|Author:||Booker, F. L. ; Fiscus, E. L. ; Miller, J. E.|
|Book Group Author:||NA|
Increasing concentrations of atmospheric trace gases such CO2 and O3 might affect agricultural crop productivity in as yet unforeseen ways. A critical issue is how changes in these trace gas concentrations will affect agricultural hydrologic cycles. In order to address part of this question, a study was undertaken to test the effects of elevated atmospheric CO2 and O3 on whole-plant water loss. In a 2-year experiment, pot-grown soyabean [Glycine max (L.) Merr., Essex] was exposed from emergence to maturity to reciprocal treatments of elevated CO2 and O3 in open-top field chambers. Plants were treated with charcoal-filtered air (CF) (18 nmol O3 mol-1) or CF air plus O3 (72 nmol mol-1) in combination with ambient (369 µmol mol-1) or elevated CO2 (718 µmol mol-1). Whole-plant water loss was monitored by measuring mass changes of potted plants placed on electronic balances in each chamber. Plants on the balances were harvested weekly to determine leaf area, and were replaced with another plant previously exposed to similar treatment conditions. Seasonal average daily whole-plant water loss was lower by 17% and 28% in plants treated with elevated CO2 and O3, respectively, compared with the control. Water loss from plants treated with both elevated CO2 and O3 was 22% lower than the control. Elevated CO2 treatments suppressed water loss per unit leaf area by 28%, whereas water loss per unit leaf area was not significantly affected by the O3-ambient CO2 treatment. Water use efficiency for seed production was increased 45% in the elevated CO2 treatments, but was not significantly affected by the O3 treatments. These results suggest that whole-plant water use was lowered by elevated CO2 because of decreased stomatal conductance despite 9% more leaf area. Decreased whole-plant water loss and seed production in the O3-ambient CO2 treatment was caused by suppressed growth and 28% less leaf area. Overall, elevated CO2 counteracted the effects of O3 on water use, growth, and yield. These results indicate that elevated CO2 should help to buffer soyabean crops against O3 injury and water stress.
|Pages:||S355 - S362|
carbon dioxide, carbon dioxide enrichment, crop yield,growth, leaf area, leaf conductance, ozone, plant water relations,soyabeans, stomata, water use efficiency, Glycine (Fabaceae), Glycinemax, Papilionoideae, Fabaceae, Fabales, dicotyledons, angiosperms,Spermatophyta, plants, eukaryotes, Glycine (Fabaceae), soybeans, FieldCrops (FF005) (New March 2000), Plant Water Relations (FF062), PlantProduction (FF100), Meteorology and Climate (PP500)