Historical prospective of Plant Classification

 

Historical prospective of Plant Classification

·     Taxonomy is the science that explores, describes, names, and classifies all organisms.

·     Angiosperms of about 300,000 species of flowering plants is the largest and most diverse group within the kingdom Plantae. Angiosperms represent approximately 80 percent of all the known green plants now living. 

·     The development of angiosperm classification has been one of the most fascinating subject.

·     A study of sequential events led to various classifications from time to time by several eminent scholars, botanists and thinkers. Plants have been known from times immemorial and remained intimately associated with human life.

·     As the number of plants known to men increased, the necessity to organize them was felt and perhaps earliest classification came into existence.

·     The knowledge of morphology, embryology, palynology, cytology, biochemistry, physiology, and phylogeny have added steps to the concept of classification.

·     The history of plant taxonomy include the emergence of the concept of natural classification, the adoption of the binomial naming system (with the major role of Linnaeus) and other universal rules for the naming of plants, the formulation of the principle of subordination of characters, and the advent of the evolutionary thought.

·     More recently, the cladistic theory (initiated by Hennig) and the rapid advances in DNA technologies allowed to infer phylogenies and to propose true natural, genealogy-based classifications. In a second part, we put the emphasis on the challenges that plant taxonomy faces nowadays.

·     The still very incomplete taxonomic knowledge of the worldwide flora (the so-called taxonomic impediment) is seriously hampering conservation efforts that are especially crucial as biodiversity has entered its sixth extinction crisis. It appears mainly due to insufficient funding, lack of taxonomic expertise, and lack of communication and coordination. 

·     Although the taxonomy of the angiosperms is still incompletely known, the latest classification system incorporates a large body of comparative data derived from studies of DNA sequences.

·     It is known as the Angiosperm Phylogeny Group IV (APG IV) botanical classification system.

·     The angiosperms came to be considered a group at the division level (comparable to the phylum level in animal classification systems) called Anthophyta, though the APG system recognizes only informal groups above the level of order.

·     Taxonomy had its earliest beginning in writings of Theoprastus and ancient Greek philosopher Aristotle-Father of botany in his book Historia plantarum and classified and described about 500 plants.

·     In India, in vedic literature several technical terms were used in description of plants and its parts.

·     A rudimentary form of classification of plants and trees can be found in the Vedas, the oldest composition by human beings. Historians assign c.1500-600 BC as time for the composition of the Vedas.

·     There are four Vedas viz. Rigveda, Samveda, Yajurveda, and Atharvaveda.

·     All the Vedas mention about plants and trees. We can clearly find some basis for classification of plants and trees in Yajurveda and Atharvaveda.

·     The Rigveda (1500-1000 BC) mentions about the healing properties of herbs which it call drava which is present in plants. The Yajurveda and the Atharvaveda (900-600 BC) classified plants on the basis of morphology.

·     The hymns say that Brihaspati (the God of plants) created various types of plants. The types of plants according to the hymns are: 1. Apushpa- Non-flowering 2. Pushpini- Having flower 3. Aphala- Without fruits 4. Phalinirya- Having fruits