CAROTENOIDS 



the United States, *'• * «' ^ !• «* 3- e 4 Russia/*^." Finland/' England, «« 

 South Africa, •» Canada, '« Australia, '^ Germany, '«•' ^ Japan,'*-'* 

 Norway, ' • and India. ^ ^ The point of maximal carotene concentra- 

 tion occurs relatively soon after germination, for example, 5 weeks 

 after drilling in oat plants ' ' and 8 days after the plants appear above 

 ground in French beans. ' ^ The failure to detect an early maximum 

 may account for the general decrease in carotene concentration during 

 the period of active growth reported in one investigation in India'* 

 and one in Palestine. ^ ^ 



A later investigation in India, ^ ^ however, showed that this maximum 

 did appear in all but one of a number of vegetable species examined ; 

 the exception was lettuce, and no explanation of this anomalous 

 behaviour has yet been offered. 



It is well established that a period of drought reduces somewhat the 

 carotene concentration of plants, « '. « s \y^^ ^j^g claim that plants which 

 have wilted slightly, with consequent loss of carotene, ^ ^ subsequently 

 recover their carotene content with the recovery of turgidity when 

 placed in water ^ ^ still requires confirmation. A period of drought often 

 coincides with the maturation of plants but there appears no doubt 

 that the fall in carotene concentration at maturation is a specific result 

 of this condition and is not due to a possible concomitant period of 

 drought. This variation in carotene concentration during maturation 

 is exhibited even on the same plant. In turnip tops s e, s 2 ^nd tobacco 

 leaves,®''^* for example, the lowest (oldest) leaves have a carotene 

 concentration somewhat lower than that of the highest leaves and even 

 more striking differences were noted in leaves of different ages taken 

 from maize plants. * ' Typical values which have been obtained for the 

 youngest and oldest leaves were 800 and 547 (Jtg./g- (dry wt.) respec- 

 tively. Similar results were obtained by Nagel ' ^ for the leaves of the 

 tobacco plant ; he also found that even in single leaves the youngest 

 parts (tips) contained a higher concentration than did the rest of the 

 leaves. Betula verrucosa behaves in the same way. ^ ' * 



The higher concentrations of carotene in the upper stem regions 

 compared with the lower regions are, in all probability, also due to 

 the age factor. * ' 



It seems possible that legume leaves do not show this drop so 

 markedly ' " and Snyder and Moore ^ ^ claim that the carotene content 

 of soya bean leaves grown in America not only increases right up to 

 maturity but also continues to do so until three weeks after the first 

 flowers appear. In Australia, however, although legumes maintain 

 their maximum concentration longer, their concentration at full 

 maturation is as low as that of any other crop. ' ^ On the other hand 



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