1098 BIOLOGICAL EFFECTS OF RADIATION 



catalytic reaction 

 o. Leucophyll (Sachs) » chlorophyllogen 



catalytic reaction (enzyme) 



6. Chlorophyllogen * chlorophyll 



or photochemical reaction (light) 



decomposition in darkness 

 c. Chlorophyllogen ► protochlorophyll 



In the photochemical reaction (6) blue light is less effective than 

 red light. 



Lubimenko and Hubbenet (39) summarize their conceptions of the 

 greening process in the following steps: (a) Synthesis of leucophyll. 

 (6) Transformation of leucophyll into chlorophyllogen. (c) Transfor- 

 mation of chlorophyllogen into chlorophyll. This transformation is a 

 photochemical reaction. When wheat seedlings were used it was found 

 that the influence of temperature on the synthesis of leucophyll and 

 on the transformation of leucophyll into chlorophyllogen, independently 

 of the exposure to light, began at a temperature of 2° to 4°C., reached 

 a maximum between 26° to 30°C., and ceased near 48°C. 



Eyster (17) concludes that protochlorophyll is not a decomposition 

 product of some other organic substance, such as leucophyll, but is a 

 pigment which develops without the influence of light and changes 

 photochemically into chlorophyll upon exposure to light. He does not 

 support the work of Monteverde and Lubimenko on the presence and 

 importance of "chlorophyllogen." 



Noack and Kiessling (47) believe that chlorophyll formation repre- 

 sents a photooxidation of protochlorophyll, the addition of oxygen 

 bringing about the formation of chlorophyll h. It seems to the reviewers 

 that this field is in need of much further work before the manner in 

 which the plant builds up chlorophyll can be comprehended. 



EFFECT OF RADIATION ON EXTRACTED CHLOROPHYLL 



Gaffron (21) found that chlorophyll, dissolved in acetone and irradi- 

 ated, takes up oxygen and is gradually oxidized. Upon addition of a 

 suitable acceptor (one that does not absorb the radiation) the oxygen 

 ab.sorption is accelerated and the destruction of the chlorophyll is pre- 

 vented. Gaffron used this experiment to check and confirm Einstein's 

 equivalence law and Warburg's (82) conclusions that every quantum 

 absorbed by chlorophyll, independently of its energy, causes the same 

 chemical effect in the living plant. Literature on the oxidation of 

 chlorophyll in acceptor-free solutions is quoted by Gaffron on page 761 

 of the paper mentioned above and in an article dealing with the chemical 

 aspect of the reaction (21a). An explanation for such photooxidation 

 of chlorophyll is given by Pfeilsticker (55), using the theory of photo- 

 oxidation of anthraquinone for that purpose. Substances like gelatin 

 or gums, which increase the stability of colloidal systems, also increase 



