EVIDENCE FOR PIGMENTS ABSORBING AT 705 710 ni/x 

 IN PHOTOSYNTHETIC ORGANISMS 



Mary Belle Allen 



Kaiser Foundation Research Institute 



Laboratory of Comparative Biology 



Richmond, California 



The recent results of Kok (5, 6) indicating changes in absorption 

 in the 705-710 m^ region during photosynthesis of the blue-green alga 

 Anacystis niduUuis have given impetus to a search for pigments ab- 

 sorbing in this region of the spectrum. The first suggestion that light 

 of wavelengths greater than 700 ni/x. might be effective for oxygen- 

 producing photosynthetic organisms came from the work of Dangeard 

 (2), who in 1927 found that a motile Oscillntoria accumulated in 

 the 710-730 m^ region of a projected spectrum, and that a strain of 

 Phormidiiim would grow in light of these wave lengths. Dangeard's 

 experiments have been criticized on the ground of an insufficient 

 spectral purity of his light, and, possibly for this reason, these experi- 

 ments seem never to have been pursued further. 



The next suggestion of pigments with absorption at longer wave- 

 lengths than that of chlorophyll came from Duysens (3, 4) , who ob- 

 tained fluorescence spectra for the red algae PorpJiyra lacineata and 

 PorpJiyridium criientum and the blue-green alga Oscillatoria. These 

 spectra suggested the presence of an unknown pigment with a fluores- 

 cence maximum at 725 mfx. Duysens first attributed this fluorescence 

 to chlorophyll d. Since this chlorophyll is not known to occur in the 

 Bangiaceae, and is certainly absent from Porphyridium and Oscil- 

 latoria, the fluorescence observed must be either an artifact of measure- 

 ment or due to a previously unknown pigment. 



In a survey of the in-vivo spectra of chlorophyll in a number of 

 algae, carried out in collaboration with Dr. C. S. French, the chry- 

 somonad Orliromonas danica was observed at times to contain a pig- 

 ment absorbing around 710 m/x, as shown in Fig. 1. Brown and 

 French (pers. commun.) have obtained similar spectra from Euglena 

 gracilis. The 710 rtXfx pigment in O. danica is somewhat evanescent; 

 studies on the conditions for its appearance are in progress. 



479 



