Mycology

Why is the world not covered with mould on hot and humid days?

The conidium does not simply germinate when it lands on a surface, there are a number of specific sequential stages it goes through before this happens:

• Conidial maturation is the internal development required to become morphologically and physiologically complete, which includes dehydration. It may mature when it lands on some substrate and then become dormant.
• Conidial dormancy is the inherent low metabolic state which prevents germination even under conducive environmental conditions. Dormancy may be caused by an internal self-inhibitor, membrane impermeability or some chemical metabolic block.
• Conidial activation is a treatment which breaks the dormancy of the conidia by counteracting the causes of dormancy, preparing the conidia for germination. The activator may be some physical or chemical factor or a combination of factors. The are no observable morphological changes in activated conidia.
• Conidial germination is an irreversible change which means that the germinating conidia cannot revert to an inactive state. It includes: swelling of the conidium, germ tube and hyphae formation and an increase in metabolic activity indicated by an increase in oxygen requirement.