Ultrastructural differences between wall apices of growing and non-growing hyphae ofSchizophyllum commune

Abstract

Newly synthesized chitin at the hyphal apex ofSchizophyllum commune was shown to be highly susceptible to chitinase degradation and solubilization by dilute mineral acid. With time this chitin became gradually more resistant to these treatments. With a combination of the shadow-cast technique and electron microscopic autoradiography it could be shown that this process occurred as the newly synthesized chitin moved into subapical parts of growing hyphae but also in non-growing apices which had ceased growth after incorporation of theN-acetyl[6-3H]glucosamine. These results are in agreement with a model which explains apical morphogenesis by assuming that the newly synthesized wall material at the apex is plastic due to the presence of individual polymer chains but becomes rigidified because of subsequent physical and chemical changes involving these polymers.