C. S. I'RENCH 



459 



synthesis than the sum of their individual rates. Furthermore, Fig. 

 10 shows that the two wavelengths do not have to be given together 

 but may be presented alternately to produce enhancement. The 

 photochemical products involved have a hall-lile of several seconds. 

 This figure also illustrates the chromatic transient effect of Blinks 

 (6, 7, 8, 9) , Avhich was nearly discovered by Li (46) . Later, Emer- 

 son (14) found that in Chlorelln the effectiveness spectrum of the 

 added shorter wavelengths clearly implicated chlorophyll b. Further 

 data of Emerson, reported by Rabinowitch (52) , led to the conclu- 

 sion that in red and blue-green algae the phycobilins, and in diatoms 

 fucoxanthin were the pigments responsible for this effect. The signi- 

 ficance of these findings is discussed by Emerson and Chalmers (15). 

 Myers and French (48) obtained identical action spectra, attributed 

 to chlorophyll b, for the Emerson enhancement and for the Blinks 

 chromatic transient effect in Chlorella (Fig. 11). Blinks (8, 9) and 

 Fork, as reported by Haxo (3) , have found that the action spectra 

 for chromatic transients and for enhancement in a number of algae 

 are due to the participation of the accessory pigments. 



Both in the enhancement and in the chromatic transient experi- 

 ments a short Avavelength pigment and a long wavelength pigment 



lAHernatel 



Dark I 70O I 



Steady rote of 

 photosynthesis in eittier 

 Deom alone 



I Alternate 



I 



l'2| 



sec 



1-2 



sec 



|o.6| 

 sec 



700 I 



(650 back- . 

 ground) 



-Base line of dark respiration 

 —I I I I L 



30 

 Ti me , mm 



Fig. 10. Rate of O,, e\oliition by Chlorella pyrenoidnsa for light of Cr^O or 700 

 mil adjusted in intensity to give equal steady-state rates. I lie chioniatic transient 

 effect of Blinks is shown between B and C, E and F, F and G, I and J, and J 

 and K. The Emerson enhancement when both wavelengths are given together is 

 siiown at L by the height of the record above the dot-dashed line. Enhancement 

 by short period alternation of the beams, as contrasted with simultaneous pres- 

 entation, is shown at D and H (From 48). 



