Table 1.

Content of free amino acids (mg/100 mg DW) in Dendrobium officinale roots in control and salinity stress treatment.

Free amino acid	Control Mean ± SE	Salinity stress Mean ± SE	Regulation
O-Phospho-L-serine	0.0202 ± 0.0014	0.0207 ± 0.0018
Taurine	0.0022 ± 0.0009	0.0110 ± 0.0010**	Up
O-Phosphoethanolamine	0.2150 ± 0.0176	0.2323 ± 0.0468
L-Aspartic acid	0.0600 ± 0.0006	0.0453 ± 0.0030*	Down
L-Threonine	0.0216 ± 0.0004	0.0187 ± 0.0017
L-Serine	0.0406 ± 0.0002	0.0740 ± 0.0045**	Up
L-Asparagine	3.8720 ± 0.0968	1.5855 ± 0.0665**	Down
L-Glutamic acid	0.0467 ± 0.0009	0.0610 ± 0.0050*	Up
D,L-α-Aminoadipic acid	0.0012 ± 0.0003	0.0012 ± 0.0002
Glycine	0.0148 ± 0.0002	0.0127 ± 0.0013
L-Alanine	0.0348 ± 0.0010	0.0430 ± 0.0040*	Up
L-Citrulline	0.0050 ± 0.0004	0.0103 ± 0.0060
L-α-Amino-n-butanoic acid	0.0017 ± 0.0003	0.0020 ± 0.0006
L-Cystine	0.0276 ± 0.0029	0.0615 ± 0.0029**	Up
L-Methionine	0.0027 ± 0.0006	0.0227 ± 0.0017**	Up
L-Isoleucine	0.0135 ± 0.0006	0.0148 ± 0.0015
L-Leucine	0.0226 ± 0.0055	0.0200 ± 0.0029
L-Tyrosine	0.0208 ± 0.0019	0.0252 ± 0.0037
L-Phenylalanine	0.0175 ± 0.0009	0.0130 ± 0.0023
β-Alanine	0.0010 ± 0.0000	0.0014 ± 0.0002
D,L-β-Aminoisobutyric acid	0.0056 ± 0.0034	0.0008 ± 0.0002
γ-Amino-n-butyric acid	0.0238 ± 0.0060	0.0468 ± 0.0093
L-Histidine	0.0350 ± 0.0011	0.0323 ± 0.0024
3-Methyl-L-histidine	0.0004 ± 0.0002	0.0005 ± 0.0003
1-Methyl-L-histidine	ND	0.0004 ± 0.00024*	Up
L-Carnosine	0.0034 ± 0.0002	0.0017 ± 0.0005*	Down
L-Tryptophan	0.0022 ± 0.0007	0.0012 ± 0.0002
Ornithine	0.0040 ± 0.0003	0.0062 ± 0.0005*	Up
L-Lysine	0.0805 ± 0.0016	0.0262 ± 0.0033**	Down
L-Arginine	0.9513 ± 0.0527	0.3297 ± 0.0182**	Down
L-Proline	0.0225 ± 0.0003	0.0240 ± 0.0003*	Up
Total	5.5923 ± 0.1356	2.7270 ± 0.2180**	Down

Mean values with an asterisk* in the same row are significantly different: * P < 0.05, ** P < 0.01, according to the Dunnet test. ND, not detected.