LIGNOPHYTA
True roots +; lateral meristems: cork cambium producing cork abaxially, vascular cambium producing phloem abaxially and xylem adaxially.
EXTANT SEED PLANTS/SPERMATOPHYTA
Plant woody, evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins derived from (some) sinapyl and particularly coniferyl alcohols, thus containing p-hydroxyphenyl and guaiacyl lignin units, (lignins derived from p-coumaryl alcohol, i.e. S [syringyl] lignin units); true roots present, apex multicellular, xylem exarch, and branching endogenous; arbuscular mycorrhizae +; shoot apical meristem multicellular, interface specific plasmodesmatal network; stem with ectophloic eustele, endodermis 0, xylem endarch, branching exogenous; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, plastids with starch grains; phloem fibres +; stem cork cambium superficial, root cork cambium deep seated; leaves with single trace from sympodium ["nodes 1:1"]; stomata ?; leaf vascular bundles collateral; leaves megaphyllous [determinancy evolved first, then ad/abaxial symmetry], spiral, simple, lamina with vein density up to 5 mm/mm2 [mean for all non-angiosperms 1.8]; axillary buds associated with at most some leaves; prophylls [including bracteoles] two, lateral; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores, i.e. no distal pore for release of gametes] +, grains mono[ana]sulcate, exine and intine homogeneous; ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development first endo- then exosporic, tube developing from distal end of grain, to ca 2 mm from receptive surface to egg, gametes two, developing after pollination, with cell walls, with many flagellae; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large", first cell wall of zygote transverse, embryo straight, endoscopic [suspensor +], short-minute, with morphological dormancy, white, cotyledons 2; plastid transmission maternal; two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.
EXTANT GYMNOSPERMS/PINOPHYTA/ACROGYMNOSPERMAE
Biflavonoids +; cuticle wax tubules with nonacosan-10-ol; ferulic acid ester-linked to primary unlignified cell walls; phloem with sieve and Strasburger cells, the sieve area with small pores generally less than 0.8 µm across that have cytoplasm and E.R., joining to form a median cavity in the region of the middle lamella; stomata perigenous, stomatal poles raised above pore, no outer stomatal ledges or vestibule; ± tracheidal transfusion tissue +; plants dioecious; microsporophylls and megasporophylls forming determinate strobili/cones; pollen tectate, infratectum alveolate [esp. saccate pollen], endexine lamellate at maturity; ovule unitegmic, with pollen chamber [developing by breakdown of nucellar cells], apex of nucellus massively thick; pollination droplet +, fertilisation 7 days to 4-6 months or more after pollination, pollen germinates in two or more days, tube, branched, haustorial, growing away from ovule at 1³-10(-20) µm/hour, breaks down sporophytic cells, wall of cellulose microfibrils, male gametophyte of two prothallial cells, a tube cell, and an antheridial cell producing a sterile cell and two multiflagellate gametes, zooidogamy, male gametes released by the breakdown of the pollen grain wall; female gametophyte monosporic, with radially-elongated cells [alveoli] that grow centripetally, the nucleus being on the open face and connected to adjacent nuclei by spindle fibres; seed fleshy, testa mainly of sarcotesta and sclerotesta, ± vascularized; chromosomes of male and female gametes line up on separate but parallel spindles, proembryo with many free-nuclear divisions; gametophyte persists in seed; genome size [1C value] intermediate, 3.5-14 pg; two copies of the LEAFY gene and three of the PHY gene, [PHYP [PHYN + PHYO]], second intron in the mitochondrial rps3 gene.
GINKGOALES + PINALES: wood pycnoxylic; bordered pits with margo-torus construction; phloem with scattered fibres alone [Cycadales?]; sporangiophore/filament simple with terminal microsporangia.
PINALES Gorozh. Main Tree, Synapomorphies.
Resin ducts/cells in phloem in vascular tissue [and elsewhere]; lignins lacking syringaldehyde [Mäule reaction negative]; cork cambium ± deep seated; bordered pits on tracheids round, opposite; compression wood +; nodes 1:1; leaves with single vein; plants monoecious; microsporangia abaxial, dehiscing by the action of the hypodermis [endothecium], pollen exine thick [³2 µm thick]; ovulate strobilus compound, with ± united flattened ovuliferous and bract scales, pollen chamber 0; pollen tube unbranched, growing towards the ovule, wall with arabinogalactan proteins, gametes non-motile, lacking walls, released from the distal end of the tube, siphonogamy; seed coat dry, not vascularized; proembryo with 2 to 4 nuclear divisions, with upper tier or tiers of cells from which secondary suspensor develops, elongated primary suspensor cells and basal embryonal cells [or some variant]; germination phanerocotylar, epigeal; plastid and mitochondrial transmission paternal, one duplication in the PHYP gene line, one copy of the chloroplast inverted repeat missing. - 7 families, 68 genera, 545 species.
Evolution. Divergence & Distribution. Because of the long history of Pinales, we cannot understand their evolution just by looking at their extant representatives, and it is clear that the apomorphies of extant conifers depend critically on fossil outgroups (e.g. Hart 1987). However, there are no known synapomorphies for a clade containing living and extinct conifers (e.g. Rothwell & Serbet 1994). The morphology of extinct conifers and coniferophytes is being re-evaluated as the morphologies of entire organisms are pieced together from what used to be separate form genera; the result is that many of the conventional taxonomic groupings are being radically overhauled (e.g. Rothwell et al. 2005; Hernandez-Castillo et al. 2009; see also below). As this is done, the extent of the diversity of these plants is becoming clear. Not only are forked leaves common, but stomatal distribution, etc., may differ dramatically on leaves from the one plant, compound microsporangiate strobili are known (cf. Gnetales!), as are megasporagiate strobili which do not terminate vegetative growth of the axis on which they occur (e.g. Hernandez-Castillo et al. 2001; Rothwell & Mapes 2001).
Davies et al. (2011: 95% credibility intervals) suggested an age for this clade (including Gnetales) of (286-)252(-212) million years.
The current distributions of many extant conifer groups is much smaller than and/or very different from their past distributions - and these in many cases go back to the Cretaceous (e.g. Manchester 1999: N. temperate distributions), thus McIver (2001) found fossils of the African Widdringtonia (Cupressaceae) in rocks of Cretaceous age in Alabama. For the early Tertiary fossil history of what are now East Asian endemics, see Ferguson et al. (1997) and Manchester et al. (2009) - genera in Taxaceae, Pinaceae, Sciadopityaceae and Cupressaceae are included. However, Biffin et al. (2010b) note that some calibration scenarios have crown-group divergence of Araucariaceae and Podocarpaceae largely a (mid-Cretaceous to) Tertiary phenomenon, which would question the attribution of early fossils at least to those families. Indeed, podocarps with broader leaves seem to have diversified considerably in the earlier Tertiary in the Southern Hemisphere (Brodribb & Hill 2004; Biffin & Lowe 2011 - see below).
