349 



L. R. Blinks 



Figure 3« pH changes 

 with the "fiW or 

 membrane te chnique , 

 using Porphyra 

 Nereocystis , a red alga, 

 in direct contact with 

 electrode as in Fig. 1. 

 The pH, nearly station- 

 ary in the dark, rises 

 rapidly when the tissue ""*"'' '^ 



is illuminated at the 



chlorophyll a peak (678 m)i); there is also a rapid fall in the 

 dark (d) with a slight overshoot (probably due to increased 

 respiration) . Green light, at the absorption peak of phyco- 

 erythrin (566 mji) caused a slower rise (with initial induction), 

 and was followed by a slower fall in the dark. The 2 wave lengths 

 were next alternated, giving chromatic transients with magnitude 

 some 15'^ of the photo synthetic steady rate . 



Rapid alternation of the two wave lengths did not cause any 

 appreciable rise of the steady state rate; this is not in agree 

 ment with the "flicker effect" in oxygen evolution ^^K 



At atmospheric CO2 content, evidence of an initial acid gush 

 was seldom found on these records. But this is to be expected, 

 since Emerson ^^-^ showed the CO2 gush to be more prominent at 

 higher CO2 tensions. 



The Second Emerson Effect (enhancement) is well shown by the 

 glass electrode. Fig. h indicates the extent of this in P. 

 Nereocystis . The rate (E=1.5) with two lights is at least '^O'fo 

 higher than that predicted from simple addition of the two mono- 

 chromatic rates. The transients following added red light (with 

 tissue now exposed to green light only), become very conspicuous, 

 the pH dropping almost to the dark base line before recovery sets 

 in. 



Lesser transients and enhancement of the CO2 exchange were found 

 between chlorophyll a (at 678 mp.) and phycocyanin (at 615 mp.), 

 probably because of a greater overlap in absorption by the latter 

 compared to phyco-erythrin. Red algae also showed CO2 transients 

 and enhancement between phyco-erythrin and the blue absorption 

 region of chlorophyll a. No evidence of carotenoid participat- 

 ion in either photosynthesis or transients was found, however. 



