724 



LIGHT ABSORPTION BY PIGMENTS IN VI VU 



CHAP. 22 



that of luteol — i. e., not much beyond 510 niju — the brown color can be 

 attributed to fucoxanthol only by assuming a very wide shift of absorption 

 bands (or their strong broadening toward longer waves). According to 

 page 706, Menke had in fact found indications that the absorption peaks of 

 fucoxanthol in live Laminaria cells are situated as far toward the red as at 

 499 and 545 mji (instead of 457 and 492 m^i in ethanol solution, according 

 to Table 21. IX). Attempts to analyze the absorption by brown algae, 

 described below, luive not taken into account the possibility of such a wide 

 shift — not to speak of any changes in the width of the bands. 



On page 657 we referred to a more recent measurement of the extinc- 

 tion curve of fucoxanthol in hexane by Karrer and Wiirgler, which showed 

 a considerably broadened band, extending to or even beyond 530 van (fig. 

 21.36). 



100 

 80 



5 60 



Q. 



< 



20 



400 500 600 



WAVE LENGTH, m/x 



700 



Fig. 22.45A. Absorption by extracted pig- 

 ments from Fucus vesiculosus (brown alga, 

 extreme sun form) (after Montfort 1940). 



400 500 600 700 



WAVE LENGTH, m/i 



Fig. 22.45B. Absorption of e.\- 

 tracted pigments from Laminaria digi- 

 tata (brown alga, 12 m. depth) (after 

 Montfort 1940). 



Figures 22.45A and B are analyses of the absorption of light by pigment 

 extracts from brown algae, as published by Montfort (1940). They are 

 reproduced here, despite their crudeness, as examples of variations in the 

 relative importance of fucoxanthol as liglit-al)SO)-bing agent in the "helio- 

 philic" surface forms of brown algae, and the "umbrophilic" forms of the 

 same algae that live in considerable depth. In the latter, fucoxanthol ac- 

 counts for most of the extract absorption between 450 and 540 m^u, while 

 in the former its importance is very much smaller. 



Seybold and Montfort discussed their results in terms of the increase 

 in light absorption in the spectral regions 550-500 and 500-450 m/x caused 

 by the presence of the carotenoids. Table 22. VIII shows that, in extracts 

 from green leaves and green algae, the presence of the carotenoids increases 



