354 



David C. Fork 



in shape and indicate that a temperature effect alone is not re- 

 sponsible for the low photosjmthetic activity of these algae in 

 red and blue light, 



THE EMERSON ENHANCEMENT EFFECT IN RED, BROWN . AND GREEN ALGAE 



Emerson and co-workers ^^' observed that the quantum yield of 

 Chlorella could be improved in longer wavelengths if supplementary 

 light was provided during the measurements. Upon closer examina- 

 tion of the wavelength dependence of this enhancement effect, 

 Emerson'^' showed in Chlorella that supplementary light most ef- 

 fectively absorbed by chlorophyll b brought about the greatest in- 

 crease in yield from a band of far-red light. In Porphvridium the 

 most effective supplementary light was that absorbed by phyco- 

 bilins. 



The Emerson enhancement effect with background illumination of 

 appropriate wavelength can be seen clearly in the action spectra 

 for O2 production of the red alga Porphvra perforata (figure 2), 



J 60 



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 O 



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 u 

 Q> 



a 



20 



400 



S.I40 



c 

 £ 



0) 



o 

 §120 



c 



0) 



100 



500 600 



Wavelength, mjj 



700 



400 500 600 



Wavelength, m/j 



700 



Fig, 2, (left) Action spectra for O2 production in Por - 

 phvra perforata determined at 20,5°C with and without 

 supplementary green (546 mja) background light. 



(right) Enhancement spectra for P, perforata 

 obtained with green (546 mi) backgrovmd and blue (436 mp) 

 background light, Fork^^\ 



The action spectrum determined without background illumination is 

 similar to that reported by Haxo and Blinks for this species ^^', 

 The action spectrum determined in background light of 546 mp 

 (strongly absorbed by phycobilins) no longer shows the "inactive" 

 chlorophyll so typical in action spectra of red algae. Green 

 background light sustains enhanced photosynthesis in both red and 



