Question

Examples of different types of tropisms

Answer 1

Phototropism

The growth movement in plants in response to light stimulus is known asphototropism. For example, the flower head of a sunflower is positively phototropic as it moves from East to West, along with the movement of the Sun.

In the above activity, the shoots showpositive phototropismwhilethe roots shownegative phototropism.

The ovary stalk of groundnut is positively phototropic before fertilization and becomes negatively phototropic after fertilization. This is the reason why fruits such as groundnuts are formed underground.

Geotropism

The growth movement in plants in response to the force of gravity is known asgeotropism. In geotropism, the roots of the plant always grow downwards while the shoots always grow upwards, away from the earth.

Chemotropism

Thegrowth movement in plants in response to chemical stimuli is known aschemotropism. For example, the growth of pollen tube towards the ovule in the ovary (through the stigma and style) is an example of positive chemotropism.

Hydrotropism

Thegrowth movement in plants in response to water is known ashydrotropism. For example, the roots of some plants grow towards the water source, even when the water source is not present directly below it.