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

Derived Forms

• geotropically
  adverb
• geotropic
  adjective

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

Geotropism, as was shown in the last chapter, excites the primary radicle to bend downwards with very little force, quite insufficient to penetrate the ground.

From The Power of Movement in Plants by Darwin, Charles