Table 1 Effects of N supply on mean (±SE, n = 3) concentrations (μg g^− 1 FW) of FAADs as well as their summation in Citrus sinensis leaves

N-Acetyl-L-tyrosine (NAT)

C₁₁H₁₃NO₄

0.143 ± 0.007b

0.167 ± 0.014ab

0.172 ± 0.001ab

0.177 ± 0.008a

0.175 ± 0.015ab

L-tyrosine methyl ester (H-Tyr-OMe)

C₁₀H₁₄NO₃

0.068 ± 0.007c

0.104 ± 0.008b

0.128 ± 0.009a

0.140 ± 0.006a

0.141 ± 0.002a

Kynurenic acid (KYNA)

C₁₀H₇NO₃

0.527 ± 0.038a

0.224 ± 0.018c

0.283 ± 0.005bc

0.288 ± 0.004b

0.290 ± 0.017b

L-Phenylalanine (Phe)

C₉H₁₁NO₂

1.351 ± 0.089a

0.701 ± 0.048c

0.782 ± 0.014c

0.912 ± 0.054bc

1.128 ± 0.138ab

L-Tyrosine (Tyr)

C₉H₁₁NO₃

10.171 ± 0.342d

15.483 ± 0.393c

16.624 ± 0.637c

18.773 ± 0.101b

20.906 ± 0.809a

L-α-Aspartyl-L-phenylalanine (α-AP)

C₁₃H₁₆N₂O₅

1.429 ± 0.027d

2.383 ± 0.029c

2.719 ± 0.149b

2.789 ± 0.029b

3.073 ± 0.109a

L-Leucine (Leu)

C₆H₁₃NO₂

0.825 ± 0.111c

0.905 ± 0.042bc

1.055 ± 0.041b

1.418 ± 0.048a

1.585 ± 0.085a

L-Isoleucine (Ile)

C₆H₁₃NO₂

4.994 ± 0.140a

2.567 ± 0.140d

2.830 ± 0.076d

3.741 ± 0.051c

4.087 ± 0.042b

L-Pipecolic acid

C₆H₁₁NO₂

10.000 ± 0.424c

10.020 ± 0.066c

34.541 ± 6.155b

28.793 ± 3.203b

48.705 ± 3.427a

N-Acetylaspartate (NAA)

C₆H₉NO₅

2.355 ± 0.141a

2.854 ± 0.662a

2.361 ± 0.619a

3.286 ± 0.263a

2.740 ± 0.081a

α-Aminoadipic acid

C₆H₁₁NO₄

2.700 ± 0.513a

1.804 ± 0.101b

2.061 ± 0.154ab

2.725 ± 0.117a

2.476 ± 0.204ab

4-Acetamidobutyric acid

C₆H₁₁NO₃

0.515 ± 0.010b

0.644 ± 0.028a

0.647 ± 0.013a

0.650 ± 0.003a

0.621 ± 0.002a

6-Aminocaproic acid (ACA)

C₆H₁₃NO₂

ND

1.142 ± 0.015a

1.169 ± 0.018a

1.186 ± 0.021a

1.186 ± 0.018a

L-Tryptophan (Trp)

C₁₁H₁₂N₂O₂

80.878 ± 6.563a

7.412 ± 0.182b

8.142 ± 0.167b

9.741 ± 0.512b

11.346 ± 2.123b

Glycylphenylalanine

C₁₁H₁₄N₂O₃

ND

ND

ND

ND

ND

N′-Formylkynurenine

C₁₁H₁₂N₂O₄

15.418 ± 1.215d

24.929 ± 1.011c

26.456 ± 0.825bc

28.228 ± 0.787b

33.954 ± 0.631a

L-Valine (Val)

C₅H₁₁NO₂

12.968 ± 0.884a

10.232 ± 0.526b

9.962 ± 0.350b

11.927 ± 0.231a

12.776 ± 0.183a

L-Methionine (Met)

C₅H₁₁NO₂S

2.542 ± 0.102c

7.612 ± 0.635b

8.192 ± 0.358b

9.776 ± 0.452a

9.888 ± 0.206a

L-Proline (Pro)

C₅H₉NO₂

645.889 ± 44.914c

2151.429 ± 78.846b

2267.012 ± 83.253ab

2425.094 ± 25.926a

2420.926 ± 50.214a

L-Glutamic acid (Glu)

C₅H₉NO₄

2700.119 ± 91.072b

6639.120 ± 317.405a

6478.371 ± 174.902a

6279.665 ± 161.942a

6820.514 ± 96.150a

5-Hydroxy-tryptamine (5-HTP)

C₁₀H₁₂N₂O

11.198 ± 0.910a

8.362 ± 0.462bc

10.089 ± 1.628ab

5.906 ± 0.266c

6.528 ± 0.381c

Trans-4-hydroxy-L-proline

C₅H₉NO₃

2.865 ± 0.039d

8.615 ± 0.421c

14.151 ± 1.189b

12.566 ± 0.507b

17.954 ± 0.745a

Methionine sulfoxide (MetSO)

