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Effects of Ozone and Water Deficit on Field-Grown Soybean: I. Leaf Gas Exchange

North Carolina Dep. Environment, Health, & Natural Resources, 3800 Barrett Dr., Raleigh, NC 27609;

Joseph E. Miller^*

USDA-ARS, Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695-7632;

Walter A. Pursley

Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695-7632;

Allen S. Heagle

USDA-ARS, Dep. of Plant Pathology, North Carolina State Univ., Raleigh, NC 27695-7616.

^* Corresponding author (jmiller{at}asrr.arsusda.gov).

ABSTRACT

Ozone (O₃) and water deficit can suppress net carbon exchange rate (NCER) of plant tissues, but little is known concerning their combined effects on NCER of field-grown plants. Soybean [Glycine max (L.) Merr. ‘Young’] plants were exposed to two soil moisture regimes (providing well-watered and periodically water-deficient conditions) and three levels of O₃ in open-top field chambers throughout the growing season. Seasonal (12 h d^–1) mean O₃ concentrations were 0.018, 0.059, or 0.085 µL L^–1. Measurements of NCER, transpiration (Tn), and stomatal resistance (Rs) were conducted periodically on center leaflet of the fifth or sixth trifoliolate from the apex. During vegetative and early reproductive growth, less visible foliar injury due to O₃ occurred on water-deficient plants. Ozone usually suppressed leaflet NCER and leaflet WUE (NCER/Tn). Leaflet NCER was usually suppressed and WUE increased in water-deficient treatments during water deficit episodes. Diurnal measurements illustrated that leaflet NCER was limited in water-deficient plants when leaf water potential fell to about –1.1 MPa. On two occasions under low photosynthetically active radiation, NCER was greater for leaflets in water-deficient treatments than in well-watered treatments. Significant O₃ x H₂O interactions for NCER were infrequent on individual days, although water deficit suppressed response to O₃ when data were analyzed over the season.

Cooperative investigations of the USDA-ARS and the North Carolina State University. Research partly supported by an Interagency Agreement (No. DW-12931347-7601) between the Environmental Protection Agency and the USDA.

Although the research described in this article was partly funded by the USEPA, it has not been subjected to the EPA's paper and policy review and may not reflect the views of the Agency.

Received for publication May 3, 1994.

This article has been cited by other articles:

				P. B. Morgan, C. J. Bernacchi, D. R. Ort, and S. P. Long An In Vivo Analysis of the Effect of Season-Long Open-Air Elevation of Ozone to Anticipated 2050 Levels on Photosynthesis in Soybean Plant Physiology, August 1, 2004; 135(4): 2348 - 2357. [Abstract] [Full Text] [PDF]