Biology – Transport mechanisms | e-Consult

Transpiration is the process by which water is lost from a plant, primarily through the leaves. It begins with water absorbed by the roots and transported upwards through the xylem to the mesophyll cells within the leaf. Evaporation plays a crucial role here. Water from the internal surfaces of the mesophyll cells evaporates into the air spaces within the leaf. This creates a water vapour gradient – a higher concentration of water vapour inside the leaf compared to the drier atmosphere surrounding it.

This water vapour then moves from the higher concentration within the leaf to the lower concentration in the atmosphere via diffusion. Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration. The rate of transpiration is influenced by various factors, including humidity, temperature, light intensity, and wind. Higher temperature and lower humidity increase the rate of diffusion, leading to increased transpiration.

In summary, transpiration involves the evaporation of water from the moist internal surfaces of the leaf, followed by the diffusion of the resulting water vapour out of the leaf and into the atmosphere.