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Everything you need to know about mycorrhizae. Some of the most frequently asked questions are as follows:-
Q.1. Who was the first to carry out mycorrhizal study?
Ans: Hartig in 1851 is believed to be the first person to study the intracellular net of hyphae in roots without knowing its fungal nature. Its structure, later on was named “Hartig net”.
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Q.2. Who coined the term mycorrhiza?
Ans: A.B. Frank, a German Forest Pathologist coined the term mycorrhiza in 1885.
Q.3. Who started work on mycorrhiza in India?
Ans: B.K. Bakshi, in early sixties.
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Q.4. Which are the main types of mycorrhizae?
Ans: The main types of mycorrhizae are:
(i) Ectomycorrhiza
(ii) Endomycorrhiza
(iii) Ectendotrophic
(iv) Host specific
Q.5. What is VAM?
Ans: It is vesicular arbuscular mycorrhiza. It has also been regarded as general mycorrhiza because of its common occurrence. This comes under endomycorrhiza.
Q.6. Which are the main two types of structures in vesicular arbuscular type of mycorrhiza?
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Ans: These are smooth oval bodies called vesicle and bushy intracellular structures called arbuscules. The vesicles are considered to be storage structures while the arbuscules break down and then release the nutrients to the plant.
Q.7. From where does the nutrient released by the arbuscules come?
Ans: These nutrients come from the soil through fungal hyphae to the arbuscules.
Q.8. How can the large spores of VAM be isolated from the soil?
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Ans: By sieving.
Q.9. What is ectomycorrhiza? Where are they formed?
Ans: In ectomycorrhiza the fungus forms a mycelial mantle over the smaller roots of the trees, e.g., in all species of Pinaceae and some families of angiosperms as Fagaceae, Betulaceae, Juglandaceae and Myrtaceae. The Pinus and Oak are typical examples.
Q.10. What sort of mycorrhizae constitutes the truffles known as culinary delicacy?
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Ans: Ectomycorrhizae.
Q.11. Why are pigs trained and used in France to find truffles and ectomycorrhizae and to root them up?
Ans: To the female pigs the odour is like that of a male mate.
Q.12. How do animals help in dispersal of ectomycorrhizal fungi?
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Ans: Animals ingest the fungus and distribute the undigested spores in new locations.
Q.13. What are endotrophic or endomycorrhizae?
Ans: They are characterized by intracellular fungus. However, a portion of fungus remains outside in the form of loose hyphae.
Q.14. What are the two subtypes of endomycorrhizae?
Ans: (1) Endomycorrhiza with aseptate fungi or the VAM.
(2) Endomycorrhiza with septate fungi, e.g., ericoid type and orchid mycorrhiza.
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Q.15. What are ectendotrophic mycorrhizae?
Ans: They combine the characteristics of both ecto and endotrophic mycorrhizae. The fungus besides forming a hyphal mantle and the ‘hartig net’ as found in ectotrophic or ectomycorrhizae develops haustoria and hyphal coils in the epidermal and cortical cells similar to endomycorrhizae are endotrophic mycorrhizae.
Q.16. Give an example of ectendotrophic mycorrhiza.
Ans: Monotrapa indica, the Indian pipe, a nonchlorophyllous plant of Ericaceae grows on the forest floors under Pinus, Fagus, Quercus, Salix and other tree species but there is no connection between the tissues of the roots of two plants. Nonchlorophyllous Monotropa indica obtains nutrients from the green trees through a fungal bridge. The fungus Boletus forms ectendotrophic mycorrhiza with Monotropa and endotrophic mycorrhiza with the trees.
Q.17. What is the function of mycorrhizae?
Ans: They extend the surface of the root performing the function of root hairs and absorb nutrients particularly phosphorus which is not easily available, being not very mobile in the soil. Ectomycorrhizae also help in conservation of water.
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Q.18. Why do orchid seeds depend on mycorrhizal fungus for germination in nature?
Ans: Because they are microscopic in size and are devoid of reserved food material (endosperm).
Q.19. Who cultured VAM mycorrhizal fungus Glomus deserticola in association with root organ culture of Ziziphus nummularia under in vitro conditions?
Ans: Nishi Mathur and Dr. Anil Vyas of J.N. V. University, Jodhpur, in 1995.
Q.20. Which are the common genera of VAM fungus?
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Ans: Glomus, Gigaspora, Sclerocystis, Scutellospora, Acaulospora, Entrophospora.
Q.21. How does the ectomycorrhiza differ from the ericoid mycorrhiza?
Ans: In ectomycorrhiza the fungal mass forms a sheath called mantle around the outside of the root with only marginal penetration inside the root tissue, while in ericoid mycorrhiza the fungal mycelium gets embedded in the root tissue.
Q.22. The beneficial effect of mycorrhizal fungus is best observed in soils poor in nutrients. Why?
Ans: In poor soils the trees which are mycorrhizal thrive but nonmycorrhizal ones do not.
Q.23. When trees are planted in prairie soils that often lack suitable fungal inoculum the trees which are inoculated artificially at the time of planting show better growth than uninoculated trees. Why?
Ans: The mycorrhizal fungus makes the nutrients available.
Q.24. How many scientists in India worked on mycorrhiza in 1989?
Ans: About 200.
Q.25. What is the ratio of scientists working on mycorrhiza in India to that of all countries of Asia?
Ans: 1:1, India: All countries of Asia.
Q.26. Who compiled the Directory of Asian Mycorrhizologists in 1989?
Ans: Mycorrhiza Information Centre, Tata Energy Research Institute, 102 Jor Bagh, New Delhi.
Q.27. What is a diazotroph?
Ans: Any organism capable of nitrogen fixation is called diazotroph.
