Original paper
The Origin, Structure and Function of Chlamydospores in Fungi
Griffiths, D. A.
Nova Hedwigia Band 25 Heft 3-4 (1974), p. 503 - 547
237 references
published: Nov 30, 1974
DOI: 10.1127/nova.hedwigia/25/1974/503
ArtNo. ESP050002503001, Price: 29.00 €
Abstract
Throughout the taxonomic range of fungi many cell types have been referred to as chlamydospores and their formation results from swelling and modification of the existing hypha or as a result of sexual fusion between segments of the haploid mycelium. The one criterion used by all authors for including the various cell types under the general term chlamydospore has been the presence of a thick, usually pigmented cell wall which confers upon the spore a characteristic function enabling it to withstand adverse environmental conditions. Some authors consider that chlamydospore formation is induced by adverse environment conditions, such as a depletion in food supply, while others have shown that chlamydospores are produced in cultures under conditions conductive to rapid hyphal extension. Other factors such as a change in oxygen tension, temperature and variations in the C/N ratio of the media have been successful in inducing chlamydospore formation in a number of fungi. It has been noted that there is a dearth of knowledge regarding the elaborative biochemical processes concerned with chlamydospore production in fungi though in general chlamydospores are characterised by the synthesis of lipid food reserve and cell wall polysaccharides. Chlamydospores are generally considered to have a multi-layered cell wall. Electron microscope evidence indicates that chlamydospores are characterised by the presence of a secondary cell wall elaborated internal to, and distinct from, the original parent hyphal wall. In fungi pathogenic to man the role of chlamydospores is obscure though there is some tentative evidence to suggest that, in deep seated mycoses, the presence of chlamydospores in vivo confers upon the organism a degree of resistance against the normal phagocytic reaction of the body. In soil fungi the role of chlamydospores is clearly one of survival under the adverse conditions encountered in the soil; the spores germinating only in the vicinity of colonizable substrate, or the presence of adequate nutrient. In the smut fungi the role of the sexually produced band spores (chlamydospore) is two-fold; firstly, they are concerned with aerial dissemination of the fungus and, secondly, because of their thick walls they function as dormant structure capable of withstanding adverse environmental conditions in the soil. From the evidence presently available, the term chlamydospore should be restricted to asexually produced, thick walled spores arising from modification of hyphal segments following the elaboration of a secondary cell wall within the parent hyphal wall. Brand spores produced by the Ustilaginales should not be termed chlamydospores because of their sexual origin, their function as an integral part of the life cycle and their role in dissemination.
Keywords
mycoses • vicinity • smut fungi • aerial dissemination • brand spores • parent hyphal wall