Question

Geotropism is an example of
(a) Change of light
(b) Plant adaptation
(c) Heat adaptation
(d) None of the above

Answer 1

Hint: Geotropism is also called gravitropism. Plant tropisms are mechanisms that allow plants to adapt to changes in the environment. A tropism is growth to or fro from a stimulus. Growth in a stimulus direction is called positive tropism, while growth away from a stimulus is known as negative tropism.

Complete answer:
Plants are trying to transform their morphology and position according to other stimuli like touch and gravity. Geotropism is the growth of plant parts in reaction to the force of gravity. Negative geotropism is the growth against the gravity of a part of the plant. Positive geotropism is when a part of a plant grows towards gravity.
In response to gravity, the roots of a plant grow towards the earth and they set an example of positive geotropism whereas the stem grows away from the earth making it an example of negative geotropism. Various parts of a plant grow in opposite directions because their roles are different. To provide support for the plant, as well as access to water and nutrients, the roots need to expand to the bottom. The stem needs to expand upward into the sunlight so that the plant can photosynthesize, or use sunlight to make food.
So, the correct answer is, ‘Plant adaptation’.

Note: Plants have organelles called statoliths which settle down at the bottom of their cells and allow plants to feel gravity. They also have a hormone called auxin, which promotes the growth and elongation in plant cells. The statoliths and auxin cause downward growth for root cells, while cells above ground are signaled to rise upward.