Clinostats

A clinostat is a rotating device used to minimize the directional effects of gravity on biological samples, especially plants. By continuously changing the orientation of the organism relative to the gravity vector, the gravitational stimulus is averaged over time, creating a microgravity-like environment that helps researchers study processes such as gravitropism, morphogenesis, and developmental pathways without spaceflight.

There are two common forms: horizontal clinostats and vertical clinostats. In a horizontal clinostat, the sample is mounted to rotate around a horizontal axis, so the gravity vector cycles through all orientations relative to the specimen. A vertical clinostat rotates about a vertical axis, which tends to alter orientation less effectively for nullifying gravity, and is used in specific experimental contexts or to reduce shear forces. The choice of rotation speed is important; speeds too high or too low can introduce centrifugal forces or insufficient averaging, respectively.

Applications of clinostats include studying how plants sense gravity, how roots and shoots respond to changing orientation, and how growth and development proceed under altered gravity conditions. They are also used in some microbiological or cell culture experiments where sedimentation or directional gravity influences outcomes. Limitations include that clinostats do not reproduce true microgravity and can introduce other physical effects such as fluid shear or centrifugal forces. They are most valuable for probing gravitropism and related processes and are often complemented by spaceflight experiments or more advanced devices like random positioning machines.