Ecology & Physiology. Ectomycorrhizae are common and important in Pinaceae. Thus appropriate ectomycorrhizal fungi may have tio be introduced if Pinus itself is to be introduced successfully. Bacteria associated with a particular kind of ectomycorrhiza, tuberculate ectomycorrhizae, a cluster of root tips surrounded by hyphae, are thought to fix nitrogen (Paul et al. 2007). Note that litter and wood decay of conifers in general is slower than that of angiosperms (e.g. Weedon et al. 2009), indeed, brown rot fungi, which can barely degrade lignin, are commoner in conifer forest that the lignin-decaying white rot fungi (Boddy & Watkinson 1995). Recent work suggests an evolutionary sequence white rot -> brown rot -> ectomycorrhizae, with development of ectomycorrhizal associations being favoured by the ecological conditions (e.g. low nitrogen) that result from the activities of brown rot fungi (Eastwood et al. 2011). White rot and brown rot fungi are widely scattered through Agaricomycetes (Eastwood et al. 2011). Within Pinales, ectomycorrhizal associations are particularly common in Pinaceae.
Pitterman et al. (2005), Hacke et al. (2005) and Sperry et al. (2006) compare water transport in tracheids that have the torus:margo pits found in many conifers (including Ginkgo), with that in other kinds of tracheids and in vessels. Pore size in the margo is relatively large, while the torus provides a valuable safety feature guarding against embolism. Indeed, hydraulic conductance in tracheids with torus:margo pits is somewhat greater than in vessels of similar diameter when expressed on a sapwood area basis, while studies of cavitation in this system suggest that it is not connected with the size of the pores in the margo, but rather with the torus:pit aperture ratio (Pittermann et al. 2010).
Plant-Animal Interactions. Ambrosia and bark beetles (Curculionidae: Platypodinae, Scolytinae: see Wood 1982; Wood & Bright 1992) seem to have been associated ancestrally with conifers - although this is perhaps questionable (Jordal et al. 2011) - then shifted on to angiosperms and finally back to conifers several times - their current diversity in Pinales is lower (Farrell et al. 2001); see also Powell et al. (1999) for other insect-conifer associations. Bark beetles make their gallery systems in phloem, ambrosia beetles in the wood (although early-branching members of the ambrosia beetle clade may still live in phloem), and they mostly live in dead or dying wood. Ambrosia beetles are haplodiploids that show parental care; they have intricate cuticular invaginations in which fungus inoculum is carried; beetle larvae eat yeast-like bodies proliferating in the galleries they make (Jordal et al. 2000; Cognato et al. 2011 and references). The blue stain fungi involved - species from a few unrelated ascomycete genera - have little host specificity and may quickly invade the sapwood and render it non-functional; the result is that the plant can die surprisingly quickly. In those weevils that cultivate and eat fungi the mouth-parts are also much modified; development of cultivation is unreversed (Beaver 1989; Farrell et al. 2001; Jordal et al. 2008 and references, 2011). Not only pine beetles and fungi, but yeasts, bacteria (some nitrogen-fixing), parasitoids of the beetles and fungus-eating nematodes all form part of a very complex association (e.g. Rivera et al. 2009: yeasts and bark beetles). Pine beetles of the genus Dendroctonus can be noxious pests and invade living pines; such species tend to have relatively few hosts, but outbreaks can be devastating (Kelley & Farrell 1998 for host specificty).
Hudgins et al. (2003) examined the diversity of bark beetles in the context of various plant structures that might be defences against such beasts; Francheschi et al. (2005) elaborate on the pine-beetle story. Conifers in general have layers of polyphenol-containing parenchyma cells in the phloem, possibly offering some protection against insects. Many bark beetles are found growing on Pinaceae despite the constitutive presence of resin ducts in both phloem and xylem (i.e. the ducts do not develop in response to some trauma, etc., but are always to be found there), and there are intracellular crystals, etc. Other families of Pinales have such ducts only in the phloem, but they also have large numbers of small, extracellular, calcium oxalate crystals and also stratified phloem (Pinaceae have scattered sclereid cells or sometimes groups of such cells), both possibly protective structures - and a lower diversity of these beetles. Keeling and Bohlmann (2006a [detailed discussion], b) describe terpenoid diversity and conifer defence mechanisms, a complex subject; it is unclear just what is responsible for the considerable diversity of terpenoids in conifers, although Hamberger et al. (2011) found that enzymes involved in Picea sitchensis (Sitka Srpuve) could produce a variety of products from a variety of substrates. Iason et al. (2011) found that some, but not all, the monoterpenes they tested protected against herbivory by capercaillie, bank voles, slugs, or red deer (see also Hamberger et al. 2011 for references to defensive properties of diterpene resin acids).
Bacterial/Fungal Associations. A number of rusts, including those on ferns, Rosaceae, Grossulariaceae, etc., have part of their life cycles on Pinales, especially Pinaceae (Savile 1979b). For foliar endophytes and their bacterial associates, see Hoffman and Arnold (2010).
Pollination Biology & Seed Dispersal. Much has been learned about pollination and pollen germination in conifers in the last few years, although important early work had been carried out about 80 years ago. Pollen directly impacts the ovulate cones of conifers rather than being swept around the cone by a turbine-like action (Cresswell et al. 2007). Previously it had been thought that the sacci on the pollen of some conifers facilitated its dispersal by wind, and indeed they may increase the distance the pollen grain can travel before it falls to the ground, so facilitating wind pollination (Schwendemann et al. 2007). However, the sacci probably function more like water wings; within Pinales there is a correlation between presence of pollen sacci or wings and exine thickness and structure, whether (no wings) or not (wings) the pollen is wettable, etc. (Tomlinson 1994). In general, it seems that pollen sacci help orient the pollen grains in the pollination droplet (Doyle & O'Leary 1935; Salter et al. 2002 and references), or, more particularly, when the ovules are inverted, a common condition, the pollen grains are wetted and float up to the micropyle where the saccus orients the grain on the nucellus, separating and exposing the sulcus through which the pollen tube germinates (Salter et al. 2002; Leslie 2010b). Sacci also help in the selection of pollen grains during pollination: The proportion of saccate pollen grains inside the ovules in higher than that outside (Leslie 2009). In Phyllocladus and many taxa with erect ovules the pollination droplet is resorbed through the micropyle, and again the pollen grains are brought close to the nucellus; in Juniperus communis and other taxa resorbtion of the ovule droplet may be an active process happening quite soon after the pollen grain lands (Mugnaini et al. 2007). There are further variants of these pollination mechanisms in Coniferales (Owens et al. 1998; Salter et al. 2002; Fernando et al. 2005 for references) and other ancient gymnosperms (Leslie 2008).
There is considerable variation in the development of the male gametophyte (Fernando et al. 2010 for a summary and terminology). Pollen germination varies, and the feature "pollen exine shed during microgametophyte germination", is likely to have evolved more than once (?three times) in Pinaceae alone (see also Rydin & Friis 2005); for cell death induced by the growing pollen tube, see Fernando et al. (2005 and references).
