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FUNGAL SPORES, SPORE DORMANCY, AND SPORE DISPERSAL 209

Fig. 10.28The rotorod air sampler (e), and some representative spores and hyphal fragments commonly seen when
rotorod tapes are examined. Images are at various magnifications. (a) Uredospore of Puccinia graminis. (b) Darkly pig-
mented hyphae of Cladosporium, with a spore of Alternaria. (c) Various pigmented spores, including Cladosporium(in
the lower part of the frame). (d) An immature spore of Epicoccum purpurascensattached to a hyphal fragment.

electric motor. In order to sample spores and other

airborne particles, the arms are covered with narrow

strips of double-sided, transparent adhesive tape so

that spores impact on the tape and can be examined

with a microscope. This apparatus is cheap and

portable, and is highly efficient at trapping relatively

large particles, in the range 10 –30μm diameter,

including pollen grains and the spores of most leaf fungi.

It is much less efficient at trapping small particles. It

can be used to home-in on the source of a particular

type of spore, by making successive samplings in a small

area. For example, it has been used in a field site

in southern Britain to find the source of spores of

Pithomyces chartarum, a toxigenic fungus that causes the

facial eczema condition of sheep (see Fig. 7.20).

The Burkard spore sampler

The Burkard spore sampler (Fig. 10.29) is a continuous

monitoring device that works on the same principle

as the rotorod sampler. It is used commonly in crop

epidemiology and for monitoring allergen levels,

including the pollen and spore counts announced on

radio and television.

This sampler consists of a sealed drum with a nar-

row slit orifice (arrowhead in Fig. 10.29) beneath a

weather-shield. Spores and other particles entering

the orifice impact as a narrow band on a reel (double

arrowhead in Fig. 10.29) covered with transparent

sticky tape. The reel rotates slowly past the orifice on

a daily or weekly cycle, providing a continuous record

of the particles present in the air throughout the

sampling period. Finally, the tape is removed, cut

into sections representing different time periods, and

examined microscopically. Like the rotorod sampler,

the Burkard sampler is based on the principle of

impaction. The air entering the orifice is travelling

at relatively low speed, so only the larger (heavier) par-

ticles are deposited on the tape. These include many

pollen grains, the larger spores of plant-pathogenic

fungi, and the spores of many common allergens.

The Anderson spore sampler

The Anderson spore sampler (Fig. 10.30) is perhaps the

most ingenious and is claimed, with some justifica-

tion, to simulate the deposition of airborne particles

in the human respiratory tract (Fig. 10.31). It consists

of a stack of perforated metal plates which fit together

to form an airtight cylinder, with space for open

agar-filled Petri dishes to be inserted between them. Each

metal plate has the same number of holes in its base,

but these holes become progressively smaller down the

stack. Air is drawn in at the top, and down through