Abstract
The osmotic water potential and turgor pressure of fungal mycelia were determined by thermocouple psychrometry. The water potential ( ψ ) of intact aerial mycelia was assumed to be the same as that of the growth substrate: the osmotic water potential ( ψ s ) of the mycelia was determined by psychrometric measurement of the water potential of disrupted samples of the mycelia. Turgor pressure ( ψ p ) of the mycelia was calculated by difference ( ψ p =ψ-ψ s ). The effect of decreasing substrate water potential on the turgor pressure, osmotic water potential and colony growth rate of Mucor hiemalis and Aspergillus wentii was evaluated, using sucrose and KCl to control substrate water potential. Mycelial turgor pressure ranged from 4 to 11 bar for M. hiemalis and 12 to 18 bar for A. wentii but showed no consistent relationship to growth rate or to substrate and osmotic water potential. The results indicate that solute-induced growth retardation of M. hiemalis probably involves an inhibitory influence of low internal osmotic water potential.
Published Version
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