transpiration pull

In botany, transpiration is the process of water loss from plants, primarily through small pores on their leaves called stomata. These stomata are essential for admitting carbon dioxide for photosynthesis and releasing oxygen. While transpiration is an unavoidable consequence of stomatal function, it is also believed to play a role in transporting water and nutrients from the roots to the rest of the plant, and may help cool the plant through evaporation.1

The upward movement of water in plants, known as transpiration pull, is largely explained by the cohesion hypothesis. This theory suggests that the attraction between water molecules (cohesion) and between water and the xylem vessel walls (adhesion) creates a continuous column of water. As water evaporates from the leaves, it pulls this entire column upward, effectively lifting water from the roots to the highest parts of the plant. While root pressure can contribute to this upward movement, it is generally insufficient on its own, especially in tall trees. Excessive transpiration can harm plants by causing dehydration.2341