Plant Kingdom: Characteristics & Classification

A plant kingdom is a type of kingdom included in the five kingdoms classification for living organisms. They are also referred to as the Kingdom of Plants. The five kingdoms are Monera, Protista, Fungi, Animalia, and Plantae.

• The plant kingdom consists of multicellular and eukaryotic organisms.
• R.H. Whittaker proposed a general classification of living things from 1969. 
• The kingdom of Plantae includes all living things. 
• Organism can synthesise their own food, which makes them autotrophic in nature.
• Cell walls are one of the primary properties of plants. 
• The cell wall gives the cell rigidity and structural stability.
• Plant kingdoms are classified based on structural and reproductive characteristics.
• The mode of nutrition in plants is photosynthesis.
• They store photosynthetic pigment in plastids. 

Read More: Plant Kingdom MCQs: Classification & Examples

Key Terms: Plant Kingdom,  Kingdom Plantae, Autotrophic, Multicellular, Photosynthesis, Organisms, Algae, Thallophytes, Bryophytes, Pteridophytes, Gymnosperm, Angiosperm, Chlorophyceae, Phaeophyceae, Rhodophyceae.

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Characteristics of Plant Kingdom

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The features of the plant kingdom are as follows:

• Plant kingdom have eukaryotes cells.
• They are referred to as autotrophs since they produce their own sustenance.
• Kingdom plantae cannot move.
• Chlorophyll, a type of photosynthetic pigment found in the plastids of plants, is present in them.
• They can reproduce sexually or naturally in an asexual manner.
• Starch is how plants store their nourishment.
• They consist of alternating haploid gametophyte and diploid sporophyte generation.
• The plant kingdom life cycle is also known as alternation of generation.     

Plant Kingdom        

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Classification of Kingdom Plantae

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Kingdom plantae consists of various subgroups. They are classified on the basis of ffollowing factors which are as follows:

Plant body

A well-differentiated plant body is present or absent. Such as the root, stem, and leaves.

Vascular system

Whether or not there is a vascular system in place to convey substances like water. Such as the Xylem and Phloem.

Seed formation

The occurrence of flowers and seeds, as well as whether or not the seeds are exposed or covered by a fruit, all affect seed production.

The characteristics listed above have been used to divide the plant kingdom into five subgroups:

Thallophyta

Thallophyta is a subclass of plants that includes all organisms with short, well-differentiated bodybuilding. Algae is the common name for thallophytes. They have a water-based appeal. 

• They include spirogyra, chara, ulothrix, and other instances.

Characteristics of Thallophyta

The characteristics of Thallophyta are mentioned below:

• Thallophyta have their beginnings in damp or wet areas.
• The reason is that "true roots" and vascular tissue needed to transfer water and minerals are absent. 
• They can, therefore, be found in wet or humid environments.
• Most of the members in this group grow their own food. 
• However, other species, like fungi, rely on alternative food sources.
• Around the cells of Thallophyta, they have a cellulose-based cell wall.
• Lack of vascular tissue appearance.
• Xylem and phloem are absent, in contrast to other plants, etc.
• After fertilisation, there is no embryonic development in the basic, single-celled sex organs.

Read More: Natural Resources Management

Classification of Thallophyta

Thallophyta can be classified into two parts:

Algae

Algae are thalloids that have chlorophyll in them. They are primarily water plants and autotrophic. These organisms are tough and water-absorbent, sloth fur. As a result, sloth fur processes create a moist, damp atmosphere that is ideal for the growth of algae. 

• In exchange, the algae provide the sloth with additional nutrition and serve as a predator decoy.

Fungi

Fungi are heterotrophic achlorophyllous thallophytes, which means they do not produce chlorophyll. On rare occasions, fungi may develop a symbiotic connection with algae or a cyanobacterium to offset this disadvantage.

• It contains chlorophyll, the algae may produce food, and in exchange
• The fungi provide a secure environment that protects the algae from UV rays. 

Plant Kingdom

Bryophytes

Bryophytes have distinctive plant parts, such as leaf and stem structures. They do not have a vascular system for distributing materials throughout the plant's body. 

