Sem V Paper V B Sc III Polyporus

Sem. V, Paper V (B. Sc. III) Polyporus Asso. Prof. Seema Gaikwad Dept. of Botany Vidnyan Mahavidyalaya, Sangola

Classification • Kingdom: Fungi • Division: Eumycotina • S. division: Basidiomycota • Class: Basidiomycetes • Order: Polyporales • Family: Polyporaceae • Genus: Polyporus

INTRODUCTION The genus is named Polyporus (Gr. poly — many; poros — pores) because of the presence of numerous fine pores on the under surface of the fruit bodies. For the above reason, members of the family Polyporaceae are commonly called pore fungi and the outer margin of the fruit body looks like first brackets and thus called bracket fungi. Out of many, 159 species are found in India. The genus has both harmful and useful members.

Habit and Habitat Polyporus (bracket fungus) is a large genus of family Polyporaceae. It is represented by about 50 cosmopolitan species. These species may grow as saprophytes on dead fallen tree trunks or as parasites on the roots, tree trunks. The species of Polyporus are known as wood rotters because they cause wood rot of various timber trees such as conifers, oak, apple, maple walnut, pear, Acacia etc. P. sulphureus, commonly called sulphur mushroom, causes wood rot of oak and other trees and has large sulphur yellow fruiting bodies P. betulinus causes the heart rot of birch and some other coniferous trees. P. squamosus causes heart rot of Ulmus.

Vegetative Structure (a) Primary Mycelium: It originates by the germination of the uninucleate and haploid basidiospores which are produced from previous fruiting bodies. It consists of many white, slender, branched and septate hyphae. The cells are uninucleate i. e. monokaryotic. It is short lived and soon becomes bi nucleate (dikaryotic) by hyphal fusion occurring between cells of the hyphae of two apposite (compatible) strains.

Vegetative Structure (b) Secondary Mycelium: It is subterranean, perennating, and originates by the fusion of two cells of the monokaryotic mycelium. The bi nucleate or dikaryotic cells by divisions and by clamp connection form the secondary or dikaryotic mycelium. It soon ramifies in the bark tissues and outer portions of the woody cylinder. The hyphae secrete enzymes which digest the lignified walls of the wood cells. Later it develops into the fruiting bodies called basidiocarps. Fresh crop of basidiocarp develops every year from this mycelium.

Reproduction

Asexual Reproduction • It is very rare. It takes place by conidia developed either on dikaryotic mycelium or on sterile germination myce lia. they fructifications. develop On dikaryotic

Sexual Reproduction Sexual reproduction is somatogamous. The species are heterothallic and the fusion between two somatic and monokaryotic mycelia (somatogamy) of opposite strains results in the formation of dikaryotic mycelium. The dikaryotic or secondary myceli umis perennial, which may survive for several years. At regular interval, during favourable con dition, fruit bodies or basidiocarps are developed.

Basidiocarp The secondary mycelium collects in hyphal knots and soon forms a small button like strand in the bark of the wood. Later these hyphal strands grow in size, bursts through the bark on the surface of the tree and form the basidocarps or fruiting bodies. The basidiocarps may be sessile or stalked bearing an umbrella shaped cap or pileus. If stalk is present it may be lateral or central in position. The pilues portion develops as an expanded bracket or shelf like body with brown colour. Its upper surface is smooth, or ridged and undulating in concentric manner. The concentric rings are often alternately brown and white in colour especially in the peripheral regions of the pileus.

Basidiocarp • The lower surface of the pileus is smooth and flat, and does not bear any gills. The characteristic feature of Polyporus is that the pileus contains numerous small pores on under surface (therefore named as polypore’s) which continue deep into the tissues as hollow tubular canals. These tubes are lined on inner surface by the fertile hymenium layer. • Each basidium is club shaped bi nucleate sterigmata. At maturity it projects slightly into the cavity of the pore. The two nuclei of the basidium fuse to form the synkaryon (karyogamy). The diploid nucleus undergoes meiosis to form four haploid nuclei. Four short sterigmata develop from each basidium from which small. • Oval and uninucleate basidiospores are abstracted. Large number of basidiospores (in billions) are formed in the pores. Through these pores the basidiospores are dispersed and after falling on suitable substratum each basidiospore germinates into a primary mycelium of plus or minus strain.

V. S. of the basidiocarp 1. Pileus Surface: It is the upper surface of fruit body and consists of a thin zone of thick walled hyphae. 2. Context: Next to pileus is the context, it con sists of very fine anatomizing hyphae with large and irregular spaces between them. Sometimes the context is differentiated into upper soft and lower hard and firm layer, called duplex. 3. Tube Layer: Next to context is the tube layer, it consists of vertically placed tubes which vary in length according to the size of the fruit body. The tissue lying between the pore tubes consists of generative and skeletal hyphae, called dissepiments.

4. pore Surface: It is the lower surface of the fruit body, where tubes open. 5. Hymenium: The hymenium is lined in the inner surface of the pore, consists of basidium along with paraphyses and rarely with cystedia.

Diagramatic Life-cycle of Polyporus

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