Question

- Most rapid water absorption is by which method?
A) Passive absorption
B) Salt absorption
C) Active absorption
D) Absorption by roots.

Answer 1

Most of the absorption occurs due to transpiration according to the transpiration pull theory which is not an active process. Water is mostly absorbed through roots but in different ways.

Complete Answer:
In plants, the water is absorbed in two ways-
->Active absorption- in active water absorption, metabolic energy is consumed by the root cells in order to absorb water from the soil.
->Passive absorption- passive absorption occurs through the root cells. Passive absorption accounts for almost 98% of the total water absorbed from the soil in plants. The rapid absorption of water via the passive method occurs due to two reasons,
The cohesive and adhesive forces of water molecules which allows a continuous flow of water from the roots to the leaves through the xylem. Water molecules stay together due to presence of H-bonds causing cohesion between them. The attraction between the water molecules and the walls of xylem called adhesion further ensures the continuity of the water column in xylem.
The transpirational pull, when transpiration takes place in leaves, water is evaporated from the leaves to the outer atmosphere through the stomata. The lost water is replaced by more water from mesophyll cells into the intercellular spaces from the mesophyll cells which causes more water to enter mesophyll cells from the xylem of the leaf. This builds up tension in water present in the xylem elements of the leaves which is transmitted downwards till the xylem elements of roots due to which water is pulled upward in the form of continuous water column to reach the apex of the plant.

Hence the correct answer is option ‘A’.

Note: Absorption of water is directly proportional to the transpiration pull which is a passive process. Transpiration pulls majorly coordinated with adhesive and cohesive nature of water molecules to absorb water and transport it through the plant.