Classification of Plants

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Introduction

Plants are autotrophic and photosynthetic to make their own food. Primarily terrestrial organisms descended from green algae, which is multicellular. Growth is indeterminate and adapted to gather diffuse resources. Roots consist of simple repeated units exhibiting serial homology. New tissues and organs are formed at meristems. These are hydrostatic in nature. Plants have complex reproductive cycles involving the alternation of generations. Plants defend themselves without moving. Plants have a cell wall that is made up of cellulose and many other components. Plants have chloroplast and vacuole has the ability to store excretion waste.  300,000 species of plants; examples of plants including shrubs, trees, and grasses. Plants play a vital role in our lives and the world’s ecosystems. Plants produce oxygen and are also essential in the food chain, as many living beings eat organisms that eat plants. The study of plants is called botany.

The plant kingdom has changed over time. Fungi and members of the Monera and Protista have now been excluded from Plantae through earlier classification and placed them in the same kingdom.

Plant Kingdom - Plantae

All the plants are included in kingdom Plantae. They are multicellular, eukaryotic, and autotrophic organisms. The plant cells have rigid cell walls that protect from external harmful materials. Plants have chlorophyll pigment, chloroplast which is held in photosynthesis.

Characteristics of Kingdom Plantae

The characteristics of the plant kingdom as follows;

They are non-movable and stay in one place their whole life.

They are autotrophs because plants make their own food.

Plants reproduce in both, they reproduce by vegetative propagation or sexually.

Plants have outer cell walls and a large central vacuole which helps to store waste products, that is why they are multicellular eukaryotes.

Plants have chlorophyll pigments which are responsible for the green colour and contain photosynthesis. 

Plants have different organelles for reproductions, support, anchorage, and photosynthesis. 

Plants show alternation of generation.

Plants have two phases of life; gametophyte and sporophyte.

Classification of Kingdom Plantae

The kingdom Plantae is further divided into subgroups. Classification is as follows:- 

Plant Body: 

Plants' body includes the presence or absence of a well-differentiated plant body. 

E.g.  leaves, stems, and roots.

Vascular System: 

It is a conducting tissue with a complicated network that interconnects all organs and transports, nutrients, water, minerals, organic compounds, and various signalling tissues throughout the body.

E.g. phloem and xylem.

Seed Formation: 

The plant allows whether flowers and seeds or not, if it does, then it is surrounded by fruit or naked.

Basically, the plant kingdom is divided into two categories i.e. Cryptograms and Phanerogams.

Cryptograms and Phanerogams

Cryptograms are the plants which don't produce any kind of flower or in another word, non-flowering plants are known as cryptograms. Cryptograms are subdivided into three parts i.e. Thallophyta, Bryophyta, Pteridophyta. 

Phanerogams produce flowers or all the flowering plants come under into phanerogams, where these are also subdivided into two parts or seedling plants i.e. 

Gymnosperm, Angiosperms

Considering all these categories, the plant kingdom has been divided into five main subcategories. They are as above points follow. 

A. Thallophyta 

Thallophyta is one that is not well differentiated. They do not have well-differentiated plant parts, body structure. They do not have true stems, roots are absent. Thallophyta is multicellular or eukaryotic organisms which means they have well-defined cell membrane-bound organisms. They are non-motile. They have different pigments. These plants are called algae. 

They are mostly aquatic which is also edible and toxic.

E.g spirogyra, ulothrix, cladophora, ulva.

B.  Bryophyta 

Bryophyta is the amphibian of the plant kingdom. The body is differentiated into stem and leaves structures. Roots-like structures called Rhizoids are also present. They are autotrophic organisms. Specialized tissue for water and food conduction is absent. They are generally found in damp and moist areas. 

E.g. ricia, moss, Marchantia 

C. Pteridophyta 

Pteridophyta is the first terrestrial plant. They have well-defined plant bodies that are differentiated into roots, leaves, and stems. Leaves are made up of leaflets. Leaflets bear spores which are also known as Sporophylls. Well-developed reproductive organs are hidden. Specialized tissue for food and water conduction is present i.e. vascular tissue is present. Found in cracks of rock, moist and shady places. 

E.g. Marsilea and fern

D. Gymnosperm 

Gymnosperm is derived from the Greek word 

Gymno - without cover

Sperma -  seed 

i.e. seeds are without fruit. 

They are primitive and simple seed plants. Usually perennials, evergreen, and most woody plants. True roots, stems, and leaves are present. Xylem vessels are absent. Phloem companion cells are absent. 

E.g. Pines and deodar

E. Angiosperms 

Angiosperms are derived from the Greek word 

Angio - covered 

Sperma - seed 

These plants are highly involved plants. They produced seeds, enclosed within the fruit. They are flowering plants which means these plants produce flowers. Seeds are developed inside the ovary. Ovary gets modified into a fruit. Seeds have embryos inside them. Angiosperms are giant in size, they have very complicated tissue.

E.g. eucalyptus 

Division of Angiosperms

Monocotyledons: 

These are types of flowering parts whose embryo stores only one cotyledon, that's why they are called monocots. 

Dicotyledons: 

Dicotyledons are also called dicots, they are members of flowering plants that have cotyledons or pairs of leaves in the embryo of the seed. 

E.g. Campanulales, Urticales, Archichlamy 

FAQ (Frequently Asked Questions)

1. Which pigment is responsible for Photosynthesis in Plants. 

Ans. Chlorophyll is the pigment that is responsible for photosynthesis in plants. 

2.  List the characteristics of Thallophyta. 

Ans. A eukaryotic and multicellular organism 

Not well-defined plant body structure 

Autotrophic and different pigments are present 

Mostly aquatic 

thallophytes are called algae 

It may be edible and toxic 

3. Explain the special Features of Gymnosperms. 

Ans: Gymnosperms are flowering plants that have well defined

A structure like roots, stems, leaves. They also bear seeds like angiosperm, but they are not enclosed within the fruit. Hence the term gymnosperm is derived from the Greek word; Gymno means naked and Sperma means seed.