geotropism

American  

[jee-o-truh-piz-uhm] / dʒiˈɒ trəˌpɪz əm /

noun

Biology.

1. oriented growth with respect to the force of gravity.

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geotropism British  

/ ˌdʒiːəʊˈtrɒpɪk, dʒɪˈɒtrəˌpɪzəm /

noun

1. the response of a plant part to the stimulus of gravity. Plant stems, which grow upwards irrespective of the position in which they are placed, show negative geotropism

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geotropism Scientific  

/ jē-ŏt′rə-pĭz′əm /

1. The directional growth of an organism in response to gravity. Roots display positive geotropism when they grow downwards, while shoots display negative geotropism when they grow upwards.

2. Also called gravitropism

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Other Word Forms

• geotropic
  adjective
• geotropically
  adverb

Etymology

Origin of geotropism

First recorded in 1870–75; geo- + -tropism

Explanation

Geotropism is when plants and fungi respond to gravity by growing in a certain direction. Typically, roots grow in the direction that gravity pulls, and stems grow in the opposite direction. Root down, stem up seems such a basic fact to us that it's easy to assume that all plants always grow in a straight line from root to tip. If that was true, though, putting a plant on its side would mean it would go from growing completely vertical to completely horizontal. Instead, if you put a houseplant down sideways, its stem will start to grow upward, curving until it's once again growing the opposite direction of gravity's pull. That's an example of geotropism.

Example Sentences

See Examples For:

geotropism

Then we studied geotropism by observing how our plant grew toward the ceiling, even after we tipped the plant on its side for a few days.

From "Because of Mr. Terupt" by Rob Buyea

The course pursued was mainly governed, as in the last case, by geotropism, but the line traced during 12 hours and magnified as before was more strongly zigzag, again showing circumnutation.

From The Power of Movement in Plants by Darwin, Charles

In whatever direction the primary radicle first protrudes from the seed, geotropism guides it perpendicularly downwards; and the capacity to be acted on by the attraction of gravity resides in the tip.

From The Power of Movement in Plants by Darwin, Charles

The relations between vegetable and animal geotropism have been more recently investigated by J. Loeb.

From Popular scientific lectures by Mach, Ernst

Uncauterised specimens similarly placed became much bent downwards through geotropism in the course of 5 or 6 hours.

From The Power of Movement in Plants by Darwin, Charles