Give three examples of chemotropism
Chemotropism may be defined as the movement or the growth of the organism in response to a chemical stimulus. This response is termed positive if the growth or movement is towards the stimulus and is termed negative if it is away from the stimulus.
Examples:
(i) The ovary of a flower secretes some chemicals which produce a positive chemotropic response attracting the pollen tube towards itself. This results in the fertilization of the flower by the pollens by the production of the pollen tubes. Also, the roots of the plant show a positive chemotropism by growing toward the useful minerals and shows negative chemotropism by growing away from the harmful chemicals.
(ii) An example of positive and negative chemotropism is shown by a plants roots; the roots grow towards useful minerals displaying positive chemotropism, and grow away from harmful acids displaying negative chemotropism.
(iii) Growth of polen tube towards ovum is an example of chemotropism.The growth of the pollen tube toward the ovule responses to the chemicals released by the stigma.