Question

Define and explain water potential.

Answer 1

Hint: Water potential is the energy of water per unit volume respective to pure water in reference conditions. Plants are responsible for bringing the water to the leaves for photosynthesis.

Complete answer:
At constant temperature and pressure, the difference between free energy of a water in a system compared to the pure water is called water potential. Slatyer and Taylor helped in describing the water potential .It is founded on two key principles of freedom of energy and chemical potential. The thermodynamics laws govern the potential of water.
The measurement of water moving free in a specific environment or system can also be known by water potential. It is measured by kilopascals and represented by psi. The water potential is never positive but has zero maximum value. The greater the solutes present in the solution, the highly negative water potential becomes, as impure water or water that has solutes decreases to the freedom of movement of water molecules by attracting water to itself.
Osmosis, gravity, mechanical pressure or matrix effects are the main factors which cause the water potential. It is important in considering the flow of water in the bottom of plants, animals and soil. Also water potential is highly used in power generation.

The water potential of plant solutions is determined by solute concentration, heat, gravity and matrix effects.
-Osmotic or solute potential: Solute decreases the potential of water by absorbing some of the potential energy present in the water. It can dissolve in water because water potential can bind to them through hydrogen bonds.
-Matrix potential: Binding of water to a matrix either eliminates or absorbs potential energy from the device. The matrix potential is similar to solute potential since it involves linking the energy in the aqueous system by creating hydrogen bonds between the water and some other portion.
-Gravitational potential: It is always negative to 0 in a plant without height. It drags water from the ground and decreases the overall energy content of plant water.
-Pressure potential: It is also known as turgor pressure; it may be positive or negative. The higher the pressure the greater the energy potential of the system and vice versa.

Note: Water potential can be defined as the relative propensity of water to pass from one location to the other and is depicted by psi. It tells about the potential energy of water and helps in the movement of water through plants.