Growth is also accompanied by nuclear division and cross wall formation. The apical compartment of the hypha is often mutinucleate, sometimes there are over 50 nuclei. This is because there are repeated mitotic divisions of the nucleus in a parasynchronous wave, beginning at the tip and moving backwards towards the first septum. The mitotic division is very rapid, taking about 4 minutes, and the hypha continues to grow forwards whilst this is happening. Undifferentiated growth does not continue indefinitely.
Fungal colonies show a differentiation from margin to the centre of the colony.
The extension zone . Hyphae are advancing into fresh media. The branches are arranged to give the most effective colonization and utilization of the substrate, and the growth of the hyphae is oriented to avoid the other hyphae. The mechanism by which this occurs is unknown, but probably relates to food gradients and toxin gradients. The productive zone .