I. Objectives: The following experiments/demonstrations are the consequence of my having selected what seemed to me to be three "Great Ideas" ln fungal ecology. They are meant to illustrate, through an inductive process, major concepts about fungal communities and the importance of fungi in ecosystems.

II. Materials:

• Shovel, pail, miscellaneous Carolina Culture Dishes for root washing
• Trees, shrubs, and herbs in their native habitats or otherwise
• Hot water bath (or facsimile)
• Dissecting and high power microscopes
• Lactophenol-Cotton Blue - combine equal parts of:
• Phenol (water-bath melted at 50-60^oC)
• Concentrated lactic acid
• Glycerine
• Distilled water or alcohol

Cotton blue may be dissolved in the lactophenol. Make a saturated solution and filter through filter paper. Can be used full-strength or diluted with clear lactophenol. Store clear lactophenol in the dark to retard color change.

III. Procedure:

• Ectotrophic mycorrhizae
  1. Remove blocks of root-containing duff from beneath conifer, beech, oak, or carefully extract roots near any woody plant species inhabiting a Sphagnum bog. This form of mycorrhiza is particularly well-developed in mor humus layers. The enlarged, infected root apices are present year round, but are perhaps most easily seen, and are most colorful, in early spring through mid-summer.
  2. Soak the root-duff blocks for several hours or preferably overnight.
  3. Then carefully remove rootlet systems and transfer through a series of washings, gently tapping the system to free entangled organic matter.
  4. Float infected root pieces in water in Petri dishes. Observe the swollen mycorrhiza pieces and fungus sheath directly, using reflected light and a dissecting microscope. Cotton blue in lactophenol can be used to heighten distinction of the fungal sheath in slide preparations.
  5. Immerse and warm the material slightly to enhance penetration and reduce trapped air.
• Endotrophic mycorrhizae
  1. Follow the procedure outlined above using blocks of soil containing the roots of any angiosperm. Fibrous roots, because of their small diameter and ease of staining, are most satisfactory.
  2. Wash the roots gently following overnight soak, cut several from the above-ground portion of plant, and immerse these in warm (50-55^oC) lactophenol and cotton blue for 20 minutes or more.
  3. Transfer and cover the roots with clear lactophenol to destain host tissue. Examine as whole mounts in clear lactophenol.
  4. Look for angular, non-septate external hyphae and intracellular coils and arbuscules (See Refs 3, 8 and B. Mosse articles).

IV. Conclusion: Hyphae are abundant on plant roots, and, under certain conditions at least, may invade cortical tissues. Is there convincing evidence in the literature of nutrient uptake and transfer via mycorrhizal fungi? What kinds of fungi are these? Are mycorrhizal fungi parasitic?

V. References:

Hacskylo, Eward (Ed.). 1971. Mycorrhizae. USDA Forest Service Misc. Publ. No. 1189.

Harley, J.L. 1971. Mycorrhiza. Oxford Biology Reader. Oxford University Press, London.

Harley, J.L. 1971. Fungi in ecosystems. J. Ecology 59: 653-668.

Harley, J.L. 1969. Biology of Mycorrhizae. Leonard Hill, London.

Marks, G.C. and T.T. Kozlowski (ed.). 1973. Ectomycorrhizae; Their Ecology and Physiology. Academic Press.

Mosse, B. 1973. Advances in the study of vesicular-arbuscular mycorrhiza. Ann. Rev. Phytopathology 11: 171-196.

Nicolson, T.H. 1967. Vesicular-arbuscular mycorrhiza--a universal plant symbiosis. Sci. Progress, Oxford 55: 561-581.

Trappe, J. M. 1962. Fungus associates of ectotrophic mycorrhizae. Bot. Review 28: 538-606.