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an orienting response to gravity

an orienting response to gravity

The directional growth of organisms in response to gravity. In plants, the main root is positively gravitropic (growing downwards) and a main stem is negatively gravitropic (growing upwards), irrespective of the positions in which they are placed. Plant gravitropism is thought to be controlled by auxin (AUXINS), a plant growth substance. (From Concise Dictionary of Biology, 1990)

Tendency to respond to stimulus of gravity by turning towards it, as the downward growth of a root.

Attraction reaction of the earth on living substances or matter, particularly noted in roots. [Gr.]