R.H. Whittaker organized the organisms into five kingdoms. He classified organisms on the basis of cell structure, mode, source of nutrition and body design. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, and Animalia. Let’s learn about the plant kingdom i.e., kingdom Plantae.
Plant Kingdom :-
Plantae is the plant kingdom which includes all plants on the earth. They are multicellular eukaryotes. Typically, they consist of a rigid structure that surrounds the cell membrane called the cell wall. Plants also have a green coloured pigment called chlorophyll that are quite important for photosynthesis. Hence, they have an autotrophic mode of nutrition.
classification is based on the following three criteria:
- Plant body– whether the body has well-differentiated structures or not.
- Vascular system-whether the plant has vascular system for transportation of substances or not
- Seed formation– whether the plant bears flowers and seeds or not; if it does, then whether it is enclosed within fruits or not.
Now we describe about the plants kingdom divides in 5 sub groups:-
- Thallophyta
- Bryophyta
- Pteridophyta
- Gymnosperms
- Angiosperms
Thallophyta :-
All the plants that lack a well-differentiated body structure belong to the subgroup Thallophyta. Thallophytes are commonly known as algae. The majority of them are aquatic. Some examples are Spirogyra, Chara, Ulothrix, etc.
Bryophyta :-
Bryophytes have differentiated plant body like stem, leaf structures. But they lack a vascular system for the transportation of substances across the plant body. Bryophytes are found in both land and aquatic habitats, hence are known as amphibians of the plant kingdom. Mosses and Marchantia belong to this subgroup.
Pteridophyta :-
Pteridophytes have well-differentiated structures such as stem, root, leaves as well as a vascular system. Ferns, horsetails, Marsilea are some common examples of Pteridophytes.
