Final answer:
Up to 90 percent of the water taken up by plant roots is lost through transpiration, a process where water evaporates at the leaf surface, which is primarily driven by atmospheric conditions and is crucial for the upward movement of water in plants.
Step-by-step explanation:
Transpiration is a vital biological process where water absorbed by plant roots is lost through evaporation at the leaf surface. A significant portion of the water absorbed by the plants, up to 90 percent, is used in this way.
This process is regulated by the atmosphere around the leaves and is a part of the cohesion-tension theory that explains the movement of water in plants.
Negative pressure caused by transpiration creates a tension that pulls water up from the roots to the leaves. During the day when the stomata are open, transpiration rates can be high, but it decreases at night when the stomata close, which helps the plant to retain water.