Submitted to American Biology Teacher

Out-of-"Focus on Fungi"

The May 2004 Biology Today column "Focus on Fungi"
(Flannery 2004) contains several errors. The statement that "Another group of fungi that are important to plant growth are the mycorrhizae.." misuses the term mycorrhizae. The correct replacement for mycorrhizae in the quoted sentence would be "mycorrhizal fungi." Mycorrhiza means "fungus-root."

Mycorrhizal experts recognize at least seven kinds of mycorrhizas (Smith and Read 1997), not just two as stated. In addition to ectomycorrhizae and arbuscular (formerly termed vesicular-arbuscular or endomycorrhizae), there are ectendomycorrhizae, orchidoid, arbutoid, ericoid and monotropoid mycorrhizas. The latter three can be grouped as ericaceous mycorrhiza. Frank Landis of the University of Wisconsin-Madison Botany Department has an informative table on the Types of Mycorrhizae

Saprophyte is an obsolete term to apply to fungi because fungi are no longer in the Plant Kingdom. Phyte means plant. The term saprobe can be used to refer to fungi that obtain their energy from dead organic matter . No plant species is now known to be a saprophyte so it is an entirely obsolete term (Hershey 1999). If the Plant Kingdom is limited to bryophytes, pteridophytes and spermatophytes, then other obsolete phyte terms are phytoplankton, dermatophyte and macrophyte if referring to algae. I cringe everytime I see the TV commercial with a cartoon foot fungus saying it is a dermatophyte.

I prefer to use phyte as a suffix only in nouns that refer to members of the Plant Kingdom, such as gametophyte, sporophyte, myrmecophyte and xerophyte. That way there is less confusion for students because -phyte terms always refer to certain kinds of plants. The bionet.plants.education newsgroup archive has a list I compiled of over 150 plant terms that have phyte as the suffix.

Endophyte is a troublesome term because it can be applied to any organism that lives inside a plant. Even people who live in hollow trees could be termed endophytes. Some authorities add further confusion by defining endophyte more broadly as any organism living inside another. Until someone coins a non-phyte term to describe nonmycorrhizal fungi that live inside plants without causing disease, the best term might be endophytic fungi, rather than endophyte.

The discussion on the largest and oldest living organisms is out of date and doesn't rely on Guinness, which is the authority for world records. World records for plants and fungi may change so relying on a 1992 reference is unwise for "Biology Today". Folkard (2004) lists the "largest living tree", the General Sherman giant sequoia (Sequoiadendron giganteum), at 2,000 tons, not 1,000 tons. The weight of the Michigan fungus also seemed to be underestimated by an order of magnitude. Heilman (1997) listed the Michigan fungus as 110 tons, not 10 tons. However, Guinness now lists a honey fungus (Armillaria ostoyae) in Oregon covering 890 hectares as the largest fungus (Folkard 2004).

The Pando clone of quaking aspen (Populus tremuloides) is still considered the "most massive plant" but only covers about 43 hectares (Folkard 2004). At an estimated 6 million kg (6,600 tons), Pando might also be the heaviest living organism and possibly also the oldest living organism at over a million years old (Minton and Grant 1996).

However, Guinness lists King's holly (Lomatia tasmanica) as the "oldest plant clone" at over 43,000 years old (Folkard 2004) because of solid evidence of its age from radiocarbon dating of fossil leaves (Lynch et al. 1998). This far surpasses the Prometheus bristlecone pine (Pinus longaeva), which was found to be 4,867 years old when stupidly cut down in 1963 to count its rings (Guinness World Records 2004). Note that Folkard (2004) erroneously lists the Eon redwood for highest ring count (Guinness World Records 2004). The Methuselah bristlecone pine is about 4,767 years old and is considered the "oldest living individual tree" (Folkard 2004).

David R. Hershey, Ph.D.
dh321z@yahoo.com

References

Flannery, M.C. (2004). Focus on fungi. American Biology Teacher, 66, 377-382.

Folkard, C. (ed.). (2004). Guinness World Records: 2004. New York, Bantam Books.

Guinness World Records. (2004).

Heilman, C. (ed). (1997). The Guinness Book of World Records 1998. Stamford, CT: Guinness Media.

Hershey, D.R. (1999). Myco-heterophytes and parasitic plants in food chains. American Biology Teacher, 61, 575-578.

Minton, J.B. and Grant, M.C. (1996). Genetic variation and natural history of quaking aspen. BioScience, 46, 25-31.

Smith, S.E. and Read, D.J. (1997). Mycorrhizal Symbiosis, 2nd ed. New York: Academic Press.

Lynch, A.J.J., Barnes, R.W., Cambecedes, J., Vaillancourt, R.E. (1998). Genetic evidence that Lomatia tasmanica (Proteaceae) is an ancient clone. Australian Journal of Botany, 46, 25-33.