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Chemo-tropism is the growth of organisms (or parts of an organism, including individual cells) such as bacteria and plants, navigated by chemical stimulus from outside of the organism or organisms part. The response of the organism or organism part is termed ‘positive’ if the growth is towards the stimulus, or ‘negative’ if the growth is away from the stimulus.
An example of chemo-tropic movement can be seen during the growth of the pollen tube, where growth is always towards the ovules. It can be also written that conversion of flower into fruit is an example of chemo-tropism.
An example of positive and negative chemo-tropism is shown by a plant’s roots; the roots grow towards useful minerals displaying positive chemo-tropism, and grow away from harmful acids displaying negative chemo-tropism.
Another example of chemo-tropic movement includes the growth of individual neuronal cell axons in response to extra cellular signals These signals guide the developing axon to innervate the correct target tissue. Evidence of chemotropism has also been noted in neuronal regeneration, where chemotropic substances guide the ganglionic neurites towards the degenerated neuronal stump. Also, the addition of atmospheric nitrogen, also called nitrogen fixation, is an example of chemo-tropism.
Chemo-tropism is different from Chemotaxis, the major difference being that chemo-tropism is related to growth, while chemotaxis is related to locomotion.
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