STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 75 



8. The Action of Animo-Acids on Sugars. 



In searching for a possible chemical explanation of the stimulating 

 effect of amino-acids on the respiration of leaves, the action of amino 

 acids on sugars deserves some consideration. In this regard the 

 work of Maillard^ has received considerable notice as offering the 

 key to the amino-acid-carbohydrate and protein relation in living 

 organisms. By the action of amino-acids on glj^cerine, Maillard 

 obtained substances to which he ascribed the properties of poly- 

 peptides. Subsequ:ently he studied the action of amino-acids 

 on a variety of sugars and obtained the well-known reactions which 

 lead to the formation of humin compounds. It is very questionable 

 whether these reactions can find application to living organisms 

 such as leaves. Maillard used very concentrated solutions, e. g., 

 4 grams of glucose in 3 to 4 c. c. of water and 1 gram of glycocoll. 

 Moreover, the reaction proceeds only very slowly at ordinary tem- 

 perature, so that his conditions can not be considered as having 

 direct biological significance. 



A solution of d-glucose, 5.6853 grams, in 100 c. c. water in a 2-dm. 

 tube, gave a rotation a= -H5.50 at 10°. To 50 c. c. of this solution 

 0.2401 gram of glycocoll was added; the rotation of this solution was 

 a= +5.47°. After 24 hours both solutions gave the same rotation. 

 The d-glucose solution containing the glycocoll was heated for 4 

 hours at 90° with a reflux condenser. After making up carefully to 

 volume, the rotation was practically unchanged, a =+5.52°. 



The experiment was repeated with d-levulose. To a solution 

 of 8.9675 grams d-levulose in 100 c. c. water was added 0.5002 gram 

 glycocoll. This gave a rotation in a 2-dm. tube of a =—16.50°. 

 After heating on a boiling water-bath for 5 hours the solution was 

 very slightly yellow and gave a corresponding rotation of a = — 16.40°. 



It is therefore very doubtful whether the amino-acids in this 

 dilution have any influence toward the mutual transformation of the 

 hexoses such as is exerted by the weak alkalies. Nor does there 

 seem to be, under the conditions of dilution and temperature em- 

 ployed in these experiments, any other profound action on the sugars. 



The foregoing experiment with solutions of glycocoll and d-levulose 

 were repeated, using instead of water the nitrogen-free mineral 

 nutrient solution employed in the respiration. Also under these 

 conditions the rotation remained unchanged in the solution kept at 

 ordinary temperature as well as in one heated on the boiling water- 

 bath for 2 hours. Similarly, only negative results were obtained in 

 experiments with solutions of d-glucose and glycocoll to which was 

 added the juice obtained by thoroughly grinding Helianthus leaves 

 with quartz sand. 



1 Maillard, L. C. Ann. de Chimie. (9 s^rie.), 5, 258-317 (1918); 2, 210-268 (1914). Ivanoff, 

 N. N. Biochem. Zeitschr., 120. 1-80 (1921). 



