. 2021 Apr 29;26(9):2602. doi: 10.3390/molecules26092602

Table 2.

Volatile organic compound (VOC) emissions (average ± SE) of five tropical crop species in (1) at optimal conditions of light, air temperature and moisture (constitutive emissions), and (2) after a 12 mm cut was made into the leaf lamina. The VOC emission rate (3) at the wounding-induced peak maximum and (4) the time to the peak maximum are also provided when the pattern of VOC emissions after wounding included a peak. Information on individual contributions to the total emissions in percentage is in Table 3.

Compound Name	Molecular Formula	Protonated Molecular Mass	(1) Constitutive Emissions (2) Wound Emissions (3) Max. Emission Rate (4) Time from Wounding	Abelmoschus esculentus	Amaranthus cruentus	Amaranthus hybridus	Solanum aethiopicum	Telfairia occidentalis
Formaldehyde	CH₂O	31.0178	pmol m⁻² s⁻¹	740 ± 80	612.3 ± 3.7	566 ± 41	542.6 ± 4.1	749 ± 7
			pmol mm⁻¹	0.65 ± 0.14	0.765 ± 0.022	0.75 ± 0.08	0.753 ± 0.049	0.66 ± 0.07
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Methanol	CH₄O	33.0335	pmol m⁻² s⁻¹	1600 ± 100	1553 ± 28	1270 ± 160	1750 ± 250	2300 ± 140
			pmol mm⁻¹	40.2 ± 4.8	2.52 ± 0.33	14.1 ± 2.0	11.3 ± 2.6	23.2 ± 4.7
			fmol mm⁻¹ s⁻¹	275 ± 30	16.0 ± 1.6	46.7 ± 4.8	47 ± 8	331 ± 49
			s	75 ± 31	111 ± 16	130 ± 17	112 ± 10	16.2 ± 2.1
Acetaldehyde	C₂H₄O	45.0335	pmol m⁻² s⁻¹	4020 ± 330	3990 ± 90	5650 ± 1000	2750 ± 150	5310 ± 260
			pmol mm⁻¹	2.74 ± 0.20	3.0 ± 1.3	3.40 ± 0.09	3.88 ± 0.53	5.7 ± 0.6
			fmol mm⁻¹ s⁻¹	-	21.9 ± 2.1	15.9 ± 0.8	14.7 ± 1.8	17.5 ± 2.6
			s	-	733 ± 45	123 ± 32	639 ± 37	461 ± 35
Formic acid	CH₂O₂	47.0128	pmol m⁻² s⁻¹	2550 ± 70	2895 ± 30	2390 ± 60	2810 ± 80	2473 ± 19
			pmol mm⁻¹	1.73 ± 0.1	1.62 ± 0.08	2.41 ± 0.40	2.34 ± 0.27	2.2 ± 0.6
			fmol mm⁻¹ s⁻¹	-	6.3 ± 1.0	10.4 ± 1.9	7.3 ± 0.9	10.9 ± 1.3
			s	-	119 ± 21	158 ± 18	205 ± 40	96 ± 8
Ethanol	C₂H₆O	47.0491	pmol m⁻² s⁻¹	622 ± 240	404 ± 31	412 ± 22	396.2 ± 4.4	457 ± 28
			pmol mm⁻¹	0.728 ± 0.028	0.56 ± 0.13	0.68 ± 0.11	1.7 ± 1.0	0.80 ± 0.18
			fmol mm⁻¹ s⁻¹	2.813 ± 0.023	3.1 ± 0.7	3.13 ± 0.10	2.8 ± 0.05	3.44 ± 0.26
			s	78.3 ± 3.7	33 ± 7	193.5 ± 3.7	297 ± 22	100 ± 11
Acetone	C₃H₆O	59.0491	pmol m⁻² s⁻¹	1430 ± 430	864 ± 5	1160 ± 410	795 ± 75	2130 ± 210
			pmol mm⁻¹	2.3 ± 0.8	0.75 ± 0.08	1.9 ± 0.7	1.7 ± 0.6	2.6 ± 0.7
			fmol mm⁻¹ s⁻¹	5.6 ± 1.0	5.0 ± 1.7	6.3 ± 0.6	5.6 ± 2.0	7.9 ± 1.3
			s	182 ± 44	15 ± 5	123 ± 13	120 ± 50	339 ± 150
Acetic acid	C₂H₄O₂	61.0284	pmol m⁻² s⁻¹	1110 ± 90	1370 ± 80	881 ± 26	1800 ± 100	1010 ± 50
			pmol mm⁻¹	0.77 ± 0.10	0.71 0.15	1.17 0.23	1.38 0.20	0.77 0.16
			fmol mm⁻¹ s⁻¹	5.3 ± 1.8	5.00 ± 0.36	4.6 ± 0.6	4.7 ± 1.3	4.6 ± 1.0
			s	83 ± 35	49 ± 30	150 ± 42	172 ± 65	56 ± 22
