SPECTRA OF PHOTOSYNTHETIC PIGMENTS 



3G9 



600 



700 



700 



600 

 WAVE UENGTH, ny/ 



Fig. 6-10. (a) Effectiveness spectra for the excitation of fluorescence of chlorophyll a, 

 phycoerythrin, a^d phycocyanin in Porphyridium cruentiim Naeg. These curves 

 were adjusted to the same height at wave length 546 m^i. (6) Fluorescence spectra of 

 Porphyridium cruentum illuminated by different wave lengths. The curves are 

 adjusted to show their relative size for equal numbers of incident quanta. These and 

 other curves of the same family, when analyzed as in part d, gave the data from which 

 the points of part a were plotted, (c) The fluorescence spectra of a very pale green 

 corn leaf and a darker green leaf of Dendromecon rigida excited by a wave length of 

 436 m/i. The corn leaf shows the true fluorescence spectrum of chlorophyll a in vivo, 

 and the other shows the distortion due to reabsorption of the fluorescence, indicated 

 by a lowering of the main peak accompanied by a shift of its position toward the red 

 end. The height of the 730-myu peak, which is relatively less influenced by reabsorp- 

 tion, is greater, the higher the chlorophyll concentration, {d) The fluorescence 

 spectrum of Porphyridium excited by a wave length of 530 m/i resolved into the spectra 

 of the three separate fluorescing pigments. The three lower curves, which add to give 

 the curve for the intact algae, represent the fluorescence spectra of phycoerythrin, 

 phycocyanin, and chlorophyll a in these live algae. {French and Young, 1952.) 



mation relevant to this problem must therefore be obtained from solu- 

 tions of individual components. The data in this regard are rather 

 nebulous. Prins (193-1) reported a lower yield for chlorophyll fluores- 

 cence in the blue region of the spectrum than in the red. Watson and 

 Livingston (personal communication, 1950) find that the yield of chloro- 



