Final answer:
Water in plants is driven by transpiration, a passive process of water evaporation from leaves and stems, creating a tension force that pulls water from the roots through the xylem vessels. This process does not require metabolic energy, and while it can lead to significant water loss, the rate is controlled by the plant and environmental factors.
Step-by-step explanation:
Water in plants is primarily driven by transpiration, which is the process of evaporation of water from the leaves and stems. Transpiration is the significant mechanism by which water moves within the xylem vessels of a plant. During this process, water evaporates at the leaf-atmosphere interface, creating negative pressure, also known as tension. This pulls water upward from the roots to replace the water that has been lost.The energy driving transpiration comes from the difference in energy between the water in the soil and the water in the atmosphere, but it is important to note that transpiration does not require metabolic energy in the form of ATP, making it a passive process. However, the rate of transpiration is tightly controlled by the plant, often through the opening and closing of stomata, as well as external environmental factors such as humidity and temperature.While transpiration is essential for maintaining the water flow within a plant, it can lead to massive water loss, with up to 90 percent of the water taken up by a plant's roots potentially being lost through this process. During the nighttime, or when stomata are closed, the cohesion-tension theory explains how water is retained within the plant's structures.