Walker 1983

Terminology by Walker (1983)

Walker (1983) was the first to propose a standard terminology to be adopted in descriptions of AMF species, based on different types of “walls” which were organized in different “wall groups” (A, B or C). Chris Walker also presented a “murogram” to graphically represent these walls and their organization into groups. In the original manuscript published in Mycotaxon, the unitary, laminated, evanescent and membranous walls are recognized. Other types of walls were later proposed by other authors as new species were described: expansive, amorphous, leathery, notched and germinative walls.

1) Unit Wall: a rigid wall, with only one layer, clearly distinct from the others and consistent among spores at the same stage of maturity within a species. Described by Walker (1983).

2) Laminate Wall: a rigid wall formed from several layers that are deposited as the spore matures. In this wall, the number of layers will increase as the spore ages. Described by Walker (1983).

3) Evanescent Wall: a laminated or unit wall that degrades and falls off as the spore matures. Described by Walker (1983).

4) Membranous Wall: a very thin wall, usually colorless, which often becomes wrinkled and collapses in hypertonic solutions. Being flexible, it usually does not break when the spore is broken. Described by Walker (1983).

5) Coriaceous Wall: colorless wall that is thicker than the membranous wall, but is also flexible and therefore difficult to break. It has a leathery appearance. Described by Walker (1986).

6) Amorphous Wall: a colorless and very plastic wall when pressure is applied to break the spores into acidic amounts such as PVLG or lactophenol. In Melzer, it reacts strongly, turning purple red. Described by Morton (1986).

7) Notched Wall: a wall characterized by the angular and regular appearance of the wall margins in broken spores. The margin consists of a series of rectangular and V-shaped notches with many right angles. Described by Koske and Gemma (1995).

8) Expansive Wall: a wall that expands markedly and forms radiating columns (gives it the appearance of a corona) in some mounting media such as PVLG or lactic acid. Described by Berch and Koske (1986).

9) Germinal Wall: an innermost wall that occurs only in Gigaspora spores. Phenotype is similar to the layers of a laminated wall but has a wart-shaped or papillae ornamentation that are differentiated before spore germination. Described by Spain et al. (1989).

References:

Berch, S.M. & Koske, R.E. 1986. Glomus pansihalos, a new species in the Endogonaceae, Zygomycetes. Mycologia 78:832-836.

Koske, R.E. & Gemma, J.N. 1995. Scutellospora hawaiiensis: a new species of arbuscular mycorrhizal fungus from Hawaii. Mycologia 87:678-683.

Spain, J.L., Sieverding, E. & Schenck, N.C. 1989. Gigaspora ramisporophora: a new species with novel sporophores from Brazil. Myco- taxon 34:667–677

Morton, J.B. 1986. Three new species of Acaulospora (Endogonaceae)from high aluminum, low pH soils in West Virginia. Mycologia78:641–648

Walker, C. 1983. Taxonomic concepts in the Endogonaceae: spore wall characteristics in species descriptions. Mycotaxon 18:443-445.

Walker, C. 1986. Taxonomic concepts in the Endogonaceae. II. a fifth morphological wall type in endogonaceous spores. Mycotaxon18:443–455