32 THE ROLE OF ALGAE AND PLANKTON IN MEDICINE 



The photosynthetic role of the various pigments can be estimated by 

 comparing the absorption spectrum with the "action spectrum" or photo- 

 synthetic capacity of light at various wave lengths. 40 ' 41 Photosynthetic 

 efficiency is usually measured in terms of oxygen production. The chloro- 

 phyll absorption bands are chiefly in the blue, blue-green, red, and infra- 

 red ranges. The yellow-orange color of the carotenoids results from 

 absorption in the blue and green. The chlorophylls and phycobilins are 

 often strongly fluorescent in solution. Tucker 203 has even used pigment 

 extraction with acetone as a method of quantitating phytoplankton. 



Despite all the emphasis on photosynthetic capacities, it must be noted 

 that not all algae contain pigment. Beijerinck 180 long ago noted the 

 natural occurrence of yellow and colorless colonies of Chlorella variegata 

 on culture media. Bogorad and Granick 200 produced colorless, pale yellow, 

 and light green mutant colonies of Chlorella vulgaris by radiation. 

 Butler 204 exposed Chlorella pyrenoidosa to ultraviolet light and obtained 

 colorless mutants without chlorophyll. He also noted that similar perm- 

 anently colorless forms of Prototheca have been observed in nature, and 

 that they were probably mutants from Chlorophyceae. Very recently 

 Tolbert and Zill 205 reported photosynthetic studies with protoplasm ex- 

 truded from Chara and Nitella. They found activity 12-15 per cent that 

 of the whole cell, as measured by C 14 fixation. Both protoplasm and cut 

 cells reduced carbon dioxide in light to sucrose and hexose phosphate. 

 Dark controls fixed C 14 into products associated with plant respiration, 

 but it is not clear whether they represented true photosynthetic pigments. 

 In fact, the whole sequence of biochemical synthesis in the dark or with- 

 out pigment remains rather obscure. This is particularly so in the light 

 of Duysens' claim 206 that light energy is convertible only through chloro- 

 phyll a or b (he maintains that in diatoms, for example, carotene must be 

 converted to chlorophyll a.) 



Radiation and natural mutation are not the only methods of producing 

 non-pigmented algae. Dubie 207 produced chlorophyll-deficient Chlorella 

 vulgaris with streptomycin. And even strong radiation does not always 

 effect alterations. Blinks 208 reported there was no significant change in 

 composition or function of marine algae one year after the atomic explo- 

 sions in the Bikini area. The only exception was an increase in catalase, 

 possibly due to an increased hydrogen peroxide concentration secondary 

 to radiation. 



Algal cells generally do not grow old and die; instead, they produce 

 more cells by binary fission. However, not all algae grow by cellular 



