Morphology and life cycle of Agaricus

Discipline Courses-I Semester-II Paper III: and Phytopathology Unit-VI Lesson: Morphology and life cycle of Agaricus Lesson Developer: Geeta Sharma College/Department: Shivaji College, University of Delhi

Institute of Lifelong Learning, University of Delhi Morphology and life cycle of Agaricus

Table of Contents

Chapter: Agaricus

 Introduction  Habit and Habitat  Somatic structure (Vegetative thallus)  Vegetative cell  Reproduction  Asexual  Sexual  Summary  Exercise/ Practice  Glossary  References/ Bibliography/ Further Reading

Institute of Lifelong Learning, University of Delhi 1 Morphology and life cycle of Agaricus

Introduction

The genus Agaricus comprises a group of 200 species which are heterotrophic, true nucleated, multicellular, macroscopic and fleshy in nature. This group includes fungi whose fruiting bodies are commonly known as mushrooms. The umbrella shaped mushrooms (which are edible), toadstools (which are nonedible or poisonous) beautify this earth with their presence in almost all seasons except the extreme summers and winters. The fruiting bodies of some species appear in early spring and disappear in summers, others appear only in rainy season and some appear sporadically whenever moisture is available. Hence the moist season (rainy weather) is the best season to explore, observe and collect the most beautiful, colourful (earthy flowers) fruiting bodies of mushrooms in hills as well as in plains.

The word mykes (from which the term Mycology is derived) means mushrooms and etymologically, mycology is the study of mushrooms. This group has been extensively studied in detail because man collected the fruiting bodies of mushrooms from diverse habitats to consume them as food, medicines etc.

Mature spores

Developing spores Gills

Pileus

Veil

Stipe

`

Figure: The image shows different stages of development of and basidiospores

Source: http://upload.wikimedia.org/wikipedia/commons/5/58/2008-08-Agaricus- Stuttgartx7.JPG

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Systematic position

Mycologists have since ancient times classified mushrooms under Basidiomycetes which in turn have been grouped in different categories of different ranks at different levels based on specific characters like the type of mycelium ,nutrition , occurrence, reproduction ,life cycle ,their molecular and phylogenetic relationship with other fungal groups .Some specific systems recognized and followed are as followed:

G.C. Ainsworth (1973) :

Division : Eumycota

Subdivision : Basidiomycotina(Basidiomycetes) .

Class : Hymenomycetes .

Alexopoulos , C.J. and Mims, C. W.(1979) :

Super Kingdom : Eukaryonta .

Kingdom : Myceteae .

Division : Amastigomycota .

Subdivision : Basidiomycotina .

Class : Basidiomycetes .

Alexopoulos C. J. Mims , C. W. and Blackwell, M.(1996) :

Kingdom : Fungi

Phylum :

Class : Basidiomycetes

Order :

Webster , J . and Weber, R.W.S. (2007) :

Kingdom : Fungi(Eumycota)

Institute of Lifelong Learning, University of Delhi 3 Morphology and life cycle of Agaricus

Phylum : Basidiomycota

Class : Homobasidiomycetes

Order : Agaricales

Family : Agaricaceae

Genus: Agaricus

Habit and Habitat

Agaricus is a multicellular, macroscopic, mostly saprophytic corticolous, parasitic and mycorrhizal in nature. are cosmopolitan in nature and occur in a wide variety of habitats ranging from the arctic to the tropics. Most of the species do show the preference to the diverse kind of substrata for example :-

 In upland woody forests on decaying wood (lignicolous), decaying fallen leaves (foliicolous) eg. A . lanipes, A. langei, on moist soils (terrestrial), compost and dung (coprophyllous) eg . A. bisporus, A. bitorquis .

Figure: Agaricus lanipes a wood decayer

Source:http://upload.wikimedia.org/wikipedia/commons/3/3d/Agaricus_lanipes_20121012w .JPG

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 In open areas like gardens, lawns, grassy lands and pastures, eg . A. fuscofibrillosus, A.arvensis, A. campestris, A. macrosporus.

