Rhizomorphs are a special morphological adaptation root-like structures found in fungi. These root-like structures are composed of parallel-oriented
hyphae that can be found in several species of
wood-decay and
ectomycorrhizal basidiomycete as well as
ascomycete fungi. Rhizomorphs can facilitate the colonization of some dry-rot fungi such as
Serpula lacrymans and
Meruliporia incrassata and cause damage to homes in Europe and North America, respectively, by decaying wood. Another genus that is very well studied for their abundance of rhizomorphs production is
Armillaria, with some species being pathogens and others
saprotrophs of trees and shrubs. Known for their role in facilitating the spread and colonization of fungi in the environment, rhizomorphs are the most complex organs produced by fungi. They are made up of highly specialized hyphae that are different in size, orientation, and function. Fungi that possess these structures can compete and grow in harsh conditions. Rhizomorphs are sometimes called mycelial cords, although they are structurally different: mycelial cords are less complex and have a loose network of
hyphae giving an appearance of a fan-like mat, Concentrations of oxygen play an important role in the production of rhizomorphs. When there is a high concentration of oxygen in the atmosphere, soil moisture, temperature and pH, rhizomorph production increases. Rhizomorphs contain four differentiated types of tissues: • The outer layers are a compact growing point that make up the
mucilage • The
melanized wall that serves as protection against colonization by another microorganisms (bacteria or fungi) • The
medulla that serves for conduction of water and dissolved nutrients • The
central line used as an air conducting channel.
Function Rhizomorphs act as a system of underground absorption and growth structures that invade and decay roots and wood, as well as sometimes propagating through the air. They can access places where food resources are not available, giving certain advantages to the fungi that produce them in terms of competition. They act as an extension of the fungal body and allow the fungus to infect, disseminate and survive for long periods of time. Rhizomorphs are composed of a medulla and central line which are responsible for water, nutrient, and gas transportation. The transportation of oxygen occurs from the base of rhizomorphs to the terminal growing part (tips). Rhizomorphs that live under free oxygen conditions are able to absorb and transport nutrients. == Example taxa ==