SYSTEMS OF CLASSIFICATION OF PLANT KINGDOM

 SYSTEMS OF CLASSIFICATION OF PLANT KINGDOM

The organised systems of classification may be divided into 1. Ancient system and 2. Modern system. The ancient systems were mainly based on habit (300 BC to 1500 AD), whereas the modern systems are based on sexual parts (1500 AD to 1700 AD), based on relationship (1700 to 1800 AD) and based on phylogeny (1800 to 1900 AD).

The variation present in Angiosperms is so enormous that classifying this variation into different groups is very interesting and as well as tough for taxonomists. The taxonomy of flowering plants originated with the classification of plants into medicinal and food value plants by prehistoric people. Later on after civilization, people used to discover more and more useful plants and started classifying them further. Therefore classification is described as the placing of a plant (or group of plants) in groups or categories according to a particular plan or sequence and in conformity with a nomenciatural system.

The three different possible types of classifications are, i. the artificial, ii. the natural and iii. the phylogenetic classifications. In artificial system of classification only a few characters of the plants are to be considered. The main draw back in this system is closely resembling plants are placed in widely separated groups, while those quite different from each other are placed in the same group. In natural system all the important characters of a plant are considered, and the plants are classified according to their related affinities. In phylogenetic system the plants are classified according to theirevolutionary and genetic affinities. Due to imperfect fossil records, it seems a bit difficult to classify. At present the plants are partly on natural and phylogenetic basis. The plant taxonomy begin with the Greeks. 

History of ancient systems of classification 

Theophrastus (372 - 287 BC) The Father of Botany'. He was a student of Aristotle. In Theophrastus's 'Historia plantarum' he has classified the plants on the basis of form and texture, as herbs, undershrubs, shrubs and trees. He described about 450 cultivated plants. Theophrastus considered the trees to be the highest evolved while herbs very primitive. He also distinguished plants based on duration as annual, biennial and perennial plants; also noted the difference between centripetal and centrifugal inflorescence. He also recognised the difference in ovary position and nature of corolla (poly or gamo). His grouping showed vague relationship and the classification was strictly artificial. In view of bis pioneering and classical work on botany, he was regarded as 'The Father of Botany'.

Dioscorides of Christian era described many plants of medicinal value in his 'Materia Medica' but his description and classification was imperfect and of little importance.

Albertus Magnus (1193 - 1280 AD) for the first time distinguished between monocotyledons and dicotyledons on the anatomical basis with the help of crude lenses available at that time.

Otta Brunfels (1489 - 1534 AD) was the first to recognise between perfect (presence of flowers) and imperfect (absence of flowers) groups of plant kingdom.

Jerome Bock (1498 -1554 AD) classified the plants as traces, shrubs and herbs. He has classified plants based on related affinities and brought many plants close to each other.

Andrea Cesalpino (1519 - 1603 AD) classified about 1500 plants chiefly on the basis of the characters of the seed and embryo and published in his book 'De plants' in 1583. He prepared a herbarium of 768 plants, which still exists as one of the oldest herbariums. Caspard Bauhin (1550 -1624 AD) a Swiss botanist described about 6000 species of plants in his book 'An introduction to Bolany H described many plants with generic and specific name and his great work 'Phytopinax' in 1596 was a great contribution to Botany. The binomial nomenclature followed by Linnaeus was actually formed by Bauhin.

M de Labolins (1528-1616 AD) differentiated between monocotyledons and dicotyledons chiefly on the basis of leaves.

John Bay (1628-1705 AD), an English botanist laid the foundation to Modern Botany, His most important work was the 'Historia Plantarum' which was published in three volumes between 1686 and 1704. He divided the plant kingdom into two main groups, a. Herbae and b. Arbores. He was the first to use the terms monocotyledons and dicotyledons. He described and classified 18,000 plants in his book 'Methodus Plantarum'.

J.P.de Tournefort (1656-1708 AD) is said to be the founder of the concept Modern genera. He was the first to provide genera with descriptions and placed them definitely apart from species.

Camerarius (1665-1721 AD), a German Botanist, for the first time demonstrated the sexuality in flowering plants on the experimental basis. He proved experimentally that pollen is absolutely necessary for fertilization and seed formation in the life history of plants.