Transsincitial potassium gradients in the polarized growth of Neurospora crassa hyphae

Electron probe microanalysis of Neurospora crassa hypha preparation reveale d significant nonhomogenety of potassium contents in the hyphae. The presen ce of areas with low potassium contents in a close proximity of the growing tip, as well as in distal part of the hyphae in the cross-membrane area ab out 1 mu m in width in discovered. It is shown that intracellular potassium concentration can change more then 3-5 times from epical to distal areas o f the leading hyphae, the potassium contents in the apical part of the hyph ae usually beind minimal. One can assume that the intracellular potassium c ontents are defined by the volume occupied by free intracellular water, i.e ., by the size of the space available for diffusion of substances (includin g inorganic ions).