EFFECT OF DESASPIDIN AND DCMU ON PHOTOKINESIS OF BLUE‐GREEN ALGAE*

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Abstract
Abstract— The effect of desaspidin and DCMU (3–(3.4‐dichlorophenyl)‐1,1‐dimethylurea) on the speed of movement in light and dark of the blue‐green alga Phormidium uncinatum has been investigated. Desaspidin, which uncouples oxidative phosphorylation and predominantly cyclic photosynthetic phosphorylations, inhibits movement in the dark and light as well, but dark movement is more sensitive. Movement in the light is more sensitive under anaerobic conditions than in air. The inhibitory effect of desaspidin is markedly increased by DCMU, which inhibits non‐cyclic electron transport and coupled phosphorylation in air as well as under argon. There is no evidence for any photodestruction of desaspidin in air, provided that no ferricyanide is present in the medium. These findings are interpreted to confirm the concept that photokinesis (i.e. a light induced acceleration of movement in microorganisms) is the result of an increased ATP production by photosynthetic phosphorylation and that both cyclic and non‐cyclic photophosphorylations supply energy for the movement in blue‐green algae.