title: Highlighting the threat from current and near-future ozone pollution to clover in pasture.
abstract: Globally, the legume-rhizobia symbiosis, contained within specialised organs called root nodules, is thought to add at least 30 Tg N annually to agricultural land. The growth and functioning of a modern white clover (Trifolium repens cv. Crusader) and red clover (T. pratense cv. Merviot) cultivar were investigated in current and future ozone scenarios in solardomes. Both cultivars developed leaf injury and had significant reductions in root biomass and root nodule number in response to ozone, with Crusader also displaying a reduced size and mass of nodules. In-situ measurements of N-fixation in Crusader by acetylene reduction assay revealed reduced N-fixation rates in a future scenario with an increased background and moderate peaks of ozone. The implications for the sustainability of temperate pasture are discussed.
authors.affiliation: Centre for Ecology & Hydrology, Environment Centre Wales, Deinol 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, Deinol Road, Bangor, Gwynedd LL57 2UW, UK.
authors.forename: G
authors.initials: G
authors.lastname: Mills
authors.affiliation: Centre for Ecology & Hydrology, Environment Centre Wales, Deinol Road, Bangor, Gwynedd LL57 2UW, UK.
authors.forename: F
authors.initials: F
authors.lastname: Hayes
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; D010126:Ozone / Q000633:toxicity*; D018517:Plant Roots / Q000254:growth & development; D029921:Trifolium / Q000254:growth & development / Q000502:physiology
chemical_list: D000393:Air Pollutants; D010126:Ozone
keywords: Background ozone; Clover; Nitrogen fixation; Nodulation; Ozone; Pasture