CHLOROPHYLL AND CHLOROPHYLL DEVELOPMENT 1099 



the resistance of chlorophyll solutions to oxidation in light. Wurmser 

 (88) has done a great deal of work on this shielding effect of the protective 

 colloid and on the velocity of decolorization of chlorophyll solutions 

 in radiations of different wave-lengths. He also determined the relation- 

 ship between photochemical susceptibility and absorption constant in 

 red, green, and violet light. 



When chlorophyll in solution undergoes photooxidation, the process 

 is accompanied by a gradual fading of the color of the solution and by 

 the decrease of the intensity of the absorption bands. The chemistry 

 of this change is still open to investigation, especially in respect to the 

 formation of intermediate products. For the spectrum change of 

 chlorophyll in the living leaf in light Wlodek (87) offers the explanation 

 that either a change of the relative amounts of the two chlorophylls 

 or the formation of unstable compounds between chlorophyll and carbon 

 dioxide takes place. The bleaching of chlorophyll in solution and 

 the products obtained under such conditions are the subject of a study 

 by Wager (81). Although the formation of aldehydes was observed, 

 the author himself doubts if the process going on in vitro actually takes 

 place in nature. 



Another phase of the influence of radiation on extracted chlorophyll 

 was studied by Roffo (58). He prepared pure chlorophyll from alfalfa, 

 exposed it to ultra-violet light and found that the radiation was gradually 

 emitted again over a period of more than a month. Roffo points out 

 that this photoactivity is similar to that of cholesterol. 



Sensitization of chlorophyll can be brought about by irradiation 

 with ultra-violet light, as Dixon (13) showed. He studied the photo- 

 electric properties the chlorophyll acquires, and based a theory for 

 photosynthesis upon his findings. 



Rudolph (59) used the polarizing spectrophotometer of Konig and 

 Martens in his investigation of the effect of colored light on the formation 

 of chloropla.st pigments. He determined the molar extinction coefficients 

 of chlorophyll a, chlorophyll 6, carotene, and xanthophyll, and the 

 relative extinction coefficient of protochlorophyll at different wave- 

 lengths. The influence of humidity, of leaf surface, of carbon dioxide, 

 and of the age of the leaf on the formation of chlorophyll in light was 

 studied, and interesting genetic relations between the pigments under 

 investigation, especially between the carotinoids and chlorophyll a 

 were found. An extensive bibliography is given. 



BEHAVIOR OF CHLOROPHYLL UNDER THE INFLUENCE OF ULTRA-VIOLET 



RADIATION 



Regarding the influence of radiation of short wave-lengths on chloro- 

 phyll in plants, whether the pigment is in the solid state or in solution, 

 most investigators have found no appreciable decomposition of the 

 pigment. Schulze (65) came to this conclusion, using radiation of 



