Book : Botany
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Posted by: CHELSEA
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Writer CHELSEA

Mucor Lifecycle

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Introduction

Mucor is saprophytic fungus and grows on dead organic material. It belongs to class Phycomycets subclass zygomycetes. Mycelium of fungus of Mucor looks like five cottony threads on the surface of break and other substances like pickles and shoes. After formation of spores it changes into a black mass called black mold. Mycelium is white five branched. These are coenocytic. Hyphae consist of many small nuclei along with glycogen and oil drops, embedded in granular cytoplasm. Fungus is heterotrophic in their mode of nutrition. Some rhizonal hyphae secrete some enzymes which convert insoluble carbohydrates into soluble sugars ant thus help in nutrition.

Vegetative Reproduction


Vegetative Reproduction: It takes place by fragmentation of hyphae. In favourable condition mycelium gives out some aerial hyphae known as sporangiophore, whose terminal ends swell to develop sporangia. Cytoplasm nutrients and many nuclei collect in the young sporangia. Protoplasm is accumulated below the sporangial wall and vacuoles are formed in the centre of sporangium and a swollen vegetative columella develops in the centre of protoplasm. Protoplasm which surrounds the columella begins to divide in small protoplasmic bits contains 2 to 10 nuclei. They are called aplanospores. On maturity the outer wall of sporangium bursts and the spores are dispersed by wind. Each spore on getting suitable conditions germinate by producing germ tubes which develops into new mycelium.

Asexual Reprodution


In Mucor the asexual reproduction may take place either by thick walled intercalary chlamydospores or by formation of oidia. The oidia are formed in liquid media. They also cause fermentation in sugar solution in which they are developed. The mycelium becomes separate and the thin walled segments of oidia are separated from each other in the liquid medium. The oidia increase in number by budding. The stage in mucor is called “torula condition.” Alcohol is produced during fermentation.

Sexual Reproduction


Mucor is dioecious and heterothallic. Male and female mycelia are morphological identical by physiologically different, thus represented by + (positive) and – (negative) strains. At the time of secual reproduction two hyphae from mycelia of different strains grow towards each other. Such hyphae are called progametangia. Their tips swell up and a transverse septum develops in each differentiating a terminal cell or gametangium. Remaining part of progametangium is called suspensor. Gametangia of both strains are multinucleate and hence gametangium is called coenogamete. These two coengomaetes fuse together, their intermediate wall dissolves and zygote or zygospore is formed. Zygote develops a thick wall of two layers, the outer layer is called as exospore and inner endospore. The zygote can tide over unfavourable environmental condition. On return of favourable condition it germinates the wall splits open and a single hyphagrowns out which terminates in a sporangium. Spores produced in sporangium give rise to new mycelium.Reduction division occurs either at the time of germination of zygote or at the time of formation of spores. When gametes fail to fuse they behave like spores and develop into new individual. Such spores are called Azygospores. They phenomenon of occurrence of two types of mycelia which are morphologically alike but physiologically is called Heterothallism.

Economic Importance

Many species of mucor cause rotting of fruits and vegetables. It cause mytosis of internal organs. Some species of mucor Takes parts in decaying organic matters in the soil and help to make it fertile. Some species used in formentation to form alcohol. Some species is also responsible for spoiling breads, pickles, leathers, foods etc.



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