Anatomical Characteristics of Tension Wood and Opposite Wood in Young Inclined Stems of Poplar (Populus Euramericana Cv 'Ghoy')

Abstract

Young shoots from poplar cuttings (Populus euramericana cv ʻGhoyʼ) 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 in 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 in opposite wood but their height did not differ between the two tissue types. Finally, there was a negative correlation between the proportion of vessel lumina (lowest in tension wood) and the proportion of fibre 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.

Relationships between growth stress and wood properties in poplar I-69 (Populus deltoides Bartr. cv. “Lux” ex I-69/55)

“…There is no agreement in the literature regarding the length of tension wood fibres in comparison with that of normal fibres. Compared with normal fibres, tension wood fibres were reported sometimes as being longer [9,27,42], sometimes as being shorter (Giovanmi 1953, cited in Zimmermann [61]) and sometimes as having no marked difference [19,51]. In this study a very significant positive correlation (r = 0.751, significant at the 1% level) was found between fibre length and GSI values (Fig.…”

“…However, Chow [9] reported that tension wood fibres were narrower than those of normal wood in beech on isolated fibres. Similarly, Wardrop [55] and Jourez et al [27] reported that in poplar (Populus alba and Populus euramericana cv. 'Ghoy', respectively), in the radial direction, the G-fibres were relatively narrower than the opposite wood fibres observed in cross-section.…”

“…5a). In the previous studies, there was a general agreement that tension wood contained a lower vessel proportion than normal wood [9,27,42,47,55], except for Kaeiser and Boyce [29] and Kroll et al [34], who reported opposite results. The decreased vessel proportion in tension wood could be partially explained by the auxin concentration.…”

“…5b). Onaka [42] and Jourez et al [27] also reported that ray proportion did not vary with wood type, normal or tension wood. A different result was reported by Chow [9], who observed that tension wood contained a larger proportion of rays, but was inconclusive.…”

The Gravitropic Response of Poplar Trunks: Key Roles of Prestressed Wood Regulation and the Relative Kinetics of Cambial Growth versus Wood Maturation

“…In many angiosperms, including poplars (Jourez et al, 2001), the formation of reaction wood is characterized by the differentiation of a specific cellulose cell wall layer referred to as the G layer (Scurfield, 1973). Reaction wood formation is often accompanied by eccentric radial growth (Sinnott, 1952).…”