Question

Briefly explain how transpiration helps in the conduction of water in plants?
A. …………………………………………………………………
B. ……………………………………………………………………

Answer 1

Hint: Transpiration is the process of loss of water vapour from the aerial parts of the plants. It provides a cooling effect to the plant and helps in the absorption of water from the roots to the leaves. It also helps in the conduction of water and minerals by developing a pull mechanism.

Complete answer:
Transpiration is the necessary evil that occurs in plants. Water evaporates from the aerial openings of the plants leaving a cooling sensation behind. It can take place in three ways-
-Stomatal transpiration- Pores present on the epidermis of the leaves which are responsible for gaseous exchange in plants are called stomata. These pores are also responsible for the loss of water.
-Cuticular transpiration—The transpiration takes place through the cuticle which is a thin layer over the epidermis. Water is also lost through this cuticle.
-Lenticular transpiration- Transpiration takes place through lenticels that are minute pores found on the stems of woody plants and epidermis of fruits.

Transpiration results in a loss in water from the aerial parts which requires compensation. So, this compensation occurs due to a vacancy created in the xylem vessels. This void creates a pull to enable the movement of water upwards to maintain the continuity of water molecules, known as the transpiration pull.
Transpiration creates a void which develops a suction force necessary for the upward movement of water. The first water molecule lost during transpiration is compensated by the conduction of one water molecule upward. This water is essential for photosynthesis.
After the first molecule goes up, again there is a void created after the first molecule. This void again acts as a pull for the second molecule to move up. This way a continuous line of water molecules is pushed upwards for conduction of water.
This is how transpiration helps in the conduction of water and minerals to the upper parts of the plant.

Note: There is a theory to the conduction of water in plants- the higher the rate of transpiration, the higher is the conduction of water and solutes from the soil. Several factors are affecting the rate of transpiration like environmental conditions and the size of the aperture through which water will go out. During conduction of water both cohesion and adhesion forces come into play, because transpiration pull is a process which works against gravity.