Changes in stomatal behaviour in the calcicole Leontodon hispidus due to the disruption by ozone of the regulation of apoplastic Ca2+ by trichomes
2001
De Silva, D.L.R. | Mansfield, T.A. | McAinsh, M.R.
Regulation of the concentration of Ca(2+) 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 Ca(2+) 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 Ca(2+) homeostasis. Therefore, we have examined the effect of this pollutant on the regulation by trichomes of apoplastic Ca(2+) 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 Ca(2+) in the rhizosphere. Analysis of total Ca(2+) levels revealed that these changes in stomatal behaviour reflect a decrease in the ability of trichomes to sequester Ca(2+). The amount of Ca(2+) present in the trichome tip cell was reduced by approximately 38%. This was accompanied by an increase in the levels of Ca(2+) 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 Ca(2+) 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.
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