Question

Water will be absorbed by root hairs because-

Answer 1

The root hair in a plant undergoes respiration to yield ATP (Adenosine triphosphate). In plants, by the process of cellular respiration, glucose breaks down into ATP. Through their entire surface- roots, stems and leaves. However the majority of the water is absorbed by the root hairs.

Complete answer:
Root hairs are thin walled unicellular outgrowths of epidermis. They are in close contact with the thin film of water surrounding the soil particles. To water and minerals, the cell wall of the root hair is permeable, but its cell membrane, and the membrane around the vacuole form semi-permeable membranes. As the cells of the cortex have high osmotic pressure, the diffusion of water from the root hair to the cortical cells. By the cortical cells certain pressure or force is developed which push the water in the xylem tubes. This pressure is called the root pressure. In the tall trees, a minor role has been played by the active absorption. The passive abortion mechanism is carried out without utilization of metabolic energy. The roots here, acts as an organ of the absorption or passage. Hence, by knowing the process of how water is being absorbed by root hairs we got the answer, why water will be absorbed by the root hairs.

Note:
At the leaf end the transpiration pull is responsible for dragging water through the water column in the xylem elements, the pull or force is transmitted down to the root. Passive transporting is nothing different from diffusion but just explaining its meaning “passive” refers to requiring no input of energy.