Peziza (Fungi)

Peziza is saprophytic, often favoring coprophilous tendencies (thriving on dung). It commonly grows on dung, decaying wood, or the nutrient-rich humus of forest soil. Certain species within this genus can be found on charred or burnt wood.

There are  100 species of Peziza. This species of fungus is considered toxic. Among its characteristics, it boasts a significant size among cup fungi and enjoys a widespread distribution. Its fruiting body, also known as Ascocarp (Apothecium), typically takes on a cup-shaped form. Indian species of Peziza include Peziza domiciliana, P. ampliata, P. arvernensis, P. badia, P. cerea, and P. echinospora, among others.

1.0Classification of Peziza

Characteristics of Peziza

• The Peziza system is extensively developed, often with five perennial components, and comprises a dense network of hyphae.
• These hyphae are branched and septate, with uninucleate cells. They intricately distribute themselves throughout the substrate (like humus-rich soil, dung, wood, etc.), extracting nourishment along the way.
• They have fruiting bodies that resemble cups, are present above the ground and are readily observable. These structures are alternatively termed Ascocarp or Apothecium.
• The ascocarps found in Peziza are sizable, have a flesh-like texture, and range in color from red to orange. 

2.0Structure of Peziza

• The mycelium displays extensive branching as it spreads across its substrate, and its hyphae also branch and contain septa. 
• Its cells are both uninucleated and multinucleated. 
• While the mycelium primarily develops within the substrate, it produces numerous cup or saucer-shaped fruiting bodies.
• The apothecia are fleshy, smooth, and typically whitish or pale brown, measuring 5 cm or more in diameter. 
• They are sessile, often with short stalks.

Peziza Structure:

A longitudinal section of an apothecium reveals three main regions:

• Hymenium: This innermost region contains the asci, ascospores, and paraphyses.
• Sub-hymenium: Positioned between the hymenium and the outermost region, it consists of thin-walled, light-colored hyphae.
• Excipulum: The outermost region of the apothecium, composed of sterile hyphae.
• Peridium: This term refers to the sterile covering of the ascocarps.

3.0Reproduction in Peziza

Asexual Reproduction in Peziza

• Asexual reproduction is not commonly observed in the majority of Peziza species. However, in a few species, it occurs through the production of external conidia on conidiophores and chlamydospores. 
• Each conidium has the potential to develop into a new mycelium. 
• Chlamydospores, thick-walled resting cells, are formed individually or in chains within the hyphae. 
• When faced with favourable conditions, they germinate and  form new mycelia.

Sexual Reproduction in Peziza

The sexual process occurs even without any sexual organs in Peziza.

• The reproductive system is absent in Peziza vesiculosa. 
• However, this does not hinder the formation of its fruiting body, the apothecium, an aerial structure with a relatively short lifespan. 
• Despite the absence of a complex sexual apparatus, a simplified sexual process occurs. This involves the pairing of two purely vegetative nuclei. 
• The mature mycelium of Peziza vesiculosa comprises a dense network of hyphae. 
• Within this network, certain vegetative cells in the central region have been observed to contain nuclei that form pairs, referred to as dikaryons. 
• The dikaryotic state arises through the autogamous pairing or somatogamous copulation of adjacent vegetative cells within the hyphal network. These cells containing dikaryon give rise to autogenous hyphae, which undergo cellular division by forming cross walls, resulting in multicellular structures. 
• Notably, the cells within these ascogenous hyphae remain binucleate throughout this process.
• At the end of each ascogenous-hyphae, the terminal binucleate cell serves as the ascus mother cell. 
• The formation of croziers has not been observed in the development of asci in Peziza vesiculosa. The ascogenous hyphae, along with the dikaryotic cells from which they originate, alongside the ascus mother cells, collectively represent the dikaryophase in the life cycle of Peziza.
• Upon fusion, the two nuclei within the ascus mother cell form the synkaryon. At this stage, the young ascus containing the synkaryon represents a transient diplophase. 
• The synkaryon subsequently undergoes three consecutive divisions, with the first and second divisions constituting meiosis. This process yields eight haploid nuclei, which eventually develop into ascospores.
• The mature ascus takes the form of an elongated, cylindrical cell. Its wall is lined by a thin layer of cytoplasm known as the epiplasm, enclosing a central vacuole filled with sap. Within the vacuole lie the oval ascospores. 
• Erect asci are aligned side by side within the cavity of the cup-shaped apothecium. Notably, those near the rim of the cup exhibit positive phototropism, bending towards the light source.
• Scattered among the asci are sterile hyphae, which are referred to as paraphyses. Surrounding the hymenium, the remainder of the apothecium comprises densely interwoven, branched hyphae forming a pseudoparenchymatous tissue that provides structural support.
• Apothecia, the cup-shaped structures, are either sessile or have short stalks. They exhibit regularity in form and considerable size, ranging from 2 cm to several inches in diameter. 
• While  Peziza vesiculosa displays apothecia of pale fawn colouration, P. aurantia boasts brilliant orange apothecia.