Figure: A. fuscofibrillosus

Source:http://upload.wikimedia.org/wikipedia/commons/1/18/Agaricus_fuscofibrillosus_797 40.jpg

 The mycorrhizal forms occur with certain type of vegetation eg. Ectomycorrhizal association with conifers—eg. Paxillus (gilled) ,Gomphidius (gilled) etc .

Figure: Gomphidius

Source:http://upload.wikimedia.org/wikipedia/commons/5/56/Gomphidius_glutinos us_131007.jpg

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 On the body of the basidiocarps of other mushrooms (fungicolous).

Figure: Volvariella surrecta mycoparasite on Clitocybe nebularis

Somatic structure (vegetative thallus)

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The fruiting bodies (sporophores) of mushrooms as seen on the surface of substratum by the naked eye do not exhibit the complete fungal thallus but these are the sexual reproductive bodies bearing meiotic basidiospores on the part of mycelium .

The somatic structure or vegetative thallus of Agaricus consists of the mycelium (mass of hyphae) which is septate, thin walled, hyaline typically a basidiomycetous type. Here it arises as a primary mycelium from the monokaryotic basidiospores, which later become dikaryotic and tertiary mycelium.

Figure: Agaricus campesteris: Diagrammatic repersentation of the anatomy of the with three types of mycelia.

Source: http://nsdl.niscair.res.in/handle/123456789/177

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The mycelium of Agaricus is of three kinds:

Primary mycelium :The monokaryotic, haploid, basidiospore of (+) and (-) strain germinates immediately after dispersal on the substratum or on the moist soil (at 10- 15 degree temperature, 80—90% relative humidity, and 5.8—6.o ph) by absorbing mineral nutrients directly in soluble form to give rise a germling or primary hyphal initial . This hyphal initial cell undergoes mitotic division to form monokaryotic, uninucleated, haploid, hyaline, thinwalled primary mycelium which has a very short life in nature.

Secondary mycelium: The primary hyphae or monokaryotic hyphae with (+) or (-) strain haploid nuclei come in contact with each other to form dikaryotic or hetrokaryotic mycelium by two methods : -

i. Somatogamy: The somatic cells ( vegetative cells) of primary or monokaryotic hyphae of opposite srains (+ and - ) when they come in contact with each other directly on the substratum , the cell wall between the two cells ( + and- ) dissolves , fusion of two protoplasms ( plasmogamy) takes place, two nuclei (+and-) lie near each other to form a dikaryotic, haploid cell (somatogamy) . This dikaryotic (n) cell undergoes multiple mitotic divisions to form thin walled, multicellular, branched secondary mycelium. Each cell of this mycelium carry two genetically distinct (compatible) nuclei (+ and-) and is strictly heterokaryotic, dikaryon. fig.

ii. Clamp connection: This method is very common to develop heterokaryotic, secondary mycelium from primary mycelium of opposite mating types. In this process the two compatible cells of opposite strain (+&-) of monokaryotic hyphae come in contact with each other, the cell wall between them dissolves, nuclear migration takes place . The nucleus of this dikaryotic cell divides mitotically and the daughter nucleus migrates in the adjuscent cell with the help of a characteristic structure or a connection i.e. a short appressed hyphal branch which bypasses the transverse septum and connects the two adjuscent daughter cells laterally called Clamp ( or buckle) connection. It sis a method which ensures that when a dikaryotic mycelium divides, each cell of these hyphae will contain two genetically distinct nuclei.

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Figure: Formation of secondary mycelium through somatogamy and clamp connections

Source: Author

Secondary, dikaryotic or heterokaryotic mycelium is multicellular, thinwalled, branched, cottony in appearance, the hyphal cells of which are binucleated or multinucleated, haploid dikaryons.

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Tertiary mycelium : The dikaryotic, secondary mycelium carrying opposite strain( +and-) haploid nuclei in the hyphal cells branch profusely by mitosis and the hyphal branches anastomose with each other to form a complex tissue of fruiting body (basidiocarp).

