Dependence of the photophobic response of the blue-green alga,Phormidium uncinatum,on cations |
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Authors: | Donat-P Häder Kenneth L Poff |
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Institution: | (1) Department of Botany, University of Marburg, Lahnberge, D-3550 Marburg, Federal Republic of Germany;(2) MSU-DOE Plant Research Laboratory, Michigan State University, 48824 East Lansing, Michigan, USA |
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Abstract: | It is suggested that photophobic responses caused by a sudden step-down in light intensity require the presence of cations in the blue-green alga, Phormidium uncinatum.Drastic removal of cations abolishes the phobic response, which recovers after addition of Ca2+ ions. Calcium can be substituted for partially by other cations with an effectivity following the sequence Ca>Mg>Na>Ba>Co=0. During the photophobic response there is a 25% increase in 45Ca binding by the cells related to a step-down in light intensity. Three seconds after a light-dark transition there is a sharp increase in the binding of labelled calcium, followed by a subsequent release.Flushing the filaments with high cation concentrations, esp. calcium causes a reversal of movement in the absence of a light stimulus similar to a photophobic reversal. This stimulus could trigger the same sequence of events in the transduction chain bypassing the primary photoresponse.Abbreviations EDTA
Ethylene diaminetetraacetic acid
- EGTA
ethylene glycol-bis (2-aminoethylether) N,N tetraacetic acid |
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Keywords: | Blue-green alga Calcium ions Cations Ion fluxes Phormidium Photophobic response |
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