Transpiration is the process of water loss through the stomata of leaves as water evaporates from the mesophyll cells into the intercellular spaces and then diffuses out through the stomata.

During transpiration, water vapour diffuses out of the stomata, creating a negative pressure or tension in the xylem vessels. This tension, known as the cohesive tension theory of water transport, causes water to move upwards in the xylem due to the cohesion and adhesion properties of water molecules.

Transpiration not only helps in the upward movement of water and minerals but also provides cooling for plants. As water evaporates from the leaf surfaces, it takes up heat, resulting in a decrease in leaf temperature. Additionally, transpiration helps in maintaining cell turgidity and the opening of stomata for gas exchange.