IV. BIOCHEMICAL SYSTEMS 2l7 



tliat the cytochrome system was involved, for the reaction was inhibited 

 1>\' cyanide, by azide, and by carbon monoxide in the dark, the effect of the 

 latter l)oinj>; reversed in light. Oxygen appeared to be necessary as the 

 terminal hydrogen acceptor. There was no evidence to .suggest the necessity 

 foi- the participation of compounds containing high-energy pho.sphate 

 bonds in the formation of the vitamin from L-galactono-7-lactone. Under 

 the same conditions, however, neither L-gulono-7-lactone nor D-glucurono- 

 7-lactone was converted to L-ascorbic acid. The reason for this remains 

 obscure, since L-gulono-7-lactone is converted to L-ascorlnc acid by intact 

 pea .seedlings, although the formation of L-ascorl)ic acid in this case is 

 much less (five to six times) than with L-galactono-7-lactone. 



3. Dependence of Biosynthesis on External Factors 

 a. Salts 



Many workers have studied the effect on ascorbic acid in plants of sup- 

 plying different fertilizers. The evidence obtained from these studies has 

 on the whole been conflicting and difficult to interpret. Plants receiving a 

 full nutrient supply have been reported as containing more ascorbic acid 

 than plants on a lower nutrient plane. ^^ Ascorbic acid in potatoes was found 

 to be increased by mixtures of salts rich in nitrogen or phosphorus but to 

 be decreased by mixtures containing potassium or calcium. Salts such as 

 KCl, Ca3(P04)2, and Ca(N03)2 were found to promote the formation of 

 ascorbic acid in pea seedlings when a properly l)alanced mixture was sup- 

 plied.^'* 



The effect of nitrogenous fertilizers on the synthesis of ascorbic acid has 

 been extensively studied, but the results obtained have again been contra- 

 dictor}'. In some cases the fertilizers lowered,*^ and in others they increased, 

 the formation of ascorbic acid in plant tissues.'® The ascorbic acid content 

 of plants fertilized with ammonium nitrate varied with the amount of the 

 fertilizer supplied. With suboptimum supplies, the ascorbic acid content 

 of adult leaves decreased, but with supraoptimum amounts the reverse oc- 

 curred. The decrease in ascorbic acid was believed to be connected with 

 osmotic changes.'^ Several workers have found that the supply of rich 



" A. Giroud, R. Ratsimamanga, C. P. Leblond, H. Chalopin, and M. Rahinowicz, 



Bull. soc. chim. biol. 18, 573 (1936). 

 " S. Von Hausen, Ann. Acad. Set. Fennicae, Ser. A46, 134 (1935). 

 '^ K. Wacholder and K. Nehring, Bodenknnde u. Pflanzenerndhr. 16, 245 (1940); 



T. Mott,Angew. Chem. 50, 75, 1937; C. R. Fellers, R. E. Young, P. Isham, and J. 



Claque, Proc. Am. Soc. Hort. Sci. 31, 145 (1934). 

 3« I. Hoffman, W. Krauss, and R. Washburn, Ohio Agr. Expt. Sta. Bull. 592, 66 



(1938); R. Balks and E. Pommer, Bodenknnde u. Pflanzenernahr . 9, 724 (1938); 



C. Pfaff and G. Pfutzer, Angew. Chem. 50, 179 (1937). 

 " B. Aberg and I. Ekdahl, Physiol. Plantarum 1, 290 (1948). 



