SOLUBLE, NITROGENOUS CONSTITUENTS OF PLANTS AI 
LEUCINE 
?” 
& ~ ALANINE 

GLUTAWIC ° 
= 
5 
‘igi z 
ASPARTIC 5 
a 
o 
U-1038 = 
< 
&. > 
oOo 
4— PHENOL 
Fig. 17. The occurrence, in an extract of the fruits of Hemerocallis sp., of y-hydroxyglutamic acid 
and the compound U-103 which also occurs in Phlox (cf. Fig. 16). 
by Nor AnD FowpeEn?!, and cases of new S-amino acids are examples. Also, other com- 
pounds which contain both the cyclopropane ring, the first example of which was dis- 
closed by BurrRouGHS’, have come to light (see the communication to this Symposium 
by FowpeEy) andstill other compounds with the hitherto rare terminal methylene group. 
One should recognize, however, that what has been said above for the compounds 
detectable by ninhydrin can be extended to other classes of compounds. Ehrlich’s 
reagent (dimethylaminobenzaldehyde) makes possible the detection of an array of 
ureides and of indole compounds, and both of these classes of compounds are more 
copiously represented in plants than at first was thought. Some nitrogen bases, 
detectable by ninhydrin (putrescine, tyramine, tryptamine, ethanolamine), occur 
as evident decarboxylation products, often under conditions of anomalous nutrition, 
but the simple nitrogen bases and betaines may well prove to be more widely occurring 
than is commonly supposed. Nitro compounds, of which f-nitropropionic acid in 
Indigofera (COOKE®) was an early example, may also be reduced and detected on 
paper as amino compounds. 
The significance of the array of nitrogen compounds in plants 
If ever the idea that the soluble nitrogen pool merely comprised the pre-fabricated 
compounds needed for condensation into protein was plausible, it cannot be so now. 
Many compounds not known to be used directly in protein synthesis exist, and they 
often occur in large amount. Their presence suggests that many normal metabolic 
routes have passed unsuspected. One compound or another may accumulate in a 
local situation by virtue of a metabolic block brought about by genetic, nutritional, 
or environmental means, or often it may be due to circumstances inherent in normal 
References p. 42 
