COMPARATIVE STUDIES ON RESPIRATION. 



VI. Increased Production of Carbon Dioxide Accompanied 

 BY Decrease of Acidity. 



By MARIAN IRWIN. 



{From the Laboratory of Plant Physiology, Harvard University, Cambridge.) 



(Received for publication, January 9, 1919.) 



In a previous paper^ I have shown that high concentrations of ether 

 greatly increase the production of CO2 by animals and that this is 

 associated with irreversible changes ending in death. It might be 

 thought that this increase could be explained on the ground that the 

 process of death is often accompanied by the production of lactic 

 acid, and this might displace CO2 from carbonates and bicarbonates 

 present in the tissues. The resulting evolution of CO2 might be mis- 

 taken for increased respiration. 



In order to obtain some light on this question it seemed desirable to 

 experiment upon an organism in which death is not accompanied by 

 an increase in acidity. Suitable material for such experiments is 

 furnished by the petals of many flowers containing natural indicators, 

 whose colors show that during the process of death the cell contents 

 become less acid.^ 



Two species of Salvia were used in these experiments, Salvia invo- 

 lucrata and Salvia spkfidens. The natural indicators contained in the 

 petals were calibrated by placing the petals in boiling water and then 

 transferring them to buffer solutions of known pH value. They re- 

 mained in the buffer solutions until complete penetration had taken 

 place (this required only a few minutes). As the color of the indica- 

 tor in various buffer solutions was known, it was a simple matter to de- 

 termine the changes in acidity^ which take place in flowers immersed 



' Irwin, M., J. Gen. Physiol, 1918-19, i, 209. 

 .2 Haas, A. R., /. Biol. Chem., 1916, xxvii, 233. 



^ The petals contain some cells which lack the indicator; their acidity was 

 consequently not determined. 



399 



