Dependence of the photophobic response of the blue-green alga,Phormidium uncinatum, on cations

✍ Scribed by Donat-P. Häder; Kenneth L. Poff

• Book ID: 104764262
• Publisher: Springer
• Year: 1982
• Tongue: English
• Weight: 448 KB
• Volume: 132
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00413387

✦ Synopsis

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 Ca 2 + 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.