DEPARTMENT OF BOTANICAL RESEARCH. 49 



proteins and amino-acids, as has been worked out by Rubner, Lusk, and others 

 in the higher animals. The same general effect has now been determined in 

 plants with a number of different amino-acids. 



Various attempts have been made to determine more precisely the nature of 

 this phenomenon. It was thought highly probable that the amino-acids 

 affected the sugars directly, exerting an isomerizing action by converting the 

 more stable sugars into those which are more easily broken down. However, 

 all experiments directed to establish such an isomerizing action of the amino- 

 acids on various hexose sugars yielded negative results. The recent work of 

 Sherman and his coworkers on the influence of amino-acids on certain enzyme 

 activity offers a new means of approach to this fundamental problem. 



Attention has also been given to a consideration of the function of leaf 

 proteins. In the plant cell the carbohydrates and fats serve as the funda- 

 mental sources of energy in respiration. The nitrogen derivatives, with which 

 the plant deals most economically, as proteinaceous compounds constitute an 

 essential portion of the medium in which the chemical reactions of the cell 

 occur. The proteins are of fundamental importance because of their ability 

 to yield amino-acids which influence the functioning of enzymes and catalysts 

 and by virtue of their amphoteric character can control the condition of 

 solution within the cell. The course of change of the nitrogenous components 

 of leaves in relation to variations in carbohydrate-content and consumption 

 were followed by analytical methods through a wide range of natural and 

 experimental conditions. This work is serving as a basis of information con- 

 cerning the respiratory activity of leaves and has already proved its funda- 

 mental value in its application to the photosynthesis problem. 



The two internal factors determining the rate of respiration, namely, the 

 supply of carbohydrates and the free amino-acids, are both influenced by 

 light. The amino-acid content increases in the dark, light apparently revers- 

 ing the reaction, so that proteins are synthesized from amino-acids under the 

 latter conditions; while the carbohydrate-content decreases in the dark, and 

 through photosynthesis increases in the light. A change in either component 

 affects the rate of respiration. Thus, a plant with high carbohydrate-content, 

 after exposure to light, shows for a certain period a decreased rate of respira- 

 tion, and light can be regarded as, under circumstances, inhibiting respiratory 

 activity. In view of the fact that determinations of photosynthesis are based 

 upon differential determinations of carbon dioxid, it is absolutely essential that 

 these conditions relative to the amino-acid and carbohydrate-content, as well 

 as to the respiration, be established before any conclusions be drawn as to 

 the rate of carbon-dioxid fixation.* This has been the principal purpose of the 

 respiration studies. 



Mechanism of Photosynthesis and the Internal Factor, by H. A. Spoehr. 



Evidence has been accumulating rapidly that in the photosynthetic process 

 there is an essential internal factor which operates independently of those 

 clearly recognizable factors, temperature, light intensity, partial pressure of 

 CO2, and water-content of the leaf. This internal factor has been variously 

 described by different workers; its existence has been established through 

 several methods. These include (a) the relation of the chlorophyll pigments 

 to photosynthetic activity (Willstaetter and StoU), (6) effect of anesthetics and 



