Fungi Online

Constitutive dormancy:

• Commonly exhibited by SEXUAL FUNGAL SPORES.
• Is imposed by some INHERENT (ENDOGENOUS) CHARACTERISTIC of the spore itself which prevents it from germinating.
• Spores may fail to germinate even when environmental conditions appear favourable for growth.
• Some may require a period of ageing or a specific activation trigger, such as heat-shock or cold-shock.
• E.g. uredospores of Puccinia graminis, cause of rust disease in cereal crops:
  • Ensure they don't germinate while in close proximity to one another and consequently compete for a limited supply of nutrients in the environment.
  • Because they contain METHYL-CIS-FERULATE, a water-soluble and volatile inhibitor of germination.
  • Germinate once thoroughly dispersed from one another and methyl-cis-ferulate has leached out of the spore and become diluted in the environment.

Exogenous dormancy:

• Commonly exhibited by ASEXUAL FUNGAL SPORES.
• Imposed by an UNFAVOURABLE ENVIRONMENT (i.e. exogenous factors).
• Factors influencing dormancy include availability of moisture and nutrients, as well as temperature and pH.
• Spores germinate only if and when environmental conditions are favourable for growth.
• E.g. conidia of Aspergillus species.

Fungistasis (mycostasis):

• A phenomenon LINKED TO EXOGENOUS DORMANCY.
• It is the inhibition of fungal growth without any effect on viability of the fungus.
• Spores may fail to germinate in natural environments (e.g. soil or leaf surfaces) because of the activities of other micro-organisms.
• This inhibition may be due to INHIBITORY METABOLITES produced by other micro-organisms and/or COMPETITION for a limited amounts of nutrients available.
• The EFFECT IS REVERSIBLE - once the inhibitory substances are removed (or become diluted) or additional nutrients become available the spores will germinate (or the mycelium will resume growth).

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