24 



THE METABOLISM OF ALGAE 



The role of carotenoids has been estabUshed most con- 

 vincingly in the case of diatoms.'''^' ^^^' ^^^ In an investiga- 

 tion with Navicula minima, for example, the quantum yield 

 of photosynthesis has been measured at different wave- 

 lengths (Fig. 4) and compared with the corresponding 



400 440 



480 520 560 600 640 

 ^AVE LENGTH IN MjU 



680 720 



FIG. 4. Quantum yield of photosynthesis by Navicula miniina as a 

 function of wavelength (after ref. 280). 



estimates of the distribution of light among chlorophylls, 

 fucoxanthin and other carotenoids (Fig. 5). The corrections 

 for band shifts necessary for the estimation of the absorp- 

 tion of the different pigments in vivo were determined using 

 cells extracted wath dilute methanol which removed chloro- 

 phyll c and fucoxanthin without extracting the other pig- 

 ments. The quantum yield of photosynthesis was found to 

 be nearly constant from 520 to 680 m//, dropping rapidly 

 at wavelengths greater than 680 m/< and showing a slight 

 dip in the blue between 430 and 520 m^. Comparisons 



