FUNCTION OF CAROTINOIDS IN PLANTS, ANIMALS 277 



(6) Carotiuoids help regulate the oxygen pressure in plant cells 

 through their great ailinity for this element (\Villstatter and Mieg). 



(7) Carotinoids lielp control the (JO a assimilation by controlling the 

 equilibrium between chlorophyll a and chlorophyll b (Willstatter and 

 Stoll). 



(8) Carotin and xanthophylls play a part in photo-synthesis because 

 they are believed to yield HCHU on photo-oxidation, xauthophyll also 

 yielding sugar (Ewart). 



There is no evidence to indicate that carotinoids originate from 

 chlorophyll, but it is possible that both classes of pigment may arise 

 from isoprene, C 5 H 8 . 



The factor for lycopin formation in tomatoes can be suppressed at 

 30 C. or above, the fruits forming only carotin and xanthophylls. 

 At lower temperatures all three types of carotinoids are formed. Syn- 

 thesis of lycopin is independent of light but depends upon oxygen, and 

 is depressed by the conditions which accompany low catalase activity 

 and decreased acidity. 



The author believes that if the carotinoid pigments in animals pos- 

 sess a definite function, this function must be linked with the physio- 

 logical processes of the body, inasmuch as the carotinoids are derived 

 from the food. There are a number of general facts, however, which 

 indicate that these pigments play no definite role in nutrition or in 

 metabolic processes, at least in the higher animals. 



A critical review of the theories regarding the possible relation of 

 carotinoids and vitamin A leads to the conclusion that the substances 

 cannot be identical, it appears that there is a fairly definite correla- 

 tion between the occurrence of carotinoids and vitamin A in plant 

 tissues but not in animal tissues or in animal fats: Animals, there- 

 fore, possess the power to separate carotinoids and vitamin A. Ex- 

 periments are suggested whereby this fact can be further substantiated. 



Xanthophylls in fowls have a definite function from the standpoint 

 of practical utility in that there is a correlation between low pigmenta- 

 tion of the visible skin parts of certain breeds of fowls and high egg 

 production. The cause of this phenomenon is a selective mobilization 

 of pigment in the ova during egg production, preventing its excretion 

 by means of the skin. An analogous phenomenon occurs in the sal- 

 mon during their fresh-water migration to the spawning beds. 



It is generally believed by certain cattle breeders that abundant 

 (carotinoid) pigmentation of the skin of Guernsey and Jersey cattle 



