Thallophyta

Thallopahyta are also known as Thallophyto and Thallobiont. Thallphyta belongs to the plant kingdom. The name “Thallophyta” comes from the characteristic feature of the “thalloid body” i.e. undifferentiated body. Thallophytes are the most primitive form of plants, mostly found in damp areas or near water bodies. In this article, we will study Thallophyta, its characteristics, and the importance of Thallophyta.

What is Thallophyta?

Thallophyta belongs to a polyphyletic group that is mainly composed of simple, lower-level thalloid plants. They are non-motile organisms. The body of thallophytes does not contain a vascular system as they lack conducting tissue in their body. They belong to the kingdom Plantae and sub-kingdom Cryptogamae. It is placed under this sub-kingdom because it lacks reproductive organs like flowers and seeds. They depend on water bodies for their reproduction as they perform external fertilization. They consist of further sub-divisions of algae, lichen, and fungi.

The name “Thallophyta” comes from the Greek word “Thallos” which means “undifferentiated” and “phyton” which means “plant”. Thallophytes can be defined as “it is a group of plants or plant-like organisms that lack differentiated stems, leaves, and roots and that were classified as a primary division of the plant kingdom”.

Characteristics of Thallophyta

Some of the important characteristics of Thallophyta are listed below;

1. Their bodies are not differentiated into well-defined stems, roots, and leaves.
2. They lack a definite body structure like the higher plants and are unable to move.
3. They lack a vascular system i.e. xylem and phloem for water conduction.
4. They also lack cellulosic cell walls.
5. They are autotrophic and store nutrition in the form of starch.
6. They are found in wet, moist, or damp areas.
7. They are the most primitive form of plants.
8. They perform external fertilization with the help of water.
9. Sex organs are simple and single-celled.
10. The life cycle of algae varies, it shows haplotic, haplodiplontic, and diplontic conditions.

Classification of Thallophyta

Thallophytes are biologically classified into; Algae, Lichen, and Fungi

Alage

Algae are mainly aquatic organisms (freshwater or marine). They are autotrophic and are capable of synthesizing their food. They bear chlorophyll for photosynthesis. The forms and sizes of algae vary. The size of algae ranges from microscopic structures (Chlamydomonas), filamentous (Spirogyra), and massive (Kelp) to colonial (Volvox) forms. They possess flexible bodies which enable them to move with the tides. Their bodies are usually covered by mucus. They can be classified into;

1. Rhodophyceae: They are also called red algae due to their reddish appearance. They are mostly marine. They contain chlorophyll a, d, and phycoerythrin. They store their food in the form of floridean starch. Examples are; Porphyra, Polysiphonia, Gelidium, and Gracilaria.
2. Phaeophyceae: They are also called brown algae due to their brownish appearance. They are mostly marine. They contain chlorophyll a, c, and fucoxanthin. They store their food in the form of mannitol and laminarin. Examples are; Fucus, Dictyota, Laminaria, and Sargassum.
3. Chlorophyceae: They are also called green algae due to their greenish appearance. They are found in freshwater, brackish water, and marine environments. They contain chlorophyll a, and b only. They store their food in the form of starch. Examples are; Chlorella, Volvox, and Ulothrix.

Lichen

It is formed when a symbiotic association between algae and fungi takes place. The algal or cyanobacterial partner is called phycobiont and is responsible for the photosynthesis and synthesis of food. The fungal part is called mycobiont and is responsible for providing anchorage, protection, minerals, and water. Examples are; Crustose lichen, Foliose lichen and Fruticose lichen.

Fungi

They are non-motile, heterotrophic, spore-bearing, non-vascular plant-like organisms. The fungal cell wall is made of chitin, glucans, and glycoproteins. Their body is composed of finger-like projections called hyphae. A network of hyphae is called mycelium. They lack chlorophyll or any other photosynthetic pigments. Hence, they are dependent on other organisms for food as they live as parasites, saprophytes, or symbionts. They can be classified into;

1. Phycomycetes: They are mostly saprophytic or parasitic. Their hypothesis is unbranched or aseptate. Examples are; Mucor, Rhizopus (bread mould) and Albugo.
2. Ascomycetes: They are mostly saprophytic, parasitic, or coprophilic. Their hyphe is branched or spetate. Examples are; Aspergillus, Claviceps, Penicillium,, and Neurospora.
3. Basidiomycetes: They are mostly saprophytic or parasitic. Their hyphe is branched or septate. Examples are; Agaricus (Mushroom), Ustilago (Smut fungus), and Puccinia (Rust fungus).
4. Deuteromycetes: They are mostly saprophytic or parasitic. Their hyphe is branched or spetate. Examples are; Alternaria, Colletotrichum and Trichoderma.

Note: Lichens and fungi are currently not placed under Thallophyta. Due to their characteristics Fungi have been assigned a new kingdom of their own i.e. Kingdom Fungi and Lichen viruses are not placed under any kingdom.

Importance of Thallophytes

Some of the importance of thallophytes are listed below;

1. Algae are responsible for fixing half the amount of carbon dioxide and releasing a huge amount of oxygen on the Earth.
2. Algae are the source of agar used to make jellies, etc.
3. Algae are a source of high-energy compounds in aquatic ecosystems.
4. Lichens can act as pollution indicators i.e. they can not tolerate pollutants.
5. Lichen extracts are used for litmus.
6. Lichens are the pioneer organisms during ecological succession.

FAQs on Thallophyta

1. What are Thallophyta?

Thallophyta are the most primitive members of the plant kingdom. They lack a well-differentiated body i.e. lacks stem, leaves, and roots. They are further classified into algae and lichen.

2. What is Thallophyta also Known as?

Thallophyta is also known as thallobionta or thallophyto. It consists of organisms that are non-mobile, lower-level plants, or plant-like organisms.

3. What is the Use of Thallophyta?

Thallophytes are used for the preparation of ice chocolates, cream, jellies, cosmetics, laxatives, paints, etc. They also act as an environmental pollution indicator.

4. Why are they Called Thallophyta?

They are called Thallophyta because of their thalloid-like bodies i.e. they lack true stems, leaves, and roots. Their body is “thallus-like” which means undifferentiated.

5. What are the Salient Features of Thallophyta?

The salient features of Thallophyta are; undifferentiated body, found in damp, moist, or water bodies, are autotrophs, lack vascular system, have single-celled reproductive organs, etc.