Mycorrhiza

 

• Mycorrhiza is the symbiotic association between roots of higher plant and fungus. Mycorrhiza is an example of symbiosis. fungus octane food and shelter from root and it helps to root in absorption of water and minerals. Mycorrhiza name was given by "Frank" (1885).

• Mycorrhiza are of two types

(a) Ectomycorrhizal/Ectotrophic mycorrhiza: (occur only in about 3% of plant species)

• In this type of  mycorrhiza, surface of root is completely covered by pseudo parenchymatous sheath, formed by fungal hyphae.

• Ectomycorrhizal fungi occurs in the roots of Pinus, Fagus, Abies, Oak, Eucalyptus etc.

• Ectomycorrhizal fungi and mainly members of class basidiomycetes. eg. Clavatia, Amanita, Hebeloma, Laccaria, Pisolithus etc.

Note:- Amanita is found in Pinus roots where as Russula is found in Fagus roots.

(b) Endomycorrhiza/Endotrophic Mycorrhiza:-

• In this type of mycorrhiza fungus does not form pseudo parenchymata sheath.

• Some fungal hyphae enter intracellularly in cortical cells of root. Intracellular fungal hyphae from unbranched knob like structures called as vesicle, and form branched trees like structures in cortical cells, called "arbuscule".So, Endomycorrhiza is called Vesicular arbuscular mycorrhiza (VAM). Arbuscule acts as haustrium.

• VAM is useful for phosphate absorption.

• Endomycorrhizal fungi are mainly members of class zygomycetes (Ex.Glomus) but some members of Endomycorrhizal fungi belongs to Basidiomycetes (Ex. Corticium,Rhizoctonia)

Note:- 

• Endomycorrhizae fungi occurs in the roots of orchids. Armillaria (class basidiomycetes) fungus is found in orchid roots.

• Orchids are obligately dependent on mycorrhiza association for seed germination & further development.