Vegetative or hyphal cell

The Agaricus hyphal cell consists of outer cell wall (chitin microfibrils and glucan),inner plasma membrane (selectively permeable), true nucleus, haploid of + and - strain or both, cytoplasm, mitochondria, ribosomes, endoplasmic reticulum, golgi apparatus, small vacuoles and glycogen granules as reserve food material etc.

 Structure of septum: The septum ( the intersecting wall between each hyphal cell of septate ) in each cell of monokaryotic and dikaryotic hyphae of Agaricus is pierced by a narrow 0.1- 0. 2 ,um width which is surrounded by a barrel called septal swelling. This kind of septal pore is known as Dolipore septum. This pore is overarched with a perforated cap i.e an extension of endoplasmic reticulum. This perforated cap is called parenthesome or pore cap which has several pores in it from which organelles like mitochondria can pass.

Figure: Dolipore septum (arrow)

Source: http://www.mycolog.com/chapter5a.htm

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Reproduction

Asexual reproduction

The species of Agaricus undergo asexual reproduction very rarely. It produces two types of asexual spores i.e. oidium (thin walled, fragmented spore), and chlamydospores (thick walled, resting spore).

 Oideum or fragmented spore : Oidia or arthrospores are thin walled, hyaline, fragmented, spores which are produced by the dissolution of middle lamellar wall between the adjuscent cells on the aerial branches of monokaryotic and dikaryotic hyphae. The monokaryotic oideum fuses with the hyphal cell of the opposite strain to form the secondary heterokaryotic mycelium .The oidia of dikaryotic type germinate directly to give rise heterokaryotic mycelium eg. Coprinus lagopus. These type of spores are produced during favourable conditions i.e temperature 10 -15Oc , relative humidity 80-90% and ph 6-6.5 .

Figure: Asexual reproduction by oidia formation (rare)

Source: Author

 Chlamydospores or resting spores: It is a thick walled resting spore or perennating spore (seed like) produced during unfavourable conditions (drying of substratum, rise in temperature, and change in ph). The hyphal cells loose extra moisture content, glycogen particles (reserve food) get converted into fat droplets, cell wall becomes thickened by chitin deposition. These spores produced in chains are initially light coloured but later become dark brown, get separated from the rest of the parental mycelium

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and parennate in unfavourable conditions in the soil or on the substratum, eg. Coprinus lagopus (Lewis 1961) and Volvariella volvacea (Chang and Yan 1971) . Chlamydospores during rainy season germinate by absorbing moisture and minerals from the substratum at 10-20Oc , ph 5.8-6.0 and give rise the young mycelium on the substratum.

Figure: Chlamydospores and their germination

Source:Author

Sexual reproduction

Agaricus does not have well defined sex organs or sexual gametes. The somatic or vegetative cells of primary hyphae of opposite mating types (+&- strains ) function as sexual gametes. The two somatic cells of haploid primary hyphae of opposite strains (+&-) come in contact with each other by a process of somatogamy, oidization or by clamp connection and fusion of protoplasms ( plasmogamy) bring two compatible nuclei (+&-) near each other. Homothallism is rare in agaricales eg. (Coprinus sterculinus). Most of the species exhibit either unifactorial or bifactorial homothallism . The two significant steps that is karyogamy (nuclear fusion of opposite mating +&- strains) and meiosis ( reduction devision) take place in the basidial cells of fertile layer () of fruiting body i.e. basidiocarp . The basidiospores (meiotic ) are produced on the probasidial cells exogenously at the abaxial(ventral) surface of the basidiocarp .

Basidiocarp

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Figure: Mature basidiocarp showing basal remnant of mycelium, annulus and pileus.

Source: http://nsdl.niscair.res.in/bitstream/123456789/178/1/Fungi- II+revised+formatted.pdf

The fruiting body or the basidiocarp formation is regulated or influenced by the interaction of multiple environmental factors:

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Light: Diffused light .

