Step-by-step explanation:
Water moves from roots to leaves through a process called transpiration, driven by a combination of factors including water potential. Water potential is the measure of the potential energy of water molecules to move from one area to another. It is influenced by several factors, including pressure potential and solute potential.
In the context of water movement in plants, water potential is primarily affected by differences in solute concentration and pressure gradients. When light intensity is high, the stomata on the leaves open to facilitate gas exchange for photosynthesis. As stomata open, water vapor escapes from the leaf surface through a process called transpiration. This loss of water creates a negative pressure gradient, resulting in lower water potential in the leaf cells.
At the same time, the roots of the plant actively take up water from the soil, creating a high water potential in the root cells due to the higher solute concentration in the root tissue. This creates a water potential gradient between the roots and the leaves, with higher water potential in the roots and lower water potential in the leaves.
Water moves from areas of higher water potential (the roots) to areas of lower water potential (the leaves) through a process called osmosis. Water molecules are attracted to solute molecules, causing them to move across cell membranes and through the plant's vascular system. This movement is facilitated by specialized cells called xylem.
Thus, when light intensity is high, the combination of transpiration and the water potential gradient between the roots and leaves drives the movement of water from the roots through the xylem vessels to the leaves. This continuous flow of water, called the transpiration stream, allows for the delivery of water and nutrients to the leaves for photosynthesis and support of other metabolic processes in the plant.