Pentenal + 3-penten-2-one	C₅H₈O	85.0648	pmol m⁻² s⁻¹	21.4 ± 1.1	28.7 ± 0.8	17.9 ± 1.5	21.9 ± 0.7	21.2 ± 0.6
			pmol mm⁻¹	0.203 ± 0.034	0.43 ± 0.09	0.64 ± 0.05	0.56 ± 0.15	0.55 ± 0.09
			fmol mm⁻¹ s⁻¹	4.2 ± 0.9	9.8 ± 2.5	5.63 ± 0.36	12.5 ± 3.2	4.8 ± 0.9
			s	11.1 ± 1.8	9.6 ± 2.4	78 ± 12	10.8 ± 1.8	26.4 ± 3.9
Pentanal + 2-pentanone	C₅H₁₀O	87.0804	pmol m⁻² s⁻¹	89.3 ± 2.5	109.8 ± 2.4	75.4 ± 3.3	96.2 ± 1.4	85.7 ± 4.5
			pmol mm⁻¹	0.252 ± 0.026	0.302 ± 0.015	0.386 ± 0.017	0.333 ± 0.022	0.390 ± 0.011
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Hexenal	C₆H₁₀O	99.0804	pmol m⁻² s⁻¹	41 ± 11	36.3 ± 0.9	24.5 ± 2.5	32.6 ± 2.4	28.9 ± 1.1
			pmol mm⁻¹	4.3 ± 1.6	3.7 ± 0.7	13.1 ± 1.7	9.7 ± 0.9	15.9 ± 1.9
			fmol mm⁻¹ s⁻¹	78 ± 35	85 ± 17	188 ± 43	136.7 ± 4.5	117 ± 8
			s	98 ± 11	9.6 ± 0.6	78 ± 10	15.0 ± 1.6	14.4 ± 2.1
(Z)-3-hexen-1-ol + hexanal	C₆H₁₂O	101.0961	pmol m⁻² s⁻¹	39.4 ± 2.6	48.7 ± 2.2	36.9 ± 1.6	48.4 ± 1.6	37.0 ± 1.7
			pmol mm⁻¹	0.210 ± 0.44	0.2045 ± 0.0042	1.11 ± 0.31	0.27 ± 0.06	0.65 ± 0.11
			fmol mm⁻¹ s⁻¹	1.88 ± 0.50	-	5.0 ± 1.3	-	3.54 ± 0.21
			s	122 ± 11	-	186 ± 8	-	70 ± 19
(E)-1-hexanol	C₆H₁₄O	103.1117	pmol m⁻² s⁻¹	5.68 ± 0.20	6.49 ± 0.22	4.8 ± 0.7	5.58 ± 0.30	5.58 ± 0.40
			pmol mm⁻¹	0.054 ± 0.006	0.0481 ± 0.0026	0.053 ± 0.005	0.043 ± 0.005	0.052 ± 0.005
			fmol mm⁻¹ s⁻¹	0.344 ± 0.026	0.52 ± 0.06	-	0.38 ± 0.05	-
			s	293 ± 18	304 ± 23	-	311 ± 18	-
Methyl benzoate	C₈H₈O₂	137.0597	pmol m⁻² s⁻¹	5.6 ± 1.0	7.0 ± 0.8	4.1 ± 0.5	4.8 ± 0.7	4.21 ± 0.28
			pmol mm⁻¹	0.059 ± 0.008	0.081 ± 0.010	0.0614 ± 0.0033	0.076 ± 0.007	0.0573 ± 0.0041
			fmol mm⁻¹ s⁻¹	0.38 ± 0.07	0.65 ± 0.06	-	0.50 ± 0.08	-
			s	284 ± 13	317 ± 18	-	322 ± 16	-
Non-oxygenated monoterpenes ^(a)	C₁₀H₁₆	137.1325	pmol m⁻² s⁻¹	44 ± 13	33 ± 6	42 ± 8	32 ± 7	48 ± 12
			pmol mm⁻¹	0.25 ± 0.17	0.092 ± 0.011	0.094 ± 0.009	0.066 ± 0.021	0.32 ± 0.08
			fmol mm⁻¹ s⁻¹	3.1 ± 1.0	-	2.5 ± 0.8	-	1.67 ± 0.42
			s	130 ± 90	-	387 ± 22	-	360 ± 120
6-Methyl-5-hepten-2-one	C₈H₁₄O₂	143.1067	pmol m⁻² s⁻¹	24.2 ± 1.3	28.05 ± 0.40	19.5 ± 0.9	26.9 ± 1.6	22.1 ± 0.5
			pmol mm⁻¹	0.089 ± 0.008	0.084 ± 0.014	0.124 ± 0.022	0.124 ± 0.012	0.089 ± 0.009
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Hexyl acetate	C₈H₁₆O₂	145.1223	pmol m⁻² s⁻¹	4.44 ± 0.21	4.93 ± 0.13	3.97 ± 0.12	4.69 ± 0.28	3.969 ± 0.017
			pmol mm⁻¹	0.0357 ± 0.0039	0.0402 ± 0.0023	0.0334 ± 0.0005	0.0341 ± 0.0031	0.0366 ± 0.0019
			fmol mm⁻¹ s⁻¹	-	0.41 ± 0.08	0.594 ± 0.026	-	-
			s	-	338 ± 47	520 ± 90	-	-
DMNT	C₁₁H₁₈	151.1481	pmol m⁻² s⁻¹	5.41 ± 0.27	6.72 ± 0.12	5.416 ± 0.035	6.1 ± 0.7	5.42 ± 0.12
			pmol mm⁻¹	0.041 ± 0.006	0.043 ± 0.006	0.040 ± 0.005	0.053 ± 0.011	0.0385 ± 0.0020