Relative humidity : 80-90 % .

Temperature : 12-18’c .

pH of the substratum : 5.8-6.0 .

Mineral nutrients (ammonium salts etc.) and aeration.

These conditions favour the formation of fruiting bodies or the basidiocarp on the substratum. The initial steps in fruiting body formation are :

1. An intricate hyphal lattice is formed by the interaction of hyphal branches .

2. From this hyphal lattice the bunch of aerial hyphae appear which eventually produce a round aggregation of tightly interwoven hyphae to form a button or a bud like structure, creamish white in colour called bud primordium ( first basidiocarp stage) on the substratum.

3. The bud primordium grows in size and as it reaches 1.0 mm in diameter , a presumptive stipe, hymenium (fertile layer) and terminal pileus (cap) get differentiated simultaneously .

4. The elongation of stipe, expansion of terminal pileus in to upper (adaxial)smooth and lower(abaxial)infolded gilled lamellar structure and production of basidiospores occur quite rapidly and dramatically in the life cycle of Agaricus .

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Figure: Diagrammatic representation of development of basidiocarp from pin head to mature fruiting body.

Source: Author

In agaricales the three basic types of basidiocarp development have been recognized(Singer 1975) :

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Hemiangiocarpous development:The hemiangiocarpous basidiocarp development is characterized by the following facts:

 The hymenium or fertile layer is enclosed by tissues (tertiary mycelium) of the basidiocarp even during early stages of its development .

 The margin of the pileus is connected to the basel stipe by a membrane called inner veil .

 The hymenium remains enclosed till the terminal cap (pileus) expands and matures .

 The veil tears from the margin of the pileus shortly before the spores mature and remains attached to the stipe as a ring or annulus .

 ( In some species the veil tears in such a manner that it hangs down from the cap(pileus) like a thin cobwebby curtain called Cortina and in others the entire primordium is covered by a universal veil. This universal veil breaks and leaves a cup shaped body around and bulbous base of the stipe. The remains of the parts of universal veil are seen as scales on the cap. These features help in classification and identification of many species as this feature is evanescent in other species ).

Gymnocarpous and Pseudoangiocarpous development : In these two methods the hymenial (fertile) layer is formed initially on the outside of the fruiting (basidiocarp) body. In gymnocarpous development the hymenial tissue is not covered and remains naked till maturity. In pseudoangiocarpous method the hymenial tissue later becomes enclosed by the development of the outgrowth of the incurving margin of pileus and the stipe. The hymenium remains enclosed till the basidiocarp matures and the pileus expands to reveal the hymenial tissue .In these methods the vestigial structures are not seen at the maturity of the fruiting bodies (basidiocarp).

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Figure: Figure representing different types of basidiocarp development

Source: Author

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Structure of Basidiocarp:The basidiocarp of Agaricus which bears basidiospores consists of the following tissues:

a) Hymenium: The fertile layer of anastomosed secondary hyphae is found beneath the pileus (terminal cap). It lines in the gills or lamellae exogenously which hang below in the ventral (abaxial) surface of the pileus.

b) Gills: The gills are the thin strips of tissues which radiate from the margin of the pileus in towards the stipe. The structure and position of the inner edge of gills towards stipe is a valuable and interesting feature in many agaricales for taxonomists. The gills in some species are free from stalk while in others they are attached directly to the stipe called adnate. The decurrent gills are attached and run down the stipe for some distance.

c) Trama : The trama ( L. Trama-Woof) is the inner most tissue which lie in the center of the gills. It is an important feature of taxonomic interest Singer (1975). The central tissue (trama) is of two types:

 The trama consists of plectenchymatous tissue which is made up of elongated hyphae.

 The trama tissue contains large, globose or oval cells called sphaerocysts scattered along the elongated hyphal cells (eg. Russula and Lactarius ). The trama is surrounded on both sides by the fertile layer (hymenium) in which closely packed layer of basidia are interspersed with basidioles or cystidia or both in some species . The cystidia are long and extend from one gill to the next to keep the gills apart from each other (Coprinus) .

