Fungi. Chapter 31. Fungi Characteristics. Despite their diversity f ungi share some key traits: Fungi are heterotrophs but do not ingest their food Fungi secrete exoenzymes into their surroundings which break down molecules and then the fungi absorbs the remaining smaller compounds
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Reproductive structure.The mushroom produces tiny cells called spores.
Hyphae. The mushroom and its subterranean mycelium are a continuous network of hyphae.
(a) Hyphae adapted for trapping and killing prey
Plant cell wall
Plant cell plasma membrane
(b) HaustoriaSpecialized Hyphae
(unfused nuclei from
(fusion of cytoplasm)
(fusion of nuclei)
SporesLife Cycle of Fungi
(a)The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus.
(b) The edible ascocarp of Morchella esculenta, the succulent morel, is often found under trees in orchards.
(c)Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open.
(d)Neurospora crassa feeds asa mold on bread and other food (SEM).Ascomycetes
Neurospora can reproduce sexually by producing specialized hyphae. Conidia of the opposite mating type fuse to these hyphae.
Ascomycete mycelia can also reproduce asexually by producing haploid conidia.
Conidia;mating type ()
Dikaryotic (n n)
A dikaryotic ascus develops.
Karyogamy occurs within theascus, producing adiploid nucleus.
The diploid nucleusdivides by meiosis, yieldingfour haploid nuclei.
Each haploid nucleus dividesonce by mitosis, yielding eightnuclei. Cell walls develop aroundthe nuclei, forming ascospores (LM).
some mycorrhizae and molds
(b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat
(a) Fly agaric (Amanita muscaria), acommon species in conifer forests in the northern hemisphere
(d) Puffballs emitting spores
(c) Shelf fungi, important decomposers of woodBasidiomycetes
A dikaryotic mycelium forms, growing faster then, and ultimately crowding out, the haploid parental mycelia.
Two haploid mycelia of different mating typesundergo plasmogamy.
Environmental cues such as rain ortemperature changes induce the dikaryoticmycelium to formcompact masses thatdevelop intobasidiocarps(mushrooms, in thiscase).
In a suitableenvironment, thebasidiospores germinate andgrow intoshort-livedhaploid mycelia.
Gills linedwith basidia
When mature,the basidiosporesare ejected, fallfrom the cap, andare dispersed bythe wind.
Basidium withfour appendages
Basidium containingfour haploid nuclei
The basidiocarpgills are lined withterminal dikaryoticcells called basidia.
Each diploid nucleus yields four haploid nuclei. Each basidiumgrows four appendages, and one haploid nucleusenters each appendage and develops into a basidiospore (SEM).
Karyogamy in the basidia produces diploidnuclei, which thenundergo meiosis.
Dikaryotic (n n)