Avoidance and Rheotropic Responses in Phycomyces
- Dr . R . I . Gamow
Stage I Vb sporangiophores of Phycomyces grow into the windthe anemotropic response-and away from gravity-the geotropic response . A procedure has been designed to measure the equilibrium bend angle that results when the two stimuli are given simultaneously over a long period of time . This angle will be referred to as the anemogeotropic equilibrium angle. This measurement of a sensory response is analogous to the photogeotropic equilibrium angle in which the variable stimulus is light instead of wind . We have found that the anemogeotropic angle, measured relative to the vertical, increases with both increasing wind speed and increasing relative humidity of the wind stimulus . This finding is new and argues against a major prediction of the mass transfer model that anemogeotropism and relative humidity are inversely related. Data from these anemogeotropic experiments further suggest that the self-emitted gas responsible for both the anemotropic response and the avoidance response is water.