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See detailComparison of cross-field pitting in fresh, dried and charcoalified softwoods
Gerards, Thomas ULg; Damblon, Freddy ULg; Wauthoz, B. et al

in Iawa Journal (2007), 28(1), 49-60

Cross-field pitting is one of the most reliable characters for softwood identifi cation. During charcoalification, a range of severe qualitative and quantitative modifications may occur in cross-field ... [more ▼]

Cross-field pitting is one of the most reliable characters for softwood identifi cation. During charcoalification, a range of severe qualitative and quantitative modifications may occur in cross-field pitting. As most fossil or archaeological wood remains are preserved as charcoal (fusain), the question arises whether these modifications hamper the accurate identification of some taxa. This work is a systematic biometric study of a wide range of gymnosperm cross-field pitting after experimental charcoalification. We focused on the window-like, piceoid, taxodioid, cupressoid, araucarioid and podocarpoid cross-field pitting types. Our main results are the following: 1) Cross-field pits of wood specimens dried out before charcoalification are hidden by a thin closing wall; in this case, it is often impossible to discriminate between the various types of cross-field pitting. 2) Piceoid cross-field pitting becomes taxodioid-like after charcoalification. 3) Biometric study of charred softwood cross-field pitting dimensions shows that the ratios between height and width of pit aperture and border allow us to distinguish and characterise four types of pitting (window-like, piceoid, taxodioid, cupressoid + araucarioid + podocarpoid [= CAP]). The discrimination within the CAP type requires further investigation. [less ▲]

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See detailAnatomical characteristics of tension wood and opposite wood in young inclined stems of poplar (Populus euramericana cv ‘Ghoy’)
Jourez, Benoît ULg; Riboux, Alain; Leclercq, André

in IAWA Journal (2001), 22(2), 133-157

Young shoots from poplar cuttings (P. euramericana cv ‘Ghoy’) were artificially inclined to 30° from vertical to quantify the anatomical modifications induced by this gravitational stimulus. At the end of ... [more ▼]

Young shoots from poplar cuttings (P. euramericana cv ‘Ghoy’) were artificially inclined to 30° from vertical to quantify the anatomical modifications induced by this gravitational stimulus. At the end of the growing season, the tension wood tissue (from the upper face of the inclined axis) was compared to the opposite wood tissue (from the lower face), with radial position taken into account. On isolated elements after maceration, fibres and vessels were significantly longer in tension wood tissue. In the cross section, the gelatinous fibres had a smaller radial diameter than normal fibres in opposite wood. Vessel frequency and porosity were significantly lower in tension wood than opposite wood. Solitary vessels in tension wood were less circular in cross section than in opposite wood, but their surface area did not differ. Rays were more numerous in tension wood than opposite wood but their height did not differ between the two tissue types. Finally, there was a negative correlation between the proportion of vessels lumina (lowest in tension wood) and the proportion of fibres lumina including the G layer. The very controlled nature of this experiment (greenhouse, young clonal material, detailed anatomical observations within one growth ring) and the image analysis technology (allowing a large number of observations) enabled us to draw conclusions that may not have been seen in less-controlled experiments and/or those with smaller sample sizes. [less ▲]

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