Basic cone morphology is very variable. Conifer seed cones have becoming more massive and strongly constructed since the Triassic, and particularly the Jurassic, presumably in reponse to animal predation pressure (Leslie 2011). looking at extant taxa, Taxus has female cones each with a single, erect ovule while the cones of other taxa are often massive structures, sometimes with a well-developed ovuliferous scale and an inconspicuous bract scale, or the bract and ovuliferous scales may be largely separate, as in Psuedotsuga, while in Cupressaceae there seems to be no evidence of an ovuliferous scale when looking at the mature cone, which consists largely of bract scales (Schulz & Stutzel 2007; Rothwell et al. 2011 for references). Understanding details of the morphological evolution of cones will depend on advances in our understanding of the fossil record, and it is likely that heterochrony has been involved; Cupressaceae can be linked with the fossil Voltziaceae (e.g. Rothwell et al. 2011). Developmental studies may also be of value; thus Englund et al. (2011) found that gene expression patterns linked the epimatium of
Bateman et al. (2011) note a correlation between dioecy and fleshy, animal-dispersed seeds and monoecy and dry, wind-dispersed seeds in gymnosperms, a correlation that is evident within Pinales.
Chemistry, Morphology, etc. For fatty acids in the seeds, see Wolff et al. (2002 and references), and for resin composition and gum production, see Tappert et al. (2011).
The interpretation of the stem apex in terms of the tunica-corpus layering is not easy (see Napp-Zinn 1966). I have not integrated much of the considerable variation in wood anatomy with the clades recognised here (see e.g. Zhou & Jiang 1992 for information). Cork cambium is often more or less deep seated, although in Sequoia and Phyllocladus (e.g.) is is superficial (Möller 1882). Calcium oxalate microcrystals are commonly found in some cell walls throughout the group (Fink 1991; Hudgins et al. 2003: ?Cephalotaxaceae, Sciadopityaceae), but their distribution in other gymnosperms is unclear; they may be absent. Their position within tissues is linked with the development of fibres, the amount of resin secreted, etc. (Hudgins et al. 2003). There is generally a single trace per leaf, but if the leaves are opposite, sometimes there are two traces, but they fuse before they enter the petiole (Namboodiri & Beck 1968a, b). Leaf traces can also make connections with xylem produced during the second and subsequent years (Maton & Gartner 2005). Secondary growth (only phloem is produced) has been reported from the leaves of a number of conifers (Ewers 1982). Organised meristems usually occur only in the axils of some leaves, although more cryptic meristems are quite widespread (Namboodiri & Beck 1968a; Fink 1984; Burrows 1999, 2009); in both Pinus and Sciadopitys axillary buds are much more common, although most produce short shoots.
Bisexual strobili that have ovuliferous scales above the microsporangia, i.e., the same basic arrangement as in angiosperm flowers, are scattered through the clade (Flores-Rentería et al. 2011). A branched pollen tube occurs sporadically in Pinales (Friedman 1987 for references). The nature of the male gametes needs more study. Some taxa have binucleate sperm cells, i.e., a cell plate does not form in the spermatogeneous cell, or, if it does, it is incomplete. In some of these taxa the male gametes are unequal, one even being extruded from the cytoplasm of the binucleate sperm cell in e.g. Podocarpus spp. and Taxus. In Dacrydium two gametes are present, but are of unequal size, while in at least some Gnetum, Podocarpus andinus, and Torreya taxifolia two unequally-sized male cells are produced (see Singh 1978 for literature; I am grateful to Ned Friedman for help in understanding this complicated pattern of variation). Double fertlization may sometimes occur in Pinales (Friedman 1992 for references). Pinales show paternal transmission of plastids; mitochondrial transmission in taxa like Taxus is both paternal and maternal. The few records in other gymnosperms all suggest that maternal plastid transmission is widespread there (Chesnoy 1987; Neale et al. 1991; Mogensen 1996, summary of literature reports for Pinales; Cafasso et al. 2001 [cycads]; Wilson & Owens 2006 [podocarps]). The free-nuclear stage in the proembryo of Pinales is shorter than that of other gymnosperms, being only 5 or 6 rounds of nuclear division in Podocarpaceae and Araucariaceae and fewer in other members of the order (Owens et al. 2003c). Embryo size is rather variable, although it is often rather larger than that of the common ancestor of extant seed plants; in Pinus it may be close to the length of the seed. There is extensive duplication of the knox-1 gene within Pinaceae, at least, although more general sampling is needed to pin down the point at which this duplication occurred (Guillet-Claude et al. 2004).
For a classic study of both fossil and extant conifers, see Florin (e.g. 1951), for cleavage polyembryony, see Doyle and Brennan (1972), and for pollination, see Doyle (1945), Tomlinson (1994, 2000), Tomlinson et al. (1997), and Tomlinson and Takaso (2002). Page (1990) gives some general information, see also Geyler (1867), Barthelmess 1935, and Kumari (1963: nodal anatomy, taxa with opposite or whorled leaves tend to have 1:2 nodes), Möller (1882: cork cambium), Butts and Buchholz (1940: cotyledon number), Herrmann (1951: extensive intergeneric grafting seems possible), Napp-Zinn (1966: leaf anatomy), Den Outer (1967: phloem anatomy, much detail unincorporated), Gifford and Foster (1988: general, still a good survey), Schulz (1990: phloem anatomy), Zhou and Jiang (1992: wood anatomy), Raubesen and Jansen (1992a), Lackey and Raubeson (2008) and Hirao et al. (2009) (loss of a copy of the inverted repeat), Hill and Brodribb (1998: southern conifers), Owens et al. (1995b: cytoplasmic inheritance, nuclei sometimes incorporate cytoplasm), Mundry (2000: cone/strobilus development, with an emphasis on Taxaceae and friends), Trapp and Croteau (2001: resin biosynthesis), Sklonnaya and Ruguzova (2003: spermatogenesis), and seed anatomy (Bobrov & Melikian 2006: mention of both testa and tegmen). Farjon (2005b) has provided a bibliography for all conifers, and Eckenwalder (2009) a general account of them.
Phylogeny. Given the uncertainty in our knowledge of the relationships between the five major seed-plant clades, direct links are provided to the four others from here: Cycadales, Gnetales, flowering plants or Magnoliophyta , and Pinales; general discussion under seed plant evolution.
Within conifers, relationships are being substantially clarified. Pinaceae (Pinus, Cedrus, etc.) are sister to the rest, as a morphological cladistic analysis by Hart (1987) suggested some time ago (but cf. Nixon et al. 1994; Doyle 1996b); note, however, that the topology in stem group calibration scenarios in Biffin et al. (2010b) is incompatible with that used here. Molecular data and additional morphological work largely confirm the relationships in the tree here, which is based on the work of Quinn et al. (2002: successive approximations weighting), see also Price et al. (1993), Tsumura et al. (1995: RFLP analysis, tree [unrooted] with the same topology as that used here), Kelch and Cranfill (2000), Gugerli et al. (2001: e.g. the mitochondrial nadI gene), and Rai et al. (2002, and especially 2008a and references). Note that many details of the relationships suggested by the early morphological phylogeny of Hart (1987) have not been confirmed. It is now becoming more likely that Gnetales are to be included in Pinales (see discussion on Cycadales page).
