, Volume 159, Issue 6, pp 554-560

First online:

The primary processes of photosystem II in purified guard-cell protoplasts and mesophyll-cell protoplasts from Commelina communis L.

  • Michael F. HipkinsAffiliated withDepartment of Botany, University of Glasgow
  • , Peter J. FitzsimonsAffiliated withDepartment of Biological Sciences, University of Dundee
  • , Jonathan D. B. WeyersAffiliated withDepartment of Biological Sciences, University of Dundee

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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.

Key words

Chlorophyll fluorescence Commelina Guard cell Oxygen evolution (guard cell) Photosystem II Protoplast