Table II.

¹⁵N labeling of soluble amino acids in pea root nodules after 8 h of incubation in ¹⁵N₂ in the perfusion system

Amino Acid	Total Amino Acid Concentration		15N Enrichment				Position of Mono-15N Label				Total 15N Concentrationa
	Meanb	se		Mean	se	n		Mean	se	n		Mean
	μmol g−1 fresh wt		atom% excess				%				μmol g−1 fresh wt
Asn	16.91	1.65	Mono-15N	8.17	0.27	11	Amino	73	6	6	Amino	1.33
							Amide	27	6	6	Amide	0.70
			Double 15N	1.91	0.12	12
GABA	5.72	0.67		33.39		2						1.91
Gln	1.55	0.20	Mono-15N	15.74	2.08	5	Amino	98	2	3	Amino	0.34
							Amide	2	2	3	Amide	0.11
			Double 15N	6.59	1.10	4
Ala	1.24	0.12		25.02	0.80	7						0.31
Asp	0.76	0.05		14.22	1.27	10						0.11
Glu	0.35	0.04		27.86	0.98	5						0.10

^aThe values given for amino and amide group total ¹⁵N concentration include both mono- and double-labeled molecules. 

^bn = 3.