52 CARNEGIE INSTITUTION OF WASHINGTON. 



constant conditions of temperature, carbon-dioxid pressure, and light-inten- 

 sity. It is now quite evident that these variations are attributable to the in- 

 fluence of the internal factor, and the work will be continued to determine the 

 photosynthetic efficiency with this factor taken into consideration. 



Carbohydrate Metabolism of Leaves, by H. A. Spoehr. 



Carbohydrates are the first products of photosynthesis. From experience 

 as well as on the basis of theoretical considerations, the sugars containing 6 

 carbon atoms are of foremost importance as the primary products of photo- 

 synthesis. This is also the form into which most sugars are converted before 

 they are utilized by most of the higher plants and the higher animals. It is, 

 however, a remarkable fact that of the 32 theoretically possible hexose sugars 

 only 4 are generally found distributed in nature. All of these sugars are 

 stereoisomers and differ only in the internal structure of the molecule. It is 

 apparent that there are in the photosynthetic process asymmetric forces at 

 work which regularly produce these highly asymmetric molecules. That 

 these forces are equally important to the life of an organism as the chemical 

 affinities was already recognized by Pasteur. 



In view of the recently developed conceptions of the structure of atoms 

 these forces take on a new significance. The influences producing an asym- 

 metric molecule are apparently of the nature of magnetism, with the same 

 attractive and repellent forces. Since the development of the theories of 

 magnetism on the basis of rotating electrons by de Haas and Einstein the 

 problem of the asymmetric forces is thrown into the domain of electrical 

 charge and is to be ascribed probably to the nature of the carbon atom itself. 

 In the chemistry of symmetrical substances the product of a reaction is solely 

 dependent upon the chemical forces of the reacting molecules. But in the 

 reactions of asymmetric substances the products are also dependent upon the 

 influence exerted on each other by the reacting asymmetric molecules. These 

 asymmetric forces can act either to accelerate or retard the chemical reaction. 

 Chemical work on asymmetric syntheses, which was begun several years ago, 

 is being continued from the point of view of the electron theory of valence. 



This work is being pursued primarily in order to apply the principles of 

 asymmetric synthesis to the photosynthesis problem. It now appears that, 

 (1) either all of the possible hexose sugars are formed in the photosynthetic 

 process and are then converted into the three sugars commonly found in plants, 

 or (2) there are forces which permit the formation of only those sugars exist- 

 ing in the plant. Experimental evidence is being sought in both directions. 



1. The situation of the first possibility is as follows: It has not been pos- 

 sible to detect even very small amounts of hexose sugars other than those 

 ordinarily found. As yet nothing is known of the behavior of these other 

 sugars (e. g., the levo sugars) in the higher plants. These substances can be 

 obtained only through very laborious synthetic chemical manipulation. The 

 work of synthesizing these sugars has been under way for some time and some 

 of the products have already been obtained. A study of the behavior of these 

 substances will then be undertaken with living organisms in order to deter- 

 mine the fate of these sugars as to a possible transformation into other sugars 

 and in the general metabolism. Furthermore, there have been prepared 

 synthetically very pure products of formose (from formaldehyde) and glycerose 



