658 S. ARONOFF 
dually disappears. Its incorporation into protein formed during photosynthesis is 
real, though minor. In contrast arginine may be the major amino acid of seed protein. 
Nevertheless, to the extent to which seedlings are unable to photosynthesize until 
the maturation of chloroplasts, the type of analysis described above may have 
meaning. 
Rough qualitative variation of the reciprocal relation (the variations in free 
TABLE I 
FREE AMINO ACIDS AND PROTEIN AMINO ACIDS OF GERMINATING ETIOLATED SEEDLINGS 
or Lupinus 
The proteins represent approx. 71% of the seed N. From VENEKAmpP». 

Free amino acids Protein amino acids 






LT) = —--- ——— ss = ve 
IER epee 7 4 21 0 7 4 ar 
Leu oO oO I I 30 27 23 5 
I-leu oO I I I 12 II 14 5 
Phe oO 2 4 6 15 13 12 5 
Val oO 2 3 4 16 13 13 7 
Met oO oO oO oO 2 I I I 
Tyr oO 2 3 I 8 4 4 oO 
Pro —- — — = 6 9 9 2 
Glu I 3 4 I 93 29 40 7 
Ala I 2 — — 28 10 9 5 
Thr oO I 2 2 12 8 7 6 
Asp I 2 3 5 64 58 45 6 
Ser I 4 5 6 24 15 II 8 
Gly oO I 3 4 55 25 20 13 
Asp-NH, oO 98 169 351 — — — 
Glu-NH, oO 2 3 5 = as = 
Arg 3 37 65 102 85 64 26 29 
Lys I 5 9 ie) 51 28 10 5 
His I 9 14 17 28 19 15 3 
Cys I 2 9 8 18 12 — 3 
? = = == -= 19 5 4 I 


amino acids in pea seeds during their development) has been given by ROBERTSON et 
al.®. The virtual disappearance of numerous amino acids coincides (Fig. 1) with the 
onset of rapid protein synthesis, so that what may be construed as a general lowering 
of the amino acid steady-state level is, in fact, a virtual extinction of some, followed 
by the eventual increase of others, as protein synthesis is concluded. 
Leaf dynamics 
Despite the most sensitive and precise chromatographic procedures, these methods 
alone provide only net changes, and it was only the use of isotopic tracers which 
allowed for considerations of metabolic rates. Thus it was shown in soybean?® that 
in brief (15 sec) photosynthesis in @CO,, the “C content of the free amino acids 
exceeded that of the sugars, though the latter predominate within 5 min time. The 
major amino acids thus produced were alanine, serine and glycine, in decreasing 
References p. 666 