There is perhaps some uncertainty in relationships in the Cephalotaxaceae-Taxaceae area, the two being tentatively bring combined here since there is some evidence that the exclusion of Cephalotaxus would make Taxaceae paraphyletic. Quinn et al. (2002) in a broad survey of Pinales found that Cephalotaxus, Torreya and relatives, and Taxus and relatives formed a polytomy in their unweighted rbcL and matK analysis; only when weights were applied did separate Cephalotaxaceae and Taxaceae become evident. Price (2006) looked at variation in the same two genes and found weak support for Cephalotaxus being embedded within Taxaceae, being sister to [Amentotaxus + Torreya]; sampling overall was poor, but good for Taxaceae s.l., and support for the monophyly of Taxaceae s.l. was strong. Somewhat similarly, these latter relationships were found by Wang et al. (2003) in analyses of trnL/F singly and when combined with rbcL data, but not in an analysis of rbcL alone, when Cephalotaxus alone was sister to Taxaceae. The work of Rai et al. (2008a) also supports a broad circumscription of Taxeae. Taxaceae s.l. lack sacci on their pollen (Anderson & Owens 2006). The sarcotesta of Cephalotaxus has been tentatively equated with the aril of Taxus (Mundry 2000), although the two would not seem to be homologous. Indeed, Taxaceae themselves have often been considered very different from all other extant conifers (e.g. Florin 1948, 1954; Miller 1999), but a reinterpretation of the nature of their reproductive structures (Stützel & Röwekamp 1999a) suggest that Taxus in particular can be linked with Torreya and then to other conifers. Of course morphological phylogenetic analyses (Hart 1987) and many molecular studies (see above) place them securely within the clade formed by the other conifers, rather than linking them to different fossil relatives (e.g. cf. Miller 1999).
Classification. Producing evolutionary classifications, or classifications that emphasise one or two favored morphological characters, seems to remain popular with those working on conifers (e.g. Keng 1975; Melikian & Bobrov 2000; Fu et al. 2004 [Nageiaceae and Podocarpaceae well separated], Bobrov & Melikian 2006 [Auraucariaceae and other conifers form a lineage quite distinct from Pinaceae and Sciadopityaceae]).
See Farjon (1990, 2005a, c) for detailed treatments of the conifers, Farjon (2001) for a checklist, etc.; Eckenwalder (2009) provides a general account of the group.
Previous Relationships. Taxus has sometimes been separated from all other conifers as a representative of a lineage, Taxopsida, supposedly well separate from Coniferopsida since pernaps the late Palaeozoic (Florin 1958).
Includes Araucariaceae, Cupressaceae, Pinaceae, Podocarpaceae, Phyllocladaceae, Sciadopityaceae, Taxaceae.
Synonymy: Abietales Link, Actinostrobales Doweld, Araucariales Gorozh., Athrotaxidales Doweld, Cephalotaxales Reveal, Cunninghamiales Doweld, Cupressales Bromhead, Falcatifoliales Melikian & Bobrov, Metaxyales Doweld, Microstrobales Doweld & Reveal, Parasitaxales Melikian & Bobrov, Podocarpales Reveal, Saxegotheales Doweld & Reveal, Sciadopityales Reveal, Taxales Knobloch, Taxodiales Heintze - Araucariidae Doweld, Cupressidae Doweld, Pinidae Cronquist, Takhtajan, & Zimmermann, Podocarpidae Doweld & Reveal, Taxidae Reveal - Araucariopsida A. V. C. F. Bobrov & Melikian, Pinopsida Burnett, Podocarpopsida Doweld & Reveal, Taxopsida Lotsy - Pinophytina Reveal
Gnetaceae clade + Pinaceae:
Evolution. Divergence & Distribution. Davies et al. (2011: 95% credibility intervals) suggested an age for this clade of (259-)219(-174) million years.
PINACEAE F. Rudolphi Back to Pinales
Plant (deciduous), ectomycorrhizal; resin diterpenes with abietane/pimarane skeletons, biflavonoids 0; resin ducts in xylem and phloem; sieve cells with nacreous walls, plastids with protein fibres [also starch grains (and protein crystals)]; phloem with sclereids, fibres scattered, calcium oxalate crystals intracellular; (axillary buds common, producing leaf fascicles; spur shoots), (plant deciduous); leaves with two vascular bundles; plant monoecious; 2 microsporangia/microsporophyll, sporangia superficial, pollen saccate (not), exine thin [2³ µm] except distally, (atectate, exine granular - Pseudotsuga, Larix [not saccate]); bracts free from the ovuliferous scale, ovules 2/scale, inverted, (pollination droplet 0); (pollen exine shed during microgametophyte germination - Larix, Pseudotsuga); "embryo tetrad" present [free-nuclear stage with only four nuclei]; seeds 2/scale, dry, winged, wing terminal, developing from adaxial side of scale, (wingless); (integument with resin canals); cotyledons (2-)4-11(-20); n = 12 (13, Pseudolarix = 22); plastid ndh genes and rps16 gene lost, PHYP gene duplicated; genome size [1C value] large, 14-35 pg; germination epigeal (hypogeal - Keteleeria).
11/210: Pinus (105), Abies (46), Picea (33). North Temperate (map: from Florin 1963; Farjon 1984, 1990a). [Photos - Collection]
Evolution. Divergence & Distribution. Pinaceae are known fossil only from the Early Cretaceous onwards (Miller 1999), although evidence suggests that they are sister to all other extant conifers. Hence the age of the lineage must be well over 200 million years, perhaps some 200-350 million years (see Eckert & Hall 2006).
For divergence times within Pinaceae, see Wang et al. (2000: Pinus diverged from the rest ca 140 million years before present) and especially Eckert and Hall (2006); using fossil constraints, Eckert and Hall (2006) suggest that Pinus diverged 128 ± 4 million years before present, a much more recent date than they obtained using molecular estimates. Willyard et al. (2007) suggested upper (permineralized wood) and lower estimates for divergence of Pinus subgenera of 85 and 45 million years respectively (for the latter, see also Magallón & Sanderson 2005), although there were bouts of speciation much later. Le Page (2003; see also Wang et al. 2000) suggests that there was an episode of diversification in the family in the Palaeocene. However, divergence time estimates are still rather up in the air. Various estimates were provided by Gernandt et al. (2008), e.g. maximum dates of 196-173 million years (Jurassic) and 165-148 million years for Pinaceae crown and Pinus stem groups respectively, with crown Pinus diverging 165-148 million years ago, others a little younger, but without constraints older. Other estimates in Gernandt et al. (2008) are more in line with those of other authors mentioned, two fossil calibrations yielding estimates of ca 87-72 million years for crown Pinus. Pinus arnoldii, a complete reconstruction from the Eocene of southern British Columbia, Canada, was placed very near the base or outside of crown Pinus (Klymiuk et al. 2011).
Dating issues aside, the restriction of Pinaceae to temperate forests of the northern hemisphere is remarkable, and for the most part they are unable to compete in tropical broad-leaved rain forests (but see the relatively broad-leaved Pinus krempfii: Brodribb & Feild 2008).
Plant-Insect Interactions. For a general discussion of resins and defence in Pinaceae, see the introduction to Pinales (above); Mumm and Hilker (2006) discuss the chemical defence of pines against foliovores in particular. Pine beetles, Dendroctonus spp., can be noxious pests and invade living pines; they tend to have relatively few hosts, but outbreaks can be devastating (Kelley & Farrell 1998 for host specificty; Wood 1982 and Wood & Bright 1992 for the weevils). Adelgidae (aphids) are restricted to Pinaceae, and include Adelges piceae and A. tsugae, serious introduced pests in North America (Havill et al. 2007). Cecidomyiid gall midges are quite common on the family in North America (Gagné 1989).
