THE PRODUCTS OF PHOTOSYNTHESIS 187 



from the point of view that carbohydrates are the first discernible prod- 

 ucts of photosynthesis and that they give rise to the tremendous num- 

 ber of compounds found in nature, the importance of carbohydrates 

 in the chemistry of hving things becomes apparent. Thus many of our 

 most prized economic substances as fats, oils, rubber, alkaloids, glucosides, 

 etc., are the result of carbohydrate transformations through the metabolic 

 activity of the plant. The mode of formation of these substances is 

 essentially a chemical problem. As yet only a feeble beginning has been 

 made in unravelling the tangle of chemical reactions involved in the forma- 

 tion of the multiplicity of compounds i)roduced by plants. 



a. Dioses and Trioses. 



Glycollic aldehyde, CHoOH . CH : O, the simplest true carbohydrate, 

 has not been found in plants.^" It is formed as an intermediate product 

 in the condensation of formaldehyde to carbohydrates by means of alkalies 

 and as Pribram and Franke ^^ shovi^ed it is also produced by the action 

 of ultra-violet light on formaldehyde solutions. Glycollic aldehyde is a 

 possible intermediate product in the synthesis of hexoses in the plant. ^^ 

 This is based upon the fact that glycollic aldehyde is easily condensed 

 to tetroses and hexoses ; the reaction proceeds much more readily than the 

 condensation of formaldehyde.^^ 



Glycollic aldehyde is also condensed to glycogen in the liver of the 

 animal organism.^* 



Glyceric aldehyde, CH.^OH . CHOH . CH : O. This sugar has also 

 not been found in plants, though we can find no record that it has been 

 searched for. It is very easily condensed to a mixture of optically in- 

 active hexose sugars. Fischer ^^ long ago suggested that, in view of the 

 difficulty of gaining reliable evidence of the existence of formaldehyde 

 in plants, it may prove more fruitful to look for glycerose. a mixture of 

 glyceric aldehyde and dioxyacetone. It has been assumed that the trioses 

 are intermediate products in the formation of hexoses from glycerine by 

 the plant. 



A triose of the constitution CH^COH) . CH(OH) . O . CH,( OH) 

 has been isolated by Buston and Schryver ^^ from cabbage leaves. The 



"Euler, Ber. chem. Ges., 39, 50 (1906). 



"Pribram and Franke. Monatsh. Chem., 33, 415 (1912). 



"Fincke, Biochcm. Zeit., 61, 157 (1914). Lippmann, Ber. chem. Ges.. 24. 3306 

 (1891). Reinke, ibid.. 14, 2148 (1881). 



"Fischer and Landsteiner, Ber. chem. Ges., 25, 2549 (1892). Nef, Aim. Chem., 

 357. 291 (1907); 376, 40 (1910). Fenton. Jour. Chem. Soc. 65, 899 (1894): 67. 

 48, 774 (1895); 69. 546 (1896); 71, 375 (1897); 73, 71 (1898); 81, 426 (1902); 

 87, 817 (1905). 



" Barrenschecn, Biochem. Zeit.. 58, 300 (1914). 



"Fischer, Ber. chem. Ges.. 23, 2138 (1890). Witzemann, Jour. Avier. Chem. 

 Soc., 36, 1766, 1908 (1914). 



"Buston and Schryver, Biochem. Jour., 17, 470 (1923). 