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A B

C D

Figure: Diagrammatic representation of a A. V.L.S. fruiting body; B. V.L.S. gills; C-D. Part of gill magnified

Source: Author

Basidium : The is a cell or a structure found at the terminal end of dikaryotic hypha in the hymenial layer of the gill exogenously. In the basidial cell the dikaryotic nuclei fuse with each other ( karyogamy) to form diploid nucleus (2n) which immediately undergoes meiosis (reduction division) to form a definite number of basidiospores (n). Each basidial cell bears a definite number of haploid basidiospores (2 or 4) which at maturity are forcibly shot off to disperse and fall below the pileus under the influence of gravity on the substratum. In still air these

Institute of Lifelong Learning, University of Delhi 19 Morphology and life cycle of Agaricus haploid basidiospores (+ and-) get deposited below the pileus in a mass to form the spore print.

Figure: Development of basidium and formation of spores

Source: Author

Basidiospore: The haploid, monokaryotic basidiospore varies in size, shape, colour and is thick walled and multilayered (3-5), eg. three layered in Psilocybe sp. and Agaricus brunnescens (bisporus). It consists of protoplasm, haploid nucleus (+or - ), ribosomes, mitochondria, lipid bodies, vacuoles, glycogen granules as reserve food material . The basidiospores exhibit distinct colours eg. in Chlorophyllum molybdites spores are green, in Russula sp. the spores are yellow and in other

Institute of Lifelong Learning, University of Delhi 20 Morphology and life cycle of Agaricus species spores are white, pink, brown, black and smoky-grey. The spore colour is not always the same as that of gills and is determined by making a spore print on white and black paper .

A B

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Figure: Basidiospores and formation primary hyphae

Figure: Diagrammatic life cycle of Agaricus sp.

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Source:Author

Figure: Life cycle of a typical (Amanita sp.)

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Fairy Rings

The fruiting bodies of mushrooms appear in rings on the moist grassy green lands, gardens and on the decaying cellulosic substrata in the forests during spring, early summers and winters exhibiting the creamish white rhizomatous subterranean peripheral mycelial growth in abundance. The term “fairy ring” for these beautiful bodies appearing on the ground was initially used by early philosophical taxonomists and naturalists for the fairies visiting these areas, dancing, roaming around and enjoying in circles the previous nights which resulted in the appearance of these beautiful (young unopened floral bud like structures) fruiting bodies on the footsteps of these fairies in the early hours of the successive mornings. Similarly multiple stories of our grannies express the miraculously emergence of white or colourful fruiting bodies in rings on the grassy lawns in the early hours of the morning of spring, summer and winters.

Figure: Fairy rings Source: http://tolweb.org/tree/ToLimages/fig2.jpg ,http://en.wikipedia.org/wiki/File:Hexenring_Nebelgrauer_Trichterling.JPG

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Scientifically the seed like mushroom (+&- strain, haploid, uninucleate ) basidiospores absorb moisture and minerals from the substratum and germinate to form (monokariotic) primary mycelia, which later by somatogamy form dikaryotic, binucleated, haploid secondary mycelia. These dikaryotic mycelia anastomose with each other longitudinally to form long thick strands of rhizomatous mycelium which spread around to form initially the discoid mycelial creamish white colony on the substratum.

Figure: Photograph of rhizomatous mycelia on substrata

Source:http://upload.wikimedia.org/wikipedia/commons/f/f1/Hyphae.JPG; http://www.erowid.org/plants/mushrooms/mushrooms_cultivation_az2.shtml

As the colony matures the primary mycelia (the life span of which is very short) in the center of the colony die and the rhizomatic strands towards the periphery of colony anastomose to form small tissues or primordial buds ( button stage) in the arcs or complete circle which is named as fairy ring. These primordial buds (basidiocarps) mature with in forty eight hours, get differentiated into basel stipe and terminal pileus, underneath of which the abaxial layer infolds to form gills or lamellae. The gills exhibit the fertile zone(hymenium)where probasidial cells undergo karyogamy and meiosis to form two or four basidiospores, initially hyaline and yellow to brown at maturity with in three to four days. The mature basidiocarps (dark brown) shed their basidiospores on the substratum and die but the rhizomatous secondary mycelia survive and perennate in the soil or on the substratum for years (400 years in Marasmius sp. Butler and Jones,1949).

