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Plant hormones - AQAAuxin and geotropism

Hormones promote growth within plants. Plant hormones are unequally distributed throughout the stems and roots, which results in parts of the plant growing in a particular direction.

Part of Biology (Single Science)±«Óătvostasis and response

Auxin and geotropism

Geotropisms

Phototropism is a response to the stimulus of light, whereas geotropism (also called gravitropism) is a response to the stimulus of .

Plants responses to gravity:

  • when the stem grows against the force of gravity, this is known as a negative geotropism
  • when a root grows in the direction of the force of gravity, this is known as a positive geotropism

Just like phototropism, geotropism is also caused by an unequal distribution of auxin.

In a root placed horizontally, the bottom side contains more auxin and grows less - causing the root to grow in the direction of the force of gravity.

The opposite happens in a stem. When a stem placed horizontally, the bottom side contains more auxin and grows more - causing the stem to grow upwards against the force of gravity.

A visual to show geotropism, a response to the stimulus of gravity. The image should show how a plant responds to gravity.
A visual to show how auxin and gravity cause the plant to grow in different directions when it is placed horizontally.
A visual to show four stages of positive geotropism.
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