Chapter 31 Fungi

General characteristics of Fungi eukaryotic mostly multicellular; some unicellular cell walls made of chitin (animal feature) usually filamentous bodies (filaments called hyphae) external heterotrophs; principal decomposers exhibit nuclear mitosis reproduce sexually or asexually Examples: Amanita muscaria - mushroom (p. 604) Penicillium and Aspergillus (p. 613) Rhizopus stolonifer (black bread mold) (p. 609) yeasts ex: Saccharomyces cerevisiae (p. 611) Candida - cause of thrush pathogens that cause athlete’s foot and ringworm Treatment of fungal diseases is difficult because of their similarity to animals

Structure and function of hyphae hyphae - the filaments of a fungus mycelium - tangled mass of hyphae *** large surface area, therefore good absorption of food septa - dividing walls in a hypha Nutrition: All fungi digest food outside their bodies (external digestion). *** Important decomposers *** Can compete for our food Body of fungus is a mass of hyphae which is separated by walls called septa. Mass of connected hyphae is called mycelium. Cytoplasm flows throughout the hyphae passing through pores thus food gets transferred throughout the hyphae.

Mitosis divides nucleus and not hyphae Some hyphae have one nucleus – monokaryotic Some hyphae have two nuclei – dikaryotic During Mitosis, nuclear envelope does not break and reform. Spindle apparatus is formed within the nucleus by spindle plaques (centrioles are absent) Secrete digestive enzymes and absorb organic molecules – external digestion

Five main groups of Fungi Fig. 31.6 Five main groups of Fungi Deuteromycetes-Imperfect fungi lack phylogenetic position, no sexual reproduction and less data to support its relation to fungi

Various groups of Fungi Chytridiomycetes are closely related to ancestors of early fungi Aquatic fungi with flagellated zoospores Glomeromycetes (asexual plant symbionts) form intracellular associations with plant roots called arbuscular mycorrhizae. No sexual reproduction Possible role in evolution of terrestrial plants

Zygomyetes: produce zygotes, example Rhizopus – (grows on bread) Meiosis (sexual)– Zygosprangium forming zoospores Mitosis (asexual) – sporangiophores form sporangia

Ascomycetes: The Sac (ascus) fungi Members are bread yeasts, common molds, morels, cup fungi and truffles. Plant pathogens are Cryphonectria parasitica – chestnut blight Ophiostoma ulmi – Dutch elm disease Penicillium and Aspergillus genera (Deuteromycetes) Candida milleri – sourdough bread Saccharomyces cerevisiae- wine preparation

Meiosis – Ascocarp forming four haploid daughter nuclei Mitosis-Ascospores with eight daughter nuclei that release conidia

Basidiomycetes: The club (Basidium) Fungi Members include Mushrooms, toadstools, puffballs, jelly fungi, and shelf fungi Pathogens – Rusts and smuts Some mushrooms can be deadly poisonous

Meiosis results in basidium - basidiopsores

Range of Symbioses Obligate Symbiosis – essential for survival Facultative Symbiosis – the fungus can survive without host Parasites and Pathogens gain resources from host and kill it Commensal – one partner is benefited but neither is harmed Mutualistic relationship – both are benefited Endophytic fungi live inside plants and protect them from parasites

Mycorrhizae Mycorrhizae are fungi associated with roots of plants Fungi aid in transfer of P, Zn, Cu and other mineral nutrients from soil into roots Plant provides organic carbon to fungus Arbuscular Mycorrhizae- the hyphae penetrates into the roots and into the surroundings of the plant Ectomycorrhizae – the hyphae do not penetrate the root and only surround it

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