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The roots of a plant always grow downwards while the shoots usually grow upwards and away from the earth. This upward and downward growth of shoots and roots is known as:
geotropism
hydrotropism
phototropic movement
chemotropism
geotropism
The phenomenon where plant growth is directed by the force of gravity is called geotropism (or gravitropism). In this process, roots exhibit positive geotropism by growing towards the earth (with gravity), while shoots exhibit negative geotropism by growing away from the earth (against gravity).
The phenomenon where plant growth is directed by the force of gravity is called geotropism (or gravitropism). In this process, roots exhibit positive geotropism by growing towards the earth (with gravity), while shoots exhibit negative geotropism by growing away from the earth (against gravity).
Think of a potted plant tipped over on its side; over time, the stem will naturally bend and turn upwards to reach towards the light while correcting its orientation relative to gravity, similar to a self-balancing mechanism.
Geotropism is regulated by the distribution of the plant hormone auxin. In roots, gravity causes auxins to accumulate on the lower side, inhibiting cell elongation and causing the root to curve downward. In stems, gravity causes auxin accumulation on the lower side to stimulate cell elongation, resulting in upward growth.
Roots show positive geotropism as they grow towards the center of gravity.
Shoots show negative geotropism as they grow away from the direction of gravity.
Auxin redistribution is the primary biological mechanism controlling this differential growth.
Ensures roots reach soil nutrients and water.
Ensures shoots grow into an environment conducive to photosynthesis.
Geotropism is also known as gravitropism.
Option B (hydrotropism) refers to growth in response to water.
Option C (phototropic movement) refers to growth in response to light.
Option D (chemotropism) refers to growth in response to chemical stimuli, such as pollen tube growth.
A is correct тАФ the upward and downward growth of shoots and roots in response to gravity is known as geotropism.
Always link root growth to 'gravity' (geo) and shoot growth to 'light' (photo) in your mind, but remember both are gravity-responsive (geotropic) in terms of orientation!
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