Plant Kingdom

Last Updated : 31 Aug, 2022

The broad classification of living organisms under the system given by Whittaker (1969) wherein he suggested the Five kingdom classification viz Monera, Protista, Fungi, Animalia, and Plantae. Kingdom Plantae is popularly known as plant Kingdom. It is further classified into different subkingdoms. Plants are important in various fields such as medicinal, food, ornaments, etc. It is economically important too. There are several plant species present all over the world. Kingdom Plantae includes all eukaryotic chlorophyll-containing organisms called plants. A few members are partially heterotrophic, such as insectivorous plants or parasites. Bladder wort and Venus fly trap are examples of insectivorous plants and Cuscuta is a parasite. The plant cells have a eukaryotic structure with prominent chloroplasts and cell walls mainly made of cellulose.

The life cycle of plants has two distinct phases—the diploid sporophytic and the haploid gametophytic- that alternate with each other. The lengths of the haploid and the diploid phases, and whether these phases are free-living or dependent on others, vary among different groups of plants. This phenomenon is called alternation of generation.

Classification Theory of Plant Kingdom

In the traditional system of classification, the plant kingdom is divided into two subkingdoms- cryptogamae and phanerogamae.

Cryptogams do not bear conspicuous reproductive structures like seeds. They are also called lower plants or seedless plants. Phanerogams have evident reproductive structures in the form of seeds. They are called seed plants. Cryptograms have three divisions- Thallophyta, Bryophyte and Pteridophyte. Phanerogams have only one division- Spermatophyta. Thallophyta includes the simplest plants which possess undifferentiated or thallus-like forms, single-celled non-jacketed reproductive organs, and a mode of development devoid of an embryo stage. Vascular tissues are absent. Asexual reproduction by accessory spores is very common. Traditionally, thallophyta includes three groups-algae, fungi, and bacteria. The distinction between eukaryotes and prokaryotes is not made.

In the five-kingdom classification system (Monera, Protista, Fungi, Planta, and Animalia), the group thallophyta has been abolished as its members have been redistributed into four kingdoms of Monera, Protista, Fungi, and Plantae. However, the term thallus is still used for the body of a fungus or an alga.

In the modern classification, the Plant kingdom consists of three groups algae, bryophytes, and tracheophytes. Algae are aquatic or semiaquatic and lack an embryo stage. Both bryophytes and tracheophytes possess an embryo stage and are collectively called embryophytes. Bryophytes and tracheophytes are terrestrial plants. Bryophytes are nonvascular, while tracheophytes possess vascular tissues. Thus, the tracheophytes are also called vascular plants. Vascular plants are of further two kinds, pteridophytes (seedless vascular plants) and spermatophytes (seed plants).

The earliest systems of classification used only gross superficial morphological characters such as habit, color, number, the shape of leaves, etc. They were based mainly on vegetative characters or on the androecium structure (system given by Linnaeus). Such a system was artificial; it separated the closely related species, since they were based on a few characteristics. Also, the artificial systems gave equal weightage to vegetative and sexual characteristics. This is not acceptable, since we know that often the vegetative characters are more easily affected by the environment. Against this, natural classification systems developed, which were based on natural features, like ultrastructure, anatomy, embryology, and phytochemistry. Such a classification for flowering plants was given by George Bentham and Joseph Dalton Hooker.

At present, Phylogenetic classification systems or Cladistics based on evolutionary relationships between the various organisms are acceptable. This assumes that organisms belonging to the same taxa have a common ancestor. Numerical Taxonomy or phenetics which is now easily carried out using computers is based on all observable characteristics. Cytotaxonomy which is based on cytological information like chromosome number, structure, behavior, and chemo taxonomy that uses the chemical constituents of the plant to resolve confusion, is also used by taxonomists these days.

Hereunder is the overview of the classification of the plant kingdom:

Algae: Algae are chlorophyll-bearing, simple, thalloid, autotrophic, and large aquatic organisms. The study of Algae is known as Phycology/Algology. The Father of Algae is F.E Fritsch and the Father of Indian Algology is M.O.P Iyengar. Volvox, Chara, Fucus are some examples of Algae.
Bryophytes: Bryophytes are called amphibians of the plant kingdom because they require water for fertilization. The Father of Bryophytes is Hedwig, and the Father of Indian Bryophytes is Prof. Shri Ram Kashyap. Examples of Bryophytes are Funaria, Anthoceros, etc.
Pteridophytes: Pteridophytes is known as the snake in the Botanical world. They are the first primitive vascular land plant. Examples include Lycopodium, Equisetum, Azolla, etc.
Gymnosperms: Gymnosperms are naked seeded plants. The plants are woody, Perennial, and range from tall trees to dwarf shrubs. e.g., Cycas, Pinus.
Angiosperms: Angiosperms are highly developed and the most advanced plants in the plant kingdom. They are plants with sporophytes organized into flowers. Examples include dandelion and grasses to the vast majority of all plant foods we eat, including grains, beans, fruits, etc.

Characteristics of Plant Kingdom

These are multicellular eukaryotes.
They synthesize their own food and thus are called autotrophs.
They are non-motile.
Plants contain photosynthetic pigments called chlorophyll, present in the plastids.
They reproduce asexually by vegetative reproduction or sexually.
Plants have the majority of transport systems.
Plants store their food as starch.

Difference Between Plantae and Animalia

plants are green-colored eukaryotic cells, whereas animals also have eukaryotic cells but do not possess green pigment.
Plants do not have any locomotion, while animals are motile.
The cells of the plant kingdom have cell walls, whereas animals do not.
Most plants won’t show any alterations in generations, but most animals show alternation.

FAQs on Plant Kingdom

Question1: What is the classification of the plant kingdom?

Answer:

The plant kingdom includes algae, Bryophyte, Pteridophytes, Gymnosperms, and angiosperms.

Question 2: What do you mean by the alternation of generation?

Answer:

Alternation of generations, also called metagenesis or heterogenesis, in biology, is the alternation of a sexual phase and an asexual phase in the life cycle of an organism. The two phases, or generations, are often morphologically, and sometimes chromosomally, distinct.

Question 3: What is the economic importance of Plants?

Answer:

Plants provide food and also feed livestock that is then consumed itself. Moreover, plants provide the raw materials for many types of pharmaceuticals, as well as tobacco, coffee, alcohol, and other drugs.

Question 4: Give a few examples of algae.

Answer: