title: N-fixation in legumes--An assessment of the potential threat posed by ozone pollution.
abstract: The growth, development and functioning of legumes are often significantly affected by exposure to tropospheric ozone (O3) pollution. However, surprisingly little is known about how leguminous Nitrogen (N) fixation responds to ozone, with a scarcity of studies addressing this question in detail. In the last decade, ozone impacts on N-fixation in soybean, cowpea, mung bean, peanut and clover have been shown for concentrations which are now commonly recorded in ambient air or are likely to occur in the near future. We provide a synthesis of the existing literature addressing this issue, and also explore the effects that may occur on an agroecosystem scale by predicting reductions in Trifolium (clovers) root nodule biomass in United Kingdom (UK) pasture based on ozone concentration data for a "high" (2006) and "average" ozone year (2008). Median 8% and 5% reductions in clover root nodule biomass in pasture across the UK were predicted for 2006 and 2008 respectively. Seasonal exposure to elevated ozone, or short-term acute concentrations >100 ppb, are sufficient to reduce N-fixation and/or impact nodulation, in a range of globally-important legumes. However, an increasing global burden of CO2, the use of artificial fertiliser, and reactive N-pollution may partially mitigate impacts of ozone on N-fixation.
authors.affiliation: Centre for Ecology & Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd, LL57 2UW, UK; Lancaster University, Lancaster Environment Centre, Lancaster, Lancashire, LA1 4YQ, UK. Electronic address: danhew@ceh.ac.uk.
authors.forename: D K L
authors.initials: DK
authors.lastname: Hewitt
authors.affiliation: Centre for Ecology & Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd, LL57 2UW, UK.
authors.forename: G
authors.initials: G
authors.lastname: Mills
authors.affiliation: Centre for Ecology & Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd, LL57 2UW, UK.
authors.forename: F
authors.initials: F
authors.lastname: Hayes
authors.affiliation: Centre for Ecology & Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd, LL57 2UW, UK.
authors.forename: D
authors.initials: D
authors.lastname: Norris
authors.affiliation: Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian, EH26 0QB, UK.
authors.forename: M
authors.initials: M
authors.lastname: Coyle
authors.affiliation: Lancaster University, Lancaster Environment Centre, Lancaster, Lancashire, LA1 4YQ, UK.
authors.forename: S
authors.initials: S
authors.lastname: Wilkinson
authors.affiliation: Lancaster University, Lancaster Environment Centre, Lancaster, Lancashire, LA1 4YQ, UK.
authors.forename: W
authors.initials: W
authors.lastname: Davies
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D018533:Biomass; D004787:Environmental Pollution; D007887:Fabaceae / Q000502:physiology*; D009586:Nitrogen Fixation; D010126:Ozone / Q000032:analysis / Q000633:toxicity*; D018517:Plant Roots / Q000737:chemistry; D013025:Glycine max / Q000502:physiology; D029921:Trifolium / Q000502:physiology; D006113:United Kingdom
chemical_list: D000393:Air Pollutants; D010126:Ozone
keywords: Background ozone; Clover; Nitrogen fixation: pasture; Nodulation; Ozone