402 



RADIATION BIOLOGY 



extracts of etiolated leaves by Monteverde (1893-1894). The values 

 reported by Monteverde for moderate concentrations of the pigment in 



alcohol are 



E.A.— 680; 640—620; 589^570; 535— E. A. m/i. 



A number of other workers have determined the positions of the absorp- 

 tion bands of protochlorophyll in crude extracts of the pigment from 

 natural sources (Liro, 1908; Monteverde and Lubimenko, 1911; Lubi- 

 menko, 1928; Noack and Kiessling, 1929; Scharfnagel, 1931). 



"Synthetic protochlorophyll" exhibits the following absorption bands 

 (Fischer and Oestreicher, 1939-1940) in ether-pyridine solution: 



628.3—617.1—599.5; 579.6—565.1—548.8; 463.0— E. A. m/z. 



Protochlorophyll isolated by chromatographic methods and dissolved 

 in various solvents possesses absorption maxima at the wave lengths 

 shown in Table 7-1. The measurements were made by means of Beck- 

 man spectrophotometers. The close agreement in the positions of the 



Table 7-1. Absorption Maxima of Protochlorophyll 



absorption maxima of ether solutions of protochlorophyll from etiolated 

 leaves and from seed coats makes it reasonable to conclude that the pig- 

 ments from the two sources are identical (cf. Fig. 7-5). 



The positions of the absorption maxima of protochlorophyll in living 

 tissues are difficult to observe directly, because only a small quantity of 

 pigment is present in etiolated leaves and because the conversion to 

 chlorophyll is usually very rapid when the tissues are brought into the 

 light. In spite of these difficulties, attempts to measure the band posi- 

 tions have been made. The results show little consistency. The posi- 

 tions of the absorption bands of protochlorophyll, as reported by Liro 

 (1908) for etiolated leaves treated in different ways, are as follows: 



Etiolated leaves of Sinapis and Helianthus killed with alcohol vapor, 



E.A.— 690; 640—625; 589—580; 545—540 m^; 

 Etiolated leaves of 12 species of plants killed by freezing, 



E.A.— 690; 640—625; 588—580 m/x; 

 Living etiolated leaves not too young, 



E.A.— 670; 640—620; 589—580; 545—540 m/z. 



