What is the Importance of Thallus?
The thallus is a special part of the body of fungi. Due to the presence of cell walls, it is known as the plant body part of fungi. This is where the fungi is similar to plants. The main thing you can find in the thallus is the filaments. No specialized tissue is present in the thallus unlike advanced organisms like trees. It can be a tricky task for you to study the thallus meaning without knowing its structure. Here, you will know about the structure and role of the thallus in case of fungi. It is very important that you observe them while studying about different types of fungi.
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Structural Description of Thallus
Thallus can also be called branched or unbranched filament. This has got cell walls, however, in the slime moles, it is absent. Here are the brief details about the different structures of thallus:
Unicellular Thallus
The unicellular thallus is mainly found in the lower fungi. It is spherical and unicellular. Thallus takes an important role in fungal reproduction. In the case of the holocarpic fungi, no reproductive and vegetative stages occur together.
The unicellular thallus is also found in Plasmodium and yeast. For the latter, it relates to the filamentous thallus. If the thallus is present in the holocarpic and unicellular form, the mycelium of the thallus might be absent.
Filamentous Thallus
When talking about fungi thallus, you can see a lot of fungi having filamentous thallus. This type of thallus develops as the spore germinates. While the germination takes place, the spore gets to a substratum. Here, all the conditions of life are favourable.
The short tubular structure develops in the case of some spores (in some species) and they directly get to the shape of the filamentous thallus. In these tubular structures, remains the thallus which is also known as hypha. The hypha is cottony and contains filaments.
In advanced stages, The hypha filaments can develop the reproductive
Organs For the Fungi.
This type of fungi is called eucarpic and some parts of the hypha manage the daily activities and the others indulge in the reproductive act. In most cases, the hype of the fungus is devoid of any colours mainly for those which remain on the substratum. The other part of the hype remaining in the aerial position can get some colours. You can find the tilts of yellow, brown, purple, red, and blue.
The pigmentation, however, does not form the living matter. It is not related to fungus physiology. Pigmentation is a natural phenomenon that just takes place with time.
Evolution of Thallus
There is an evolutionary process of the Thallus in fungi. Here, you can go through the details.
Aquatic fungi: all lower levels of fungi are aquatic and there is no mycelium in them. Mostly, the thallus is unicellular in this type of fungi.
Reproduction Stages:
Formation of zoospore
Presence of Rhizoids
Conversion of coenocytic thallus into the reproductive organ
Arrangement of Filamentous Lower Fungi
The arrangement of filamentous lower fungi occurs in series. They live their life like an amphibian. These later take the shape of the weather mold.
Did You Know?
Fungi have a lot of importance in human life. Some of the leading importance are given below:
Fungi Help Things to Decompose: Fungi is one of the primary organisms that help things to decompose real fast. It is good for the environment and mostly for the soil.
Edible Fungi: Yeast and mushrooms are edible fungi. You can make some outstanding dishes with the help of mushrooms and yeast can be used as a fermentation agent. It is mainly used for softening pieces of bread. You should however make sure that the yeast is activated.
Fungi-based medicines are present- Multiple medicines are produced on the basis of fungi. These variants of fungus are generally cultured in the office.
Solved Examples
1. What is Thallus Made of?
Answer: The Thallus is made of cell plates and filaments. It is present in all the lower-level fungi. You can find the Thallus in the unicellular fungi and the multicellular ones too. These are found in the case of fungus which generates spores.
2. What is the Work of Thallus?
Answer: The Thallus mainly works as the reproductive organ for fungi. It allows the organism to reproduce both asexually and sexually. The fungi can make colonies easily as the Thallus connects.
3. Do Aquatic Fungi Have Spores?
Answer: No, the aquatic fungi do not have spores in them. As a result, the thallus in such organisms does not look the same as the amphibian fungi variants.
4. What is Holocarpic Thallus?
Answer: When an entire thallus differentiates into a sporangium that enables the reproduction of fungi, it is known as Holocarpic Thallus.
