Abstract
The wood anatomy of 132 species of the genera Abies, Cathaya, Cedrus, Keteleeria, Larix, Nothotsuga, Picea, Pinus, Pseudolarix, Pseudotsuga and Tsuga was studied to determine the elements that characterise the xylem of each genus and discuss possible groupings by wood anatomy for comparison with clades established by molecular phylogeny. The presence of resin canals and ray tracheids supports the family Pinaceae, although the absence of ray tracheids in Keteleeria and their occasional presence in Abies and Pseudolarix weakens it. Based on wood structure, Pinaceae clearly supports division into two groups, coinciding with molecular phylogeny: Pinoideae (Cathaya-Larix-Picea-Pinus-Pseudotsuga) and Abietoideae (Abies-Cedrus-Keteleeria-Nothotsuga-Pseudolarix-Tsuga). Although differences between genera are slight in Pinoideae, the Abietoideae group presents problems such as the presence of only axial resin canals in Keteleeria and Nothotsuga, absence of ray tracheids in Keteleeria and presence of traumatic radial resin canals in Cedrus. However, other features such as pitted horizontal walls and nodular end walls of ray parenchyma cells, indentures, scarce marginal axial parenchyma and presence of crystals in ray parenchyma strengthen the Abietoideae group.
Highlights
The family Pinaceae, consisting of 11 genera and 236 species, is the largest conifer family [1]
Comparative anatomy studies of the wood of this family have dealt with the presence/absence of resin canals and their arrangement, and elements of the rays, axial parenchyma typology, axial tracheids and the presence of crystals [4,5,8,16,17,18,19,20]
Normal axial resin canals have been recorded in Nothotsuga by other authors [11], none were observed in the sample studied, probably because the wood was juvenile and this type of wood has very few resin canals
Summary
The family Pinaceae, consisting of 11 genera and 236 species, is the largest conifer family [1]. Hu [4] subsequently divided Pinaceae into three groups: Cathaya, Larix, Picea, Pinus and Pseudotsuga, with normal resin canals; Abies, Cedrus, Pseudolarix and Tsuga without normal resin canals; and Keteleeria, with or without normal resin canals. Lin et al [5], after confirming the constant presence of axial resin canals in mature wood of Keteleeria and the arrangement of traumatic resin canals in this genus, proposed a classification of Pinaceae in three groups, more in line with the wood anatomy of the family: Cathaya, Larix, Picea, Pinus and Pseudotsuga with radial and axial resin canals; Keteleeria and Nothotsuga with only axial resin canals; and Abies, Cedrus, Pseudolarix and Tsuga, without resin canals. Comparative anatomy studies of the wood of this family have dealt with the presence/absence of resin canals (both normal and traumatic) and their arrangement, and elements of the rays (horizontal and end walls of ray parenchyma cells, cross-field pitting, ray tracheids), axial parenchyma typology (presence/absence, arrangement, smooth/nodular transverse end wall), axial tracheids (presence/absence of helical thickenings, organic deposits in tracheids, warty layer) and the presence of crystals [4,5,8,16,17,18,19,20]
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