Biophysical considerations concerning gravity receptors and effectors including experimental studies on Phycomyces blakesleeanus.
Part I. Migration and Diffusion of Graviceptors: The physical action of gravitational and inertial forces on graviceptors is considered. The motion of graviceptors as influenced by physical dimensions, density, electric charge, composition of the suspending medium and flow variables is demonstrated. Part II. Observations on Geotropism in Phycomyces blakesleeanus: Mutants of Phycomyces blakesleeanus exhibit strikingly different rates of geotropic response. It is shown that Phycomyces grown in the dark lack normal geotropic responses: pre-exposure to light is necessary for the synthesis of structures responsible for geotropism. A physical model is presented that may account for some of the geotropic phenomena observed in Phycomyces.