In order for Achlya to grow, its hyphae must be able to extend. The mechanism of hyphal growth is not completely understood however. Cytoplasmic vesicles appear to fuse with the apical plasma membrane, thereby donating their contents and their membranes to the growing cell surface, as Figure 1 illustrates below. As Figure 2 demonstrates, vesicles are also present where lateral branches are initiated. Lateral walls need to be softened at points where branches form.
Vesicles appear at the tips of lateral cell walls where branching occurs.
It is possible that these vesicles could contain wall-hydrolyzing enzymes, like cellulases. Cellulases are enzymes involved in cell wall degradation of many organisms. They break down the major component of Oomycete cell walls, called cellulose. Bonds of the lateral cell walls would be broken in order to initiate a hyphal branch. It has been shown that Achlya normally releases multiple cellulases during hyphal growth and that osmotically stressing Achlya causes an elevated release of cellulase enzymes with a simultaneous increase in wall plasticity.