C₅H₁₁NO₃S

1.079 ± 0.020d

1.953 ± 0.125c

2.477 ± 0.087b

2.416 ± 0.014b

2.927 ± 0.088a

5-Aminovaleric acid

NH₂(CH₂)₄CO₂H

0.529 ± 0.529b

1.799 ± 0.015a

1.865 ± 0.012a

1.810 ± 0.034a

1.825 ± 0.002a

L-Aspartate (Asp)

C₄H₇NO₄

56.124 ± 1.650c

713.182 ± 56.401b

1043.476 ± 37.160a

1041.208 ± 55.672a

1161.492 ± 8.634a

L-Threonine (Thr)

C₄H₉NO₃

66.646 ± 2.734d

111.219 ± 4.981c

112.264 ± 7.045c

156.143 ± 3.358b

189.988 ± 5.612a

Homoserine

C₄H₉NO₃

2.073 ± 0.202b

4.841 ± 0.705a

5.168 ± 1.067a

5.788 ± 0.381a

4.102 ± 0.352a

N6-Acetyl-L-lysine

C₈H₁₆N₂O₃

0.522 ± 0.025c

0.653 ± 0.018b

0.831 ± 0.042a

0.879 ± 0.008a

0.869 ± 0.032a

(5-L-Glutamyl)-L-amino acid

C₈H₁₄N₂O₅S

ND

16.118 ± 0.631b

18.517 ± 0.816ab

20.437 ± 0.767a

19.994 ± 1.624a

N-Glycyl-L-leucine

C₈H₁₆N₂O₃

0.388 ± 0.052a

0.370 ± 0.006a

0.372 ± 0.009a

0.432 ± 0.012a

0.392 ± 0.024a

γ-Glutamate-cysteine

C₈H₁₄N₂O₅S

51.107 ± 1.171b

74.516 ± 2.935a

69.447 ± 7.705a

66.172 ± 4.770a

67.760 ± 1.597a

2-Aminobutyric acid

C₄H₉NO

0.418 ± 0.036c

0.657 ± 0.030b

0.740 ± 0.029ab

0.813 ± 0.042ab

0.918 ± 0.137a

(S)-β-Aminoisobutyric acid

C₄H₉NO

ND

ND

ND

ND

ND

γ-Aminobutyric acid (GABA)

C₄H₉NO

2695.942 ± 88.538b

4725.078 ± 206.671a

4886.078 ± 250.541a

5135.903 ± 64.712a

5100.838 ± 244.809a

N,N-Dimethylglycine (DMG)

C₄H₉NO₂

ND

ND

ND

ND

ND

L-Cystathionine (LCYH)

C₇H₁₄N₂O₄S

0.608 ± 0.080c

1.235 ± 0.127b

1.637 ± 0.162a

1.662 ± 0.028a

1.684 ± 0.040a

Glycyl-L-proline (GLY-PRO)

C₇H₁₂N₂O₃

0.756 ± 0.014d

1.099 ± 0.030c

1.011 ± 0.027b

1.069 ± 0.025ab

0.980 ± 0.0170a

Nα-Acetyl-L-glutamine (NAG)

C₇H₁₂N₂O₄

0.132 ± 0.007e

0.997 ± 0.100d

1.963 ± 0.311c

2.966 ± 0.192b

4.193 ± 0.153a

Glutathione oxidized (GSSG)

C₂₀H₃₂N₆O₁₂S₂

1854.060 ± 53.315d

7915.502 ± 682.289c

14,138.470 ± 703.316b

15,289.299 ± 1396.802b

18,558.053 ± 1028.213a

L-Alanine (Ala)

C₃H₇NO₂

111.211 ± 4.295c

308.191 ± 13.137b

339.559 ± 8.060ab

366.460 ± 9.366a

368.487 ± 15.608a

L-Serine (Ser)

C₃H₇NO₃

272.336 ± 20.443d

975.161 ± 39.892c

1159.738 ± 30.190b

1163.465 ± 10.628b

1339.013 ± 22.170a

L-Lysine (Lys)

C₆H₁₄N₂O₂

24.672 ± 1.606e

53.614 ± 1.669d

74.418 ± 6.176c

93.404 ± 1.124b

136.712 ± 7.862a

Beta-Alanine (β-Ala)

C₃H₇NO₂

ND

12.461 ± 1.018b

17.243 ± 1.392a

16.776 ± 0.469a

18.423 ± 0.481a

Trimethylamine N-oxide (TMAO)

C₃H₁₃NO₃

0.00612 ± 0.0006a

0.00348 ± 0.0003b

0.00265 ± 0.0001bc

0.00235 ± 0.0001c

0.00213 ± 0.00006c

N8-Acetylspermidine (N8AS)

