DYNAMICS OF AMINO ACIDS IN PLANTS 659 
order of total and specific activity. Furthermore, the equivalent 15-sec activities of 
the a- and f-carbons of serine and of alanine, as well as the two of glycine, showed 
that considerable photosynthetic cycling had occurred even in that brief period. 
These rapid transformations were often lost in the changes of pool size with time. 
Thus, there was very little aspartic acid in the initial photosynthesis of soybean 
DAYS FROM BLOSSOM 
ACID 14 18 20 23 26 29 32 35 4 
ea. lee le einen es gle ier Ce 
oC ANG ee 
B-ALANINE 
Y-AMINOBUTYRIC — oo =i ee 
° 

ASPARAGINE es 2 
ASPARTIC 

CYSTEIC 
GLUTAMINE 
GLUTAMIC 
GLYCINE 
HOMOSERINE 
LEUCINE 
LYSINE 
METH. SULPHONE 
METH. SULPHOXIDE oS 
PHENYLALANINE 

PIPECOLINIC Se _ 
PROLINE SS SS 
SERINE 
THREONINE 
VALINE 
+ x “> + + * + 
ARGININE 2 + 5 i Pa i > + ¥ 
¥ + 
+ > + + + 
HISTIDINE + *: + a + + + aS 
i + x > fe + 
- + + + 
TRIGONELLINE + ¢ + t + A Y + “ 
+ + 3 + + + + 
+ 
TYROSINE e: + + + + oe + + + 
> + + + + + + 
UREA + + + + + + + + + + 
Fig. 1. Changes in amino acids of pea seeds with time after blossoming. The width of the line 
represents the amount of amino acid as estimated from the size of the chromatographic spot. 
From McKee, NESTEL AND ROBERTSON’. 
leaves, and, on the contrary, there was considerable in tobacco, but the similarity 
of the distribution of radioactivity in the leaves of the two plants following photo- 
synthesis was remarkable (Table IT). 
Furthermore, the change, with time, of the specific activities, showed that the size 
of the pools bore no simple relation to the rate of formation of the amino acids 
(Table III). 
Indeed, a variety of models must be considered in interpreting such data. For 
example, pools may be either fixed or variable in size. If fixed, there may be only 
a single pool, or they may be multiple. If variable, the variability may be functions 
either of concentration, or time, or both; and without knowledge of the specific 
functions, discrete models cannot be constructed. The kinetics of fixed pools, while 
relatively straightforward in themselves, may be complicated by dilutions, 7.e. 
synthetic pathways other than the one under consideration. In any event practical 
References p. 666 
