On Spectral Control of Pigmentation in Anacystis Nidulans (Cyanophyceae)¹,²

Growth of Anacystis nidulans (Richt.) Drouet & Daily in wavelengths of light predominantly absorbed by chlorophyll a causes a dramatic lowering in chlorophyll content and in the chlorophylllphycocyanin ratio. A limit to the effect is reached in far red (680 nm) light where the ratio chlorophylllphycobilinogen falls to <0.3. A special water bath for culture tubes was illuminated by tungsten‐halogen lamps through far red (>650 nm)filters; it gave the same extreme pigment ratio together with a high specific growth rate of 2.5 day ‐1 . Compared with normally pigmented cells there are three features which accompany the low‐chlorophyll condition of far red light. At 677 nm relative quantum efficiency increases but action decreases. Synthesis of total pigment and total cell material in far red light also decreases. These observations suggest that the low chlorophyll response to far red light reflects an incompetence rather than an adaptation .