Report on Some Recent Results at Wageningen 



B. KOK, T. N. 0. Solar Energy Research Project, Laboratory for Plant Physio- 

 logical Research, Agricultural University, Wageningen, Netherlands 



I. TRANSITORY RATES 



B. KoK AND C. J. P. Speuit 



In open manometers we could ol)serve high initial pressure changes 

 after illuminating or darkening Chlorella suspensions. The calculated 

 rates, accepting the photosynthelic qvotient y = —1, corresponded 

 to quantum numbers close to one. 



But it appeared that in the transitory phases y deviated largely 

 from minus unity: The newly developed recording volumeter allows 

 a wide variation of the ratio liquid phase to gas phase (V{/Vg). 

 High transitory rates were only observed in this apparatus (c/. Fig. 1) 

 in case a small liquid phase was used (i.e., if both oxygen and carbon 

 dioxide contributed appreciably to the volume changes). If the 

 liquid phase is large {Vf/Vg = 4 to 6), CO. exchange contributes very 

 little to the total volume change, even if acid suspension media are 

 used. In the latter case the transitory effect is hardly noticeable and 

 the volumetric time course is very similar to the one observed if the 

 cells are suspended in buffer mixtures (which also obscure the in- 

 fluence of CO2 on the readings). 



In other experiments standard size vessels were used with the re- 

 cording volumeter, additionally equipped with electrodes for meas- 

 uring polarographic current and pH. This made it possible to make 

 simultaneous records of changes in volume, pH (CO2), and oxygen. 



Under conditions of high O2 and COo concentrations, the response 

 of oxygen exchange to light was instantaneous with the possible ex- 

 ception of a small induction. With sufficiently high CO2 pressures 

 a marked delay in the response of CO2 exchange to a change in in- 

 tensity occurs (e.g., during 30 seconds). In addition outbursts of CO-j 

 upon illumination are very often observed. This anomalous CO2 ex- 

 change can quantitatively explain the high transitory rates, as ob- 

 served with the manometric method. 



Under conditions of low oxygen concentration we observed in sev- 



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