]00 BIOCHEMICAL SYSTEMATICS 



Botanical investigations of amino acid patterns, while 

 initially lagging somewhat behind zoological studies, now seem to be 

 providing even more information of direct taxonomic utility, probably 

 because unusual amino acids are more often involved. 



Bell (1962a) has recently examined forty-nine species of the 

 legume genus, Lathyrus, and has presented data which appear to be 

 potentially quite valuable in interpreting species affinities within the 

 genus (compare the work of Pecket on the phenolics of Lathyrus, 

 Chapter 11). A new guanidine amino acid (homoarginine) is present 

 in seeds of thirty-six species; seven unidentified ninhydrin-reacting 

 compounds in concentrations of the order of 1 per cent have been de- 

 tected in the seeds of one or more species. Some of the substances are 

 probably those responsible for the toxic condition known as neuro- 

 lathyrism (Chapter 10), and others may be related to the lathyrus 

 factors. Bell believes that these non-protein amino acids may con- 

 stitute a highly concentrated form of nitrogen storage in leguminous 

 seeds, and many of these amino acids, in fact, contain additional 

 nitrogen. Although free amino acids are not typically found in the 

 seeds of most plants in high concentration, the content of free amino 

 acids in seeds of the Leguminosae is often high. 



The most important immediately significant taxonomic con- 

 clusion from the work of Bell is contained in the following statement 

 by the author: 



Within the genus there existed well defined groups of species that were 

 characterized, not by the presence of an arbitrary concentration of 

 one specific ninhydrin-reacting compound, but rather by the presence 

 of associated groups of such compounds. These groups of associated 

 compounds appeared as characteristic patterns after the seed extracts 

 had been chromatographed or subjected to ionophoresis on paper. In 

 the extracts of most, but not all, of the species examined the spots 

 forming the characteristic patterns were of comparable size and 

 intensity. 



(Table 6-2 illustrates the grouping of Lathyrus species on the basis of 

 the patterns described by Bell.) 



Another recent systematic study of plant amino acids is that 

 of Renter (1957) who studied the principal forms of soluble nitrogen 

 in various parts of sixty-six species representing forty-eight families 

 (Fig. 6-2). Renter did not exaggerate the systematic imphcations of 

 the work. He noted that since the substances considered were fre- 

 quently common metabolites of plants and animals, their relative 

 quantities rather than strict presence or absence were of most signif- 

 icance. In some species the principal amino acids in various parts of 



