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The growth of a plant part due to chemical stimulus is known as chemotropism
'Chemotropism is growth of organisms such as bacteria and plants, navigated by chemical stimulus from outside of the organism or organism's 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.
Chemotropism in plantsEdit
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 chemotropism.
An example of positive and negative chemotropism is shown by a plant’s roots; the roots grow towards useful minerals displaying positive chemotropism, and grow away from harmful acids displaying negative chemotropism.
Chemotropism in animalsEdit
Another example of chemotropic movement includes the growth of individual neuronal cell axons in response to extracellular signals. These signals guide the developing axon to innervate the correct target tissue. The neuronal growth cones are guided by gradients of chemoattractant molecules emanating from their intermediate or final targets. There is evidence that the axons of peripheral neurons are guided by chemotropism and the directed growth of some central axons is also a chemo-tropic response, it remains to be determined whether chemotropism also operates in the central nervous system. Evidence of chemotropism has also been noted in neuronal regeneration, where chemotropic substances guide the ganglionic neurites towards the degenerated neuronal stump.
Other examples of ChemotropismEdit
The addition of atmospheric nitrogen, also called nitrogen fixation, is an example of chemotropism.
Chemotropism is different from Chemotaxis, the major difference being that chemotropism is related to growth, while chemotaxis is related to locomotion.
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