Multilayered structure of tension wood cell walls in Salicaceaesensu latoand its taxonomic significance

Abstract

Salicaceae have been enlarged to include a majority of the species formerly placed in the polyphyletic tropical Flacourtiaceae. Several studies have reported a peculiar and infrequently formed multilayered structure of tension wood in four of the tropical genera. Tension wood is a tissue produced by trees to restore their vertical orientation and most studies have focused on trees developing tension wood by means of cellulose‐rich, gelatinous fibres, as in Populus and Salix (Salicaceae s.s.). This study aims to determine if the multilayered structure of tension wood is an anatomical characteristic common in other Salicaceae and, if so, how its distribution correlates to phylogenetic relationships. Therefore, we studied the tension wood of 14 genera of Salicaceae and two genera of Achariaceae, one genus of Goupiaceae and one genus of Lacistemataceae, families closely related to Salicaceae or formerly placed in Flacourtiaceae. Opposite wood and tension wood were compared with light microscopy and three‐dimensional laser scanning confocal microscopy. The results indicate that a multilayered structure of tension wood is common in the family except in Salix, Populus and one of their closest relatives, Idesia polycarpa. We suggest that tension wood may be a useful anatomical character in understanding phylogenetic relationships in Salicaceae. Further investigation is still needed on the tension wood of several other putatively close relatives of Salix and Populus, in particular Bennettiodendron, Macrohasseltia and Itoa.

ATR-FTIR Microspectroscopy Brings a Novel Insight Into the Study of Cell Wall Chemistry at the Cellular Level

“…In addition, a positive loading on the first dimension of PCA was found for a group of bands corresponding also to lignins (1,330-24 cm -1 , S ring plus G ring condensed). This suggests that some lignins, likely different from the fiber S-layer lignins, are actually present in the G-layer, as previously reported in poplar (Joseleau et al, 2004;Gierlinger and Schwanninger, 2006) and in other species (Ghislain et al, 2016;Higaki et al, 2017). Thus, the in situ technique described in this paper is validated on TW fiber G-layers, since the results we obtained on individual G-layers were in accordance with other studies made at the tissue level or on isolated G-layers.…”

Diversity in the organisation and lignification of tension wood fibre walls – A review

“…they did not specify if sampling was done during the process of maturation or in a transition zone between normal wood and tension wood. Furthermore, it cannot be checked, since the observation was made on an unidentified Flacourtiaceae (currently split into two families Achariaceae and Salicaceae sensu lato) and, as we now know, many Flacourtiaceae newly classified as Salicaceae sensu lato are able to form multi-layered fibre walls in their tension wood (Ghislain et al 2016). The illustration of Wardrop and Dadswell (1955) does not allow us to confirm the presence of an S 3 layer or a multi-layered G-layer, since Ruelle et al (2007c) described the thin lignified layers in multi-layered tension wood as similar to the S 3 layer.…”

Critical review on the mechanisms of maturation stress generation in trees

“…Other types of TW have been identified, the most frequent of which was previously called 'tension wood without G-layer' [26,39,40], which is actually formed of a G-layer which was later lignified [41]. Multi-layered TW, formed of alternating Glayers and S3-layer, has been observed in some botanical families [26,29,42]. In some angiosperm species, no G-layer (whether or not lignified) has yet been identified [43], but it is reasonable to speculate that tissues able to generate stresses amounting to several MPa exist in these species, to ensure their motor function.…”