Transpiration in leaves

Transpiration is the loss of water vapour from leaves. It happens in two connected stages: water first evaporates inside the leaf, then water vapour diffuses out.

Water on the surfaces of mesophyll cells evaporates into the air spaces between the cells. During evaporation, liquid water changes into water vapour.

The water vapour then diffuses through the air spaces and leaves through small openings called stomata. Diffusion is the net movement of water vapour from a region of higher concentration to a region of lower concentration. Thus, evaporation supplies water vapour inside the leaf, and diffusion carries it out.

Pathway of water through a plant

Water enters the plant from the soil through root hair cells on the surface of the root. It then passes through the cells of the root cortex and enters the xylem.

The xylem carries water through the root and stem into the leaf. In the leaf, water leaves the xylem and reaches the mesophyll cells inside the leaf. Together, these structures provide a continuous route for water from the root to the leaf.