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Methyl salicylate	C₈H₈O₃	153.0546	pmol m⁻² s⁻¹	6.1 ± 1.0	5.17 ± 0.26	3.50 ± 0.10	4.5 ± 0.5	5.2 ± 1.1
			pmol mm⁻¹	0.0272 ± 0.0041	0.0330 ± 0.0049	0.0426 ± 0.0013	0.0386 ± 0.0036	0.0351 ± 0.0011
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Oxygenated monoterpenes ^(a)	C₁₀H₁₈O	155.1430	pmol m⁻² s⁻¹	4.08 ± 0.08	4.73 ± 0.43	5.8 ± 2.7	4.04 ± 0.21	3.90 ± 0.43
			pmol mm⁻¹	0.0521 ± 0.0022	0.049 ± 0.006	0.089 ± 0.010	0.0534 ± 0.0019	0.047 ± 0.006
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Sesquiterpenes ^(a)	C₁₅H₂₄	205.1951	pmol m⁻² s⁻¹	6.19 ± 0.35	9.21 ± 0.21	6.3 ± 0.6	6.96 ± 0.17	6.9 ± 1.5
			pmol mm⁻¹	0.0357 ± 0.0018	0.0472 ± 0.0049	0.0341 ± 0.0029	0.0391 ± 0.0006	0.041 ± 0.011
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Jasmonic acid	C₁₂H₁₈O₃	211.1329	pmol m⁻² s⁻¹	1.845 ± 0.022	2.286 ± 0.026	1.84 ± 0.16	2.02 ± 0.15	1.77 ± 0.17
			pmol mm⁻¹	0.0263 ± 0.0019	0.0221 ± 0.0010	0.0234 ± 0.0014	0.0243 ± 0.0035	0.0247 ± 0.0029
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
TMTT	C₁₆H₂₆	219.2107	pmol m⁻² s⁻¹	5.84 ± 0.06	7.55 ± 0.20	4.78 ± 0.28	6.13 ± 0.19	5.25 ± 0.24
			pmol mm⁻¹	0.0350 ± 0.0032	0.0344 ± 0.0044	0.0396 ± 0.0019	0.038 ± 0.007	0.0373 ± 0.0017
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Methyl jasmonate	C₁₃H₂₀O₃	225.1485	pmol m⁻² s⁻¹	2.38 ± 0.19	2.371 ± 0.044	2.56 ± 0.13	2.52 ± 0.11	2.21 ± 0.13
			pmol mm⁻¹	0.0265 ± 0.0021	0.0292 ± 0.0018	0.0239 ± 0.0018	0.0246 ± 0.0031	0.0280 ± 0.0007
			fmol mm⁻¹ s⁻¹	-	-	-	-	-
			s	-	-	-	-	-
Total constitutive emissions			nmol m⁻² s⁻¹	12.03 ± 0.19	12.6 ± 1.5	12.4 ± 0.8	10.53 ± 0.30	14.73 ± 0.43
Total wound emissions			pmol mm⁻¹	55 ± 8	15.2 ± 2.9	40 ± 6	35 ± 6	54 ± 9

The measurements were conducted with a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) for 5 min before (constitutive emissions) and for 30 min after wounding (integrated emissions, peak emissions). Abbreviations: DMNT-(E)-4,8-dimethyl-1,3,7-nonatriene; TMTT-(E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene. ^(a) Thermal desorption gas-chromatography mass-spectrometry (GC-MS) analysis was used to confirm the identity of emitted compounds and analyse the composition of released volatiles classes (see Table S1, Supplementary Material). GC-MS analysis demonstrated that monoterpenes (C₁₀H₁₆) were composed of camphene, Δ³-carene, p-cymene, limonene, α-myrcene, β-ocimene, α-pinene, β-pinene, α-phellandrene, β-phellandrene, and α-terpinene; oxygenated monoterpenes (C₁₀H₁₈O) were composed of (E)-dihydrocarvone, camphor, β-cyclocytral, 1,8-cineole, linalool, and α-terpineol; and sesquiterpenes (C₁₅H₂₄) were composed of cubebene, (E)-β-farnesene, longifolene, and aromadendrene.