title: The primary processes of photosystem II in purified guard-cell protoplasts and mesophyll-cell protoplasts from Commelina communis L.
abstract: Guard-cell protoplasts were isolated by enzymic digestion of the epidermis peeled from the abaxial surface of leaves from Commelina communis L. The protoplasts were separated from mesophyll-cell protoplasts and other contaminants by density-gradient centrifugation, and the purity of the preparations carefully and quantitatively assessed by light microscopy. The preparations of guard-cell protoplasts were then compared with mesophyll-cell protoplasts in terms of the activity of photosystem II as assessed by a) the light-induced evolution of oxygen under both steady-state and flashing light and b) the characteristics of photosystem-II chlorophyll fluorescence. In all experiments, clear photosystem-II activity was found in guard-cell protoplasts, although some subtle distinctions between guard-cell and mesophyll-cell protoplasts were found. The contribution of any contaimination by mesophyll-cell chlorophyll to guard-cell-protoplast signals was estimated to be less than 3% in all cases. The results indicate that photosystem II is present and active in guard cells of Commelina.
authors.affiliation: Department of Botany, University of Glasgow, G12 8QQ, Glasgow, UK.
authors.forename: M F
authors.initials: MF
authors.lastname: Hipkins
authors.forename: P J
authors.initials: PJ
authors.lastname: Fitzsimons
authors.forename: J D
authors.initials: JD
authors.lastname: Weyers