Table I. Metabolite abundances in poplar wood samples determined by GC-MS.

Values represent means ± se (n = 3–6) of relative metabolite abundance per g fresh weight. All samples were taken in early spring (es) and summer (su). Statistical significances between early-spring and summer samples were analyzed by a paired Student’s t test. P values were adjusted by the Benjamini-Hochberg method. n.d. = not detected.

Class	Compound	Early Spring	Summer	Fold Change (es/su)	P Value	Adjusted P Value
Amino acids	4-Aminobutyric acid	0.107 ± 0.039	0.218 ± 0.029	−2.04	0.046	0.094
	Ethanolamine	0.128 ± 0.019	0.065 ± 0.021	1.96	0.037	0.094
	l-Glu	0.098 ± 0.032	0.163 ± 0.007	−1.67	0.335	0.396
	Orn	0.362 ± 0.034	0.248 ± 0.101	1.46	0.369	0.399
Carbohydrates	Fru	2.54 ± 0.53	0.809 ± 0.416	3.14	0.024	0.079
	Glc	4.92 ± 0.57	0.539 ± 0.287	9.14	0.004	0.019
	Maltotriose	0.385 ± 0.132	0.197 ± 0.025	1.95	0.056	0.094
	Myoinositol	1.91 ± 0.53	16.3 ± 4.9	−8.50	0.001	0.008
	Suc	8.52 ± 0.87	23.3 ± 9.6	−2.74	0.125	0.18
Glycerol and derivatives	Galactosylglycerol	0.308 ± 0.068	n.d.	n.d.	n.d.	n.d.
	Glycerol	11.5 ± 2.8	0.305 ± 0.152	37.60	0.001	0.008
Organic acids	Citric acid	3.61 ± 0.34	3.03 ± 1.18	1.19	0.156	0.203
	Malic acid	2.05 ± 0.56	2.32 ± 0.38	−1.13	0.559	0.559
Sugar alcohols	Galactinol	0.377 ± 0.062	n.d.	n.d.	n.d.	n.d.
	Galactitol	0.461 ± 0.111	0.185 ± 0.009	2.48	0.058	0.094
	Threitol	0.108 ± 0.024	n.d.	n.d.	n.d.	n.d.