ONTOGENETIC ADAPTATION OF THE PIGMENT SYSTEM 425 



algae, particularly of some species of Cyanophyceae, can be changed by 

 illumination with colored light. 



As mentioned above, this phenomenon became the subject of a 

 protracted controversy. Engelmann did not doubt that it was due to 

 "complementary chromatic adaptation." The algae became green in 

 red light, blue in green light, yellow in blue-green light, and blue in 

 yellow light. These changes occurred only in living cells, and were 

 different from (often opposite to) the discoloration effects observed in 

 dead cells and pigment extracts. The color acquired in a certain colored 

 light often was maintained for months in white light. In a later paper, 

 Gaidukov (1906) described the rapid chromatic adaptation of Phormidium 

 tenue (blue) and Porphyra laciniata (red) when placed on the plate holder 

 of a spectrograph and illuminated with the light of a carbon arc. Ten 

 hours were sufficient to produce a complete change in color. 



The conclusions of Gaidukov were confirmed by Boresch (1919, 

 1921), who repeated the experiments because he thought that his own 

 studies, as well as those of Schindler (1913) on color changes induced in 

 algae by nitrogen or iron deficiency, made the interpretation of Gaidu- 

 kov's experiments doubtful. However, working under controlled condi- 

 tions of nutrition, Boresch (1919) confirmed the occurrence of chromatic 

 re-adaptation, although only a few out of a large number of species 

 investigated by him showed this phenomenon. While Gaidukov origi- 

 nally thought that color variations reflect changes in the nature of the 

 pigments, Boresch ascribed them to changes in their relative concentrations, 

 particularly in the ratios of the different forms of phycocyanin. Mothes 

 and Sagromsky (1941) found that the diatom, Chaetoceras, changes from 

 dark brown in green light to yellow in red light, and that this change is 

 caused by a shift in the [chlorophyll] : [carotenoid] ratio; a similar 

 change was observed in Chlorella. 



Extension of the theory of Berthold and Oltmanns from algae living 

 in different depths to algae in differently colored artificial light led 

 some investigators to the belief that, in the latter case, too, intensity of 

 light rather than its spectral composition is responsible for the color 

 changes. This problem was studied, by Nadson (1908), Harder (1917, 

 1922, 1923), and Sargent (1934). Nadson found that Cyanophyceae 

 become yellowish brown in direct sunlight, and regain their blue color 

 in the shadow. Harder (1922) found that, although change is correlated 

 with the color of the light, as suggested by Engelmann and Gaidukov, 

 a certain minimum intensity is required to bring it about. Harder 

 thought that the individual re-adaptation of algae, similarly to their 

 phylogenetic adaptation, is a combination of intensity adaptation and 

 chromatic adaptation; algae may respond with color changes to changes 

 in either color or intensity of light, thus using the same regulating 



