Question

Which of the following is absent in the root hair?
A) Cell wall
B) Vacuole
C) Nucleus
D) Chloroplast

Answer 1

Hint: The root is a non-green, cylindrical descending part of the plant that normally grows downwards into the soil. It lacks leaves, nodes and buds and is concerned with anchorage of the plant and absorption of water and mineral salts. Roots often serve as storehouses of food materials.

Complete answer:
Root hairs lie above the region of elongation and bear a cluster of very fine tubular outgrowths. They are produced from the outermost layer of the root, the epiblema and look like soft cotton fibres. The root hairs increase the exposed surface of the root for absorption. As the root increases in length, the root hair in the old region gets shrivelled and is shed. However, new root hair appears in the younger part of the zone of elongation.

Now, look at the options that we are provided with.
A) In root hairs, thin cell walls are present for intake of water at a very high speed during osmosis and not to restrict the movement of water because root hairs have a large surface area.
B) Root hairs having large vacuoles to absorb water rapidly and transfer it to the next cell of the plant.
C) The root hairs also contain nuclei as a storehouse of genetic material or DNA. It also prevents too much expansion when the water enters the cell of the root hairs.
D) Root hairs do not contain chloroplast because root hairs are present in dark and do not carry out the process of photosynthesis.

Therefore, the correct answer is option (D) chloroplast.

Note: Roots are non-green cylindrical organs that constitute the descending axis of the plant. A functional root is covered at the tip by a root cap. Near the tip, the roots bear unicellular tubular root hairs. The geotropic response is always positive for the main root.