Influence of Ozone Stress on Soybean Response to Carbon Dioxide Enrichment: I. Foliar Properties
- A. S. Heagle *,
- J. E. Miller and
- F. L. Booker
- U SDA-ARS, Air Quality - Plant Growth and Development Research Unit, 1509 Varsity Drive, Raleigh, NC 27606 and Dep. of Plant Pathology, North Carolina State Univ.
U SDA-ARS, Air Quality - Plant Growth and Development Research Unit, 1509 Varsity Drive, Raleigh, NC 27606 and Dep. of Crop Science, North Carolina State Univ.
A ir Quality Research Unit, 1509 Varsity Drive, Raleigh, NC 2706, and Dep. of Crop Science, North Carolina State Univ.
Tropospheric O3 can cause foliar injury, decreased growth, and decreased yield, whereas CO2 enrichment generally causes opposite effects. Little is known about plant response to mixtures of O3 and CO2. Open-top field chambers were used to determine if foliar responses of soybean [Glycine max (L.) Merr.] to CO2 enrichment are affected by O3 stress and vice versa. Plants were grown in 14-L pots and exposed to four CO2 and three O3 concentrations in 12 combinations. The CO2 treatments were ambient (366 μL−) and three treatments with CO2 added for 24 h d 1 at approximately 1.3, 1.6, and 2.0 times ambient. The O3 treatments were charcoal-filtered air (CF), nonfiltered air (NF), and NF with O3 added for 12 h−1 ( NF+), resulting in seasonal concentrations of approximately 20, 46, and 75 μL L−1. Foliar effects of CO2 enrichment were dependent on the amount of stress caused by O3. In the CF treatment, plants were not stressed by O3, and CO2 enrichment caused chlorosis and decreased chlorophyll. In the NF and NF+ treatments, plants were stressed by 03, and CO2 enrichment suppressed chlorosis and increased chlorophyll. Ozone decreased specific leaf weight, increased foliar N and C, and decreased C/N ratios, whereas CO2 caused opposite responses for these measures. Ozone increased foliar S and B but did not affect P or K concentrations. Conversely, CO2 enrichment suppressed foliar S, B, P, and K concentrations. These interactions between O3 and CO2 emphasize a need to consider the amount of plant stress caused by O3 in studies to measure effects of CO2 enrichment.
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