Introduction to Fungi, Third Edition

498 BASIDIOMYCOTA
Fig18.9 Diagrammatic
interpretation of a basidiomycete
dolipore/parenthesome septum.
Reprinted from Moore and
Marchant (1972), by copyright
permission of the National Research
Council of Canada.
adjacent to the damaged segment (Aylmore et al.,
1984; Markham, 1994).
18.7.4 Plasmogamy, dikaryotization,
clamp connections
When two compatible monokaryotic mycelia
make contact, the hyphal walls separating
them break down and cytoplasmic continuity
(i.e. plasmogamy) of the two monokaryons is
established. In Coprinus cinereus and some other
fungi, plasmogamy may also occur following
fusion of an oidium of one mating type with
a hyphal tip of a compatible monokaryon.
Nuclear migration follows and is associated with
the breakdown of the dolipore/parenthesome
complex to permit transfer of a compatible
nucleus from one compartment to another
(Giesy & Day, 1965; Marchant & Wessels, 1974).
The mycelium which develops after plasmogamy
is dikaryotic and the process of conversion
of a monokaryon to a dikaryon is termed
dikaryotization.
Nuclear fusion (i.e. karyogamy) is delayed
until the basidia have formed, and is thus
preceded by a prolonged dikaryotic state. As a
result of nuclear migration, the tip of a dikaryon
contains two nuclei which are of different
mating types in heterothallic basidiomycetes.
The speed of nuclear migration can be much
higher than the hyphal growth rate. Nuclear
migration rates have been measured in a
number of fungi, e.g. Coprinus cinereus