Gravity-Related Behavior of the Accelular Slime Mold Physarum polycephalum

Abstract

The graviresponse of Physarum plasmodia was investigated in actual weightlessness (0 g) during the IML-1 Spacelab mission. The transi- tion of the cells from 1 g to 0 g induced a transient increase in the contraction activity an in the velocity of the cytoplasmic shuttle streaming. This confirmed 0 g-simulation experiments performed on the fast-rotating clinostat as well as D-1 Spacelab experiment. The simultaneous and separated induction of the opposed gravity and white-light responses revealed mutual influences of the acceleration- and light-stimulus reaction chains. It is concluded that the two stimulus-reaction chains share their last members (from the mitochondria onwards to the contracting acotmyosin fibrils). A model about the primary graviperception and the involvement of mitochondria is discussed.