Question

Give one example of chemotropism.

Answer 1

Plants, Bacteria, and fungi respond to certain chemicals that are released by their own body or from outside and they can respond to these chemicals either negatively or positively depending upon the chemicals and organisms.

Complete answer:
It is the phenomenon where chemical stimulus from outside of the organism that navigates the growth of the organism. Bacteria, fungi, and plants respond to chemotropism. The organism can respond to chemical stimuli both in a positive and negative way. Growing towards the chemical stimulus is a positive response and growing away from the chemical stimulus is a negative is a response. Chemotaxis is different from chemotropism. Chemotaxis results in locomotion whereas chemotropism results in the growth of the organism.
- Fertilization and elongation of pollen tubes in angiosperms is one example of chemotropism. Plants cannot move like animals, so it requires a delivery mechanism to reproduce sexually. Male gametophyte is transferred via wind or insects or other means of Pollinating agents to other plants. For the development of the pollen tube, the ovary releases some chemicals that show a positive response. Elongation of the pollen tube is due to the calcium gradient. Due to these chemicals, pollen tubes grow towards ovules.
- Roots of plants also show positive chemotropism and negative chemotropism. If they grow towards minerals it is positive chemotropism and if they grow away from harmful acids it is negative chemotropism.

Note:
- Animals and fungi also show chemotropism. In animals, due to extracellular signals, individual neurons grow. They help the neuron to innervate with the target tissue.
- Fungi like yeast show chemotropism. They release chemicals called pheromones to attract mates.
- Nitrogen fixation is also an example of chemotropism.