Geotropism

Geotropism (also known as gravitropism) is a turning or growth movement by a plant or fungus in response to gravity. This natural phenomenon is a key component of the adaptive response of plants to environmental stimuli.

Overview

Geotropism is a type of tropism characterized by the directional growth of an organism in response to gravity. It is a complex process that involves a range of physiological and biochemical mechanisms. The direction of growth is determined by the direction of the gravity vector.

Types of Geotropism

There are two types of geotropism:

• Positive geotropism - occurs when parts of the plant grow towards the gravitational pull. This is typically seen in roots.
• Negative geotropism - occurs when parts of the plant grow against or away from the gravitational pull. This is typically seen in stems.

Mechanism of Geotropism

The mechanism of geotropism involves the sensing of gravity by the plant's statocytes, which are specialized cells located in the root cap and the shoots of the plant. These cells contain amyloplasts, which are dense, starch-filled organelles that sediment in response to gravity. This sedimentation is perceived by the plant as a directional cue, triggering a signal transduction pathway that leads to differential growth and the bending of the plant organ.

Role in Plant Development

Geotropism plays a crucial role in plant development and survival. It helps in the proper orientation of the plant, ensuring that the roots grow downwards into the soil to absorb water and nutrients, and that the shoots grow upwards towards the light for photosynthesis.

See Also

• Phototropism
• Thigmotropism
• Hydrotropism

References

Geotropism Resources
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