M.Sc. Botany (Semester II) MBOTCC-6: Taxonomy, Anatomy & Embryology Dr. Akanksha Priya Assistant Professor RLSY College, Bakhtiyarpur, Patliputra University Unit-III: Post Mendelian Approaches Chemotaxonomy The chemical constituent of plants differ from species to species. Chemotaxonomy, also called chemosystematics, is to classify and identify organisms according to confirmable differences and similarities in their biochemical compositions. In a nutshell, the biological classification of plants and animals based on similarities and differences in their biochemical composition is Chemotaxonomy. Chemotaxonomy is the modern approach, especially for plants. The chemical compounds studied mostly are proteins, amino acids, nucleic acids, peptides etc. Chemotaxonomic Classification: The phenolics, alkaloids, terpenoids and non-protein amino acids, are the four important and widely exploited groups of compounds utilized for chemotaxonomic classification. The system of chemotaxonomic classification relies on the chemical similarity of taxon. Three broad categories of compounds are used in plant chemotaxonomy: primary metabolites, secondary metabolites and semantics. i) Primary metabolites: Primary metabolites are compounds that are involved in the fundamental metabolic pathways, which is utilized by the plant itself for growth and development, for example, citric acid used in Krebs cycle. ii) Secondary metabolites: Secondary metabolites are the compounds that usually perform non-essential functions in the plants. They are used for protection and defense against predators and pathogens and performs non-vital functions. For example, alkaloids, phenolics, glucosinolates, amino acids. iii) Semantics: Information carrying molecules like DNA, RNA, proteins. Importance / significance of Chemotaxonomy: Chemotaxonomy has been used in all levels of classification. Chemical evidence has been in all the groups of the plant kingdom, starting from simple organisms like fungi and bacteria up to the most highly advanced and specialized group of angiosperms. Chemotaxonomy-based plant selection is a prerequisite for the successful natural product research. The rise of chemotaxonomy is mainly due to the advancement in analytical techniques for chemical analysis that can detect even trace amounts of chemical compounds. Main purpose of chemotaxonomy: i) To improve the existing system of plants differentiation. ii) To develop the present day knowledge of natural relationship of plants. .