The Structure of Fungi
Fungi are a diverse group of organisms that belong to the fungal kingdom. They are eukaryotic and heterotrophic, meaning that they do not produce their own food but obtain it from other sources. Unlike plants, fungi do not have chlorophyll and cannot photosynthesize. Fungi can take many different forms, from unicellular yeasts to complex multicellular organisms such as mushrooms and molds. The structures produced by fungi can be highly diverse and can vary greatly depending on the species of fungus and the environmental conditions in which it is growing.
Learn more about fungi and their structure in this article from thedailyECO.
The sporocarp, also called the fruiting body, is a structure produced by some species of fungi as a means of reproduction. It is the visible part of the fungus and contains the spores, that is, the reproductive cells that are spread by wind or other means to produce new fungi. Such spore-forming structures are unique to each fungal species.
Sporocarps come in a variety of shapes and sizes, depending on the species of fungus that produces them. Some common examples of sporocarps are mushrooms, puffballs, and truffles. The fruiting bodies can grow either above the soil, called epigeous, or below the soil, called hypogeous.
Although the sporocarp is commonly referred to as the fungus, it represents only a fraction of the total fungal structure. The formation of sporocarps is an important part of the life cycle of many fungi and is often triggered by environmental factors such as temperature, humidity, and light.
We can distinguish the following parts of the sporocap:
It is a temporary, membranous layer that envelops the entire young sporocarp, protecting it from external factors such as desiccation, predation, or competition from other microorganisms. The universal veil is composed of hyphae, which are the thread-like structures that make up the body of the fungus. These hyphae are interwoven to form a thin, translucent layer that covers the surface of the sporocarp. As the sporocarp grows, the universal veil ruptures, leaving remnants or scars on the surface of the cap or stipe.
Pileus or cap
The top part of the sporocarp, which is typically dome-shaped or flat, and can vary in color and texture. It is covered by a thin cuticle and sometimes may have "scales". These scales can vary in size and color and are often used as a key feature to help identify the species.
The hymenium is a specialized reproductive structure located beneath the mycelium of a fungus. It comprises of sheets, folds, sponges, gels, or tubes that produce and store spores. The compartments formed by the hymenium allow for a larger quantity of spores to be accommodated. Identification of fungal species relies heavily on the distribution and coloration of these compartments. For instance, lamellae may be partially branched, radially arranged, or even branched, and these differences aid in distinguishing between similar mushroom species.
Stipe or stem
This is the supportive structure that connects the cap of the mushroom to the substrate. It is often cylindrical and can vary in length and thickness.
Annulus or ring
This is a ring-shaped structure located on the stipe, often near the cap, that serves as a support for the developing sporocarp. It can also aid in spore dispersal by creating air currents.
Volva or cup
This is a cup-like structure located at the base of the stipe that envelops the mycelium or the young sporocarp. It can be used to identify some mushroom species and can play a role in nutrient uptake by the fungus.
The stipe is in fact the stalk or stalk-like feature that supports the cap of a mushroom. The stipe can vary in size, shape, and color depending on the type of fungus. It is usually composed of hyphae, the branching filaments that make up the body of the fungus. The sipe plays an important role in the overall morphology of the mushroom. It supports the cap and allows the spores to spread.
Mycelium (plural mycelia) is the vegetative part of a fungus that consists of a network of branching, filamentous structures called hyphae. The mycelium serves several functions for the fungus.
First, it serves as the primary nutritional structure by absorbing nutrients and breaking down organic material through the secretion of enzymes.
Second, it plays a critical role in fungal reproduction by producing spores that are dispersed to new sites for growth and development.
Third, the mycelium can form symbiotic relationships with other organisms, such as plants, in which the fungus provides nutrients to the host plant in exchange for carbohydrates.
Mycelium can grow and spread rapidly, sometimes forming large interconnected networks that can cover vast areas of land. It does not have a defined color or shape, but it does contain clear and internal structures, these are:
Hyphae are the branching filaments that grow and spread through the substrate in search of nutrients, water, and other resources needed for the fungus to grow and thrive. There are different types of hyphae that make up the mycelium. These include:
- Vegetative hyphae: these are the primary hyphae that grow and spread through the substrate, absorbing nutrients and breaking down organic matter.
- Aerial hyphae: these are the hyphae that grow above the surface of the substrate, forming the fruiting bodies of the fungus such as mushrooms or other types of spore-bearing structures.
- Rhizomorphs: these are dense, cord-like hyphae that grow in a linear fashion, often forming bundles or strands that can be used for nutrient transport or structural support.
- Clamp connections: these are specialized structures that connect different hyphae together, allowing for the rapid movement of nutrients and other resources throughout the mycelium.
Septa or septum in singular, are the cross-walls that divide the hyphae of some fungi into individual cells. These walls are made up of chitin, a tough, protective polysaccharide that also makes up the exoskeletons of arthropods such as insects and crustaceans.
The septa perform several functions in the mushroom body. First, they help compartmentalize the mycelium, allowing different parts of the hyphae to function independently and preventing the spread of damage or infection from one part of the hyphae to another. Second, septa can regulate the movement of nutrients and other resources within the mycelium by controlling the flow of cytoplasm and organelles between cells. Finally, septa can serve as a barrier to protect the fungus from environmental stressors such as drought or high salt concentrations.
There are many structures that can be produced by fungi during different stages of their life cycle, and the exact number depends on how the structures are categorized and defined. Here is a list of some other less common structures produced by fungi:
- Sclerotia: compact mycelial masses commonly used by fungi to survive adverse environmental conditions such as drought or extreme temperatures.
- Rhizomorphs: dense, cord-like structures of aggregated hyphae that can be used for nutrient transport or as structural supports.
- Ascocarps: specialized reproductive structures formed by fungi of the phylum Ascomycota. Ascocarps are typically cup or bottle shaped and contain the sexual spores of the fungus.
- Basidiocarps: specialized reproductive structures formed by fungi of the phylum Basidiomycota. Basidiocarps are typically mushroom-shaped and contain the sexual spores of the fungus.
- Pseudoparaphyses: filamentous structures that grow between the ascogenous cells in ascomycetes and help support and protect the developing spores.
These are just a few examples of the many structures that fungi can produce during their life cycle. The exact number and classification of these structures may vary depending on the specific characteristics of the fungus being studied.
You may also be interested in this other article, where we explain what the Protista kingdom is.
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- Beatty, R., Beer, A. & Deeming, C. (2010). The Book of Nature . Great Britain: Dorling Kindersley
- Faculty of Chemistry UNAM (sf) Fungi (fungi) . Available at: http://depa.fquim.unam.mx/microbio/1410MG-06/T-Presentaciones/Tema07/T-07-Hongos-211.pdf