Determination of relationships between water potential and water saturation deficit in leaf tissue

The mutual relationship between the water potential and water saturation deficit (w.s.d.) was studied on samples of leaf tissue of fodder cabage. Definite values of water potential were obtained by long-term exposure of plant material to an atmosphere with definite constant pressure of water vapour. The resulting w.s.d. values were determined gravimetrically. Water saturation deficit varies indirectly with the water potential. This dependence was linear for values of water potential from −4·4 to −43·9 atm. Since the stabilization of equilibrum of water potential between the leaf tissue and surrounding atmosphere was very slow the relationship between water potential and w.s.d. was influenced by the size of samples and by the length of exposure. Therefore this method was more suitable for relative than for absolute measurement.