Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2004
Publication Date: 5/1/2005
Citation: Burkey, K.O., Heagle, A.S., Miller, J.E., Fiscus, E.L. 2005. Assessment of ambient ozone effects on vegetation using snap bean as a bio-indicator species. Journal of Environmental Quality. 34(3):1081-1086. Interpretive Summary: Ozone is an air pollutant that is toxic to plants, causing visible injury to foliage and a reduction in the growth and yield of many agronomic, horticultural and forest species. Ground level ozone is formed by the action of sunlight on volatile hydrocarbons and nitrogen oxides produced during fossil fuel combustion. Although frequently considered an urban problem, ozone is actually a regional problem because weather systems transport the pollutants into agricultural areas and forests. One approach to assess and compare ozone effects on vegetation in different locations is to identify ozone-sensitive plants that can be used as bio-indicators. The Air Quality Research Unit has previously developed a white clover bio-indicator system where suppression of forage production under elevated ozone is used to assess ambient ozone effects. The clover system is currently being used throughout the United States and Europe. The present study identified snap bean as a potential alternative to clover. Ambient ozone levels in Raleigh, NC suppressed the pod yield of selected snap bean genotypes by as much as 60%, evidence that the ozone sensitivity of snap bean is sufficient to detect effects under real world scenarios. Additional research will be required to develop and test a snap bean system that can be used effectively over wide geographical areas.
Technical Abstract: Tropospheric ozone is an air pollutant that is toxic to plants, causing visible injury to foliage and a reduction in growth and yield. The use of plant bio-indicators is one approach to assess the impact of ozone in diverse geographical areas. The objective of this two-year study was to evaluate snap bean (Phaseolus vulgaris L.) as a potential bio-indicator species. Three snap bean genotypes known to exhibit a range of ozone sensitivity were grown in pots under charcoal-filtered (CF) or non-filtered (NF) treatments in open-top chambers, or under ambient air (AA) conditions to assess the impact of ambient ozone. Treatment effects on biomass were not significant at 56 days after planting, but a midseason foliar assessment revealed increased injury in the NF and AA treatments relative to CF controls. Ozone effects on pod yield were significant at the end of the season. An increase in ozone from 25-30 nL L-1 in CF controls to approximately 50 nL L-1 in the NF and AA treatments was found to suppress final pod dry weight per plant by 40-60% in the most sensitive genotype S156. The same treatments suppressed final pod dry weight by 20-30% in a moderately sensitive genotype Oregon-91 and by 10% or less in a tolerant genotype R123. An S156/R123 yield ratio of approximately one was observed under CF conditions. The S156/R123 yield ratio declined to 0.6-0.7 in the NF treatment and declined further to 0.4-0.5 in the AA treatment, suggesting that the impact of ozone was underestimated in the open-top chambers.