Chemotropism

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 the example of chemo-tropism.

Fertilization of flowers by pollen is achieved because the ovary releases chemicals that produce a positive chemo-tropic response from the developing pollen tube.

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 of includes the growth of individual neuronal cell axons in response to extra cellular signals, which guide the developing axon to innervate the correct target tissue.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.

See also

• Chemotaxis