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| Other names | Klinostat, horizontal clinostat, single axis clinostat |
|---|---|
| Uses | reduces the effect of gravity on organisms, chiefly used with plants |
| Inventor | Julius von Sachs |
| Related items | random positioning machine |
A clinostat is a device which uses rotation to negate the effects of gravitational pull on plant growth (gravitropism) and development (gravimorphism). It has also been used to study the effects of microgravity on cell cultures, animal embryos and spider webs.
A single axis (or horizontal) clinostat consists of a disc attached to a motor. They were originally clockwork but nowadays an electric motor is used. The disc is held vertically and the motor rotates it slowly at rates in the order of one revolution per minute. A plant is attached to the disc so that it is held horizontally. The slow rotation means that the plant experiences a gravitational pull that is averaged over 360 degrees, thus approximating a weightless environment. Clinostats have also been used to cancel out effects of sunlight and other stimuli besides gravity. This type of clinostat must be exactly horizontal to simulate absence of gravity. If the clinostat is at an angle from horizontal, a net gravity vector is perceived, the magnitude of which depends on the angle. This can be used to simulate lunar gravity (ca. 1/6 g) which requires an angle from the horizontal of ca. 10 deg., i.e. sin−1(1/6).
A plant only reacts to gravity if the gravistimulation is maintained for longer than a critical amount of time, called the minimal presentation time (MPT). For many plant organs the MPT lies somewhere between 10 and 200 seconds, and therefore a clinostat should rotate on a comparable timescale in order to avoid a gravitropic response. However, presentation time is cumulative, and if a clinostat's rotation is repeatedly stopped at a single position, even for periods as short as 0.5 s, a gravitropic response can result. [1] The presentation time for animals is one or two orders of magnitude faster than this, thus precluding the use of the slow rotation clinostat for most animal studies. However the fast rotation clinostat can be, and is, used for the study of animal cell cultures and embryos.
A number of problems have been pointed out in the use of clinostats to simulate microgravity:
The clinostat was invented in 1879 by Julius von Sachs, [7] who built a clockwork-powered machine. However a similar concept had been pioneered as early as 1703 by Denis Dodart. The first electric-powered clinostat (1897) was made by Newcombe. [8]
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Sarah Wyatt is an American, plant molecular biologist. She is a Professor in the Department of Environmental and Plant Biology at Ohio University, as well as director of the Ohio University Interdisciplinary Graduate Program in Molecular and Cellular Biology. Wyatt's research interests include molecular biology, genomics, and signaling events. She is considered one of the world's experts on gravitational signaling in plants, and some of her recent research includes an experiment on board the International Space Station (ISS).
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Cell culture (Class 435/297.400)