722 



LIGHT ABSORPTION BY PIGMENTS IN VIVO 



CHAP. 22 



participation of the carotenoids in total absorption Is indicated between 450 

 and 520 m/x in methanol, and up to 550 m/x in carbon disulfide. 



A considerably more precise analysis was made by Emerson and Lewis 

 (1941, 1942, 1943). They measured the transmission of a Chlorella sus- 



400 



700 



500 600 



WAVE LENGTH, m/i 



Fig. 22.42. Absorption by all pigments {a + b -\- c + x) from 100 cm.* 

 of leaves of Phaseolus vulgaris in methanol, compared with absorption by 

 an extract of the chlorophylls a + 6 in methanol, and by extracts of the caro- 

 tenoids c + X in methanol (1) and carbon disulfide (2) (Seybold 1936). 



1.2 



1.0 

 p 0.8 

 b 0.6 



o 

 o 



_) 



0.4 



0.2 



400 440 480 520 560 600 640 680 

 WAVE LENGTH, m^ 



Fig. 22.43. Absorption spectra of 

 ethanol solutions of pigments extracted 

 quantitatively from Chlorella cells 

 (after Emerson and Lewis 1943). At 

 wave lengths over 520 m^, the spec- 

 trum of chlorophyll fraction coincides 

 with that of the total extract. 



o 

 o 



LJ 



I- 



o 



< 

 O 



m 



80 



c 60 



Q. 



tr 

 o 



IT) 

 CD 

 < 



O 



40 



20 



X 400 440 480 520 560 600 640 680 720 

 X WAVE LENGTH, m/i 



Fig. 22.44. Comparison of absorption 

 spectra of extracted pigments (shifted as 

 described in text) and of intact Chlorella 

 cells (after Emerson and Le\vis 1943). 

 Curve for intact cells shows absorption 

 due to cell suspension 1.4 cm. thick, con- 

 taining 0.96 mm.^ cells/ml. 



pension and the spectra of the total pigment extract and of the individual 

 pigments. The results are represented in figures 22.43 and 22.44. The 

 first one refers to conditions in the extract, and shows that, in ethanol, the 

 absorption by the Chlorella carotenoids becomes marked below 520 m^t 



