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  

/ 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

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Etymology

Origin of geotropism

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

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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

After 24 h. several of the amputated radicles remained horizontal, but some showed a trace of geotropism, and one was plainly geotropic, for it was inclined at 40o beneath the horizon.

From The Power of Movement in Plants by Charles Darwin

We will therefore speak of circumnutation, which is always in progress, as modified by epinasty, hyponasty, geotropism, or other agencies, whether internal or external.

From The Power of Movement in Plants by Charles Darwin

But their sensitiveness to geotropism lasts for only 2 or 3 days; and the terminal part alone, for a length of between .2 and .4 inch, is thus sensitive.

From The Power of Movement in Plants by Charles Darwin

But after three or four days when new vegetative points were formed, the radicles were again acted on by geotropism, and now they curved themselves perpendicularly downwards.

From The Power of Movement in Plants by Charles Darwin

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