MORCHELLA

TAXONOMIC POSITIONAlexopoulos (1962)Division Mycota

Subdivision Eumycotina

Class Ascomycetes

Sub-class Euascomycetidae

Series Hymenoascomycetes

Sub-series Discomycetes

Order Pezizales

Family Morchellaceae

Genus Morchella

Species esculenta

Alexopoulos and mims(1979)Superkingdom Eukaryonta

Kingdom Mycetae

Division Amastigomycota

Subdivision Ascomicotina

Class Ascomycetes

Sub-class Hymenoascomycetida

Series Discomycetes

Order Pezizales

Family Morchellacea

Genus Morchella

Species esculenta

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MORCHELLA

The genus includes a numbers of species. The important ones are Morchella conica, M. elata, M. esculenta, M. hybrid, and M. crassipes. All the species grow as saprophytes. There is a suggestion that some species of Morchella are mycorrhizas but there is no proof to substantiate this. In India it is known as Guchhi.

Occurrence- It mostly grows in soil rich organic matter usually in the dense deciduous forest litter and fruits in spring.

Economic Importance- It is one of the delicious, edible fungi which are tasteful articles in human diet. The edible part is the fructification. The fructifications are cooked with rice and vegetables and eaten all over India.

Mycelium- It is inconspicuous but extensive and subterranean. It grows a few inches deep in the soil and thus hidden from view. The mycelium consists of a mass of loosely interwoven branched hyphae. The hyphae ramify through the interstices of the soil nourishing them on the organic material. Each segments or cell contains several nuclei. Under adverse circumstances the mycelia produce sclerotia.

Development of Ascocarp- It begins as a dense knot of hyphae. Under favourable conditions of food and moisture the mycelium hyphae grow rapidly and branch repeatedly. They get interwoven to form dense compact masses. These masses of hyphae are called the hyphal knots. They are formed just beneath the surface of the soil. Each hyphal knot in the presence of abundant food and moisture develops into an aerial stalked fructification called an Ascocarp.

Ascocarp- The fructification or the Ascocarp is a spore producing structure. The mature ascocarp consists of a stalk like portion the stipe surmounted by a hollow conical cap like object the pileus. It is thick, Fleshy and hollow with a waxy surface. The colour varies from a dirty greyish white to a dark brown depending on the species and the age. The terminal conical cap or the pileus constitutes the fertile portion of the ascocarp. The ridges unite the fertile areas which form an irregularly distributed hymenium or thecium. A thin section (figure Morchella Sp. Section through depression of the pileus showing paraphyses and asci) through the depression reveals that it is lined by a fertile layer called the hymenium or thecium. Intermingled with the asci are elongated sterile slender hyphae called the paraphyses? Beneath the hymenium is the sub-hymenium or hypothecium. A cross-section through the stipe reveals that it is made up of pseudoparenchymatous tissue. This tissue in the region of the depression of the pileus forms the hypothecium.

Dehiscence of Asci- The tips of mature asci above the level of the hymenium and turn towards light being positively phototrophic. The residual cytoplasm within each ascus changes into sugars of high osmotic value. The latter absorb water. As a result considerable amount of pressure is set up in the asci. The pressure set up within the asci aided by the turgor pressure set up in the paraphyses causes the release of ascospores through a preformed apical pore which opens by a lid hinged at the top of the ascus. The internal force projects the ascospores high up into the air where they are caught up by the air currents. The explosions of the asci are successive and not simultaneous. The pileus gradually shrinks as it dries up. Eventually it withers. The ascospores are large colourless oval and multinucleate when mature.

Dispersal of Ascospores- It is reported that the catabolic activities in the ripe fruiting body are high during the period of dehiscence. This is indicated by the marked rise in the temperature of the tissue. Conventional currents are set up in the surrounding air. These are induced by the warm tissue of the ripe fructification. These conventional currents of air are suggested to play an important role in the dispersal of the liberate ascospores. They are carried by wind to distant places.

Ascospores germination- On falling on a suitable soil each ascospore germinates to produce a new mycelium soon after release. The ascospores that happen to fall on unsuitable soil perish. Ascospores do not remain viable after one year near the soil surface. According to the latter the ascospores germinate and develop extensive mycelium at 15◦c under highly nutritious non-competitive conditions.

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MORCHELLA

Sexual Reproduction- The sex organs which constitute the accessory parts of sexual process are completely suppressed in Morchella. Consequently the sexual process is extremely simplified. It involves two distinct processes:

a) Plasmogamy- It consists in the union of cytoplasmic contents of two cells without nuclear fusion which is delayed. This results in a sequence of binucleate cell generations constituting the dikaryophase.

b) Karyogamy- The two nuclei in the ascus mother cell fuse. The fusion cell with a diploid nucleus is called the young ascus. It represents the transitory diplophases in the life cycle.

c) Meiosis the young ascus cell elongates. The synkaryon in the ascus undergoes two successive divisions. These constitute meiosis.

(Graphic representation of the lifecycle of morchella)

Salient Feature- 1 Morchella is a saprobic discomycete.2 The so called morels (guchhi) are the aerial fructifications or ascocarps of the fungus.3 The pileus has a pitted surface.4 Asexual reproductions by spores are lacking.5 No hook formation takes place.

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