title: Dynamic responses of photosystem II in the Namib Desert shrub, Zygophyllum prismatocarpum, during and after foliar deposition of limestone dust.
abstract: The effects of limestone dust deposition on vegetation in desert ecosystems have not yet been reported. We investigated these effects in a succulent shrub from the Namib Desert at a limestone quarry near Skorpion Zinc mine (Namibia). Effects of limestone dust were determined in Zygophyllum prismatocarpum (dollar bush) plants with heavy, moderate and no visible foliar dust cover by means of chlorophyll a fluorescence measurements. Limestone dust deposition decreased overall plant performance through loss of chlorophyll content, inhibition of CO(2) assimilation, uncoupling of the oxygen-evolving complex and decreased electron transport. Importantly, dynamic recovery occurred after termination of limestone extraction at the quarry. Recovery was accelerated by rainfall, mainly because of dust removal from leaves and stimulation of new growth. These results indicate that limestone dust has severe effects on photosynthesis in desert shrubs, but that recovery is possible and that, in arid environments, this process is modulated by rainfall.
authors.affiliation: Section Botany, School of Environmental Sciences and Development, North-West University, Hofmann Street, Potchefstroom 2522, South Africa. plbpdrvh@puknet.puk.ac.za <plbpdrvh@puknet.puk.ac.za>
authors.forename: P D R
authors.initials: PD
authors.lastname: van Heerden
authors.forename: G H J
authors.initials: GH
authors.lastname: Krüger
authors.forename: M
authors.initials: M
authors.lastname: Kilbourn Louw
mesh_terms: D000397:Air Pollution; D001673:Biodegradation, Environmental; D002119:Calcium Carbonate; D003889:Desert Climate; D004391:Dust; D004784:Environmental Monitoring / Q000379:methods; D007221:Industry; D009276:Namibia; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D011891:Rain; D032445:Zygophyllum / Q000378:metabolism*
chemical_list: D004391:Dust; D045332:Photosystem II Protein Complex; D002119:Calcium Carbonate