Factors Affecting Water Potential

When both temperature and pressure are held constant, the water potential is the potential energy of water in a system. It can also be defined as a measurement of how readily water molecules in a given environment or system can travel. It is denoted by the Greek letter Psi (Ψ) and is measured in kilopascals (kPa). The greatest value of water potential of pure water is 0, which is the same as pure water at atmospheric pressure. When it comes to impure water or water that contains solutes, the more solute there is, the more negative it gets, because the solute molecules will attract the water molecules, limiting their ability to move.

The formula for Water Potential

The following is the formula that was used to calculate:

 Ψ = ΨS + ΨP + ΨG + ΨM

However, it is frequently reduced to the following formula, which is also correct: 

Ψ = ΨS + ΨP

The solute potential is denoted by Ψs, pressure potential is denoted by Ψp, the gravitational potential is denoted by Ψg, and matric potential is denoted by m. The pressure potential is the physical pressure put on water molecules by objects or cell membranes, and it rises as pressure rises. It’s worth noting that plant cells’ pressure potential is normally kept positive for them to keep their shape, allowing the plant to remain rigid.

 Matrix potential also considers the forces that exist between water molecules and other surfaces or substances, such as soil or cell membranes. Because water particles are closely connected to soil particles, the matric potential is always negative and is more relevant in dry systems, such as soils.

Factors Affecting Water Potential

Pressure, concentration, and gravity are the key elements that determine the water potential in plants. The total of these elements is as follows:

Ψ = Ψs + Ψp + Ψg

1.Solute effect on water potential –

The influence of dissolved solutes on water potential is indicated by solute potential or osmotic potential. The dilution of water by the solutes reduces the free energy of water, which is primarily an entropy impact. In other words, combining solutes and water increases the system’s entropy or disorder, and so lowers the free energy. This means that the osmotic potential is unaffected by the solute’s specific properties.

2.Pressure’s effect on water potential –

The water potential of a plant cell is determined by the effect of hydrostatic pressure on the free energy of water is known as the pressure potential. The water potential is increased by positive pressure, whereas it is decreased by negative pressure. Plants experience both negative and positive pressure. The positive hydrostatic pressure in the cells is known as turgor pressure. Tension typically arises in the xylem conduits as a result of negative hydrostatic pressure.

3.Gravity’s effect on water potential –

Water moves downward due to gravity until the gravitational force is counteracted by an equal and opposite force. The height of water above the reference state water, the water density, and the acceleration owing to gravity all contribute to this gravitational potential. In terms of symbolism, it goes like this:   

        Ψg = ρw gh (value of ρwg is 0.01 MPa m-1)  

The gravitational factor (Ψg) is frequently overlooked in the water transport criterion at the cell level, as differences in this factor between adjacent cells are minor in comparison to variances in pressure potential and osmotic potential.

Conclusion 

Hence, Understanding and computing water movement within plants, animals, and soil has proven to be beneficial. The Greek ψ letter is frequently used to represent water potential, which is usually expressed in potential energy per unit volume. When both temperature and pressure are held constant, the water potential is the potential energy of water in a system. It can also be defined as a measurement of how readily water molecules in a given environment or system can travel. It is measured in kilopascals (kPa). The greatest value of water potential of pure water is 0, which is the same as pure water at atmospheric pressure.