Geotropism: what is it, positive, negative and tropisms

Geotropism or gravitropism refers to the growth of plants guided by gravity.

Geotropism is one of the forms of tropism. We give the name of tropism to plant growth movements in response to an external stimulus.

Plant parts respond differently to gravity's stimulus.

The roots present positive geotropism, grow towards the ground, in the direction oriented by gravity. the stems present negative geotropism, grow in the opposite direction of gravity.

Geotropism example

Geotropism. Despite the horizontal position, the stem grew against gravity.

This difference in the pattern of growth, in response to the stimulus of gravity, is due to the action of a plant hormone, the auxina. Auxin is responsible for cell elongation, allowing plant parts to grow.

The greater concentration of auxins in the lower part of the stem stimulates the growth of this region, causing it to curve and grow in the opposite direction to the stimulus of gravity. Thus, the stem tends to grow upwards.

Learn more about plant hormones.

Tropisms

The types of

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tropisms are determined by the nature of the stimulus. The main ones are phototropism and geotropism.

O phototropism it is the growth of plants oriented towards the light stimulus. As with geotropism, it can also be positive or negative.

When growth occurs towards the light stimulus it is called positive phototropism. When it occurs in the opposite direction, it is called negative phototropism.

O tigmotropism it is plant growth based on the stimulus when it comes into contact with an object. One example is tendrils, which curl up on physical supports.

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