types of control and cordination in plants
Asked by vshrikanth | 10th Sep, 2010, 12:25: PM
Plant shows two types of movements- one dependent on growth and the other independent of growth.
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.
5. The directional growth movement of a plant part in response to the touch of an object is called Thigmotropism.
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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