Question

Transpiration is said to be price paid for photosynthesis

Answer 1

Plants absorb water from the soil aided by transpiration pull. Transpiration pull is explained by Dixon and Joly theory. Dixon- Joly theory is also known as Cohesion-Tension theory. This theory is based on the upward movement of water from the root to aerial parts of the plant body which is called as ascent of sap or often called translocation of water.Water molecules stick to one another through cohesion forming a column in the xylem. The negative pressure created by transpiration pull exerts a force on these water particles causing their upward movement in xylem.
Transpiration is the evaporation of water from the leaves in the form of water vapour. Transpiration occurs in leaves through special structures present on them called as stomata. Transpiration always occurs against the gravity. Transpiration involves mainly the xylem cells which become active during absorption process by the roots.
Hence, transpiration is considered as the cost paid by the plants for performing photosynthesis.

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