EFFECTS OF HYDROSTATIC PRESSURE ON INDUCTION 

 TRANSIENTS OF OXYGEN EVOLUTION 



William Vidaver 



SUMMARY 



A transient oxygen evolution spike was seen at about the first 

 second of illumination in the induction period of some species of 

 brown and green algae. The transient normally occurred in 

 Ankistrodesmus . but required abnormally high or low temperatures 

 in Ulva and Ilea . It never appeared in Porphyra . Hydrostatic 

 pressure high enough to generally reduce subsequent oxygen evolu- 

 tion rates scarcely lowered the very rapid transient rates. 



Lack of pressure sensitivity suggests that the transient is due 

 to a non-enzymatic system which produces oxygen in the light. It 

 appears that unless the products of this system are consumed as 

 they are produced, steady rate oxygen production does not occur. 



INTRODUCTION 



Polarographic detection shows a complex time course of oxygen 

 evolution for many algae as a response to illumination. With a 

 possible exception, the induction responses of algae are generally 

 similar. Usually only the relative magnitude of time course re- 

 sponse components differs between various kinds of algae. 



Figure 1 represents a recording of the induction time course of 

 oxygen evolution upon exposure of the marine alga Porphyra perfor - 

 ata to white light of approximately one-half saturation intensity. 

 The relatively rapid rise to a peak (designated the a spike) was 

 followed by a downslope (b) and a slow rise (c) and eventually 

 culminated in a more or less steady rate under continued illumin- 

 ation. Some algae display a distinct pre-a transient during the 

 spike rise^lj ^z. 



The parameter of varied hydrostatic pressure has been useful 

 in elucidating kinetic data pertaining to rates of some biological 

 and biochemical reactions''^* ^> ^^. In photosynthetic plants, 

 oxygen evolution can also be observed umder changing physical con- 

 ditions, including variation of hydrostatic pressure. Hydrostatic 

 pressure applied to photosynthesizing algae alters the induction 



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