Kingdom Plantae is one of the divisions of The Five Kingdom Classification Model. The organisms under this kingdom are multicellular and eukaryotes. Their cells are of cellulose. They use chlorophyll for photosynthesis thus are autotrophs.
The insectivorous plants like Venus trap and parasite luke Cuscuta are heterotrophic. They follow the nutrition process of holozoic which is ingestion of food. They have two phases in their life cycle – diploid sporophytic and the haploid gametophyte. These phases are different in different plant groups.
This idea is the alternation of generation. This kingdom includes five divisions – Thallophytes, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms.
The division in kingdom Plantae is on the basis of criteria like plant body, vascular system, and seed formation. It looks like the plant has a well-defined structure like roots, stem, and leaves. Then it has a transportation system with xylem and phloem.
Lastly, if it bears flowers and fruits or not. These criteria decide their subgroups further. We will look at the Classification of the Plant Kingdom. Let’s look at Thallophytes, Bryophytes, and Pteridophytes in detail.
Thallophytes
These organisms do not have a well-defined body structure and are usually called algae. They don’t have roots, stems, or leaves and are mostly aquatic and autotrophic. They possess chlorophyll and don’t have a vascular system as well.
Their location of habitat is mostly moist, soil, or in the woods. Their size varies from microscopic to colonial. They can reproduce by following vegetative, asexual, and sexual methods.
The vegetative propagation follows fragmentation and each fragment grows into a thallus. The asexual reproduction is by spores or zoospores. They are motile and give rise to new plants.
Sexual reproduction is by the fusion of two gametes similar in size their motility can vary. When they are similar in size, the process is isogamous and when they are different, the process is anisogamous.
Chlorophyceae
They are also referred to as green algae because of the presence of chlorophyll. They are unicellular, colonial, and thin in diameter and usually have one or more storage units – pyrenoids for chloroplasts. These units also store starch and protein, even food in the form of oil droplets.
They commonly have a cell wall with two layers, inner layers of cellulose and outer of pectose. This makes it rigid in nature. They are capable of reproducing by vegetative, asexual, and sexual methods. Some examples of green algae are – Chlamydomonas, Volvox, Ulothrix, etc.
Phaeophyceae
These organisms are mostly found in marine habitats and are called brown algae. They again vary in size and shape, some common forms are simple branched and filamentous forms.
They have chlorophyll a and c which leads to ranges of color like olive green to brown. Their cell wall is cellulose and has a thin algin coating. Their protoplast contains plastids, vacuole, and nucleus. They are also capable of reproducing by vegetative, asexual, and sexual methods.
All three can take place underwater as well. Some examples of brown algae are – Ectocarpus, Dictyota, Laminaria, etc.
Rhodophyceae
These organisms have large amounts of red pigment or r-phycoerythrin which make them red algae. Most of them are marine and find their habitat in humid areas. They can live on water surfaces as well as deep under the oceans. They have a complex body structure and are multicellular.
Their food is stored in the form of floridean starch. They mostly prefer vegetative propagation for reproduction. But they are capable of sexual and asexual reproduction too. Some examples of red algae are – Polysiphonia, Porphyra, Gracilaria, etc.
Uses of Algae
- Carbon dioxide fixation through photosynthesis.
- Increase the level of dissolved oxygen in the immediate environment.
- Produces energy-rich compounds that form food cycles of all aquatic beings.
- Produce hydrocolloids that are used commercially.
| Basis | Chlorophyceae | Phaeophyceae | Rhodophyceae |
| Names | Green Algae | Brown Algae | Red Algae |
| Pigments | Chlorophyll a and b | Chlorophyll a and c fucoxanthin | Polucoerythin
Chlorophyll a and d |
| Food Storage | Starch | Mannitol | Floridean Starch |
| Cell wall | Cellulose | Algin and Cellulose | Cellulose, Pectin, and Polysulphasters |
| Flagella | 2 – 8 | 2 | Absent |
| Habitat | Fresh, salt, and brackish water | Water – Fresh, salt, and brackish water | Fresh, salt, and brackish water |
Bryophytes
They are the amphibians of the plant kingdom as they can live in soil and depend on water for sexual reproduction. They have a body structure with a stem and leaf-like things. Though they lack a proper transportation system to supply water and nutrients.
They are of three types – mosses, hornworts, and liverworts. They usually live in humid and shaded localities.
