Transient Changes in Cellular Gas Exchange 



ROBERT EMERSON and RUTH V. CHALMERS, Botany Department, 

 University of Illinois, JJrhana, Illinois 



We ha\'e completed a detailed study of the two-vessel manoinetric 

 technique, giving special attention to the conditions under which 

 this technique was applied by Warburg and co-workers to the meas- 

 urement of efficiency of photosynthesis with dense (totally absorbing) 

 suspensions of algae. Our results and conclusions are published: 

 "Transient Changes in Cellular Gas Exchange and the Problem of 

 Maximum Efficiency of Photosynthesis," Plant Physiology, 30, 505- 

 529(1955). 



We have found that vessel pairs of the shapes used by Warburg and 

 co-workers show CAddence of differences in diffusion lag which would 

 lead to significant errors in the application of the two-vessel method to 

 the measurement of rapidly changing rates of gas exchange. We have 

 been able to match vessel pairs of different design, for equality of 

 diffusion lag for one gas (oxygen) , but we emphasize that equality of 

 diffusion lag for one gas precludes equality with respect to a second 

 gas of different solubility. This is an unavoidable limitation on the 

 application of the two- vessel method to the study of changing rates. 

 However, by matching vessel pairs for diffusion lag with respect to 

 oxygen, it becomes possible to predict the magnitude of error to be 

 anticipated from the inequality in lag with respect to carbon dioxide, 

 and vessel volumes can be chosen to limit this error. 



By such application of the method, we have studied transient 

 changes in gas exchange of two species of Chlorella, and one of Scenedes- 

 mus, under conditions widely used for measurement of maximum 

 quantum efficiency of photosynthesis. With different algae, we found 

 great differences in the pattern of transient gas exchange. Measure- 

 ments with Chlorella pyrenoidosa confirmed the findings of Emerson 

 and Lewis and of Brown and Whittingham with regard to carbon 

 dioxide "l)urst." There was sometimes evidence of an oxygen "burst" 

 in the light, and in general there was evidence of a maximum in 

 respiratory oxygen consumption during the first minutes of darkness. 



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