THE CHLOROPLAST PIGMENTS 



475 



factors, but must be attributed to increase 

 in some internal factor other than chloro- 

 phyll. Further indications seem to show- 

 that this factor is dependent upon chloro- 

 phyll and some other factor working in 

 correlation with chlorophyll. 



Irving also has concluded that the 

 development of photosynthetic activity in 

 the young leaves of seedlings lagged 

 behind greening, which means that it is 

 dependent upon some factor other than 

 chlorophyll. 



Willstatter and Stoll have come to the 

 opposite conclusions and think that 

 chlorophyll is a limiting factor. 



Briggs believes that there are three 

 lines of evidence indicating that chloro- 

 phyll is not the limiting factor in the 

 young stage of leaf development. He says 

 that in the case of Irving 's experiments 

 the chlorophyll continues to increase to a 

 certain point without any sign of assimila- 

 tion. In the case of Willstatter's young 

 leaves, as in the case of those of Irving, 

 when they once reached the stage of 

 beginning to assimilate, the assimilation 

 increased out of proportion to the increase 

 in chlorophyll and lastly Briggs has found 

 that assimilation increases while there is 

 no increase in chlorophyll. 



ATTEMPTS MADE TO RELATE VIT AMINES TO 

 THE CAROTINOIDS AND TO PHYTOL 



For years attempts have been made to 

 find out a possible relation of the vitamines 

 to the chloroplasts of leaves and especially 

 to the carotinoids . A review will now be 

 made of this possible relation. Before 

 proceeding with the discussion it may be 

 stated that no attempt has yet been made 

 by anyone to associate vitamines with the 

 water soluble pigments, flavones and 

 anthocyanins. Vitamines, especially A, 

 have always been associated with the 



Hpochromes, which association will now 

 be taken up. 



Since vitamine A is closely associated 

 with the Hpochromes in animal fats many 

 workers were led to speculate on the 

 possible identity of vitamine A with one of 

 the Hpochromes. Drummond showed 

 that there was no foundation for this 

 belief by preparing pure carotin from 

 carrots and demonstrating its complete 

 lack of growth promoting power. Others 

 have shown that many animal fats which 

 were rich in carotin were relatively poor 

 in vitamine A and that in other fats the 

 reverse relation held. Steenbock, Sell and 

 Bluell pointed out that the concentrations 

 of Hpochromes and vitamine A in butter 

 were not closely parallel though they were 

 in general agreement and suggested that 

 this might be due to their having the same 

 source in the green food of the cow. In 

 six different varieties of dried peas a 

 greater vitamine content ran parallel with 

 a greater lipochrome content. White 

 sweet potatoes and white carrots, in 

 marked contrast to the yellow varieties, 

 contained little vitamine A. 



Coward says that Hpochromes are 

 present in many seedlings before the 

 appearance of vitamines. A comparison 

 of the lipochrome in shoots which will not 

 promote growth with that in shoots which 

 will promote it proves that the activity of 

 the tissue is not measured by its lipo- 

 chrome content. Other instances of asso- 

 ciation of vitamine A with lipochrome in 

 plant tissues are afforded by tomato pulp, 

 cucumber skin, yellow sepals and petals, 

 orange juice and red and yellow capsicum 

 fruit. The absence of vitamin A is asso- 

 ciated with absence of Hpochromes in 

 mangolds, swedes, cauliflower, corollas of 

 Shasta daisy and of purple aster. Lipo- 

 chrome (generally carotin) is always 

 associated with vitamine A in plant 





