Plants are excellent hydraulic engineers. Plants can transport water to the top of a tree close to 116 m (381 ft) tall using simply the fundamental rules of physics and basic potential energy management. Plants can generate enough force to fracture rocks and crumble sidewalks due to their water potential.
Water potential combines various water movement-related potential forces which may work in parallel or opposition to one another. Many different elements might be active at once in complicated biological systems. For instance, the potential (negative vector) is decreased when solutes are added, and the potential (positive vector) is increased when pressure is increased.
Table of Contents
- Meaning of Water Potential
- Water Potential Formula and Components
- Significance of Water Potential
- Frequently Asked Questions (FAQs)
Meaning of Water Potential
Water potential is defined as the potential energy of water in the system to pure water when the pressure and temperature are held constant. The ability of water molecules to flow freely inside a given environment or system can also be measured using water potential. It is represented by the Greek letter Psi (Ψ) and is calculated in kilopascals (kPa).
Water potential is always negative and rises as high as pure water at atmospheric pressure, which equals zero. The more solutes there are in dirty water or water that contains solutes, the more negative Psi (Ψ) gets because the solute particles would attract the molecules of water and limit their ability to move freely.
Water Potential Gradient
The difference between the water potentials of two liquids is known as the water potential gradient. Water potential is the ability of water to travel between two locations because of variations in pressure, dissolved solutes, and other factors. The rate of osmosis is directly influenced by the water potential gradient between two solutions; the greater the difference, the faster osmosis advances from higher to lower water potential.
Water Potential Formula and Components
The following formula is used to calculate water potential:
Ψ = Ψs + Ψp + Ψg + Ψm
However, it is usually shortened into the following formula:
Ψ = Ψs + Ψp
Here, Ψs represents solute potential, Ψp represents pressure potential, Ψg represents gravitational potential, and Ψm represents the matrix potential or matric potential.
Solute Potential (Ψs)
Osmotic potential, also known as solute potential, is the amount by which the presence of a solute in pure water reduces the water potential. The free mobility of the water molecules decreases when solutes are introduced to pure water.
Since pure water has a zero solute potential, the potential of solute is either negative or less than zero. It is shown by the symbol Ψs. At atmospheric pressure, Ψw = Ψs.
Pressure Potential (Ψp)
The water potential increases when a pressure greater than atmospheric pressure is exerted on the solution. A cell becomes turgid when its internal pressure increases, which also increases its turgor pressure. The symbol for this is (Ψp). It is almost zero in plasmolysed cells. It can be harmful in the xylem vessels, where water is drawn by an open system and creates a tension of roughly –2 MPa on the surface of a plant leaf.
Gravitational Potential (Ψg)
It results from the gravitational force of attraction on the water potential. It is dependent on the acceleration brought on by gravity, the height of the water above the fixed value, and the density of the water. Since this gravitational potential is so small, it is usually ignored.
Matrix Potential (Ψm)
Matrix represents things that are on the surface, such as soil particles, cell walls, and protoplasm. Matrix potential results from the intermolecular interactions and H-bonds assisting in the bonding of water to the cytoplasm and cell wall. The matrix potential is usually ignored in plant cells and tissues because it has little effect on osmosis. The matrix potential always has a negative value. It is written as Ψm.
Dry seeds have significant matrix potential. If it is considered, the equation would be Ψw = Ψs + Ψp + Ψm.
Significance of Water Potential
One method for describing the transport of water from a region with high to low water free energy is water potential. This idea helps in the explanation of how water is capable of defying gravity and moving freely. Water potential explains how water travels via osmosis, capillary action, and against gravity throughout the body of plants.
Life, as we know, would not exist without the continuous movement of water. Plants can carry out photosynthesis due to the water. The food chains that are sustained by metabolism at the base would not exist without water potential. There would also be no known biodiversity without water potential.
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