- Any viable spore should eventually germinate. If the spore is that
of a mycelial fungus germination usually involves the production of
one or more germ-tubes. But before emergence of a germ-tube
many spores will require an exogenous supply of nutrients to be
available, will undergo hydration and swelling, and will experience
an increase in metabolic activity.
- Availability of nutrients:
- Some spores are able to germinate in the absence of any exogenous nutrients
in the environment because they possess sufficient ENDOGENOUS
RESERVES (within the spore) to sustain initial growth of the
- Others must be supplied with one
or more EXOGENOUS NUTRIENTS (e.g. a carbohydrate source) before
they are able to germinate.
- Hydration (water uptake):
- The presence of liquid water or a high relative humidity is essential
for the germination of spores of most species - few spores
are capable of germinating at low relative humidities.
- Since most spores have a low water content, hydration is an essential
first step in the germination process.
- Water uptake is an ACTIVE PROCESS and requires a change in permeability
of the spore wall.
- Swelling is due to:
- Deposition of new wall material within the spore - some of which is
destined to form the wall surrounding the developing germ-tube (see
- Germ-tube emergence:
- The small vesicles accumulating near the plasma membrane are involved
in the synthesis of new wall materials.
- As the germ-tube develops these vesicles become arranged to form a cresent-shaped
zone at the tip of the germ-tube - known as the APICAL VESICULAR
CLUSTER or COMPLEX (AVC).
- Emergence of the germ-tube through the spore wall is due to a combination
of enzymic degradation of a small localised region of the spore
wall and the physical pressure being exerted by the protoplasm.
- The germ-tube may emerge from a pre-determined thinner region of spore
wall (GERM PORE) or from some random site.