Biology – 8.1 Transport in plants | e-Consult

Transpiration is essential for the uptake of water by plants because it creates a water potential gradient between the soil and the plant. Here's how it works:

Water moves from the soil into the roots via osmosis, driven by the water potential gradient. The water potential in the soil is typically higher than that in the root cells due to dissolved minerals and other solutes. As water moves through the root xylem, it travels upwards towards the leaves.

In the leaves, water evaporates from the mesophyll cells into the air spaces within the leaf. This evaporation creates a lower water potential in the leaf compared to the xylem in the leaf veins. This difference in water potential (higher in the xylem, lower in the leaf) drives the continuous flow of water up the xylem, pulling water from the roots. This process is known as the transpiration stream.

Therefore, transpiration is not just the loss of water; it's the driving force behind water uptake. The water potential gradient, created by transpiration, ensures a continuous flow of water from the soil, through the roots, and up to the leaves, enabling the plant to stay hydrated and function properly. Without transpiration, the water potential gradient would be absent, and water uptake would cease.