types of control and cordination in plants

Asked by vshrikanth | 10th Sep, 2010, 12:25: PM

Expert Answer:

Plant shows two types of movements- one dependent on growth and the other independent of growth.

 
Movements Due to growth or Tropic Movements

A growth movement of a plant part in response to an external stimulus in which the direction of a stimulus determines the direction of response is called tropism. Thus tropism is a directional movement of the part of a plant caused due to its growth.

Types of tropism:

1. The movement of a plant part in response to light is called phototropism. The stem of a growing plant bends towards the light (positive phototropism), while roots of a plant move away from light (negative phototropism).
2. The movement of a plant part in response to gravity is called geotropism. The roots of a plant move downwards in the direction of gravity. On the other hand the stem of a plant grow upwards and away from the earth.
3. The movement of a plant part in response to chemicals is called chemotropism.

4. The movement of a plant part in response to water is called hydrotropism. The roots of a plant always grow towards water.
5. The directional growth movement of a plant part in response to the touch of an object is called Thigmotropism.

Nastic Movements:
In nastic movements the movement of plant part is neither towards the stimulus nor away from the stimulus. This movement is not a directional movement of the plant part with respect to the stimulus. In nastic movements growth may or may not take place.

Answered by  | 10th Sep, 2010, 07:34: PM

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