Statocyte

Statocyte

Diagram of a root tip showing the location of statocytes in the root cap.

A statocyte is a type of plant cell found in the root cap of plants. These cells are specialized for the perception of gravity, a process known as gravitropism. Statocytes contain dense, starch-filled organelles called statoliths, which play a crucial role in the plant's ability to sense its orientation relative to the gravitational field.

Structure

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Diagram of a statocyte showing statoliths settling at the bottom of the cell.

Statocytes are located in the columella region of the root cap. They are characterized by their large central vacuole and the presence of numerous amyloplasts, which are specialized plastids that store starch. These amyloplasts act as statoliths, settling at the bottom of the cell in response to gravity. This sedimentation is thought to trigger a signal transduction pathway that leads to differential growth on either side of the root, causing it to bend towards the direction of gravity.

Function

The primary function of statocytes is to detect the direction of gravity and initiate the plant's gravitropic response. When a plant root is displaced from its vertical orientation, the statoliths within the statocytes move in response to the change in gravitational pull. This movement is detected by the cell's cytoskeleton, which transduces the mechanical signal into a biochemical response. The result is the redistribution of the plant hormone auxin within the root, leading to differential growth rates on opposite sides of the root and causing it to curve downward.

Mechanism of Gravitropism

The process of gravitropism in plants involves several steps:

1. Perception: Statocytes perceive the direction of gravity through the movement of statoliths. 2. Signal Transduction: The movement of statoliths is converted into a biochemical signal via the cytoskeleton and other cellular components. 3. Response: The signal leads to the redistribution of auxin, which promotes cell elongation on one side of the root, causing it to bend.

Related Pages

• Gravitropism
• Root cap
• Amyloplast
• Auxin
• Cytoskeleton