In geotropic growth, which statement correctly describes positive and negative geotropism?

In geotropic growth, which statement correctly describes positive and negative geotropism?

• A. Positive geotropism is growth toward gravity (roots); negative geotropism is growth away from gravity (stems)
• B. Positive geotropism is growth away from gravity (stems); negative geotropism is growth toward gravity (roots)
• C. Geotropic growth is only found in leaves
• D. There is no distinction between positive and negative geotropism

Answer: (A)

Gravitropism is directional growth in response to gravity. In plants, roots exhibit positive geotropism, growing toward gravity, while stems show negative geotropism, growing away from gravity. This occurs because gravity is sensed by cells in the plant’s tip, where statoliths settle in the direction of gravity and influence hormone signals (like auxin) that control cell elongation. In roots, more auxin on the lower side inhibits elongation there, so the upper side grows relatively more and the root bends downward toward gravity. In stems, the auxin distribution promotes more elongation on the lower side, pushing the stem to bend upward, away from gravity. Therefore, the statement that positive geotropism is growth toward gravity (roots) and negative geotropism is growth away from gravity (stems) is the best description.

Gravitropism is directional growth in response to gravity. In plants, roots exhibit positive geotropism, growing toward gravity, while stems show negative geotropism, growing away from gravity. This occurs because gravity is sensed by cells in the plant’s tip, where statoliths settle in the direction of gravity and influence hormone signals (like auxin) that control cell elongation. In roots, more auxin on the lower side inhibits elongation there, so the upper side grows relatively more and the root bends downward toward gravity. In stems, the auxin distribution promotes more elongation on the lower side, pushing the stem to bend upward, away from gravity. Therefore, the statement that positive geotropism is growth toward gravity (roots) and negative geotropism is growth away from gravity (stems) is the best description.