FAQs on Thallus
1. What is a thallus in biology?
In biology, a thallus refers to a simple, undifferentiated plant-like body that lacks true roots, stems, and leaves. This type of body structure is characteristic of lower organisms such as algae, fungi, lichens, and some bryophytes (like liverworts and hornworts). Since it lacks a vascular system (xylem and phloem), a thallus absorbs water and nutrients directly from its surroundings.
2. What are the main characteristics of a thallus?
The primary characteristics that define a thallus include:
Lack of Differentiation: The body is not divided into true roots, stems, or leaves.
No Vascular Tissues: It does not contain specialised transport tissues like xylem and phloem.
Simple Structure: The internal structure is simple, often composed of parenchyma-like cells.
Direct Absorption: Nutrients and water are absorbed over the entire surface.
Attachment: It is often attached to a substrate by simple, root-like structures called rhizoids.
3. What is the thallus of a fungus called and how is it structured?
The thallus of a fungus is known as a mycelium. It consists of a vast, interconnected network of microscopic, thread-like filaments called hyphae. These hyphae branch out and grow through the substrate (like soil or decaying organic matter), absorbing nutrients. The mycelium represents the main vegetative body of the fungus, while the visible part, like a mushroom, is typically the reproductive structure.
4. What are the different types of thallus organisation found in algae?
Algae exhibit a wide range of thallus organisation, from simple to complex forms. The main types include:
Unicellular: Consists of a single cell (e.g., Chlamydomonas).
Colonial: A group of individual cells living together, sometimes with coordinated functions (e.g., Volvox).
Filamentous: Cells are arranged in a thread-like chain, which can be branched or unbranched (e.g., Spirogyra).
Siphonaceous: Composed of a single, large, multinucleate cell without cross-walls (coenocytic), forming a tube-like structure (e.g., Vaucheria).
Parenchymatous: A complex, tissue-like thallus formed by cell division in multiple planes (e.g., Ulva, the sea lettuce).
5. How does a thallus in bryophytes differ from that in algae?
While both are simple, the thallus in bryophytes (like Marchantia) is generally more complex than in most algae. The bryophyte thallus often shows some degree of internal tissue differentiation, such as an upper photosynthetic region with air pores and a lower storage region. It is also anchored to the soil by rhizoids. In contrast, most algal thalli are simpler and fully adapted for an aquatic environment, with less internal specialisation.
6. Why is the thallus body form considered a significant evolutionary step?
The thallus represents a critical evolutionary step from unicellular to multicellular life. While it is a simple structure, it allowed organisms to increase in size and begin to specialise functions, such as anchorage and photosynthesis, across different parts of the body. This primitive organisation paved the way for the development of more complex, differentiated body forms with specialised organs like true roots, stems, and leaves seen in higher plants.
7. How does a thallus fundamentally differ from the body of a higher plant?
A thallus differs from a higher plant's body in two key ways. First, a thallus is undifferentiated, meaning it lacks the distinct organs of roots, stems, and leaves that perform specialised functions in higher plants. Second, a thallus lacks vascular tissues (xylem and phloem), which transport water, minerals, and food in higher plants. This absence limits the size and complexity a thallus can achieve and restricts these organisms to moist habitats.
8. What is the difference between the terms 'thallus' and 'thalloid'?
The terms refer to the same concept but are used differently. 'Thallus' is a noun that names the undifferentiated plant body itself. For example, "The body of a seaweed is a thallus." In contrast, 'thalloid' is an adjective used to describe a structure that resembles or has the characteristics of a thallus. For example, "Liverworts have a thalloid body structure."
9. Why can't organisms with a thallus grow as tall as trees?
Organisms with a thallus cannot grow tall like trees primarily due to the lack of two critical structures: vascular tissues and true stems. Without xylem and phloem, there is no efficient system to transport water and nutrients up from the ground or sugars down from photosynthetic areas. Furthermore, without the rigid, supportive structure of a true stem containing woody tissues, a thallus cannot support its own weight to grow vertically and compete for sunlight.