• Bryophytes have their origins in both terrestrial and aquatic habitats. 
• This subcategory includes Mosses and Marchantia.
• The absence of real vascular tissue is the only distinguishing characteristic of bryophytes. 
• Due to the lack of lignin, some organisms contain tissues that are employed to transport water.
• They are not recognised as true vascular tissue.

Characteristics of Bryophytes

The characteristics of Bryophytes are as follows:

• Bryophyte plants lack roots and have simple stalks and leaves.
• They have "rhizoids" in place of roots, which aid in the plant's ability to cling to the surface.
• The roots do not absorb nutrition.
• Mosses spread spores from their leaves, which travel through water and establish new mosses in different locations.
• Water is essential for the growth and spread of mosses. 
• They can endure total desiccation. 

Read More: Species, Population and Community

Pteridophytes

Pteridophytes have distinct features such as stems, roots, leaves, and vascular tissue. They include several plant species like ferns, horsetails, and marsilea. It can be classified into two categories, which are as follows:

• Lycopodiopsida
• Polypodiopsida

Characteristics of Pteridophytes

The characteristic of pteridophytes are as follows:

• First True Terrestrial Plants Are Pteridophytes.
• These plants were among the first plants to adapt to terrestrial life successfully.
• Pteridophytes Are Vascular Cryptogams, Seedless Plants.
• They are spore-producing seedless plants. 
• The plants don't need to conduct tissues to transport minerals and water. 
• They demonstrate a real transformation in generations: 
• Pteridophytes contain members of the sporophyte group and the gametophyte group.
• Advanced Sporangia Spores Are Homosporous.
• The groups in which spores are created are called sporangium. 
• They are frequently both heterosporous.
• It means that two different types of spores are generated.
• Sporophyte's Early Leaves Reveal Circinate Vernation.
• The tips of the leaves often curl inward to protect the growing regions that are more susceptible to predators.

Gymnosperm

Gymnosperms are plants with distinct plant bodies, vascular structures, and the ability to produce seeds. Gymno, which means "naked," and spermatic, which means "seed," are the names of the place. 

• The gymnosperm seeds are bare.
• They are not walled inside of a fruit.
• This group includes the steady, woody trees that are evergreen.

Characteristics of Gymnosperm

The characteristics of gymnosperm are mentioned below:

• Self-pollination and dissemination are primarily caused by wind. 
• As one of the largest and tallest tree species, the sequoia is a gymnosperm.
• The body of the plant is differentiated into leaves, stems, and roots.
• The leaves are often needle-like, with a thick cuticle and depressed stomata. 
• This characteristic encourages a reduction in transpiration-related water loss.
• The gymnosperms have a taproot system for their root system. 
• These roots in some plants are associated with fungus to generate mycorrhiza; Pinus is one example. 
• Few additional species, like the Cycas, have roots that are linked to cyanobacteria.
• They can fix nitrogen and are known as coralloid roots.

Read More: Red Data Book

Angiosperm

Angiosperms are plants that have distinct plant bodies and carry seeds. The name comes from the Greek terms angio, which means enclosed, and sperma, which means seed. 

• Angiosperm seeds, in contrast to gymnosperm seeds, are enclosed within the fruits.
• Typically, angiosperms are thought of as flowering plants. 

Classification of Angiosperm

Angiosperms are divided into two groups depending on how many cotyledons are present in the seeds: Dicotyledons (dicots) and monocotyledons (monocots).

Dicotyledons

The dicotyledonous plants have two cotyledons that are arranged as taproots. The leaves' apparent venation is reticulate. They are also known as dicots.

• Tetramerous and pentamerous flowers exist. 
• Vascular bundles often come in groups of two to six and are arranged in a ring. 

Monocotyledons 

The monocotyledons differ from other plant groups in that they frequently have adventitious roots, simple leaves with identical venation, and trimerous blooms. They are also known as monocots.

• Vascular bundles are present in greater numbers.

Read More: Difference between Algae and Fungi

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Classification Theory of Plant Kingdom

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The plant kingdom is split into two subkingdoms, Cryptogams and Phanerogamae, according to the traditional classification theory.

Cryptogams

Cryptogams don't have obvious reproductive mechanisms, like seeds, to show off. Other names for them include lower plants and seedless plants. The simplest plants belong to the phylum Thallophyta and have undifferentiated or thallus-like shapes

• There are no vascular tissues.
• Accessory spores frequently reproduce asexually. 
• Algae, fungus, and bacteria are the three traditional groupings that make up Thallophyta. 
• Eukaryotes and prokaryotes are not distinguished from one another.

