vízpotenciál

Vízpotenciál, often translated as "water potential," is a thermodynamic concept used to describe the potential energy of water in a system. It is a key factor in understanding water movement through soils, plants, and the atmosphere. Water potential is influenced by various factors, including pressure, solute concentration, and gravity.

The basic unit of water potential is pressure, typically measured in units such as megapascals (MPa) or bars. Pure water at standard temperature and pressure has a water potential of zero. The presence of solutes, such as salts and sugars, lowers the water potential, making it negative. This is because solutes bind to water molecules, reducing their free energy.

Pressure potential, also known as turgor pressure in plants, can increase water potential, making it positive. Gravitational potential accounts for the effect of gravity on water, with water at higher elevations having a higher gravitational potential. Water naturally moves from areas of higher water potential to areas of lower water potential. This movement can occur through osmosis, diffusion, or bulk flow.

In plant physiology, water potential is crucial for understanding transpiration, the process by which water is lost from plants through evaporation. The water potential gradient between the soil, the plant, and the atmosphere drives the upward movement of water from the roots to the leaves. Soil water potential is a measure of how tightly water is held by soil particles and is a critical factor in plant water availability. A lower (more negative) water potential indicates that water is less available to plants.