NEET BIOLOGY

Detailed explanation-1: -Stems grow upward, or away from the center of Earth, and towards light. Roots grow downward, or towards the center of Earth, and away from light. These responses to external stimuli are called tropisms. Plants’ growth response to gravity is known as gravitropism; the growth response to light is phototropism.

Detailed explanation-2: -’Gravitropism’ is the reason for roots growing downwards and the stem growing upwards. Gravitropism is simply a plant’s growth movement in response to gravity. The roots of a plant show ‘positive gravitropism’ as the roots respond to the stimulus of gravity and grow in the direction of gravity (downwards).

Detailed explanation-3: -Gravity perception is important to plants because they need to send their roots downwards towards water and nutrients and their shoots upwards towards light. Plants are known to detect gravity using statoliths, which are small starch-filled packets that settle at the bottom of gravity-sensing cells.

Detailed explanation-4: -In plants, the general response to gravity is well known: their roots respond positively, growing down, into the soil, and their stems respond negatively, growing upward, to reach the sunlight.