Essay on the Classification Of Plant Kingdom

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Plant kingdom was divided by Eichler in 1883 into two subkingdoms on the basis of presence or absence of seeds. (I)Cryptogams – non flowering, seedless plants.

Under this sub kingdom are divisions such as Thallophytic, Bryophytes and Pteridophytes (II) Phanerogams- higher plants with prominent sex organs bearing flowers and seed It consists of divisions such as Gymnosperms and Angiosperms.

Later, there were certain modifications to this classification like placing Thallophytic, Bryophyte among nonvascular plants and Ptcridophytes Gymnosperms and Angiosperms among the vascular plants. Still the Eichlcr system of classification is much in vogue though with necessary modifications. The indentifying features of each group are

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a) Division – Thallophyta

This term was coined by Endlicher in 1836. Algae, Fungi, bacteria and lichen are placed under this division. Whittaker (1969) separated fungi, lichens and bacteria from this and placed in other kingdoms.

Thallophytic are simplest, flowerless, seedless, nonvascular plants. The plan body is thallose i.e. it cannot be differentiated into root, stem and leaves as seen in normal plants.

The thallus is gametophytic or haploid (n). Saprophytic generation only restricted to zygote. Vascular system is completely absent. The sex organs lack sterile cells like jacket. Gametophytic generation is dominant in the life cycle. The division is divided into two sub-divisions algae and fungi.

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Characteristic features of algae

1. Algae are thallose, haploid, gametophytic plants.

2. They are autotrophic, chlorophyllose, eukaryotic.

3. The plants are aquatic, may occur in fresh or marine water.

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4. Reserve food material is starch.

5. Asexual reproduction generally takes place by zoospores. Nonmotil spores like aplanospores or hypnospores may develop under unsuitable conditions.

6. Sex organs are unicellular and no sterile jacket layer develops around the sex organs or gametes.

7. Zygote formed never develops into an embryo.

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8. True alternation of generations absent.

Characteristic features of fungi

1. The fungi are thallose, eukaryotic, achlorophyllose, heterotrophic cryptogams.

2. The organisms are found in any habitat where a trace of organic substance is available.

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3. The fungal thallus is called mycelium which is variously branched into thread like structures. Individual branches are called hyphae.

4. The major component of the cell wall is chitin or cellulose or both.

5. Reserve food material is glycogen.

6. Nutrition is heterotrophic and absorptive.

7. The reproduction is by vegetative, asexual and sexual methods. Vegetative and asexual means of reproduction is evident during favorable conditions of environment.

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