title: Changes in stomatal behaviour in the calcicole Leontodon hispidus due to the disruption by ozone of the regulation of apoplastic Ca2+ by trichomes.
abstract: Regulation of the concentration of Ca2+ in the apoplast of plants is essential in order to allow Ca(2+)-dependent processes, such as Ca(2+)-mediated signal transduction in stomatal guard cells, to function correctly. This is particularly important for plants growing with high levels of Ca2+ in the rhizosphere. Recently, we have shown that in two calcicoles, Leontodon hispidus L. and Centaurea scabiosa L., trichomes play a key role in this regulatory process. Ozone is known to have a marked effect on plant Ca2+ homeostasis. Therefore, we have examined the effect of this pollutant on the regulation by trichomes of apoplastic Ca2+ in the calcicole L. hispidus. Treatment with 100 nl l-1 ozone resulted in a reduction in stomatal conductance of approximately 25% in plants grown with 15 mM Ca2+ in the rhizosphere. Analysis of total Ca2+ levels revealed that these changes in stomatal behaviour reflect a decrease in the ability of trichomes to sequester Ca2+. The amount of Ca2+ present in the trichome tip cell was reduced by approximately 38%. This was accompanied by an increase in the levels of Ca2+ in the guard cells and other tissues of the leaf. These data suggest that ozone has a detrimental effect on the ability of trichomes to regulate the concentration of apoplastic Ca2+ in L. hispidus, resulting in altered stomatal behaviour, and hence gaseous exchange, possibly due to the disruption of guard-cell Ca(2+)-mediated signal transduction. This has important implications for the growth and survival of plants growing in Ca(2+)-rich soils.
authors.affiliation: Institute of Environmental and Natural Sciences, Department of Biological Sciences, Lancaster University, Lancaster, LA1 4YQ, UK.
authors.forename: D L
authors.initials: DL
authors.lastname: De Silva
authors.forename: T A
authors.initials: TA
authors.lastname: Mansfield
authors.forename: M R
authors.initials: MR
authors.lastname: McAinsh
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000393:Air Pollutants / Q000633:toxicity; D019659:Asteraceae / Q000187:drug effects / Q000378:metabolism*; D002122:Calcium Chloride / Q000008:administration & dosage / Q000378:metabolism*; D022081:Cell Surface Extensions / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D010126:Ozone / Q000008:administration & dosage / Q000633:toxicity*; D018514:Plant Structures / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction; D012987:Soil / Q000032:analysis
chemical_list: D000393:Air Pollutants; D012987:Soil; D010126:Ozone; D002122:Calcium Chloride