THE DETERMINATION OF THE FAR‐RED EFFECT IN MARINE PHYTOPLANKTON

Abstract

A far‐red effect exists in 4 marine phytoplankton species: the diatom Ditylum brightwelli, the coccolithophorid Coccolithus huxleyi, the green flagellate Dunaliella tertiolecta, and the dinoflagellate Pyrocystis lunula. The effect is reversible and is manifested through a change in cell division rate. Cultures of algae which received 30‐min far‐red (FR) light (750 nm) prior to the dark period were compared to controls which received, no FR. Reversal of the FR effect was studied by exposing experimental cultures to 30 min FR followed by 5‐min red (R) light (650 nm) prior to the dark period. Controls received only FR. Cultures were exposed to light at 6 different enumerated wavelengths between 460 and 750 nm. A decrease in division rate runs evident only with light at 750 nm. These results give evidence for the presence of the phytochrome system in these phytoplankton species. Copyright © 1973, Wiley Blackwell. All rights reserved