glyoxylate and another product, which may be alanine. The 

 presence of y-hydroxyglutamic acid in green leaves has been 

 reported by Virtanen and Hietala (40). The dehydration and 

 reduction of y-hydroxyglutamic acid to give glutamic acid 

 would be common types of biochemical reactions, analogous 

 to the formation of succinic acid from malic acid. However, 

 we have at present no experimental evidence for such a path- 

 way. 



Threonine does not become labeled as rapidly as the 

 amino acids so far discussed, and it may well be secondary in 

 origin. That is, it may be an example of conversion of pri- 

 mary amino acids (aspartic acid, alanine, serine, and glutamic 

 acid) to other amino acids of their respective families, a proc- 

 ess that presumably occurs in photosynthesis. 



The small amount of labeled glycine formed during 

 steady-state photosynthesis may come from either serine or 

 glyoxylic acid. 



36 