The parennating rhyzomatic (commonly called shoe string) mycelia in the soil are responsible for the reccurrence of fairy rings in the same areas every year. The most common examples are Marasmius oreades,hlorophyllum molybdites, Agaricus arvensis, A. campestris,A. tabularis, Coprinus sp., Clitocybe sp. etc. The area inside the fairy ring exhibits a distict zone of grass, more greener than the grass of the rest of the lawn. This

Institute of Lifelong Learning, University of Delhi 25 Morphology and life cycle of Agaricus effect is due to the degeneration of older hyphae of the fungal mycelium which released the nitrogenous compounds in the soil and became available to the grass as fertilizer along with the moisture available in the center.

Bioluminescent fungi

The rhyzomatic mycelium of some basidiomycetes exhibit an interesting feature of emitting visible light at night in the decaying woods, old exposed roots of the trees and the decaying organic matter in the forests. These fungi are bioluminescent in nature.

Figure: Bioluminescent fungi A. Marasmius elegans, B. Omphalotus C. haematopus; D. Mycena chlorophos; E. M. interrupta ; F. O. olearus

Source: http://en.wikipedia.org/wiki/File:Marasmius_elegans.jpg, http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/Omphalotus.jpg/250px- Omphalotus.jpg, http://upload.wikimedia.org/wikipedia/commons/7/75/Mycena_haematopus_56359.jpg, http://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Mycena_interrupta_01_Pengo .jpg/220px-Mycena_interrupta_01_Pengo.jpg, http://en.wikipedia.org/wiki/File:Omphalotus_olearius_33857.jpg

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The mycelium of these fungi produce the compact mass of hyphal strands of great length in which the hyphae loose their individuality and the entire strands act like thick units of creamish white or black, brittle rhizomorphs (commonly called shoe strings) which penetrate and spread extensively under the bark (outer ligno-cellulosic protective zone) and in the cortical layers of old forest trees to nourish the parasitically and glow in the dark. This parasitic nature of bioluminescent basidiomycetes kill the infected trees and continue to live saprophytically on dead trees which are left glowing as `ghost` trees in the forests eg. Armillariella mellea(Honey agaric) , Clitocybe illudens, Mycena galericulata, Omphalotus olearius etc. This phenomenon of glowing of rhizomatous mycelium on woods or trees is called fox–fire.

The luminescent effect of the fungus can be exhibited in the mycology laboratory by bringing in the piecies of wood completely colonized by mycelium of Armillariella mellea and also by culturing the mycelium of this fungus or some other agarics on PDA agar medium which show this effect.

The basidiocarps, the gills and basidiospores of bioluminescent fungi can be used in the labs to demonstrate the glowing effects e.g. Omphalotus olearius (jack-o`lantern), Lampteromyces japonicus(poisonous moon light),Mycena lux –coeli and Mycena rorida respectively.

The bioluminescent fungi exhibit the best luminous effect at 10-25 ± 1 temperature and 80- 90% relative humidity on the substratum and the light given off is the byproduct of the biochemical (chemiluminescent) reaction which involved the direct conversion of chemical energy in to light energy which is actually responsible to remove oxygen from the fungal cells.

