1096 BIOLOGICAL EFFECTS OF RADIATION 



After 10 min., the relative intensities of the bands were: I, II a, II 6, 



o 



III; band II a occurs between X6300 and 6220 A and band II 6 between 



o 



X6180 and 6020 A. After 24 hr. band II a had disappeared completely. 

 Monteverde gives a good review of the literature concerning protochloro- 

 phyll and the effect of radiation in chlorophyll formation. The fluores- 

 cence spectrum of protochlorophyll was investigated by Dhere (11). 



In 1912 Monteverde and Lubimenko (45) reported in Russian on 

 the formation of chlorophyll and their conclusions are perhaps not so 

 well known. They confirmed the observations of Monteverde to the 

 effect that when etiolated plants are exposed to diffuse light for increasing 

 intervals of time the amount of chlorophyll present increases while the 

 amount of protochlorophyll decreases. By use of a microspectroscope 

 the formation of chlorophyll by illumination of live, etiolated plants was 

 studied. In the first moment of illumination two bands were observed: 

 band I, X7000 to 6800 A; band II, X6500 to 6300 A, or 6500 to 6250 A, 

 depending on the concentration of the preparation. Band I after a 



o 



short time changed to X6800 to 6600 A. At the same time band II soon 



o 



disappeared, and after 5 to 10 sec, a band X5650 to 5500 A appeared. 



o 



This was called band IV. Band III, X5950 to 5800 A, also appeared at 

 about the same time. Thus, the first complete spectrum observed upon 

 illumination was: band J, X6800 to 6600 A; band II, X6300 to 6200 A; 

 band III, X5950 to 5800 A; band IV, X5600 to 5400 A, the order^of intensity 

 being I, IV, III, II. A little later a band X5100 to 4800 A appeared. 

 These observations were repeated with the use of dried, etiolated wheat 

 plants and it was found that the same changes took place in the absorption 

 as was found in that of the live plants, with one exception. In the dried, 



o 



etiolated plants the band X6300 to 6200 A did not definitely disappear 

 but remained visible no matter how long the illumination. The investi- 

 gators believed that this band belonged to that part of the original 

 pigment which was transformed into protochlorophyll prior to illumina- 

 tion, during the period of drying. After repeating these observations 

 many times with live and dried wheat and luffa, they offer the following 

 explanations for their observations : " In view of the facts described above, 

 we have come to the conclusion that etiolated plants that cannot green 

 in the darkness, form, in the absence of light, a special pigment having an 

 absorption spectrum very much like chlorophyll. This pigment, under 

 the influence of light, changes so that the result is the formation of 

 chlorophyll or perhaps a pigment close to it. In such a way, from the 

 point of view of the formation of chlorophyll, there is not much difference 

 between those plants that can green and those that cannot green in 

 darkness. Both types of plants form in darkness out of the colorless 

 chromogen a certain pigment which we shall call 'chlorophyllogen.' 

 The further change in this very unstable pigment is a transformation 