Phanerogams

Phanerogams contain seeds as their obvious reproductive structure. They're known as seed plants. Spermatophyta is the sole division that exists in phanerogams. 

Classification of Plant Kingdom

Read More: Economic Importance of Gymnosperms

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Algae

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Algae are mostly aquatic (freshwater and marine), simple, thalloid, autotrophic organisms that contain chlorophyll. They can also be found in moist stones, soils, and wood, among other environments. 

• Algae come in a wide variety of shapes and sizes.
• It includes filamentous forms like Ulothrix and Spirogyra as well as colony forms like Volvox. 
• Some aquatic life, like kelps, create enormous plant bodies.
• The algae can reproduce sexually, asexually, and vegetatively.
• Plants reproduce through fragmentation. 
• Each piece grows into a thallus.
• The most prevalent type of spore produced during asexual reproduction is called a zoospore. 
• They are flagellated (motile) and produce new plants after germination. 
• In order to reproduce sexually, two gametes must fuse. 
• These gametes can be similarly sized and flagellated, like Ulothrix.
• They can be non-flagellated and non-motile, like Spirogyra.

Read More: Species Biodiversity

The three primary classes of algae are Chlorophyceae, Phaeophyceae, and Rhodophyceae.

Chlorophyceae

The family of chlorophyceae includes the organisms known as green algae. The body of the plant could be filamentous, colonial, or unicellular. Due to the prevalence of chlorophyll a and b pigments, they are often grass-green. 

• The pigments are restricted to specific chloroplasts. 
• In various species, the chloroplasts might form a discoid, plate-like, reticulate, cup-shaped, spiral, or ribbon structure. 
• The chloroplasts of the members include one or more pyrenoid storage bodies. 
• Along with carbohydrates, pyrenoids also include protein. 
• Food may be stored by some algae as oil droplets.
• The stiff cell wall of green algae typically comprises an inner layer of cellulose and an outside layer of pectose.

Phaeophyceae

Brown algae, also known as phaeophyceae, are most frequently found in maritime settings. Their size and form exhibit significant variety. They can be as simple as branched, filamentous forms (Ectocarpus) or as complex as kelps, which can grow to a height of 100 metres. 

• They have xanthophylls, carotenoids, chlorophyll a, and c. 
• Depending on the amount of the xanthophyll pigment, fucoxanthin, present in them, they range in hue from olive green to various brown colours.
• Complex carbohydrates from food, such as mannitol or laminarin, are stored in the body. 
• The cellulose wall is typically covered in a gelatinous layer of algin.
• In addition to plastids, the protoplast also has a central vacuole and nucleus.
• The plant body, which comprises a stalk called the stipe and a frond that resembles a leaf
• Fragmentation is the method used in vegetative reproduction. 
• The majority of brown algae reproduce asexually by producing pear-shaped biflagellate zoospores.
• They have two uneven flagella that are laterally connected.

Read More: Biosphere reserves

Rhodophyceae

Members of the Rhodophyceae family are often referred to as red algae due to the preponderance of the red pigment r-phycoerythrin in their bodies. Most red algae are marine, and warmer regions tend to have higher quantities of them. 

• They can be found in well-lit areas near the water's surface.
• Rhodophyceae can be found at extremely deep oceanic levels where relatively little light can reach.
• Most red algae have multicellular red thalli. 
• Some of them have intricate body plans. 
• Food is stored as floridean starch.
• It has a structure remarkably similar to that of amylopectin and glycogen.

Algae

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Things to Remember

• Plants kingdom known as bryophytes, can survive in soil but require water for sexual reproduction.
• A gametophyte is the name for the main plant body of a bryophyte, which produces gametes.
• Algae are simple, thalloid, autotrophic, mostly aquatic creatures that contain chlorophyll.
• The primary kingdom Plantae in pteridophytes is a sporophyte.
• It is distinguished by its true root, stem, and leaves.
• The dicotyledons and the monocotyledons are the two classes of angiosperms.

Read More: The NCERT Solutions for class 11 Biology Chapter 3: Plant Kingdom

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