Question

The graviperception (geotropic response) of the roots is due to starch grains (statoliths) in?
A. Cells of root cap
B. Cells of root hair
C. Cells in root apex
D. Cells in growing point

Answer 1

Hint:
> Plants have the ability to sense the Earth’s gravity in various ways, and one of them is - statoliths.
> Statoliths (dense amyloplasts) produce starch from simpler materials and store it. This starch is actively involved in the graviperception by the plant.

Complete answer:
> Gravitropism basically refers to the directive growth due to which the plants align in response to the vector of gravity.
> Statoliths are present in the cells of the root cap; they induce the root’s growth towards gravity.
> When an erect flower-stem is made to undergo a positional change, it responds by geotropic curvature, and eventually retrieves the vertical position.
> Statoliths’ function is performed by the starch grains which are mobile, and drop down to the cell’s lower end.
> As long as the plant is in a vertical position, the starch grains rest in the cells’ basal wall’s layer.
> If the plant is placed obliquely or horizontally, the dropping starch grains quickly take a different position.
Option A) Cells of root cap - according to the information mentioned above, this is the Correct option.
Option B) Cells of root hair - according to the information mentioned above, this is the incorrect option.
Option C) Cells in root apex - because the statoliths are present in the cells of root cap and not apex, this is the incorrect option.
Option D) - Cells in growing point - according to the information mentioned above, this is the incorrect option.

So, the correct option: - (A).

Note: Geotropism refers to the resultant adaptive response of the growing parts of plants.
Roots are positively geotropic - meaning that they grow downwards (in the direction of gravitational force) towards the Earth’s center.
Whereas, shoots are negatively geotropic, that is, they grow up towards the surface (in the direction opposite to the gravitational force).