350 



L. R. Blinks 



7.-: 



Figure h. Photosynthetic 

 erihancement in Porphyra 

 Nereocystis . Exposures to 

 red light (678 m|i) and 

 green ( 566 mp.) were ad- 

 justed to give essentially 

 equal responses. Doubling 

 the intensity of each light 

 doubled the response. 

 Adding red to green light 

 (566 + 678) however, pro- 

 duced some 50^ greater 

 rise of pH, with an enhance- 

 ment factor (E) of about 1.5« 

 Note the very profound undershoot, almost reaching the respi- 

 ration base line, when red was turned off. There is conversely 

 a rather slow fall of pH on darkening after green light. 



7.- 



In green algae, good chromatic transients and enhancements 

 between chlorophylls a and b were obtained by the glass 

 electrode. Brown algae have not yet been tested by this method, 

 most of them having thalli too thick for rapid gas equilibration, 

 hence giving slow responses. 



Perhaps the greatest surprise in the CO2 transients is the 

 direction of the cusps due to chlorophyll and the accessory 

 pigments. Oxygen evolution is initially much higher when the 

 accessory pigments are absorbing (though followed by a pronounced 

 depression); however, CO2 fixation starts more slowly during 

 accessory pigment absorption and then rises. Conversely, absorp- 

 tion by chlorophyll causes a slower rise of oxygen evolution, 

 whereas CO2 consumption starts off quickly and falls away with 

 time . 



These differences are no doubt to be related to the different 

 rates of TPKH and ATP formation by the chlorophyll and accessory 

 pigments; but also to the ribulose and other pool sizes in the 

 carbon fixation cycle. Until these biochemical factors (and 

 their rates) are related to individual pigment participation, 

 external measurements of such raw ms.terials or products as carbon 

 dioxide and oxygen can only suggest, but certainly not answer, 

 the kinetic problems which must be involved. 



