Table 4.

Pearson correlation coefficients (r) of heterosis for biomass-related traits and the mean percentage of each locus in triploid progeny attributable to the respective diploid parent (diploid %).

Trait	Trait description	Trait class	Timea	Year 1b		Year 2
Field study
HT	Plot height	Stem growth	1, 2	−0.82	***	−0.53	**
STN	Stem number	Stem growth	1	−0.41	*	–	n.s.
MDIA	Mean stem diameter	Stem growth	1, 2	−0.47	*	−0.40	*
DIA	Stem diameter	Stem growth	1, 2	−0.54	**	−0.51	**
MSA	Mean stem area	Stem growth	1	−0.41	*	–	n.s.
SA	Stem area	Stem growth	1, 2	−0.51	**	−0.47	*
VOL	Stem volume	Stem growth	1, 2	−0.53	**	−0.52	**
LFL	Leaf length	Leaf growth	2	–	n.s.	0.45	*
LFP	Leaf perimeter	Leaf growth	2	–	n.s.	0.5	**
LFR	Leaf ratio	Leaf growth	2	–	n.s.	0.42	*
LFF	Leaf shape factor	Leaf growth	2	–	n.s.	−0.51	**
SLA	Specific leaf area	Leaf growth	1	0.58	**		n.s.
CDIA	Basal crown diameter	Architecture	1, 2	−0.40	*	−0.65	***
FORM	Crown form	Architecture	1, 2	0.46	*	0.65	***
DEN	Wood density	Composition	2	–	n.s.	−0.41	*
DVOL	Wood density × stem volume	Biomass	1, 2	−0.56	**	−0.58	**
Greenhouse study
SDW	Stem dry mass	Biomass	70	−0.52	**
LDW	Leaf dry mass	Biomass	70	−0.57	**
RDW	Root dry mass	Biomass	70	−0.73	***
AGB	Aboveground dry mass	Biomass	70	−0.56	**
TBM	Total dry mass	Biomass	70	−0.65	***
HT	Plot height	Stem growth	42, 21–56	−0.68	***
MSL	Mean stem length	Stem growth	42, 21–56	−0.60	***
TSL	Total stem length	Stem growth	42, 21–56	−0.59	**
SA	Stem area	Stem growth	70	−0.48	**
VOL	Stem volume	Stem growth	70	−0.60	***
SLA	Specific leaf area	Leaf growth	70	0.31	*
PHE	Vegetative phenology	Leaf growth	11, 13	−0.52	**
SPAD	Chlorophyll content	Leaf growth	14	−0.39	*

^aTime in years since coppice (field study) or days after planting (greenhouse study).

^bAsterisks ***, **, * denote significant at P-value < 0.001, P < 0.01, and P < 0.05, respectively.