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United States Department of Agriculture

Agricultural Research Service

Title: Combined Effects of Elevated Atmospheric Carbon Dioxide and Ozone on Soybean Whole-Plant Water Use

Authors
item Booker, Fitzgerald
item Fiscus, Edwin
item Miller, Joseph

Submitted to: Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 27, 2003
Publication Date: March 4, 2004
Citation: Booker, F.L., Fiscus, E.L., Miller, J.E. 2004. Combined effects of elevated atmospheric carbon dioxide and ozone on soybean whole-plant water use. Environmental Management 33:S355-S362.

Interpretive Summary: As atmospheric carbon dioxide concentration continues to rise from pre-industrial levels, it has in the past 50 years been accompanied by significant increases in pollutant ozone. A critical issue is how these changes will affect agricultural hydrologic cycles. To address part of this question, a study was undertaken to test the effects of elevated atmospheric carbon dioxide and ozone on whole-plant water loss. In a two-year experiment, pot-grown soybean was exposed from emergence to maturity to reciprocal treatments of elevated carbon dioxide and ozone in open-top field chambers. Plants were treated with charcoal-filtered air (CF) or CF air plus 1.5 times ambient ozone in combination with ambient or twice ambient carbon dioxide. Biomass, leaf area and yield were increased more than 16% by elevated carbon dioxide, but they were lowered about 30% by ozone in ambient carbon dioxide. Seasonal average whole-plant water loss was up to 28% lower in plants treated with elevated carbon dioxide and ozone. The efficiency of water use for seed production was increased 44% in the elevated carbon dioxide treatments, but was not significantly affected by the ozone treatment. These results indicate that elevated carbon dioxide should help to buffer soybean crops against ozone injury and water stress, especially during pod-fill. An additional aspect of this research is that it provides information directly related to how changes in plant water use, which will be influenced by climate change, may in turn influence weather and climate on a regional scale. Ultimately this information should benefit ecosystems managers and plant breeders who may be able to optimize the effects of global climate change on agricultural productivity.

Technical Abstract: With increasing atmospheric concentrations of trace gases such as carbon dioxide and ozone, a critical issue is how these changes will affect agricultural hydrologic cycles. To address an important part of this question, a study was undertaken to test the effects of elevated atmospheric carbon dioxide and ozone on whole-plant water loss. In a two-year experiment, pot-grown soybean (cv. Essex) was exposed from emergence to maturity to charcoal-filtered air (CF) or CF air plus 1.5 times ambient ozone in combination with ambient or twice ambient carbon dioxide in open-top field chambers. Biomass, leaf area and yield were increased more than 16% by elevated carbon dioxide, but they were lowered about 30% by ozone in ambient carbon dioxide. Seasonal average whole-plant water loss was lower by 20% and 28% in plants treated with elevated carbon dioxide and ozone, respectively, compared with the control. Whole-plant water loss from plants treated with both elevated carbon dioxide and ozone was 22% lower than the control. Elevated carbon dioxide treatments suppressed water loss per unit leaf area by 26% whereas water loss per unit leaf area was not significantly affected by the ozone treatment. Production water use efficiency was increased 44% in the elevated carbon dioxide treatments, but was not significantly affected by the ozone treatment. These results suggest that whole-plant water use was lowered by elevated carbon dioxide due to decreased stomatal conductance. Decreased whole-plant water loss in the ozone treatment was due to suppressed growth. Overall, elevated carbon dioxide counteracted the effects of ozone on water use, growth and yield. These results indicate that elevated carbon dioxide should help to buffer soybean crops against ozone injury and water stress, especially during pod-fill.

Last Modified: 4/17/2014
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