Table 4.

Statistical tests (ASL) obtained by comparing the estimated onset and cessation dates and the duration of the main phases of tracheid differentiation for P. sylvestris and P. nigra trees of different defoliation classes (D, severely defoliated; I, intermediate defoliation; N, scarcely or not defoliated).

Species	Event	Xylogenesis phase	D vs. N	D vs. I	I vs. N
Scots pine (Pinus sylvestris)	Onset	Radial enlargement	0.012	0.136	0.076
		Cell-wall thickening	0.059	0.362	0.081
	Cessation	Radial enlargement	0.021	0.042	0.047
		Cell-wall thickening	0.069	0.188	0.073
	Duration	Radial enlargement	0.075	0.251	0.212
		Cell-wall thickening	0.061	0.080	0.287
		Xylem formation	0.026	0.333	0.109
Black pine (Pinus nigra)	Onset	Radial enlargement	0.078	0.091	0.080
		Cell-wall thickening	0.084	0.054	0.069
	Cessation	Radial enlargement	0.019	0.037	0.025
		Cell-wall thickening	0.065	0.056	0.077
	Duration	Radial enlargement	0.032	0.190	0.154
		Cell-wall thickening	0.237	0.066	0.187
		Xylem formation	0.048	0.190	0.084

Significant (P < 0.05) ASL values, based on 10,000 bootstrapped iterations, appear in bold characters. Note that the smaller the value of ASL, the stronger the evidence to support a significant difference.