Question

Give one example of chemotropism.

Answer 1

Hint: Chemotropism is defined as the growth of an organism in a direction of the chemical stimulus. It is mainly observed in plants, fungi and animals. A chemical stimulus or gradient can influence the growth in negative or positive direction.

Complete answer:Tropism is a biological phenomenon that indicates the growth or turning movements in the plants in response to environmental stimulus. Chemotropism is the growth of an organism due to the chemical stimulus generated from the environment. Growth can be positive growth or negative growth.
Positive growth: It means the growth of an organism in the direction of the stimulus.
Negative growth: It means the growth of an organism away from the direction of the stimulus.
Chemotropism can occur in plants, animals, and fungi. In plants, the process of chemotropism is seen during fertilization and pollen tube. Plants need a delivery system for sexual reproduction. Pollen Insects or with the help of wind the pollen which contains male gametophyte is transferred from one flower to another. The ovary releases a chemical that initiates a positive chemotropic response from the developing pollen tube. In response to the tube develops a defined tip growth area that promotes directional growth and elongation of the pollen tube due to a calcium gradient. This calcium gradient is essential for the growth to occur. It has been shown that inhibiting the formation of the calcium gradient results in no growth. The pollen tube continues to grow towards the ovules and the male sperm remains in the apical region and is further transported to the female ovule.

Note: As growth can be positive or negative growth. Positive and negative growth in plants is mainly observed in the roots of plants. The roots grow towards useful minerals displaying positive chemotropism and grow away from harmful acids displaying negative chemotropism.