Bacterial/Fungal Associations. Despite these defences, a number of rusts, including those on ferns, have their aecial stages on Pinales, especially Pinaceae (Savile 1979b; Durrieu 1980). These include the white pine blister rust, Cronartium ribicola (alternate host Ribes, Grossulariaceae) which is a serious pathogen of white pine and its relatives.
In Pinus strobus endophytes have been shown to synthesize antifungal metabolites (e.g. against Microbotryum violaceum, parasitic on some Caryophyllaceae: Sumarah et al. 2010, 2011), and endophyte metabolites in spruce may be toxic to insects (Findlay et al. 2003).
Economic Importance. The majority of the world's lumber comes from softwood, and the majority of that comes from members of Pinaceae [?details].
Chemistry, Morphology, etc. Schultz (1990) notes that there are no phloem fibres in Pinaceae. Pinus cuticular wax tubules look almost scalloped (cf. commelinids!), but this is because the tubules are densely aggregated (Wilhelmi & Barthlott 1997). The seed coat of Cedrus is vascularized. The seed wing of Pinaceae is derived from the middle or stony layer of the integument. Cleavage polyembryony is common, as is true polyembryony (more than one archegonium is formed), but the seed generally contains only a single embryo.
For Pinus, see Mirov (1967: monograph), Millar (1998: ecology and biogeography), and Farjon (2005a: monograph); for other Pinaceae, see Farjon (1990: general). For aspects of ovuliferous cone morphology and anatomy, see Hu et al. (1989), Napp-Zinn and Hu (1989), and Gernandt et al. (2011: also morphological analysis), for the embryo, see Buchholz and (1931), for seed coat development, see Owens and Smith (1964), and for general information, see the Gymnosperm Database. Esteban and de Palacios (2009) and Esteban et al. (2009) describe the wood anatomy of Abietoideae, and Braukmann et al. (2009) chart the extent of the loss of the ndh gene (see also Hirao et al. 2009).
Phylogeny. Relationships within Pinaceae are unclear, details depending on data analysed (morphology, molecules) and methods of analysis (parsimony, Bayesian); see Tsumura et al. (1995), Wang et al. (2000), Rydin and Källersjö (2002), Liston et al. (2006b), and Gernandt et al. (2008). Studying the mitochondrial rps3 gene, Ran et al. (2010) found that Larix and Pseudotsuga were sister to all other Pinaceae, however the common problem is the poisition of Cedrus respect to and Abietoideae (Abies, Keteleeria, Nothotsuga, Pseudolarix, Tsuga) and a Pinoideae (Cathaya, Larix, Picea, Pinus, Pseudotsuga) (Holman et al. 2010). Holman et al. (2010) nicely summarize the morphological evidence that is compatible with the relationship of Cedrus with either of those groups, or as sister to the whole family...
For the phylogeny of Pinus, see Syring et al. (2005), Gernandt et al. (2005, 2011), and Eckert and Hall (2006). Pinus has two subgenera (see Gernandt et al. 2005 for an infrageneric classification). Leaves of subgenus Pinus, the hard pines, have two vascular bundles, plesiomorphic, while those of subgenus Strobus, the soft pines, have but a single bundle. Analysis of nuclear ITS variation was largely uninformative in suggesting relationships between sections in Abies, but at lower levels was more useful (Xiang et al. 2009).
Synonymy: Abietaceae Gray, Cedraceae Vest, Piceaceae Gorozh.
[[Araucariaceae + Podocarpaceae] [Sciadopityaceae [Cupressaceae + Taxaceae]]]: resins as diterpenes with labdanoid skeletons; xylem and phloem resin ducts 0; calcium oxalate crystals numerous, extracellular; phloem stratified, with tangential bands of fibres, sclereids 0; (leaves opposite, sometimes then with two vascular traces); pollen grains atectate, exine granular; euAP3 + TM6 genes [duplication of paleoAP3 gene: B class], mitochondrial nadI gene intron 2 and both rps3 introns lost, duplication in the PHYN clade.
Evolution. Divergence & Distribution. For other possible synapomorphies of this group, see Hart (1987). Isoflavonoids are known from Cupressaceae, Podocarpaceae and Araucariaceae (Reynaud et al. 2005).
Genes & Genomes. For mitochondrial genes, especially the rps3 gene, see Ran et al. (2010).
[Araucariaceae + Podocarpaceae]: gums +; roots with endomycorrhizal nodules; prothallial cells divide [Phyllocladaceae?]; ovule one/ovulate scale; proembryo with 5 or 6 free-nuclear divisions; 2nd intron in nad1 gene lost.
Chemistry, Morphology, etc. Chamberlain (1935) notes that there is no stalk cell per se in the male gametophyte, but when the generative cell divides, one of the cells produced dies, the other produces the gametes.
ARAUCARIACEAE Henkel & W. Hochst. Back to Pinales
Branches whorled, plagiotropic; stem apex with tunica/corpus construction; only resin plugs present in vascular tissue; pits on radial walls of tracheids touching, hexagonal in outline; single leaf trace branching profusely in the cortex; stomata tetracytic, usu. traversely oriented; branches shed; leaves multiveined, axillary meristems present on the trunk, undifferentiated, submerged by cork, persistent; (plants dioecious); to 20 microsporangia/microsporophyll; bract and ovulate scales fused (not in Araucaria); ovule inverted, pollination droplet 0, nucellus protrudes from the micropyle [?Araucaria]; pollen germinates on ovuliferous scale and tubes grow over the scales, prothallial cells numerous; seeds 1/scale, winged, wing developing from the the entire bract scale (wingless); free nuclear stage in proembryo many nucleate, central, embryonal cells surrounded by cap cells that degenerate; (cotyledons 4 - some Araucaria0; (germination cryptocotylar).
3/33. Southern South America, Malesia to E. Australia and New Zealand (map: from Florin 1963). [Photos - Collection]
Evolution. Divergence & Distribution. The origin of stem group Araucariaceae can be dated to ca (237-)205(-237) million years ago (Biffin et al. 2011, 95% HPD; cf. text and figs). Consistent with this, Araucariaceae are well known as fossils from the Mid Jurassic onwards ca 175 million years ago, and Araucaria in particular to have been found in even older Triassic deposits in many parts of the world in both hemispheres (Florin 1963; Stockey 1982, 1994; Hill & Brodribb 1989). However, Biffin et al. (2010b, esp. 2011) note that stem-group calibration scenarios have crown-group divergence of Araucariaceae largely a (mid-Cretaceous to) Tertiary phenomenon (see also Crisp & Cook 2011). This would question the identification of these early fossils to extant sections and it would make the long-term persistence of Agathis in New Zealand since the Eocene or before unlikely (cf. Knapp et al. 2007). Similarly, although Araucaria is diverse on New Caledonia, there is little genetic divergence between the species there, suggesting that divergence is recent (Gaudeul et al. 2012).
