4 STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



for the contradictory observations and reports which have been 

 made by different investigators on various phases of the phenomenon 

 of photosynthesis. Furthermore, wherever consideration must be 

 given to the respiratory activity of plants, it is essential that all 

 possible information be obtained regarding the internal conditions, 

 as, for instance, available carbohydrate supply. Such data can be 

 obtained only by rather laborious analytical methods. 



If such an interdependence between photosynthesis and respiration 

 actually exists, a better understanding of the nature of respiratory 

 activity is an absolute prerequisite to further investigation of this 

 relationship. 



WMle any consideration of the relation of photosynthesis to 

 respiration must take into account the carbohydrate economy of 

 the plant, it is evident that respiratory activity itself can not be 

 interpreted solely on the basis of carbohydrate balance and supply. 

 In fact, it has been known for some time that there is no direct 

 relation between the amount of available carbohydrates and the 

 rate at which the organism uses this material in its respiratory 

 activity. Although carbohydrates constitute the major portion of 

 the material used by the plant in its process of respiratory com- 

 bustion, the other agencies and factors which play a role in this 

 process are still but vaguely known. Our knowledge of the chemical 

 possibihties which would find application here is still very incomplete. 



Plant physiologists have generally accepted the dictum that, 

 given an adequate supply of carbohydrates, water, certain inorganic 

 salts, and the proper temperature, the rate of life processes in the 

 higher plants depends upon the active mass of protoplasm. To the 

 activity of protoplasm have been ascribed all those functions and 

 reactions which could not be described in the terms and through 

 existing conceptions of physics and chemistry. The attempts of 

 MacDougal, Loeb, and others to describe the physical behavior of 

 protoplasm on the basis of colloidal phenomena have done much 

 to break away from this tendency and to determine to what extent 

 protoplasmic activity is amenable to physical simulation. Simi- 

 larly, attempts have been made by Palladin to correlate certain 

 components of the protoplasm with the respiratory activity of the 

 plants. 



The carbohydrate-nitrogen relation has of late found appHcation 

 in the investigations of Kraus and Kraybill,i who have formulated 



'Kraus, E. S., and H. R. Kraybill. Vegetation and reproduction with special reference to 



the tomato. Oregon Agr. Exp. Sta. Bull. 149 (1918). 

 Kraus, E. S. The modification of vegetative and reproductive functions under some varying 



conditions of metabolism. Amer. Jour, of Bot., 7, 400-416 (1920). 

 Harvey, E. M., and A. E. Murneck. The relations of carbohydrates and nitrogen to the 



behavior of apple spurs. Oregon Agr. Exp. Sta. Bull. 176 (1921). 

 Hooker, H. D., Jr. Seasonal changes in the chemical composition of apple spurs. Misaouri 



Agr. Exp. Sta. Research Bull. 40 (1920). 



