Taxonomy is the Science of classification which makes the study of wide variety of organisms easy and helps us to understand the interrelationships among different groups of organisms. In Plant Kingdom the first level of classification depends whether plant body is differentiated, have special tissues for transportation, ability to bear seeds and whether the seeds are enclosed within fruits or not.
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Classification of Plant Kingdom
Plant Kingdom is divided in to:
(I) Thallophyta: Various types of microorganisms like algae, fungi and bacteria have been kept under it. Algae are classified in to three categories: Red, Brown and Green algae.
Chief characteristics of algae are:
- Cell wall of algae is made up of cellulose.
- Sex organs of algae are unicellular.
- Algae store their food in the form of starch.
Reproduction: Vegetative, Asexual and Sexual reproduction.
Economic Utilities: It is useful in the form of food stuffs, agriculture, in trade and business, in biological research, as the fodder of domestic animals, in the form of medicines and in the formation of land. But there are many algae which act like pollutants and contaminate the drinking water. Also, watery equipments are rottened by the algae. Celphaleuros algae produce a disease called red rust in the tea plants.
(I) Bryophytta: Plants are found at land and water but are amphibians like Liver warts, Horn warts, Moss etc. These plants are also autotrophic as chloroplasts are present.
Economic Utilities: These plants have good absorption capacity of water and thus can be used as flood preventive measure. Also used in stopping soil erosion. Moss plant is used as a fuel called peat energy and as antiseptics.
(II) Tracheophyta: These plants have well developed vascular tissues and divided in to xylem and phloem. Further it is divided in to three subgroups: Pteridophyta, Gymnosperms and Angiosperm.
(a) Pteridophyta: In these plants there are lack of seeds and flowers.
Examples: Club Mosses, horsetails, ferns etc.
- These plants are sporophyte. As spores of these plants are produced in sporangia.
- The leaves in which sporangia produces is called sporophyll.
- On Gametophyte there exist male and female sex organ.
- Alternation of genes is also appeared.
- Zygospores are formed through zygote.
Utilities: This plant is used as fodders for the domestic animals, while the seed is used as medicines.
|1. They contain photosynthetic pigments.
3. Most of them are aquatic in habitat.
4. The cell wall is made up of Cellulose.
5. It contains starch as a stored food material.
|1. Photosynthetic pigments are absent.
3. Most of them are terrestrial.
4. The cell wall is made up of chitin.
5. It contains glycogen and oil as the stored food material.
(b) Gymnosperm: The plants whose seeds are completely uncoated and there is complete lack of ovary.
Examples: Cycas, Pinus (Pines), Cedrus (Deodar) etc.
- These plants are perennial and xerophytic.
- Have clear cut annual rings.
- Undergo wind- pollination and have polyembryony- characteristics.
- One or more cotyledons in an embryo exists with radicle and plumule.
Economic Utilities: Used in the form of food, timber & medicine. For decorative and domestic use. In making volatile oils & also used in the form of tanning and resin.
(c) Angiosperm: This is the most- important subgroup of plants, whose seeds are coated and developed in an organ or ovary. Our major food, fibre, spice and beverage crops are flowering plants (angiosperms). Also used as medicinal plants and the respondent flavour species, latex products like rubber etc. These plants are also utilised in making perfumes, soaps and cosmetics from their oils.
- The reproductive organ of this plant is flower and double fertilization takes place.
- Are saprophytic, symbiotic and parasitic. Some are autotrophic also.
- Normally appear on land but few are aquatic.
- The vascular tissues are extremely well developed.
Further Angiosperm is classified into two categories:
(a) Monocotyledonae (monocot): Leaves of these plants are much longer rather than broad. Stems of monocot lack cambium and hence they increase little in girth except palm tree. Examples: Maize, wheat, rice, onion, sugarcane, barley, banana, coconut etc.
- In the seed of these plants one cotyledon is found.
- Their leaves have parallel venation.
- The roots of these plants are not developed.
- The flowers are trimerous i.e have three or multiple of three petals.
- In the vascular part, cambium doesn’t exist.
(b) Dicotyledonae (Dicot): These plants have two seed leaves. Have veins forming a network in their leaves. Almost have all the hardwood tree species, pulses, fruits, vegetables etc. Examples: Pea, potato, sunflower, rose, banyan, apple, neem etc.
- In the seed of these plants two cotyledons are found.
- In the vascular part cambium exists.
- The flower of the plant has multiples of four or five petals.
- These dicots plants have secondary growth.