The divergence of Wollemia from other Araucariaceae has been dated to (37-)18(-younger) million years ago (Crisp & Cook 2011), suggesting that comparison of Wollemia with Cretaceous fossils identified as Araucariaceae may be inappropriate (cf. Chambers et al. 1998).
Pollination Biology. The time from pollination to fertilization in Agathis australis is about twelve months, although this includes three months after pollination before the pollen grain germinates, and then another three months over winter when nothing much happens (Owens et al. 1995b).
Plant-Animal Interactions. Sequeira and Farrell (2001) suggest that the association between Araucaria and the scolytine Tomicini bark beetles is probably Cretaceous in age; the beetles seem to have moved on to Araucaria from angiosperms, and from thence moved on to Pinaceae. Agathiphagidae, a small group of near-basal lepidoptera with jaws, are also found on the family (Shields 1988).
Other. The recent discovery very close to Sydney of a few trees of the remarkable Wollemia, very similar to some fossil Araucariaceae (see e.g. Pastoriza-Piñol 2007 for a general account), occasioned some excitement.
Chemistry, Morphology, etc. For the essential oils of Wollemia, see Staniek et al. (2010 and references), and for a possible taxol-producing endophyte, see Strobel et al. (1997). Tomlinson (2008) notes that the axillary branches of Wollemia are evident in the resting terminal bud, but do not grow out until extension growth of the latter starts; there are undifferentiated resting meristems in the axils of the leaves of the main axis which develop if the apical meristem is destroyed (Tomlinson & Huggett (2011). The single leaf trace divides into three or more as it proceeds into the leaf (Tomlinson 2008; Tomlinson & Murch 2009). Araucariaceae also have platelet structures in their cuticular waxes (Wilhelmi & Barthlott 1997); the stomata of Araucaria have a wax plug which may block penetration of fungal hyphae (Mohammadian et al. 2009 - see also Winteraceae).
Cones of Araucaria have a "ligule" that is more or less adnate to the ovule. The pollen grains do not rupture when placed in water (Tomlinson 1994).
For general information, see Stockey (1982), Bieleski and Wilcox (2009), Gee and Tidwell (2010: literature from late Triasssic to end Cretaceous), and especially the Gymnosperm Database, for comparative anatomy, see Thompson (1913), for axillary buds, see Burrows (1999 and references, 2009), for details of reproductive biology compared with those of other Pinales, see Owens et al. (1995a, b, c), for pollen morphology, see Dettmann and Jarzen (2000), for phylogeny, see Setoguchi et al. (1998), for growth patterns, see Tomlinson (2008) and Tomlinson and Murch (2009: Wollemia, also anatomy), and for possible apomorphies, perhaps including "dehiscent" seeds (i.e. separating from the cone-scale), see Cantrill and Raine (2006).
Phylogeny. Wollemia has been placed variously sister to Agathis or sister to the rest of the family (Gilmore & Hill 1997; Setoguchi et al. 1998; Knapp et al. 2007).
PODOCARPACEAE Endlicher Back to Pinales
Sclereids numerous, with large lumen; transfusion tissue in patches lateral to vascular bundles in leaf, laterally-elongated sclereids in middle of lamina +; (leaves opposite [Microcachrys] and nodes 1:2), (leaves broad, with transfusion tissue, [multiveined - Nageia]); plants dioecious (monoecious); staminate plant: microsporophylls with two sporangia; pollen saccate, (Saxegothea, Phylocladus not), exine thin, except distally, alveolate, (granular - Saxegothea); male gametophytes with 3-6(-8) prothallial cells, sperm nuclei unequal in size (one extruded); ovulate plant: ovulate scales not aggregated into cones, ± reduced, fused with ovule; ovule ± inverted (erect), with epimatium; epimatium fleshy or not, (seed arillate - Phyllocladus); proembryo [E tier] cells binucleate; n = (9 - Phyllocladus)10(-13, 15-19).
17/125: Podocarpus (100), Dacrydium (20). Largely southern Hemisphere, scattered, N. to Japan, Central America and the Caribean (map: from Florin 1963). [Photos - Collection, Phyllocladus trichomanoides, Phyllocladus megasporangia, microsporangia.]
Evolution. Divergence & Distribution. The origin of stem group Podocarpaceae has been estimated as ca (237-)205(-237) million years ago (Biffin et al. 2011, 95% HPD; cf. text and figs). Podocarpaceae are known as fossils from the Middle Triassic ca 225 million years ago (Axsmith et al. 1998; Supplement 4 in Biffin et al. 2011). Their distinctive root nodules are also known from the Triassic (Schwendemann et al. 2008, esp. 2011) and are represented by very well-preserved fossils from the Early Triassic, ca 240 million year ago.
Although Podocarpaceae are still quite common and may dominate the vegetation, they are largely restricted to the southern hemisphere, including Antarctica, where they are found as fossils; for the biogeography of the group, see Mill (2003). Biffin and Lowe (2011, see also Biffin et al. 2011) suggest that podocarps with broad leaves or functionally equivalent structures (the phylloclades of Phyllocladus) evolved only in the Tertiary and so were diversifying along with canopy-forming angiosperms. When compared with some Cupressaceae and other Podocarpaceae with narrower, imbricate leaves, they are shade tolerant and prefer warmer and higher rainfall conditions, and as Australia dried out during the Tertiary, podocarps became less common there (e.g. Brodribb & Hill 1997, 2004; Biffin et al. 2011). Diversification in podocarp clades whose members have imbricate leaves began in the Late Jurassic ca 150 million years ago (Biffin et al. 2011). However, diversification in clades whose members have flattened foliage of one sort or another (this evolved perhaps four times) is largely a Tertiary phenomenon; it is also notably greater than in clades with imbricate leaves, and has been dated to a time slightly after the venation density of angiosperm leaves increased - (94-)64(-38) versus 109-60 million years ago (cf. Biffin et al. 2011; Brodribb & Feild 2010). The foliar units of podocarps with flattened foliage have transfusion tissue or there are several veins, unlike the single vein and absence of transfusion tissue in the leaves of other podocarps (Biffin et al. 2011).
Ecology & Physiology. Root nodules in Podocarpaceae occur in longitudinal rows and represent modified lateral roots (Duhoux et al. 2001 and references). The fungus Glomus is involved, and nitrogen does not seem to be fixed (Russell et al. 2002; for nodulation, see also Becking 1965).
The New Caledonian Parasitaxus usta is hemiparasitic on the roots of Falcatifolium taxoides, another podocarp, from which it obtains water and nutrients (the stomata of Parasitaxus are insensitive to light), and is also a mycoheterotroph, obtaining carbon from an ?ectomycorrhizal fungus that is also associated with its host, and whose hyphae grow through the vascular systems of both host and parasite (Feild & Brodribb 2005); its closest relatives are Lagarostrobus and Manoao, from Tasmania and New Zealand (Sinclair et al. 2002; Rai et al. 2009; Lam et al. 2009).
Pollination & Seed Dispersal. For pollination, see Tomlinson et al. (1991, especially 1997: useful comparative tables) and Rydin and Friis (2005). There is a correlation between the absence of pollen wings and the shedding of the pollen exine when the microgametophyte germinates. In Phyllocladus, which has erect ovules, the pollination droplet is actively resorbed.
