Introduction to Fungi:
A fungus is a heterotrophic eukaryotic organism different from plants, animals and bacteria. It includes molds, yeast and mushrooms, etc. Earlier fungi were placed in plant group but later on, it was suggested that fungi should be placed in a separate group. Its classification would be discussed in later chapter.
Some fungi are unicellular but majority of them is multicellular depending upon the type of fungi. As far as the occurrence of fungi is concerned, fungi are present in everywhere, either in form of saprobes (saprophytes) or in parasitic form (on other living organisms).
Multicellular fungi are composed of thread like filaments which are called Hyphae. Different hyphae aggregate together to form Mycellium. Body of fungi is thallus type due to undifferentiating of body into stem, leaves, and roots and division of labor among different cells is also absent.
Different fungi comprises different types of hyphae, it may be Aseptate i.e., without divided into cells or compartments as in simple fungi or Septate i.e., divided into cells with a cross wall. This cross wall is called Septa. Septa usually formed at the base of sexual organs or separate the old dead hyphae from living portion.
In some fungi, for example in Basidiomycetes, the septa is perforated which allows nuclei of different cells to pass through between different cells. Many nuclei are embedded in cytoplasm; this condition is known as Coenocytic. The thallus of fungi may be intercellular or intracellular depending upon either it confines itself to the intercellular spaces or penetrates the host tissues respectively. In few cases as in rust and smut, the thallus form patches it is called Localized fungus, on the other hand if it spread in whole body it is called Systemic fungi. Although the fungal thallus is smpler but still some modifications can be observed. As in case of Basidiomycotina and in some other fungi, modified hyphae Rhizomorph can be seen. It is specialized complex hyphae which are resistant in adverse conditions. Another structure is Appresoria which is found in parasitic fungi e.g., in members of Uredinales, Glomorella, etc. It is a swollen structure that arises either from germ tubes or infecting hyphae.
Haustorium is other modified hypha which is a knob like, elongated or branched outgrowths of somatic hyphae which enter into host cells through a minute pore in host cell wall. Other structures forms due to modifications are Hyphal traps and Rhiziods (root like hyphae).
Guest Post by: Amna Nabeel
