NEET BIOLOGY

Detailed explanation-1: -The downward growth of roots towards the direction of water availability is called positive hydrotropism . The downward growth of roots towards the pull of gravity is called positive geotropism .

Detailed explanation-2: -One of the key parameters that every plant must respond to is the direction of gravity: stems go up (opposite to the pull of gravity) and roots go down (in the same direction as the force of gravity).

Detailed explanation-3: -Plants respond directly to Earth’s gravitational attraction, and also to light. 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.

Detailed explanation-4: -The reason plants know which way to grow in response to gravity is due to amyloplasts in the plants. Amyloplasts (also known as statoliths ) are specialized plastids that contain starch granules and settle downward in response to gravity. Amyloplasts are found in shoots and in specialized cells of the root cap.

Detailed explanation-5: -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.