Figure 4.

Estimated onset and cessation dates and durations (±SD) of the main phases of xylogenesis (E, radial enlargement; L, lignification and cell-wall thickening; M, mature tracheids; X, xylem formation) in Scots pine (P. sylvestris) and black pine (P. nigra) trees of different defoliation classes (D, severe defoliation; I, intermediate defoliation; N, scarce or no defoliation). Onset and cessation dates of selected xylogenesis phases are represented by diamond-crossed-by-a-line marks whose left (right) end of the line represents the minimum (maximum), the left (right) end of the diamond the first (third) quartile and the middle of the diamond corresponds to the median.