Q.17. Draw neat labeled diagrams of section of - (2006)
(a) Brassica leaf through a white rust pustule.
(b) Barberry leaf through a pycnidium and aecium.
Or. Draw the labelled diagram of T.S. of leaf of Barberis plant showing Aecidial and Pycnidial stages. (2014)
Ans. (a) Brassica Leaf Through a White Rust Pustule: -
(b) Barberry Leaf Through a Pycnidium and Aecium: -
Agaricus
Q.18. Give an illustrated account of genus Agaricus. Comment upon its systematic position and economic importance. (2008)
Related Questions -
Q. Write a short note on Agaricus. (2009)
Q. Give systematic classification and characteristics of Agaricu fungus. (2010, 11)
Ans. Systematic Position: -
Division - Mycota
Sub-division - Eumycotina
Class - Basidiomycetes
Order - Agaricales
Family - Agaricaceae
Genus - Agaricus
The genus A garicus also called psalliota is a saprophyte fungus. It grows on damp rotten logs of wood, dead and decaying organic matters,
soil rich in humus and manure piles. It includes many species, the majority of them being edible. Agaricus compestris is by far the best known species and is quite commonly known as field mushroom. It is the edible species.
Vegetative Structure: -
The vegetative body is the mycelium which is found growing below ground. It is popularly called as the mushroom which is the edible portion refers only to the aerial fructification, the basidiocarp, produced at the time of reproduction. The mycelium when young is haploid and consists of much branched loosely tangled sepatate hyphae which ramify the substratum just beneath the surface. The cells of these hyphae are uninucleate and contain granular, vacuolated protoplasm and oil globules. The primary mycelium is produced by the germination of a basidiopore and is of short duration in nature. From this primary mycelium is developed a secondary mycelium with binucleated cells as a result of dikaryotisation either by hyphal fusions or by the union of oidium with the somatic hypha.
The secondary mycelium perenates in the substratum and persists for many years. It is composed of filamentous, septate and branched hyphae, the cells of which are binucleated and communicate with one another by a minute central pore in the septum. The secondary mycelium later produce much compacted masses of hyphal strands called rhizomorphs, which form the fruiting bodies or sporophores above the ground.
The mycelium lying within the substratum is perennial and grows from the center with the result that it increases in diameter from year to year. The centrifugal growth of mycelium is followed by the death of older hyphae in the center. At the time of sporulation the fruiting body or mushrooms are developed in a ring above the ground in lawns and pastures. Such circles of mushrooms are commonly called the fairy rings.
Reproduction: -
Asexual Reproduction: -
It is accomplished by the formation of chlamydospores.
Sexual Reproduction: -
It occurs by the development of basidiocarps.
Structure of Mature Basidiocarp: -
Stipe: -
The mature basidocarp of Agaricus consist of a shoot, fleshy stalk or stipe and an umbrella like cap the pileus. The stipe is fleshy and cylindrical structure and is pinkish white in colour. It is uaually btoader at the base. The remains of the strands of the mycelium are some times seen still sticking to the base of stipe. The remnants of the inner veil may be seen usually in the form of a ring, the annulus about midway up of the stipe of a mature mushroom.
Pileus: -
The Pileus ranges from 2- 4 inches in diameter. The upper surface of pileus is more or less convex and is cream coloured. The flesh is white at first but later on becomes pinkish. On the underside of pileus there are large number of thin, vertical plate like structures called gills which radiate from the stipe towards the edge of the pileus. Each gill is covered on both sides by a spore bearing layer the hymenium.
Economic Importance: -
Many of them are edible and are cultivated commercially. The common edible mushroom is the psalliota compestris or agaricus copmpestris. In India it is cultivated in some parts of the south India. Several members are however poisnous. Poisnous mushrooms are known as toadstools. It is very difficult to distinguish the edible mushroom from the poisnous ones. Therefore one should be very cautious in picking wild mushroom to eat. Amantia muscaria, A.verna and Phalloides are the most deadly poisonous of all mushrooms.
Q.19. Write short note on fairy rings. (2011)
Ans. Fairy rings: -
The mycelium lying within the substratum is perennial and grows from the centre with the result that it increases in diameter from year to year. The centrifugal growth of mycelium is followed by the death of older hyphae in the centre. At the time of sporulation, the fruiting lody or mushrooms are developed in a ring above the ground in lawns and pastures. Such circles of mushrooms are commonly called “fairy rings”, a name based on the ancient belief that mushrooms growing in a ring marked the path of dancing fairies. These fairy rings are best seen in Agaricus praerimosus and Marasmius oreades. Fairy rings by Agaricus campestris are less common.