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According to Webster's Dictionary - A clinostat is an apparatus consisting of a slowly revolving disk, usually regulated by clockwork, by means of wich the action of external agents, as light and gravity, on growing plants may be regulated or eliminated.
This definition is a bit antiquated as illustrated by the following descriptions and pictures.
Clinostats Simulate Reduced Gravity.
As long as the response time is less than the
stimulation time, the constant changing of the gravity vector prevents a directional
response.
this concept allows the simulation of gravity levels: If a (small) plant is
rotated horizontally at 1- 3 rpm artifical weightlessness (aka microgravity)
is simulated. Placing the rotating device at an angle simulates a fraction of
gravity. The residual gravity (simulating e.g. the Moon's gravity of 1/6 g)
requires an angle of sin -1(1/6) or ~10 deg.
Hypergravity can also be simulated!
If accelerations (gravity) of bodies larger than Earth are to be simulated a
centrifugal force is needed and the clinostat turns into a centrifuge. The force
depends on the angular velocity and radius of the device (see Theory).
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| One of the first clinostats. This model was used by Wilhelm Pfeffer (~1900) and is already an improvement (smaller version) of the original machine, which was built by Julius Sachs (~1879) | A simple but specialized one-dimensional (1-D) clinostat that accommodates a Magnetic Field Chamber (shown without cover plate and seed cassettes). This device was used for the preparation of the shuttle experiment on STS-107. |
| The devices below show specialized clinostats that exceed the original attempt to eliminate a directional response of plants. Some historical information about these clinostats.... | |
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Another 1-D clinostat that is driven by a belt and rotates many samples simutaneously. The device may hold many samples all of which rotate at ca. one revolution per minute around a horizontal or (if the device is tilted) vertical axis.
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The two-dimensional (2-D) clinostat
represents a particular design. The relative velocity between the two
large wheels determines the 'tumbling' rate (clinorotation) around the
horizontal 'spokes' of the experimental chambers (translucent plastic
cups). The average speed of the two wheels determines the rotational
velocity around the vertical axis (post that supports the chambers).
This design provides a smooth transition between clinorotation and (superimposed)
centrifugation. Because both clinorotation and centrifugation can be
controlled (the latter depends on the radius of the device) an entire
gradient of centrifugal forces can be tested. |
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The most thorough elimination gravitational effects is achieved with a 3-D clinostat, which is built around a Cartesian suspension. The three independent axes of rotation provide complete randomization of the gravity vector and achieve the best micro-gravity simulation for ground-based experiments. |