11th Class

Blakeslee, (1904) while working with Mucor sp. observed that in some species sexual union was possible between two hyphae of the same mycelium, in others it occured between two hyphae derived from 'different' spores. He called the former phenomenon as homothallism and the latter as heterothallism. Thus, the homothallic species are self-fertile whereas the heterothallic are self sterile. In heterothallic species the two 'thalli' are sexually incompatible. They are said to belong to opposite strains. Blakeslee designated them as + and ? i.e., belonging to opposite strains or mating types. Bipolar heterothallism found in Mucor and Rhizopous.

(1) Phycomycetes (Oomycetes/Algal fungi) : It is also called lower fungi, mycelium is coenocytic. Hyphal wall may contain chitin or cellulose (e.g., Phytophthora). Asexual reproduction occurs with the help of conidio-sporangia. Under wet conditions they produce zoospores. Under dry conditions, the sporangia directly function as conidia. Zoospores have heterokont flagellation (one smooth, other tinsel). Sexual reproduction is oogamous. It occurs by gametangial contact where male nucleus enters the oogonium through a conjugation tube. The fertilized oogonium forms oospore. e.g., Saprolegnia, Albugo (Cystopus), Phytophthora, Phythium, Sclerospora, Peronospora, Plasmopara. (2) Zygomycetes (Conjugation fungi) : Mycelium is coenocytic. Hyphal wall contains chitin or fungal cellulose. Motile stage is absent. Spores (Sporangiospores/aplanospores) are born inside sporangia. Sexual reproduction involve fusion of coenogametes through conjugation (Gametangial copulation). It produces a resting diploid Zygospore. On germination, each zygospore forms a germ sporangium at the tip of a hypha called promycelium e.g., Mucor, Rhizopus, Pilobolus, Abscidia, Saksenea. more...

The fungi are achlorophyllous organisms and hence they can not prepare their food. They live as heterotrophs i.e., as parasites and saprophytes. Some forms live symbiotically with other green forms. Parasites : They obtain their food from a living host. A parasite may be obligate or facultative. The obligate parasites thrive on a living host throughout their life. The facultative parasites are infact saprophytes which have secondarily become parasitic. Some forms produce rhizoids for absorbing food. The parasitic fungi produce appressoria for adhering to the host. For absorbing food, the obligate parasites produce haustoria. The haustoria may be finger-like, knob-like or branched. Each haustorium is distinguishable into a base, stem and body. Saprophytes : They derive their food from dead and decaying organic matter. The saprophytes may be obligate or facultative. An obligate saprophyte remains saprophytic throughout it's life. On the other hand, a facultative saprophyte is infect a parasite more...

(1) Vegetative reproduction Fragmentation : Some forms belonging to Ascomycotina and Basidiomycotina multiply by breakage of the mycelium. Budding : Some unicelled forms multiply by budding. A bud arises as a papilla on the parent cell and then after its enlargement separates into a completely independent entity. Fission : A few unicelled forms like yeasts and slime molds multiply by this process. (2) Asexual reproduction Oidia : In some mycelial forms the thallus breaks into its component cells. Each cell then rounds up into a structure called oidium (pl. oidia). They may germinate immediately to form the new mycelium, e.g., Rhizopus. Chlamydospores : Some fungi produce chlamydospores which are thick walled cells. They are intercalary in position. They are capable of forming a new plant on approach of favourable conditions, e.g., Rhizopus, Saprolengnia Ustilago. Sporangiospores : These are thin-walled, non-motile spores formed in a sporangium. They may be uni-or multinucleate. more...