1116 BIOLOGICAL EFFECTS OF RADIATION 



group of plants he found a normal cathodal migration without any further 

 treatment of the tissue, while in a third group there was no migration. 

 While the work of Blinks does not prove, or even indicate, that there is a 

 migration of pigment from cell to cell it demonstrates that pigments, 

 under certain conditions, can be moved comparatively rapidly within 

 the cells. 



A continued, intensive study of the development of pigment in such 

 isolated plant organs, held under constant environmental conditions, 

 offers considerable promise of a very rapid advancement of our knowledge 

 on the formation of pigment in plants, as well as the effect of external 

 factors on such formation. This has been pointed out before by Mirande 

 (21) in a discussion of his work with the scales from lily bulbs, but so 

 far it has failed to stimulate any great amount of work in the field. The 

 problem in such cases is reduced to its simplest form, that is, production 

 of a pigment in an isolated plant organ induced by light and other 

 external factors, where the process is not accompanied by the photo- 

 synthesis of other carbohydrate materials. 



ABSORPTION AND TRANSMISSION OF ANTHOCYANIN PIGMENTS 



There is general agreement among various investigators that the blue- 

 violet and often the ultra-violet regions of sunlight are especially effective 

 in anthocyanin production. It is also interesting to recall that many 

 of the anthocyanins have absorption bands in these general regions. 

 Schou (30) studied the absorption bands of several purified antho- 

 cyanidins, the colored constituents of the anthocyanin molecules. Many 

 of these had absorption bands in the ultra-violet near X2700 A. The 

 maximum-absorption regions for one of these, pelargonidin, was found 

 to be at the following wave-lengths: 2670, 3310, 4000, 4540, and 5040 A. 

 Most of the other anthocyanidins studied were found to have primary 

 bands near wave-lengths 5000 to 5200 A. Schou observed that the 

 position of the OH groups caused shifts in the positions of the bands. 

 Murakami, Robertson, and Robinson (23) found the region of absorption 

 of both natural and synthetic chrysanthemum chlorides to be between 

 wave-lengths 4800 and 5700 A. Arthur (1) observed that both the red 

 peel and extracted red pigment of apples had an absorption band in 

 this same general region. The green peel was found to have a transmis- 

 sion five to seven times as great as the red peel in both the ultra-violet 

 and visible regions. The formation of the pigment in the epidermis 

 acts, therefore, as a protective covering as regards the penetration of 

 light into deeper layers of cells. 



CONCLUSION 



It should be stated that the exact mechanism of anthocyanin forma- 

 tion in living cells brought about by light, low temperature, and other 

 factors, yet remains unknown. Even the effect of these factors on the 



