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NEGATIVE PHOTO‐PHOBOTACTIC REACTIONS IN PHORMIDIUM UNCINATUM *
Author(s) -
Haeder Donat P.,
Nultsch Wilhelm
Publication year - 1973
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1973.tb06426.x
Subject(s) - photosystem , dcmu , photosystem i , photochemistry , absorption (acoustics) , photosynthesis , photosystem ii , chemistry , wavelength , optoelectronics , materials science , optics , biochemistry , physics
— The photo‐phobotaxis of Phormidium uncinatum has been studied by means of a double‐beam arrangement for simultaneous irradiation with two wavelengths in trap and background. Under these conditions the photo‐phobotactic reaction depends on whether one or both photosynthetic photosystems are excited by the two wavelengths. If far red or infrared is used as trap light, negative reactions occur under ail background wavelengths investigated. Furthermore, negative reactions are not as sensitive to 3‐(3,4‐dichlorophenyl)‐1, 1‐dimethylurea (DCMU) as positive ones. These results suggest that negative photo‐phobotactic reactions might be caused by light absorbed mainly by photosystem I, while both photosystems I and II can participate in mediating positive phobotactic reactions. In the range in which the absorption spectra of both photosystems overlap, the type of response depends on the photosystem with the stronger absorption.