Explain co-ordination in plants with the help of suitable examples.
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[Textbook Question 6c pg no.178]
Animals ( including human beings) have a nervous system for their coordination but plants do not have such a nervous system for the coordination the show tropism or tropic movement. Now, what is tropism.
- Tropism (tropic movement): the growth, development or movement of any plant part towards an external stimulus (pl. stimuli) is called tropism or tropic movement.
These tropic movements can be of several types like :
1.Phototropism: the movement of any plant part in response to the source of light is called photo-tropism or phototrophic movement. For example, the sunflower moves from east to west along with the Sun.
2.Geotropism: the movement of any plant part in response to the source of gravity is called geotropism or geotropic movement. For example, the growth of roots towards the gravitational force is positive geotropism whereas the growth of the shoot system (like stem, branches and leaves etc) against the force of gravity is called negative geotropism.
3.Hydrotropism: the movement of any plant part in response to the source of water is called hydrotropism or hydrotropic movement. For example, the roots of a plant grow towards the source of water even when the water source is not directly below it.
4.Chemotropism: the movement of any plant part in response to a chemical stimulus is called chemotropism or chemotrophic movement.
The growth of the pollen tube towards the ovule of the ovary (via stigma and style) is an example of positive chemotrophic movement.
5.Thigmotropism: the growth or movement of any plant part in response to a touch stimulus (generally of a solid and stiff body) is called thigmotropism or thigmotropic movement. For example, the growth of tendrils of Cucurbitaceae plants when it contacts solid and stiff support.
Animals ( including human beings) have a nervous system for their coordination but plants do not have such a nervous system for the coordination the show tropism or tropic movement. Now, what is tropism.
- Tropism (tropic movement): the growth, development or movement of any plant part towards an external stimulus (pl. stimuli) is called tropism or tropic movement.
These tropic movements can be of several types like :
1.Phototropism: the movement of any plant part in response to the source of light is called photo-tropism or phototrophic movement. For example, the sunflower moves from east to west along with the Sun.
2.Geotropism: the movement of any plant part in response to the source of gravity is called geotropism or geotropic movement. For example, the growth of roots towards the gravitational force is positive geotropism whereas the growth of the shoot system (like stem, branches and leaves etc) against the force of gravity is called negative geotropism.
3.Hydrotropism: the movement of any plant part in response to the source of water is called hydrotropism or hydrotropic movement. For example, the roots of a plant grow towards the source of water even when the water source is not directly below it.
4.Chemotropism: the movement of any plant part in response to a chemical stimulus is called chemotropism or chemotrophic movement.
The growth of the pollen tube towards the ovule of the ovary (via stigma and style) is an example of positive chemotrophic movement.
5.Thigmotropism: the growth or movement of any plant part in response to a touch stimulus (generally of a solid and stiff body) is called thigmotropism or thigmotropic movement. For example, the growth of tendrils of Cucurbitaceae plants when it contacts solid and stiff support.
