CAROTENOIDS 



It is perhaps relevant to indicate here that in a possibly related 

 problem, the biogenesis of unsaturated fatty acids, |;he available 

 evidence points away from the production of these acids by dehydro- 

 genation of the saturated fatty acids. * ^ 



Nitrogen metabolism and carotenogenesis 



A number of investigators have attempted to relate carotenoid 

 production to nitrogen metabolism in the plant. A positive relation- 

 ship exists between the crude protein of forages and their carotene 

 content.*^'*' A similar relationship was demonstrated between 

 carotene content and plant non-protein nitrogen/*' {see Fig. 15). It 

 is difficult to decide whether the results of these investigations indicate 

 metabolic inter-relations or whether they are merely fortuitous owing 

 to the fact that the concentration of all three factors are directly pro- 

 portional to the growth of the plant. The loss of carotenoids from iso- 

 lated leaves parallels the loss of protein. ^ ^^ 



-C Carocene concentrotiic 



Ju Jy 



Month 



Fig. 15. — Showing the correlation between carotene concentration and non- 

 protein nitrogen concentration in the developing carrot {after Watkins, 

 W. E. {1947) J. Agric. Res., 75, 63). 



Widening the experimental approach, Barrensheen, Pany and 

 Srb'^ followed changes in ammonia-N, amide-N, amino-acid-N and 

 carotene in developing wheat seedlings. Whilst the amide and amino- 

 acid-N remained constant, an increase in ammonia-N paralleled the 



70 



