COMPARATIVE STUDIES ON RESPIRATION. 

 XVII. Decreased Respiration and Recovery. 



By O. L. INMAN. 

 {From the Laboratory of Plant Physiology, Harvard University, Cambridge^ 



(Received for publication, March 17, 1921.) 



In a previous paper the writer^ has shown that exposure to hypo- 

 tonic or hypertonic solutions may greatly lower the production of 

 carbon dioxide by Laminaria agardhii. The object of the present 

 investigation was to determine whether the respiration would become 

 normal when the plant was replaced in sea water. The work was 

 done at Woods Hole, where material could be obtained under the most 

 favorable conditions. 



The normal rate of respiration was determined (in the manner 

 previously described) and the tissue was exposed to the hypertonic 

 or hypotonic solution for a definite time ; it was then removed and its 

 respiration was measured. ^ The piece of tissue was then replaced in 

 ruiming sea water. At varying intervals it was removed and the 

 rate of respiration was determined. As in the previous investigation^ 

 these determinations were made in van't Hoff's solution in order to 

 avoid the buffer effect of the sea water. 



Fig. 1 shows that in strongly hypertonic sea water respiration 

 steadily decreases and that the degree of recovery depends on the 

 length of the exposure. After an exposure of five minutes recovery 

 is practically complete : as the period of exposure is lengthened recov- 

 ery is less and less complete and when the exposure amounts to 20 

 minutes there is no recovery whatever. 



It is evident that the upper curves dip sHghtly after the tissues are 

 returned to normal sea water. This is not seen in the experiments 

 with hypotonic solutions and isotonic sodium chloride and may 



^ Inman, O. L., /. Gen. Physiol., 1921, iii, 533. 



^ The measurement of respiration was always made with the tissues in the dark. 



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