C₉H₂₁N₃O

2.476 ± 0.057a

2.340 ± 0.087ab

2.292 ± 0.017ab

2.216 ± 0.092bc

2.072 ± 0.066c

D-Alanyl-D-alanine (D-Ala-D-Ala)

C₆H₁₂N₂O₃

1.678 ± 0.076d

10.542 ± 0.310a

9.204 ± 0.099b

9.441 ± 0.157b

8.308 ± 0.110c

L-Cysteine (Cys)

C₃H₇NO₂S

5.224 ± 0.854a

ND

ND

ND

ND

5-Hydroxylysine (Hyl)

C₆H₁₄N₂O₃

ND

ND

ND

ND

ND

L-Glutamine (Gln)

C₅H₁₀N₂O₃

353.734 ± 22.747e

1815.399 ± 89.840d

3624.851 ± 266.384c

4727.936 ± 162.809b

6030.362 ± 238.848a

L-Ornithine (Orn)

C₅H₁₂N₂O₂

8.172 ± 0.341d

14.600 ± 1.112d

36.474 ± 3.917c

59.289 ± 3.386b

100.013 ± 6.793a

Argininosuccinic acid (ASA)

C₁₀H₂₀N₄O₆

ND

ND

5.642 ± 2.824b

8.339 ± 0.421ab

9.846 ± 0.330a

L-Homocitrulline (HC)

C₇H₁₅N₃O₃

ND

ND

0.759 ± 0.003b

0.767 ± 0.007b

0.782 ± 0.007a

3-N-Methyl-L-histidine (3-N-Methyl-L-His)

C₇H₁₁N₃O₂

2.473 ± 0.039b

2.542 ± 0.089b

2.629 ± 0.107b

2.678 ± 0.038ab

2.853 ± 0.026a

S-(5-Adenosy)-L-homocysteine

C₁₄H₂₀N₆O₅S

1.717 ± 0.052b

4.225 ± 0.297a

4.153 ± 0.051a

4.498 ± 0.146a

4.459 ± 0.089a

L-Carnosine

C₉H₁₄N₄O₃

1.894 ± 0.025ab

1.882 ± 0.022ab

1.841 ± 0.051ab

1.926 ± 0.031a

1.789 ± 0.034b

L-Asparagine anhydrous (Asn)

C₄H₈N₂O₃

13.734 ± 0.973d

1003.304 ± 128.749c

3083.540 ± 397.933b

3376.453 ± 160.504b

4580.323 ± 136.984a

L-Citrulline (Cit)

C₆H₁₃N₃O₃

3.149 ± 0.163e

43.396 ± 3.843d

163.437 ± 20.155c

216.965 ± 14.841b

319.212 ± 13.408a

Glycine (Gly)

C₂H₅NO₂

6.946 ± 1.082d

44.294 ± 3.368c

123.118 ± 5.959b

125.389 ± 5.278b

168.703 ± 3.520a

Nα-Acetyl-L-arginine

C₈H₁₆N₄O₃

10.478 ± 0.18b

19.97 ± 1.10a

22.48 ± 0.98a

21.84 ± 0.68a

23.36 ± 2.90a

2-Aminoethanesulfonic acid

C₂H₇NO₃S

1.673 ± 0.007 cd

1.654 ± 0.011d

1.709 ± 0.008ab

1.685 ± 0.002bc

1.735 ± 0.011a

Ethanolamine (EtA)

C₂H₇NO

20.179 ± 3.581c

71.230 ± 0.489a

60.926 ± 1.657b

65.651 ± 2.804ab

61.441 ± 2.380b

Homo-L-arginine (homo-Arg)

C₇H₁₆N₄O₂

0.993 ± 0.126d

2.530 ± 0.170c

3.010 ± 0.176bc

3.415 ± 0.325b

4.152 ± 0.031a

3,7-Dimethyluric acid

C₇H₈N₄O₃

0.187 ± 0.001c

0.197 ± 0.002c

0.225 ± 0.021bc

0.303 ± 0.014a

0.262 ± 0.034ab

L-Arginine (Arg)

C₆H₁₄N₄O₂

8.876 ± 0.888e

231.915 ± 16.001d

500.928 ± 55.152c

773.747 ± 19.609b

912.786 ± 37.763a

Creatine-phosphate (CP)

C₄H₈N₃Na₂O₅P

380.690 ± 12.393a

188.519 ± 17.603bc

247.029 ± 26.919b

218.475 ± 13.702bc

156.963 ± 42.067c

Creatine

C₄H₉N₃O₂

0.329 ± 0.006a

0.136 ± 0.136ab

ND

ND

0.122 ± 0.122ab

Succinic acid

C₄H₆O₄

715.448 ± 23.935a

706.139 ± 78.683a

574.498 ± 24.891b

532.770 ± 14.402b

454.466 ± 7.096b

Summation of FAADs (TFAADs)

10,185.614 ± 352.688d

27,980.176 ± 1172.927c

39,231.767 ± 1400.485b

42,368.673 ± 1244.381b

49,243.660 ± 1676.003a