N.C. 



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PREFACE. 



The experiments on photosynthesis which were begun at the 

 Desert Laboratorj'- in Tucson, Arizona, about eight years ago 

 yielded, among other things, the conclusion that prerequisite to an 

 understanding of the nature of the energy transfer in photosynthesis 

 was a more extensive knowledge of the metabolism of chlorophyllous 

 organs. It became clear that, before attempting to follow the 

 course of the synthesis of carbohydrate material in illuminated 

 leaves, it was essential to know more about the conditions governing 

 the equilibria and mutual transformations of the various groups of 

 carbohydrates, quite independent of the photosynthetic process. 



In publication No. 287 some of the more essential of these con- 

 ditions were described. A further prerequisite to an understanding 

 of the carbohydrate economy of chlorophyllous leaves is more 

 precise information regarding the nature of the carbohydrate catabo- 

 lism and the conditions governing this phenomenon. In the present 

 publication are described the results of experiments on the relation 

 of the amino-acid and carbohydrate content to the respiration of 

 leaves. The information gained from these studies, as well as from 

 those of a number of other workers in this field, helps to emphasize 

 the fact that photosynthesis is an exceedingly complex process. 

 The present status of the problem is, however, exceedingly encourag- 

 ing in that refinement of methods of observation and experimentation 

 and the utilization of the results and conceptions of allied physical 

 sciences are contributing greatly to a better understanding of the 

 phenomenon of photosynthesis. 



This publication comprises the results of investigations carried 

 out during 1919-1922. It is a pleasure to acknowledge here the 

 assistance rendered in the preliminary part of this work by Dr. 

 Frances Long. 



H. A. Spoehr. 

 Coastal Laboratory, 



Carmel, California, June, 1922. 



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