The formula of bioluminescent reaction involved in emission of light energy(cold) and the expulsion of oxygen from fungal cell:

ATP + Luciferin + Luciferase + O2 = CO2 + Light

Molecular energy+ substrate + enzyme + anaerobic condition=Removal of O2 + light energy (cold)

The fungal luminescence is a function of living tissue in which a continuous process of chemical reaction involves a substrate (D-luciferin) combining with molecular energy (ATP) and oxygen, that is regulated by the fungal enzyme (luciferase) releasing a specific molecule (luminescent) , energy level of which increases and results decay of the substratum, which in turn it releases the photons hence producing the light. This process does not require any

Institute of Lifelong Learning, University of Delhi 27 Morphology and life cycle of Agaricus light stimulus and continues during day and night in the hyphal cells to produce light energy called cold light e.g. the Mycena lampadis, a singal large specimen that exhibits the emission of the light through its hyphal cells in an excellent amount that it is sufficient to read a book even at night.

The is an important function in the bioluminescent (glowing fungi) fungi, also called wood decayers, to release the photonic light energy responsible to remove the oxygen from fungal hyphal cells which do not require oxygen and direct sunlight for their growth andnutrition.

Summary

Basidiomycetes are highly advanced fungi .The thallus or mycelium is well developed septate , hyaline , uni, bi or multinucleated, highly branched ,creamish white in colour. They are either saprophytes or parasites and exhibit mycorrhizal association with roots of forest trees . They reproduce asexually by fragmented spores. The sexual reproduction takes place by simple fusion of two somatic cells of opposite strains of primary hyphae by somatogamy .The basidiospores or meiospores are produced on the secondary probasidial cells in the hymenial layer of the gills exogenously on the basidiocarp . There is no differentiation of sex organs in basidiomycetes which reflects that there is degeneration of sex organs and it is same in ascomycetes where the ascogenous hyphae take part in sexual reproduction and produce ascospores or meiospores in ascus mother cell endogenously in ascocarp (fruiting body) . There is no motile phase in both of these classes .

Exercise/ Practice

1. Define the following with example :  Basidium  Hymenium  Clamp connection  Somatogamy  Dikaryon  Basidiocarp 2. Draw well labelled diagram of the following :

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 Dolipore septum

 V.S. Gill

 L .S. Basidiocarp

 Clamp connection

3. Fill in the blanks :

 The terminal cap of basidiocarp is called ------.

 The fruiting body of mushroom is called ------.

 The fertile layer of basidiocarp is ------.

 The mass of hyphae is called ------.

 Fusion of two somatic cells is called ------.

 Fairy rings are formed by ------.

3. Illustrate with the help of labeled diagrams only the life cycle of Agaricus bisporous.

4. Write the salient features of basidiomycetes .

Glossary

Annulus : (ring) A remnant of the inner veil (a ring) around the stipe in some mushrooms. Basidiocarp: (Gr. Basidion- small base;karpos – fruit) A fruiting body that bears basidia . Basidiospore : (Gr. Basidion – small base + spora – spore , seed) A spore borne on the outside of a basidium , following karyogamy and meiosis . Basidiole or basidiolum : (L. dimin. Of basidium) A type of sterile element in the hymenium of certain basidiomycetes ; resembles a basidium without basidiospores . Basidium : (pl. basidial ; Gr. Basidion – a small base) A structure bearing on its surface a definite number of basidiospores (typically four) that are usually formed following karyogamy and meiosis . Binding hyphae : Thick walled , typically aseptate , highly branched hphae present in the basidiocarps of some fungi .

