Question

How does water potential affect osmosis?

Answer 1

Hint: Osmosis is the process of movement of solvent molecules from the region of higher concentration to the region of lower concentration through a semipermeable membrane. The semipermeable membrane is a selectively permeable membrane like cell membrane etc.

Complete answer:
Water potential helps in determining the tendency of water from one region to another as a result of osmosis, gravity, capillary action, mechanical pressure etc. Water potential can be defined as the potential energy of water per unit volume with respect to pure water in reference condition. Thus water potential is the measure of how freely molecules can move in a particular medium.

If the solvent concentration is greater than solute in a medium then the medium is said to have higher water potential. The water always moves from the region of higher water potential to the region of lower water potential. So the rate of osmosis is directly proportional to the water potential. If a solution has high water potential (low solute concentration) then osmosis will take place.
For example in plants the xylem vessels in the leaves have low water potential as they have high solute concentration due to transpiration.

Note: The water potential is measured in kilopascal. Water potential of pure water is zero. Its value is always negative with the maximum value of zero. The water potential of internal parts of the plant is more negative than pure water. This value causes water to move from soil to plants through osmosis.