Fungal Nutrition 1ay5a

FUNGAL NUTRITION

Prilya Dewi Fitriasari, M.Sc. UIN Maulana Malik Ibrahim

Malang 2017

Absorptive nutrition enables fungi to live as decomposers and symbionts • Fungi are heterotrophs that acquire nutrients by absorption • Secrete hydrolytic enzymes and acids to decompose complex molecules into simpler ones that can be absorbed

• Specialised into three main types: • Saprobes - absorb nutrients from dead organic material • Parasitic fungi - absorb nutrients from cells of living hosts; some are pathogenic • Mutualistic fungi - absorb nutrients from a host, but reciprocate to benefit the host

• Fungi are heterotrophic in nutrition • They are chlorophyll deficient plants and hence they cannot manufacture carbohydrates using carbon dioxide, water and sunlight

• Fungi are with simple structural organization, thus they always depends on dead or living organic matter for their energy requirements

• On the basis of mode of nutrition, fungi are classified into four groups: (1). Saprophytes (2). Parasites (3). Symbionts (4). Predacious fungi

(1). Saprophytes • Saprophytic fungi obtain nutrition from dead organic matter

• These fungi lives on dead organic matter or excreta of both plant and animal origin

• Examples: Mucor, Rhizopus, Penicillium andAspergillus • Vegetative hyphae of these fungi directly absorb food materials from organic matter

Rhizopus (source wikipedia)

• Saprophytic fungi may be of two types:(1). Ectophytic saprophytes: grown on the surface of organic matter (2). Endophytic saprophytes: grown inside the organic matter

• In some ectophytic fungi such as Rhizopus, special absorptive structures such as rhizoids are developed for the easy absorption of food materials

• Saprophytic fungi produce exo-enzymes (enzymes which acts outside the cell)

• These enzymes digest the complex organic matter in the substratum into simpler compounds to facilitate easy absorption by the hyphae

Rhizopus infection in Jack-fruits (wikipedia)

(2). Parasites • Parasitic fungi take food from other living plants or animals • The living organism on which the fungi parasitize are called host • Parasitic fungi are harmful to the host and they produce disease condition in host organisms

• The relationship of host and parasite in pathology is known as parasitism

• Parasitic fungi are of three types: (1). Obligate parasites: these fungi can live only as parasite on a living host. Obligate parasites cannot live on dead organic matter Example: Puccinia which cause rust disease in several crop plants including wheat (2). Facultative saprophytes: They are parasites, but they can also survive on dead organic matter in the absence of living host Example: Taphrina (3). Facultative parasites: these fungi usually follow saprophytic mode of nutrition

Rust Disease of Wheat by Puccinia

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Under certain conditions, they parasitize suitable host plants Example: Fusarium and Pythium which cause soft rot disease in crop plants On the basis of location of parasite in host organism, the parasites may be: Endoparasite: parasite live inside the host tissue Ectoparasite: parasite fungi which live on the outside surface of host

• Parasitic fungi possess specialized absorptive structures called haustoria for the absorption of nutrients from the host cells

• Haustoria are specialized hyphal modifications • Haustoria may be inter-cellular (occupy between two cells) in intra-cellular (occupy within the cell)

• Size and shape of haustoria varies in different fungal groups • Haustoria may be round, knob like, club like or branched

Haustoria of Parasitic Fungus (source wikipedia)

(3). Symbionts • These fungi grow on or with other living organism but both of them are mutually

benefited • Lichens and mycorrhiza are examples • Lichens are the symbiotic association between algae and fungi, both fungi and algae are mutually benefited -Algae synthesize carbohydrates where as the fungi provides shelter for algae • Mycorrhizae are the symbiotic association between fungi and roots of some higher plants -Mycorrhizae helps in the absorption of nutrients by the host plant

• Mycorrhiza may be ectophytic or endophytic • Ectophytic mycorrhiza are external mycorrhiza and they are confined to the outer region of the roots

• Endophytic mycorrhiza are internal mycorrhiza and they are found deeply in the root cells

Foliose Lichen (source wikipedia)

Amanita Mycorrhiza (wikipedia)

(4). Predacious fungi • They are animal capturing fungi (predators) • These types of fungi possess special hyphal traps called snares to tap and capture small animals such as nematodes and protozoa

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They usually inhabit in the soil They possess rapidly constricting hyphal traps which hold the captive for long time They also have haustoria which directly inserted into the tissue of the prey Some predacious fungi also produce sticky secretions for capturing nematodes

Examples of predator fungi: Arthrobotrys, Dactylella, Dactylaria

Hyphal modifications in fungi • In majority of fungi, hyphae are simple • In some advanced fungi, hyphae may undergo certain modification in response to functional needs

• Hyphal modifications are hyphal aggregations are required to do specific functions during the life cycle of fungi

(1). Prosenchyma • Prosenchyma is formed by the loosely packed tissue like organization of fungi

• Prosenchyma is formed when the component hyphae is arranged more or

less parallel to one another and the whole mass become a felt like structure

• The hyphae unite to form a loosely interwoven structure • In prosenchyma, the individuality of fungal hyphae is not lost • Prosenchyma is also known as Plectenchyma or Proso-plectenchyma

(2). Pseudo-parenchyma • Here hyphae are closely intertwined and forms a tissue like structure in cross section

• In pseudo-parenchyma, the hyphae lose their individuality and they are not distinguishable from each other

• Pseudo-parenchyma resembles with the parenchyymatous tissue of higher plants in cross section

• They are also called as Para-plectenchyma

(3). Rhizomorphs • • • • • • • •

Rhizomorphs are thick strands or root like aggregation of somatic hyphae in some fungi They are also called as mycelial cords They are gelatinous, dark brown and rope like coiled structures In rhizomorphs the intertwining of hyphae is too tight so that hyphae loose its individuality

Individual hyphae are arranged in parallel way Rhizomorphs has higher infection capacity than individual hyphae They are perennating structures with high penetration capacity Rhizomorphs survives for many years and they give rise new mycelia in the favourable conditions

(4). Sclerotium (Sclerotia) • Sclerotia is a compact globose structure formed by the aggregation of hyphae in some fungi

• The interwoven hyphae are very much compact so that the individuality of hyphae is lost and the mass become rounded and cushion like structures

• Sclerotia survives for long periods, sometimes for many years

• They are the resting stage of some fungi • They accumulate food materials and helps in vegetative reproduction • Outer portion of sclerotia become dark brown, while the inner cells are colourless

Ergot Sclerotium of Wheat (source wikipedia)

(5). Appressorium (appressoria) • Appressorium is a terminal simple or lobed swollen structure of germ tubes on infecting hyphae

• Appressorium is found on many parasitic fungi such as rusts and powdery mildews

• It adheres to the surface of host and help in the penetrating of hyphae • The infection peg is originated from the appressorium

(6). Haustorium (Haustoria) • • • • •

Haustoria are the intracellular absorbing structures of obligate parasites They are meant for absorbing food materials from the host tissue The size and shape of haustoria varies The shape may be knob like, elongated, finger like or branched They secrete some special enzymes which help in hydrolyzing proteins and carbohydrates of host

(7). Stroma • Stroma are compact somatic structures • They are flat cushion like pseudoparenchymatous structures • Fructifications are usually found on or in them

(8). Snares (Hyphal traps) • Snares are trap like structures produced by predaceous fungi to capture small animals such nematodes and protozons

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