DEPARTMENT OF BOTANICAL RESEARCH. 53 



which are mixtures of many of the possible sugars. A careful study of the 

 behavior of these substances in the chlorophyllous leaf is now in progress. 



2. If there are asymmetric forces which direct the course of sugar synthesis 

 in the photosynthetic process, these are either (a) physical forces or con- 

 ditions which can be regarded as part of the environment of the plant, or (6) 

 the influence is within the plant mechanism. As to the first possibility, it has 

 been impossible to attain a permanent asymmetric synthesis through any 

 agency applied from without. The synthesis of formose through the conden- 

 sation of formaldehyde is greatly accelerated, it was found, by light. How- 

 ever, no orienting effect by polarized light on the formaldehyde molecules 

 could be accomplished. This was also found to be the case with the highly 

 polarized sky-light. The second possibihty of an asjonmetric force within the 

 leaf has been followed in several directions. It is well known that an asym- 

 metric molecule extends an asymmetric influence in its chemical reactions. 

 The effect of a number of asymmetric substances on the condensation of for- 

 maldehyde to formose has been extensively investigated. These asymmetric 

 substances include many which are found as normal constituents of leaves. 

 However, thus far no definite asymmetric synthesis has been obtained. These 

 investigations are being continued and have recently been extended to include 

 a study of the mutual transformation of sugars in the plant. 



Influence of Various Sugars on Respiration, by H. A. Spoehr and J. M. McGee. 



As the first step in the investigations of the behavior of various sugars in 

 chlorophyllous leaves, a study was made of the influence of those sugars on 

 respiratory activity. This work was done in conjunction with that on the 

 carbohydrate-amino-acid relation in the respiration of leaves. The same 

 methods and apparatus were used, thus assuring a high degree of accuracy. 

 Moreover, the rates of respiration were determined with the leaves in the dark 

 for 95 hours. It was found that periods of this length were essential in order 

 to arrive at a fair estimate of the respiratory work of the leaves. In all experi- 

 ments the leaves were also analyzed for carbohydrates and amino-acids. 



When dextrose is fed to leaves, the carbohydrate-content is maintained or 

 increases. However, the rate of respiration is not dependent on the amount 

 of available carbohydrates alone. If the amino-acid content of the leaves is 

 low, even a very high carbohydrate-content will not result in high respiratory 

 activity. Conversely, a high respiratory activity may be attained with high 

 amino-acid and low carbohydrate content. When both factors are high, the 

 respiration reaches a maximum. For this reason, in comparing the effect of 

 different sugars, it is essential that the amino-acid content of the leaves be 

 also taken into consideration. It appears, however, that under all conditions 

 dextrose produces the highest rates of respiration. With leaves which are 

 given dextrose the stimulating action of amino-acids is very noticeable. 



When leaves are fed sucrose the effect on the rate of respiration is in general 

 of the same nature but less marked. Thus, also, the influence of amino- 

 acids on leaves given sucrose is not as intense as when dextrose is given. 



The purely chemical experiments of Nef as well as the physiological investi- 

 gations of Lusk on higher animals point to the conclusion that levulose is more 

 easily oxidized than any of the other hexose sugars. Among the lower plants 

 there is a great diversity in the capacity for using this sugar. The experiments 



