CAKOTENOID BANDS IN PLANTS 705 



{d) Blue-Violet Bands of Chlorophyll 



The position, in live cells, of the second main band of chlorophyll or 

 bacteriochlorophyll — that situated in the blue-violet part of the spectrum — 

 has received much less stud}^ than that of the red band, the main reason 

 being that the presence of carotenoids and other yellow pigments tends to 

 make absorption in this region very heavy and diffuse. Table 22. VI con- 

 tains some values read from figures reproduced earlier in this chapter. 

 This table indicates a "red shift" by 5 or 10 mju. On the frequency scale, 

 this shift (250-500 cm.~0 is about equal to that of the main red band. 



Table 22. VI. lii.rE-VioLKx Absorption Maxima in Living Plants 



Organism ''max.' ™'' 



Fatsia {rf. fig. 22.13) 438 



Chlorella {cf. fig. 22.22) 432 



Chroococcus {rf. fig. 22.23) 436 



Chlorophyll a in ether 427.5 



(c) Protochlorophyll 



French (1951) estimated, from the action spectrum of chlorophyll 

 formation, that the red absorption band of protochlorophyll lies, in vivo, 

 at 650 m/x. Because of its weakness, it has not yet been directly observed. 



3. Absorption Bands of Accessory Pigments in Live Cells 



Lubimenko (1927) could not find, in the spectra of green leaves, ab- 

 sorption maxima identifiable with the absorption bands of the carotenoids 

 (which could easily be observed, at 510-480 m^u, in the spectra of yellow 

 leaves or yellow parts of variegated leaves) . He pointed out that the first 

 carotenoid maximum may be masked by band VI of chlorophyll (cf. Table 

 22. IV) and that the second one, at 470-450 mix, should be visible between 

 the chloroph3'll bands VI and VII. Lubimenko concluded that the yellow 

 pigments do not exist "as such" in the green plastids. This conclusion, ob- 

 tained b}^ a purely ciualitative examination of the spectra, is untenable. 

 The spectra of leaf extracts, in which the chlorophylls and the carotenoids 

 certainly exist as separate entities, also do not alwaj's show the individual 

 maxima of all these pigments. In figure 22.47, for example, the absorption 

 curve of the extract from barley leaves shows only three maxima between 

 400 and 500 m^ — at 410, 428 and 450 niju — instead of the six maxima of 

 the separated green and mellow ])igmeiits. The two main carotenoid 



