SEROTAXONOMY

            A. INTRODUCTION

            Serology is a branch of biology dealing with the nature and interaction of antigens and antibodies, or otherwise the study of antigen and antibody reactions is called ‘serology’, and the application or utility of serology in solving taxonomic problems is called ‘serotaxonomy’.

            The substances or proteins capable of inducing the formation of antibodies are called ‘antigens’. Antigens may be proteins, nucleoproteins, lipoproteins, many saccharides, synthetic polypeptides, etc. Antigens are mostly proteins having molecular weights above 10,000. The proteins having molecular weight less than 10,000 do not stimulate antibody production. These types of proteins are called ‘haptens’.

            While ‘antibodies’ are complex protein molecules produced by plasma cells in the immune system. The antibodies combine chemically with specific kinds of antigens and serve as a weapon to kill or destroy the antigens. The antibodies are gamma globulin called ‘immunoglobulin’. There are five classes of antibodies. These are – IgM, IgG, IgA, IgD and IgE where Ig stands for immunoglobulin.

            Nuttal (1901), was the first serotaxonomist to compare the immunochemical specificity of serum proteins for systematic purposes. Kowarski (1901) distinguished seed proteins of several species serologically and verified the species specificity of wheat, rye, oat and pea proteins. Dunbar (1910), showed that proteins from pollen, seeds and leaves of rice were serologically distinct. Other notable serotaxononists were Garis (1908), Zade (1914), Rives (1923), Mez (1926), Moritz (1934), Hawkes & Lester (1966), Smith (1968, 1969, 1972), Kolz (1971), etc.

           B. IMPORTANCE OF SEROLOGY IN TAXONOMY

Serology is useful in serotaxonomy in the following ways –

1. It expresses similarities and dissimilarities among different taxa, and these data are helpful in taxonomy. It determines the degree of similarity between species, genera, families, etc. by comparing the reactions of antigens from various plant taxa with antibodies raised against the antigen of a given taxon.

2. It helps in comparing non-morphological characteristics, the knowledge of which is useful in taxonomy.

3. Single proteins from different plant taxa are also compared by serology techniques.

 C. ROLE OF SEROLOGY IN SOLVING TAXONOMIC PROBLEMS

Several serological data are reported in solving the classification of angiosperms. A few of them are mentioned below –

1. According to Fairbrothers (1983), serological data are useful in the classification of orders and the assignment of families like Apiales, Capparales, Caryophyllales, Fagales, Magnoliales, Papaverales, Primulales, Rannunculales, Rubiales, Scrophulariales, Typhales, etc.

2. Fairbrothers and Johnson (1959) separated six species of Bromus on the basis of serological data.

3. Hawkes and Tucker (1968) observed a strong serological relationship amongst the members of the family Solanaceae like Solanum, Nicotiana, Datura, etc.

4. On the basis of serological investigations, Johnson and Firebrothers (1965) suggested that the genera Magnolia and Michelia show closest affinity within Magnoliaceae.

5. Simon (1971) showed a close relationship between Nympheaceae and Nelumboniaceae on the serological ground.

6. Hydrastis of Berberidaceae has more serological similarities with Rannunculaceae than Berberidaceae.

        7. Firebrothers and his co-workers (1975) supported the separation of Illicium from Magnoliaceae to Illiciaceae and of Schizandra from Magnoliaceae to Schizandraceae on the basis of serological investigations.

************