The pathway of photosensory transduction in Physarum polycephalum.

Irradiation of the plasmodia of Physarum with blue and white light results in a transient change of theie oscillatory contraction frequency. This reaction to light decreases with increasing distance from the illuminated area (Block and Wohlfarth-Bottermann, 1981). The first local appearance of light response in non-illuminated parts of the plasmodia was used to analyse the sensory pathway of the light stimulus modulating the contractile apparatus. Different experimental assays revealed that the direction of photosensory transduction is determined by the momentary direction of protoplasmic shuttle streaming. The endoplasmic flow carriers the signal responsible for photosensory transduction and light reaction to the force generating ectoplasmic tube.