 783 g/kg when exposed to ambient air (50 nL/L O3). Laminae neutral detergent fiber (NDF), total nonstructural carbohydrates (TNC), total nitrogen (TN), and total amino acid concentrations changed differently between clones causing an O3 by clone interaction. In the greenhouse experiment, laminae IVDMD declined linearly with increasing O3 exposure, while the enriched CO2 atmosphere resulted in increased IVDMD. The laminae NDF was linearly increased by O3 concentration, but an O3 by CO2 interaction occurred.