Photopolarization of the Fucus sp. Zygote by Blue Light Involves a Plasma Membrane Redox Chain

Zygotes of fucoid algae are photopolarized by unidirectional blue light (BL). Polar axes are formed, fixed, and expressed by germination of a rhizoid. Hexacyanoferrate(III) ions (HCF) specifically inhibit transduction of the BL signal. HCF reduction by Fucus sp. zygotes occurs on the outer surface of the plasma membrane at higher rates in BL than in dark. These observations suggest that BL signal transduction involves a redox chain in the plasma membrane. Low doses of HCF (<50 pmol cell-1) inhibit photopolarization but not germination, hence uncoupling both processes. Exposure during the photosensitive period to higher doses of HCF together with BL significantly inhibits germination. Further results suggest that BL transduction is dependent on photosynthetic products that could also interact with redox processes.