ACTION SPECTRUM OF BROWN ALGAE 



1173 



synthesis. They found, similarly to Dutton, ISIanning and Duggar 

 (Chapter 24, p. 814), that chlorophyll fluorescence in li\'ing diatoms can he 

 excited also by light absorbed by fucoxanthol; from this they concluded 

 that the energy absorbed by fucoxanthol is transferred to chlorophyll be- 

 fore it is used for photosynthesis. 



440 520 600 



WAVE LENGTH, m^ 



680 



Fig. 30.9B. Absorption spectra of 

 methanol solutions of pigments ex- 

 tracted quant ittitively from cells of 

 \'avic>da minima (after Taiiada, 

 1951). 



o 

 o 



1.0 

 0.9 

 0.8 

 0.7 



0.6 

 OS'* 



0.4 L-, 



0.3 



0.2 



440 520 600 



WAVE LENGTH, m^i 



680 



Fig. 30.9C. Comparison of absori)- 

 tioii spectra of extractefl pigments, and 

 of intact cells of A', minima suspended 

 in glycerol. The whole .spectrum of 

 each pigment shifted to\v;iid the red 

 by an amount equal to that l)y which 

 the blue maximum shifted by extrac- 

 tion. 



A reinvestigation of the quantum yield of brown algae in light of differ- 

 ent color was undertaken by Tanada (1951) in Emerson's laboratory. 

 The conclusions of Dutton and Manning were confirmed by much more 

 precise measurements, taking into account the presence of chlorophyll c. 



Tanada worked with the diatom Navicula minima in pure culture. 

 He measured the quantum yield in narrow spectral bands, from 400 to 

 700 m/i. Fig. 30.9A shows the results: 7 is constant between 520 and 680 

 mju; as in Chlorella, it drops sharply to almost zero above 710 m/i. The 



