Effects of simulated hypogravity on respiration and photosynthesis of higher plants.

Clinostat rotation about a horizontal axis mechanically cancels the directional component of the gravity force vector which is biologically sensed by plants. However, efficiency of clinostats as simulators of weightlessness for prolonged periods has not been demonstrated conclusively. Morphological appearance of plants in orbital flight may resemble their counterparts on earth-based clinostats, but physiological responses may differ. Photosynthesis experiments with algae have been performed in satellites orbiting the earth, but similar experiments with higher plants have not been conducted. This paper describes an experimental apparatus for measurement of photosynthetic and respiratory rates of whole plants on rotating clinostats. Initial experiments show an enhancement of gas exchange during rotation about a horizontal axis.