PHOTOSYNTHESIS OF CARBON COMPOUNDS 



449 



constant rates during the course of the experiment. Moreover, the rates of photo- 

 synthesis in experiments which will be reported here were between 30 and 80 % of 

 the maximum rates at which these algae are capable of photosynthesizing at room 

 temperature. 



EXPERIMENTAL 



Plant material 



The plants used in all experiments were the unicellular green algae, Chlorella 

 pyrenoidosa, raised in continuous automatic culture tubes as described previously*. 

 The algae were raised and harvested as a 0.5 °o (volume wet packed cells/volume) 

 suspension. The algae were centrifuged from the culture medium and then suspended 

 in a special nutrient solution (described later). This suspension (80 ml) was placed 

 in the illumination chamber of the steady state apparatus. 



Fig. 2. Steady state apparatus. (1) algae chamber. (2) water or nutrient solution reservoii, (3) acid 

 or base reservoir, (4) pH electrodes, (5) solenoid operated pH control valve, (6) solenoid operated 

 sampling valve, (7) small lamp, (8) photovoltaic cell, (9) large gas reservoir, (10) four-way stopcock. 



Steady state apparatus 



In the steady state apparatus, shown schematically in Fig. 2, a stream of gas 

 (i to 2 % CO 2 in air) is cycled through a closed system. The gas is bubbled through 

 the 0.5 % or 1.0% suspension of algae (80 ml) at a rate of approximately 1 1/min. 

 Gas and liquid mix rapidly in the algae chamber, which is 3/8" thick and 4" in 

 diameter (inside dimensions). The algae chamber is illuminated from both sides 

 by G.E. RSP2 photospot incandescent lights through an infrared absorbing glass in 

 a water bath, or in some experiments from one side by an incandescent lamp and 

 from the other side by a bank of eight 8", 6 W fluorescent lamps (blue and cool white). 

 In either case, the voltage to the incandescent lamps is adjusted just to give hght 

 saturation of the oxygen evolution rate. The algae chamber is water jacketed, and 



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