(turgor potential) A component of * water potential, represented by the symbol ψρ. Pressure potentials may be negative, in which case they represent tensions. Tensions arise as a result of transpiration and are caused by resistance of the tissues to water flow. In extreme conditions very low (-150 bar) pressure potentials can develop. Pressure potential gradients are responsible for the upward movement of water in the xylem (see cohesion theory). Positive pressure potentials are termed hydrostatic pressures. |