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Clamp connection : A bridge like hyphal connection characteristic of the secondary mycelium of many basidiomycetes . Cortina : (L. Cortina – curtin) A curtin like , cobwebby veil hanging from the margin of the cap of certain mushrooms . : (kystis – bladder + idion, dimin. Suffix) A sterile element Occurring in the hymenium of certain basidiomycetes; Cystidia are generally larger than other hymenial elements and protrude beyond them . Dikaryon : (NL. Di – two + Gr. Karyon – nut, nucleus) A pair of closely associated nuclei , each usually derived from a different parent cell . Dikaryotic : It is pertaining to cell that contains a dikarion . Dolipore septum : (L. dolium - large jar + pore) A septum with a central pore surround by a barrel-shaped swelling of the septal wall and covered on both sides by a perforated membrane termed either the septal pore cap ; common in many basidiomycetes . Fairy ring : A ring of fruiting body of mushrooms on the substratum or the ground representing the periphery of the mycelial growth of a basidiomycete . Inner veil : The hyphal membrane covering the gills of some young mushrooms . Karyogamy : (Gr. karyon- nut , nucleus + gamos –marriage , union) The Fusion of two nuclei. Meiosis : (Gr. meiosis – reduction) A saries of two nuclear divisions usually in a quick succession in which the chromosomenumber is redused by one- half . Monokaryotic : (Gr. monos – single+ karion – nucleus , nut) A cell containing a single nucleus . Mushroom : A fleshy , sometimes tough umbrella-like basidiocarp or Fruiting body of certain basidiomycetes . Mycelium : (pl. mycelia; Gr. mykes – mushroom , fungus) The mass of hyphae constituting the body (thallus) of a fungus . Mycology : (Gr. mykes – mushroom , fungus + logos – discourse) The study of fungi . Mycophagy : (Gr. mykes – mushroom + phagein – to eat) The eating of Mushrooms . Oidiophore : (Gr. oidion – small egg + phoreus – bearer) A specialized hypha that bears oidia . Oideum : (pl. oidia; Gr. oidion – small egg) A thin walled , free , hyphal cell derived from the fragmentation of a somatic hypha in to its component cells or

Institute of Lifelong Learning, University of Delhi 30 Morphology and life cycle of Agaricus from an oideophore; it behaves as a sporeor as a spermatium ; normally used in reference to such cells produced by some basidiomycetes . Pileus : (L. pileus – cap) A terminal portion or cap of certain types of ascocarps and basidiocarps . Plasmogamy : (Gr. plasma- a molded substance , gamos – union , marriage )The fusion of two protoplasts . Plectenchyma : (Gr. pleko – 1weave;enchyma – infusion , i. e. a woven tissue) The general term employed to designate all types of fungal tissues; the two most common types of tissues are prosenchyma and pseudoparenchyma . Primordium : (L. primordium –beginning) The first stage of any structure . Probasidium : The portion of the basidium in which karyogamy takes place . Somatogamy : The fusion of somatic cells during plasmogamy . Sphaerocyst : The spherical cells present in the trama of the russullaceae. Spore : A minute propagative unit functioning as a seed , but from it as the spore does not contain an embryo . Stipe : The stalk of the stipitate basidiocarp . Trama : The fungal tissue composing the pileus or bearing the hymenium of the Holobasidiomycetidae . Zygote : Adiploid cell resulting from the union of two haploid cells .

References

Greuter ,B . and D , Rast . 1975 . Ultrastructure of the dormant Agaricus bisporus spore . Can . J . Bot . 53 : 2096-2101 . Litten. W .1975 . The most poisonous mushrooms . Scientific American. 232: 91-101. Malloch, D .1976 . Agaricus brunnescens , the cultivated mushroom .Mycologia 68: 910-919 . Singer,R .1975 . The Agaricales in Modern . 3rd Edition. J . Cramer , Weinheim . Stocks,D . L . and W . M . Hess .1970 .Ultra structure of dormant and germinated basidiospores of a species of Psilocybe . Mycologia 62:176-191 . Alexopoulos C . J . and Charles W . Mims . 1979 . Introductory Mycology .3rd edn . Wiley Eastern Ltd . Alexpoulos, C . J ., Mims ,C . W . and Blackwell , M .1996 . Introductory Mycology . 4th edn . John Wiley and Sons, New York .

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Talbot , P . H . B . 1971 . Principles of fungal taxonomy . Macmillon , London . Webster , J . and Weber , R . 2007 . Introduction to Fungi . 3rd edn .Cambridge University . Sharma , P . D . 2005 . Fungi and Allied Organisms .Narosa Publ . N . Delhi . Inderjeet , K . Sethi , and Walia , S . K . 2011 . Textbook of Fungi and their Allies . Macmillan Publ . India , Ltd .

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