Vegetative Variation.Phyllocladus has phylloclades, flattened, photosynthetic stems; these bear highly reduced, scale-like leaves, and it is in the axils of these leaves that the reproductive structures are found. The seedling has more conventional needle-like leaves. A number of taxa have flattened leaves, and these seem to have diversified in the Tertiaty (Biffin & Lowe 2011 for a summary).
Chemistry, Morphology, etc. Accessory transfusion tissue extends to the lamina margin in Podocarpus macrophyllus (Gifford & Foster 1989), but how widely this character occurs is unclear.
The pollen of Phyllocladus has often been described as having a wing (e.g. Singh 1978), but a wing seems to be absent. The morphological nature of the epimatium is controversial; Chamberlain (1935) interprets it as possibly being equivalent to the ovuliferous scale (see also Tomlinson & Takaso 2002; Englund et al. 2011 [similarity confirmed by gene expression data]), and functionally, perhaps, it can be considered equivalent to the second integument of an angiosperm ovule - hence the anatropy of the ovules here (Endress 2011b). Although the single ovules of Podocarpaceae do seem very different from the cones of other Pinales, however, Lower Cretaceous podocarps with more conventional bract-scale complexes have been described (X. Wang et al. 2008). For nucleus number in the E-tier cells, see Quinn (1986). Quinn et al. (2002) note the tendency to dysploid chromosome evolution in the group.
For cuticle morphology, see Mills and Schilling (2009), for wood anatomy, see Woltz et al. (2009 and references), and for general information, see the Gymnosperm Database.
Phylogeny. RbcL analyses (Conran et al. 2000; Wagstaff 2004b) tend to result in Phyllocladus being embedded in Podocarpaceae, other analyses, whether (Quinn et al. 2002) or not (Sinclair et al. 2002) including rbcL sequences, have the two as sister groups. Peery et al. (2008) using the nuclear XDH gene also found Phyllocladus to be embedded in Podocarpaceae, and it is looking as if that is where it will go (see also Biffin et al. 2011). Even if its position within the family is uncertain, major groupings of genera are becoming evident there (Kelch et al. 2010). For phylogeny, see also Kelch (1998), a comparison of morphology and molecules.
Classification. Phyllocladus, with its phylloclades, highly reduced leaves that may lack any associated leaf gaps, distinctive pollen capture, etc., has long been considered very distinctive, sometimes being separated from all other conifers (e.g. Keng 1974, 1979; see also Tomlinson et al. 1989, 1997; cf. Quinn 1986).
Synonymy: Acmopylaceae Melikian & A. V. Bobrov, Dacrycarpaceae Melikian & A. V. Bobrov, Falcatifoliaceae Melikian & A. V. Bobrov, Halocarpaceae Melikian & A. V. Bobrov, Microcachrydaceae Doweld & Reveal, Microstrobaceae Doweld & Reveal, Nageiaceae D. Z. Fu, Parasitaxaceae Melikian & A. V. Bobrov, Phyllocladaceae Bessey, Pherosphaeraceae Nakai, Prumnopityaceae Melikian & A. V. Bobrov, Saxegotheaceae Doweld & Reveal
[Sciadopityaceae [Cupressaceae + Taxaceae]]: pollen without sacci, exine shed on microgametophyte germination [microgametophyte naked]; prothallial cells 0; seed with wing developing from the integument.
Chemistry, Morphology, etc. The pollen grains expand and rupture when placed in water (Tomlinson 1994), and the intine-clad pollen may deform more easily and so be tranferred along the narrow micropylar canal (Takaso & Owens 2008). Whether or not all taxa have male gametes each surrounded by cell walls needs to be confirmed (see Singh 1978).
SCIADOPITYACEAE Luersson Back to Pinales
Roots with endomycorrhizal nodules; leaves reduced to scales, short shoots with with apically bifid phyllodes; microsporophyll with flattened apical expansion, (1-)2 microsporangia/microsporophyll; pollen surface microtuberculate (microechinate) exine granules confluent by sporopollenin deposition; sterile cell?; ovules 7-9 /ovuliferous scale, inverted, pollen chamber?; seeds ?/scale, narrowly winged; n = 10.
1/1: Sciadopitys verticillata. C. and S. Japan (map: from Florin 1963). [Sciadopitys Photos - Collection]
Evolution. Divergence & Distribution. Fossils of Sciadopitys are known from the Upper Cretaceous and are common in the European Tertiary.
Chemistry, Morphology, etc. There has been much debate over whether the photosynthesising structures ofSciadopitys are some kind of phylloclade - perhaps formed by the connation of two leaves - or cladodes, basically stem structures. The two vascular bundles, each with its own endodermis, tend to have have abaxial xylem and adaxial phloem, a rather odd arrangement. Sporne (1965) noted that on occasion branches develop from these leafy structures, so perhaps favoring the latter alternative (see also Farjon 2005c). However, Dörken and Stützel (2011) examined probably only the second known case of intermediate structures, and consider the photosynthesizing structures to be two congenitally connate needle leaves, the orientation of the vascular tissue resulting from the relation of the leaves to the axis that bore them.
For pollen, see Page (1990) and Uehara and Saichi (2011), for a monograph, see Farjon (2005c), and for general information, see the Gymnosperm Database.
[Cupressaceae + Taxaceae]: cone scales opposite; megasporangia hypodermal [?level].
Chemistry, Morphology, etc. Burrows (2009) notes that axillary buds occur in several members of this clade, but they remain superficial and so do not form shoots in older branches - cf. Araucariaceae. Gene expression studies suggest little in common between the scaly structures of the Cupressaceae cones studied and the arils of Taxus with the ovuliferous scales of Pinaceae... (Englund et al. 2011; Groth et al. 2011).
CUPRESSACEAE Bartling Back to Pinales
(Stem apex with tunica/corpus construction); xylem or phloem resin ducts inducible [seperate clades]); branchlets deciduous; leaves shed along with branches, scale- or needle-like, (opposite - Cupressus, etc., and nodes 1:2); (plant dioecious); (1-)2-10(-14) microsporangia/microsporophyll; pollen surface microverrucate; ovuliferous scales small (usu. not obvious at all; large, Taxodium and relatives), (bract scale fleshy - Juniperus; with adaxial development), ovules 1-9(-many)/scale, erect or inverted; male gametophyte without sterile cell, gametes with separate cell walls; seeds /scale, winged or not; (cotyledons -9(-15)); n = 11.
30/133: Juniperus (67), Callitropsis (18), Callitris (14), Cupressus (12). Esp. Northern Hemisphere, more scattered in south temperate regions, also N.E. Africa; individual genera are from either Northern or Southern Hemispheres (map: from Florin 1963, 1966; Farjon 2004c). [Photos - Collection]
Evolution. Divergence & Distribution. For the biogeography of Juniperus, initially Eurasian, that includes dates for various clades, see Mao et al. (2010).
Ecology & Physiology. For details of xylem function with relation to the environment in Cupressaceae, see Pittermann et al. (2010).
