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

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

With the pea, therefore, the irritation from an attached object, and from geotropism when acting at right angles to the radicle, are nearly balanced forces.

From The Power of Movement in Plants by Darwin, Charles

Concluding Remarks.—Abundant evidence has now been given, showing that with various plants the tip of the radicle is alone sensitive to geotropism; and that when thus excited, it causes the adjoining parts to bend.

From The Power of Movement in Plants by Darwin, Charles

These two kinds of sensitiveness conquer for a time the sensitiveness to geotropism, which, however, ultimately prevails.

From The Power of Movement in Plants by Darwin, Charles

Ten other radicles similarly placed were touched on the lower side; and this would tend to make them bend from the cauterised side; and therefore, as now placed, upwards, or in opposition to geotropism.

From The Power of Movement in Plants by Darwin, Charles