Question

The rupture and fractionation do not usually occur in the water column in vessel/tracheids during the ascent of sap because of
a. Lignified thick walls.
b. Cohesion and adhesion.
c. Weak gravitational pull.
d. Transpiration pull.

Answer 1

Hint: Xylem is the complex tissue, usually found in the vascular plants, it consists of elements such as the trachea, tracheid cells, tracheal parenchyma, and the main function of this xylem in plants is to transport the water from the roots of the plants to other parts.

Complete answer:
- The vertical conduction of water from the roots to the other parts or aerial parts of the plants, or upper parts of the plant is called Ascent of sap.
- During the conduction of water from roots to aerial parts, mainly two forces exist.
- They are cohesion and adhesion forces.
- Cohesion forces are the forces that are present in between the water molecules, it is due to the presence of hydrogen bonds in between them, so because of this cohesive forces, the continuity of the water flow, never rupture, these cohesive forces are very strong enough, even gravitational pull also do not the effect the flow.
- Another force that presents in conduction is adhesive forces, which are present in between the water molecules and the walls of the trachea, because of this no breakdown of the flow happens and water easily enters all parts of the plants.
- So cohesion and adhesion are very strong forces which enable the water flow without any rupture and fractionation.

Hence, The correct answer is option (B).

Note: Generally because of transpiration, water evaporates and forms droplets, due to this loss of water, veins of leaves obtain the more pressure to get the water flow, and this strong transpiration pull is also one of the reasons for the proper water flow.