ABSTRACT
The ability to continuously regenerate hyphal tips gives fungi the potential for indeœnite growth. This is manifested by the circular development of aerial fruiting bodies (basidiocarps) known as the “fairy ring” (Figure16.1) from underground mycelium. According to a myth, the circular pattern of basidiocarps represents the path of fairies dancing in the night. Actually, the fairy ring develops from the perennial, subterranean mycelium that extends outward and produces ephemeral fruit bodies, year after year at the periphery of the mycelium. From the rate of expansion of the diameter of the fairy rings, the age of mycelium in some cases has been estimated to be several hundred years. In Chapter 1, we learned about a colony of Armillaria bulbosa that is more than a millennium old. The most important reason for the immortal nature of fungi is the cytoplasmic continuity of the hyphal compartments. Aged or dysfunctional nuclei and mitochondria can be recycled and replaced by the migration of functional copies from other cellular compartments. Additionally, the multinuclear condition of hypha enables any potentially deleterious nuclear gene mutation to be complemented by its functional allele in other nuclei. However, in the rare cases of senescing cultures, cytoplasmic continuity of hyphal compartments enables the altered mitochondria to populate the mycelium, resulting in respiratory deœciency and death of the culture.
