336 BIOCHEMICAL SYSTEMATICS 



Chemical changes in the course of growth and development 

 are the rule. Griffiths (1958) illustrates the distribution of flavonoids 

 and other phenols of different mature organs of Theobroma cacao 

 (Table 16-1). During leaf development and maturation there is first 

 anthocyanin and flavonol with traces of phenolic acids; then the 

 flavonoids diminish and increased amounts of the phenolic acids 

 appear. In the mint {Mentha piperita) menthol content of leaves in- 

 creases with maturity while menthol content drops. Light, however, 

 may be a factor in keeping the menthol content higher. Thus an 

 interplay between intrinsic and extrinsic factors is present which 

 further complicates the situation. The present writers, who have 

 examined the fluorescent components of various species of Prosopis 

 (mesquite) at different seasons, found that a large number of phenolic 

 compounds accumulate in the leaves during the growing season— the 

 chief increase apparently involving phenolic acids. 



Methods of presenting comparative 

 biochemical data for systematic purposes. 



At the present time, many biochemical systematic studies in- 

 volve primarily paper chromatographic screening methods. In the 

 writers' Baptisia work, paper chromatography is now used to detect 

 species-specific compounds for diagnostic purposes as well as for 

 hybridization studies. Certain of the components originally detected 

 by chromatography were selected for intensive study and analysis by 

 more rigorous procedures because of their special biological or chemical 

 properties. It is possible to obtain a great deal of useful systematic 

 information from paper chromatographic investigations alone, even 

 without a knowledge of the chemical nature of the spots obtained. In 

 Baptisia, for example, an absolute minimum of fifty species-restricted 

 compounds has been detected among only four species. These com- 

 pounds, even without being identified, represent an important pool of 

 variation for systematic comparisons. Of course, it is important that 

 their presence or absence in a given species be validated. In Baptisia 

 many hundreds of individual plants have now been examined. Alston 

 and Turner (1959) referred to such data as representing a "biochemical 

 profile." Although the original concept was rather naive, the principle 

 is valid, and with sufficient information the idea is quite practical. 



In the early stages of a chromiatographic investigation, there 

 may be Httle knowledge of the identity of specific substances. There 

 is no doubt but that the identification of the chromatographic spots 

 would add immeasurably to the elegance and inherent vahdity of the 



