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Joined 2026-09-21 Message
Incoming links: Plant physiology
Allan H. Brown 2026-11-05
Allan H. Brown investigated plant physiology, including how plants respond to gravity and how accurately a clinostat simulates altered gravitational stimulation. His 1976 paper with colleagues tested a central assumption behind using continuous rotation as a gravity compensator.[ref]
Limitation on the Use of the Horizontal Clinostat as a Gravity Compensator by Allan H. Brown and others. Plant Physiology58,127–130; byline, affiliation and Abstract
The apparatus combined a clinostat with centrifugation: plants rotated while experiencing an additional chronic acceleration transverse to the rotation axis. If the rotation removed the relevant directional information completely, changing this imposed acceleration should not change the tested developmental outcomes. Several morphological endpoints nevertheless depended on its magnitude, demonstrating incomplete compensation under those conditions.[ref]
The reasoning distinguishes an apparatus's intended function from a validated approximation. Rotation changes the direction of the imposed stimulus relative to a specimen; it does not remove gravity itself. Brown's experiment therefore motivates testing each biological readout against an actual change in acceleration, rather than assigning weightlessness to every rotating preparation.
Francis Darwin 2026-11-05
Francis Darwin (1848–1925) was a botanist who collaborated with Charles Darwin on experimental plant physiology. The title page of The Power of Movement in Plants by Charles Darwin, published in 1880, explicitly credits his assistance.
Their phototropism experiments compared seedlings with transparent versus opaque coverings over their tips. Blocking light at the tip greatly reduced bending below it, whereas transparent coverings allowed bending. The comparison separated the location of light perception from the region that curved, suggesting transmission of an influence down the growing structure. It did not identify the chemical nature of that influence.[ref]
The Power of Movement in Plants by Charles Darwin. Chapter IX, Phalaris canariensis, pp. 469–474: glass tubes, opaque caps and transparent controls
Stephen Hales Created 2026-10-31 Updated 2026-11-05
Stephen Hales (1677–1761) made plant physiology quantitative by measuring water loss, sap movement and pressure. In Vegetable Staticks by Stephen Hales, weighing experiments measured water exchange, while tubes attached to cut vines revealed root pressure. Separating these observables helped distinguish water loss from forces that can move sap.[ref]
External portrait: www.npg.org.uk/collections/search/portrait/mw02821/Stephen-Hales