Question

with the help of labeled diagram. briefly discuss the stricture of mature basidocarp of agaricus

Answer 1

Structure of Agaricus:

It can be studied in two parts:

(a) Vegetative mycelium (living inside the soil)
b) Fruiting body or basidiocarp (present above the soil and edible in young stage)

(a) Vegetative Structure:

Vegetative mycelium is of three types:

Primary Mycelium:

It originates by the germination of uninucleate basidiospores carrying either ‘+’ or ‘-‘ strain. The cells are uninucleate i.e., monokaryotic. It is short lived and becomes bi-nucleate by fusing of two compatible hyphae (Fig. 1 A).


Secondary Mycelium:

It originates from primary mycelium. After fusion of the hyphae of two opposite strains, the nucleus from one hypha migrates to the other and later gives rise to the bi-nucleate secondary mycelium i.e., dikaryotic. It is long lived and abundant (Fig. 1 B).

Tertiary Mycelium:

The secondary mycelium grows extensively under the soil and becomes organised into special tissue to form the fruiting body or basidiocarp. The fruiting body appears like umbrella above ground. It is made up of dikaryotic hyphae. These hyphae are called tertiary mycelium. The mycelium is subterranean. The hyphae are septate and branched. The cells communicate with one another by means of a central pore in the septum. It is a typical dolipore septum.

Structure and Anatomy of Basidiocarp:

The mature fruiting body can be differentiated into three parts i.e., stipe, pileus and annulus (Fig. 5).

1. Stipe:

It is the basal part of the basidiocarp. In this region the hyphae run longitudinally parallel to each other. A transverse section of stipe shows that it is made up of two kinds of tissue, i.e., (a) Compactly arranged hypahe in the peripheral region known as cortex, (b) loosely arranged hyphae (with inter spaces), in the central region known as medulla (Fig. 6).

2. Pileus:

The stipe at its top supports a broad umbrella shaped cap called pileus. The mature pileus is 5 to 12.5 cm in diameter. From the underside of the pileus hang approximately 300 to 600 strips or plates of tissues known as gills or lamellae. The gills are white or pinkish in young condition and turns brown or purplish black at maturity.

A transverse section of the gill (T. S. of gill) shows the following 3 distinct, structures (Fig. 7 A):

1. Trama:

It is the middle part of the gill. This region is made up of loosely arranged interwoven mass of plectenchymatous tissue of long, slender hyphae. These hyphae run, more or less, longitudinally.

2. Sub-Hymenium or Hypothecium:

The hyphae of the trama region curve outwards towards each surface of the gill. They end in small diametric cells forming a compact layer known as sub-hymenium.

3. Hymenium or Thecium:

It is the outermost layer and lies on the surface of sub-hymenium covering both sides of the gill. Some branches emerge out almost at right angle to the sub-hymenium and develop a palisade like layer consisting of basidia (fertile) and the paraphyses (sterile) (Fig. 7A). Some of the sterile cells become enlarged and project beyond the basidial layer. They are called as cystidia.