Bacterial/Fungal Associations. The telial stage of Gymnosporangium rust is common on some Cupressaceae, especially Juniperus, while the aecial stage characterises Rosaceae-Maloideae (Savile 1979b).
Pollination Biology. In Cupressus dupreziana paternal apomixis, a phenomenon unknown from any other seed plant, occurs; here the embryo develops from unreduced male gametes (Pichot et al. 2000, 2001).
Chemistry, Morphology, etc. Characters of wood anatomy may yield phylogenetically interesting variation (Schulz & Stützel 2007), but state delimitation is difficult; for epidermal morphology, see Ma et al. (2009). Proliferation of the ovuliferous cones is common, and its distribution, too, may be of phylogenetic interest (Schulz & Stützel 2007). Scales on the ovuliferous cones are wedge-shaped to peltate. A number, perhaps a majority, of Cupressaceae lack ovuliferous scales, having only bract scales (Zhang et al. 2004; see also Farjon 2005c), while Cryptomeria has several "teeth" on the ovuliferous scale - perhaps a reversion to a plesiomorphic morphology (see also Schulz & Stützel 2007).
Page (1990) suggested that there were "fundamental" differences between Cupressaceae and Taxodiaceae in the morphology of their reproductive parts, but in the tree of Quinn et al. (2002) Cupressaceae s. str. are embedded in a paraphyletic Taxodiaceae which form a basal grade. Phenetic analyses had earlier suggested the combination of the two (Eckenwalder 1976), and they are combined in Farjon (2005c). Cupressus has turned out to be polyphyletic and is now restricted to the Old World (Xiang & Li 2005; especially Little 2006).
For cone morphology, see Farjon and Garcia (2003) and Schulz and Stützel (2007: interesting analysis, but unfortunately Juniperus etc. not included).
Phylogeny. For relationships within Cupressaceae, see Brunsfeld et al. (1994), Gadek et al. (2000), Kusumi et al. (2000), Farjon et al. (2002), Brunsfeld et al. (2003), and Little et al. (2004). Callitris is paraphyletic, although morphological (Piggin & Bruhl 2010) and molecular (Pye et al. 2003) do not agree as to exactly how extensive the paraphyly is...
Classification. Ca 30 genera and 22 possible families says a lot about the past. For a monograph (and far more) see Farjon (2005c); general information can of course be found in the Gymnosperm Database. For generic limits around Cupressus, see Price and Adams (2009) and Little (2006) and around Callitris, see Pye et al. 2003) and Piggin and Bruhl (2010); for an account of Juniperus, see Adams (2010).
Botanical Trivia. Juniperus forms the highest known forest growing at some 4,900 m altitude on the Tibetan Plateau (Opganoorth et al. 2010). The tallest living tree in the world is a coast redwood Sequoia sempervirens, at about 115.5 metres (379 feet), although the giant redwood (Sequoiadendron giganteum is larger.
Synonymy: Actinostrobaceae Lotsy, Arceuthidaceae A. V. C. F. Bobrov & Melikian, Arthrotaxidaceae Doweld, Callitraceae Seward, Cryptomeriaceae Gorozh., Cunninghamiaceae Siebold & Zuccarini, Diselmaceae A. V. C. F. Bobrov & Melikian, Fitzroyaceae A. V. C. F. Bobrov & Melikian, Juniperaceae Brechtold & J. Presl, Libocedraceae Doweld, Metasequoiaceae Hu & W. C. Cheng, Microbiotaceae Nakai, Neocallitropsidaceae Doweld, Pilgerodendraceae A. V. C. F. Bobrov & Melikian, Platycladaceae A. V. C. F. Bobrov & Melikian, Sequoiaceae Luersson, Taiwaniaceae Hayata, Taxodiaceae Saporta, Tetraclinaceae Hayata, Thujaceae Burnett, Thujopsidaceae Bessey, Widdringtoniaceae Doweld
TAXACEAE Berchtold & J. Presl Back to Pinales
Bands of fibres in phloem crystalliferous, sclereids + [Taxus]; plant dioecious (monoecious); pollen inaperturate; ovules erect; pollen chamber +, pollination drop +; male gametes unequal in size; seed associated with fleshy structures.
6/30. Northern Hemisphere, scattered, also New Caledonia.
2-3 microsporangia/microsporophyll; ovuliferous scale much reduced, ovules 2/scale; female gametophyte with 1024-4096 free nuclei; seed coat vascularized, with sarco- and sclerotesta; ?embryo; n = 12.
1/6. E. Himalayas to Japan (map: from Florin 1963). [Cephalotaxus koreana Photos - Collection, C. fortunei, Collection.]
Synonymy: Cephalotaxaceae F. W. Neger
Wood and phloem lack resin canals; 2-6 microsporangia/microsporophyll; ovule solitary, on shoot in axil of vegetative leaf; female gametophyte with ca 256 free nuclei; seed arillate; embryo short/minute (cotyledons 3); n = 7, 11, 12.
5/24: Taxus (8). Scattered in the Northern Hemisphere, esp. South East Asia, also New Caledonia (map: from Florin 1963). [Photos - Collection.]
Synonymy: Amentotaxaceae Kudô & Yamamoto, Austrotaxaceae Nakai, Torreyaceae Nakai
Evolution. Bacterial/Fungal Associations. Taxol and related compounds are synthesised by Taxus and also by several fungi that either grow in the soil around the plant or are endophytes (Cassady et al. 2004 and references), and it has been suggested that the fungus may have acquired the ability to synthesize taxol from the plant (Strobel et al. 1996). Pestalotiopsis guepinii, which can synthesize taxol, is also endophytic in Wollemia (Araucariaceae), etc. (Strobel et al. 1997)
Chemistry, Morphology, etc. (S)norcolaurine synthase activity is high in both Cephalotaxus and other Taxaceae; this might suggest that benzyisoquinoline alkaoids may be found here (Liscombe et al. 2005). Cephalotaxus contains some very distinctive alkaloids (Parry et al. 1980).
The scales subtending the ovules of Austrotaxus are spiral. Taxus and its immediate relative have female cones with a single ovule and the seed is surrounded by an aril.
For the morphology of Taxus and relatives, see Hart and Price (1990), for male reproductive structures, see Wang et al. (2008), for male gametes, see Chamberlain (1935) and Singh (1978), for the megasporangiate cone, see André (1956) and Liang and Wang (1989), for embryology in general, see Chen and Wang (1990: the sperm range from somewhat to very unequal in size), and for a general account, see Cope (1998).
Phylogeny. Page (1990) included Amentotaxus in Cephalotaxaceae, although he noted that affinities between the two were "somewhat enigmatic"; a family as so delimited appears para- or polyphyletic to Taxaceae s. str. in Quinn et al. (2002), Price (2003) and Hao et al. (2010). Although Hao et al. (2008) preferred to keep the two families separate, support for this was low; for phylogeny, see also Cheng et al. (2000). Rai et al. (2009) also found Cephalotaxaceae were sister to Taxaceae. For general information, see the Gymnosperm Database.
Previous Classifications. Cephalotaxaceae and Taxaceae have sometimes been separated (see introduction to Pinales above), and Taxus has sometimes been considered quite distinct from all other conifers (e.g. Florin 1958).