692 



LIGHT ABSORPTION BY PIGMENTS IN VIVO 



CHAP. 22 



the last-named observer. Transmission spectra of suspensions of unicellu- 

 lar algae were studied by Noddack and Eichhoff (1939), Katz and Wassink 

 (1939), Emerson and Lewis (1941), Wassink and Kersten (1946), Van 

 Norman, French and Macdowall (1948) and Tanada (1951). Several such 

 curves are reproduced in figures 22.21-22.24. 



Albers and Knorr (1937) measured the absorption spectra of single 

 chloroplasts, in the narrow region 664-709 mix (cf. fig. 22.35). Vermeulen, 

 Wassink and Reman (1937), Katz and Wassink (1939), Wassink, Katz and 



540 



1 — r-T — I — r— 1 — r—r- 



800 900 960 



600 700 



WAVE LENGTH, m/i. 



Fig. 22.24. Transmission spectrum (To/T) of Oscillatoria (l)lue alga) (after Katz and 

 Wassink 1939). Curve 1, cell suspension; curve 2, chlorophyll extract. 



Dorrestein (1939) and French (1937, 1940) observed the transmission spec- 

 tra of purple bacteria (figs. 22.25 to 22.28). 



Egle (1937) and Loomis, Carr and Randall (1941) investigated the trans- 

 mission and reflection of leaves in the infrared. Figures 22.29 and 22.30 

 show that, from 800 to 1300 ni/x, T -\- R accounts for 85 or 90% of the inci- 

 dent light in the (comparatively thin) potato leaf, and for 75 or 85% in the 

 (0.6 mm. thick) leaf of Ficus elastica. This region includes most of the 

 infrared radiation of the sun that reaches sea level. (About 75% of the 

 latter belong to the region 700 to 1500 m^.) Absorption bands at and 

 above 1.5 n, shown in figures 22.29 and 22.30, are due to water and carbon 



