Comparative wood anatomy of Taxaceae Balkrishna Ghimire A,C , Chunghee Lee B and Kweon Heo A,D A Department of Applied Plant Science and Oriental Bio-herb Research Institute, Kangwon National University, Chuncheon 200-701, South Korea. B Korea National Arboretum, Korea Forest Service, Pocheon 487-829, South Korea. C Present address: Plant Conservation Division, Korea National Arboretum, Korea Forest Service, Pocheon 487-829, South Korea. D Corresponding author. Email: laurus@kangwon.ac.kr Abstract. Comparative wood anatomy of Taxaceae s.l. was examined to elucidate the differences in wood features among genera. In total, 25 samples, comprising three varieties and seven species from five genera (Pseudotaxus was not included), were examined. Sliding microtome, wood maceration and scanning electron microscopy methods were used for the study. The growth rings are well developed and early and late wood are distinguishable in a cross-section. In general, there is remarkable uniformity in the characteristics of the five genera of Taxaceae, although some differences in quantitative traits were found. Wood of Taxaceae s.l. differs from that of most conifers by having helical thickening in the tracheid inner walls, with the exception of Austrotaxus spicata R.H.Compton. All genera are characterised by the absence of resin canals, predominantly uniseriate pits on the radial wall of the axial tracheids, and the presence of pits on the tangential walls of the axial tracheids. The rays are composed solely of parenchyma cells and are uniseriate (occasionally biseriate in Torreya nucifera (L.) Siebold et Zucc.), with a height of 1–22 cells. The genus Taxus shares more characteristics with Torreya than with Amentotaxus, Austrotaxus and Cephalotaxus. Correspondingly, Amentotaxus and Cephalotaxus resemble each other, marked by the presence of either diffuse or sparse axial parenchyma with nodulated transverse walls. Austrotaxus spicata is the sole species that lacks helical thickenings in the tracheid walls and has sparse axial parenchyma with smooth transverse walls. These two features, namely, the absence of helical thickenings and axial parenchyma with smooth transverse walls, are plesiomorphic and might be considered a more primitive character in wood anatomy. Among the other four genera, Amentotaxus appears to have an annular type of wall thickening that could be considered plesiomorphic to the spiral thickenings found in Taxus, Torreya and Cephalotaxus. Additional keywords: axial parenchyma, Cephalotaxus, resin canal, wall thickenings. Received 31 December 2014, accepted 6 August 2015, published online 13 November 2015 Introduction Wood anatomy is informative and useful for taxonomic classification in some groups of conifers (Greguss 1955; Visscher and Jagels 2003; Immo 2004; Esteban and de Palacios 2009). Helical thickening in the secondary walls of the axial tracheids is a notable feature of the wood of the Taxaceae s.str. and the genus Cephalotaxus (Phillips 1948; Greguss 1955), although it is apparently absent in Austrotaxus (Price 1990) (note that for the purposes of the present study, Cephalotaxus Siebold & Zucc. ex Endl. was included in the family Taxaceae s.l.). Helical thickening in the secondary xylem appears as a ridge of cell- wall material, usually deposited on the lumen side of the xylem in the tracheids of certain conifers, and in angiosperm fibres and vessels (Yoshizawa et al. 1985). Such types of helical thickening in normal as well as compressed wood of Taxus L., Torreya Arn. and Cephalotaxus have already been reported (Gothan 1905; Wardrop and Dadswell 1951; Casperson 1962; Patel 1963; Timell 1978; Panshin and de Zeeuw 1980; Yoshizawa et al. 1985). These are also found sporadically in the late-wood tracheids of Picea Mill. and Larix Philip Miller (Sudo 1968). However, the form and distribution of helical thickening in Taxaceae s.str. are strikingly similar to those in Cephalotaxus, but differ from those found in some other conifers (Yoshizawa et al. 1985). Wood of Taxaceae s.str. and Cephalotaxus typically lack resin canals, which is a characteristic feature of many conifers such as Cathaya Chun & Kuang, Larix, Picea, Pinus L., Pseudotsuga Carrière (axial and radial), Keteleeria Carrière and Nothotsuga Hu ex C.N.Page (axial only), although it is present in the leaves and aril of Torreya and Amentotaxus Pilg., as well as in the leaves and seed coat of Cephalotaxus (Singh 1961; Keng 1969). Pilger’s(1926) original classification of conifers into seven families was modified by Buchholz (1934) and Chamberlain (1935), who maintained that the order could be more naturally divided into the following two suborders: Pineae, with the Journal compilation Ó CSIRO 2015 www.publish.csiro.au/journals/asb CSIRO PUBLISHING Australian Systematic Botany, 2015, 28, 160–172 http://dx.doi.org/10.1071/SB14050