Its body is divided and has a thallus like erect form attached to rhizoids.
They lack a proper structure with stems and roots. Their haploid produces gametes and is thus called gametophyte. They follow sexual reproduction with antheridium (Male Part) and archegonium (Female Part).
These organisms release the eggs in water where they fuse to reproduce. The zygotes produce multicellular sporophyte and it lives free but gets nutrition from gametophyte only.
| Basis of Differentiation | Liverworts | Mosses | Hornworts |
| Growth | Defined | Defined | Continuous |
| Structure | Small | Large | Large |
| Chlorophyll | Absent | Present | Present |
| Columella | Absent | Present | Present |
| Persistence | Ephemeral | Persistent | Persistent |
| Dehiscence | Longitudinal | Transverse | Longitudinal |
| Maturation of spores | Simultaneous | Simultaneous | Graduate |
| Form | Simple | Differentiated | Elongated |
| Seta | Present | Present | Absent |
| Stomata | Absent | Present | Present |
Uses of Bryophytes
- Moses gives food to herbaceous mammals, birds, and animals.
- Moses is used as fuel, and as packing material for living material.
- They can decompose rocks for suitable growth of plants.
- They prevent soil erosion as well.
Pteridophytes
These organisms have a well-defined body structure with roots, stem, and leaves. It also has a good transportation system for supplying food and nutrients.
They are the first plants to have xylem and phloem or vascular systems. They mostly live in cool, damp, shady places. Their main plant body is the sporophyte. Their leaves are small and large.
They are multicellular but small and are mostly photosynthetic. They are also seedless and cryptograms. Because of their location, they grow in narrow geographical regions. Many of them have medicinal qualities and help in soil binding.
Some of the examples are Pteris, Dryopteris, Adiantum, and more. They are further divided into four categories – Psilopsida, Lycopsida, Sphenopsida, and Pteropsida.
Psilopsida
- Earliest form of Pteridophytes.
- They are photosynthetic and the stems are divided into two parts.
- Have Rhizoids present in the roots.
- They usually don’t have leaves.
- Tree ferns and water ferns are examples of this.
Lycopsida
- They are also called club moss.
- They have well-defined structures with roots, stems, and leaves.
- Their sporophyte is homosporous.
- Huia and Lycopodium are examples of this.
Sphenopsida
- It is usually called horseball.
- They have well-defined structures with roots, stems, and leaves.
- Equisetum is one example of this.
Pteropsida
- They are called a fern.
- They have well-defined structures with roots, stems, and leaves.
- Their sporophyte is homosporous/heterosporous.
- Pteris and Dryopteris are two examples of this.
Life Cycle of Pteridophytes
- The first stage is the Dioecious. In this, the individual gametophyte produces sperm or egg cells.
- The second stage is Monoicous. In this gametophyte may produce both and function as both genders.
- The third stage is Protandrous where the antheridia mature.
- The last stage is Protogynous and the archegonia mature.
Cryptogamae
The naked embryos of the thallophytes, the bryophytes, and the pteridophytes are spores. The reproducing organs of these are hidden and thus become cryptogamae.
| Difference between Thallophytes, Bryophytes, Pteridophytes | |||
| Basis | Thallophytes | Bryophytes | Pteridophytes |
| Vascular System | Absent | Not Proper | Present |
| Structure | Not Defined | Not Well Defined | Well Defined |
| Reproduction | Vegetative, Asexual, and Sexual | Sexual | Sexual and Asexual |
| Location | Marine | Soil | Cool and Shady |
| Cells | Unicellular | Multicellular | Multicellular |
| Chlorophyll | Present here | It’s Present here | Present |
| Examples | Volvox and Ulothrix | Moss and Hornworts | Pteris and Dryopteris |
Conclusion
This article is a biology article for competitive exams like UPSC, RRB, SSC, and more. It comes under intermediate science which may not be present in most of the competitive exams. This article covers the classification of Kingdom Plantae, Its divisions, and its distinctive features.
We looked at Thallophytes, Bryophytes, and Pteridophytes at large. This has a high chance of appearing in the UPSC Biology and Science exam. It is because it is an intermediate level topic. The chances of it coming in UPSC Mains is comparatively high.
But again if you are a science aspirant then this article will help you build your basic understanding of the subject. All the aspirants must read this article before appearing for the exams.