Comparison of the effects of the physical and chemical components of soil water energy on seed germination

Abstract

The components of total soil moisture energy of consequence to a biological system are matric potential and osmotic potential. An experimental procedure, which allows the effects of the potentials to be considered independently, is described and discussed. Germination behaviour does not support the hypothesis that matric and osmotic potentials should have similar biological consequences because their free energy measurements are identical. The results support a diffusion phenomenon hypothesis with movement of solute from the soil solution through the cell membranes, so that any biological consequence is that of an internal "toxicity" rather than an osmotic "drought". For some osmotic systems, 100 cm of matric potential is as effective as 10 000 cm of osmotic potential in retarding seed germination rates.