EXTANT SEED PLANTS

Plant woody, evergreen; nicotinic acid metabolised to trigonelline; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins rich in guaiacyl units; true roots present, xylem exarch; shoot apical meristem complex; arbuscular mycorrhizae +; stem with ectophloic eustele, endodermis 0, xylem endarch; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; stem cork cambium superficial, root cork cambium deep seated; nodes ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores] +, mono[ana]sulcate, pollen exine and intine homogeneous, ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development endo/exosporic, gametes two, with cell walls; 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 duplication, mitochondrial nad1 intron 2 and coxIIi3 intron present.

MAGNOLIOPHYTA

Plant woody, evergreen; lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, cyanogenesis via tyrosine pathway, lignins derived from both coniferyl and sinapyl alcohols, containing syringaldehyde [in positive Maüle reaction, syringyl:guaiacyl ratio less than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0; stem with 2-layered tunica-corpus construction; wood fibers and wood parenchyma +; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides; tracheids +; sieve tubes eunucleate, with sieve plate, companion cells from same mother cell that gave rise to the tube, the sieve tube with P-proteins; nodes unilacunar; stomata with ends of guard cells level with aperture, paracytic; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, vein endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, numbers unstable, P not differentiated, outer members not enclosing the rest of the bud, A many, development centripetal, with a single trace, introrse, filaments stout, anther ± embedded in the filament, tetrasporangiate, dithecal, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally by action of hypodermal endothecium, endothecial cells elongated at right angles to long axis of anther, tapetum glandular, binucleate, microspore mother cells in a block, microsporogenesis successive, pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous, endexine compact, lamellate only in the apertural regions, pollen tube elongated, with callose plugs, penetrating between cells, growth rate moderate, siphonogamy occuring, nectary 0, G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte ?type, stylulus short, stigma ± decurrent, wet [secretory]; P deciduous in fruit; seed exotestal; double fertilisation +, endosperm ?diploid, cellular [first division oblique, micropylar end initially with a single large cell, chalazal end more actively dividing], copious, oily and/or proteinaceous, embryo cellular ab initio; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)n]; whole genome duplication, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and PHYA/PHYC gene pairs.

Possible apomorphies are in bold. Note that the actual level to which many of these features, particularly the more cryptic ones, should be assigned is unclear, because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied. Furthermore, details of relationships among gymnosperms will affect the level at which some of these characters are pegged.

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates; pollen tectate-columellate, tectum reticulate [perforated]; nucleus of egg cell sister to one of the polar nuclei; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]: ethereal oils in spherical idioblasts [lamina and P ± pellucid-punctate]; tension wood 0; nucellar cap + [character lost where?]; 12BP [4 amino acids] deletion in P1 gene.

[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: benzylisoquinoline alkaloids +; P more or less whorled, 3-merous [possible position], carpels plicate; embryo sac bipolar, 8 nucleate; endosperm triploid.  Back to Main Tree

For the distribution of isoquinoline alkaloids (alternatively - 1-benzyltetrahydroisoquinoline alkaloids, 1-btiq alkaloids), see Waterman 1999, 2007). The betalains of core Caryophyllales have biosynthetic similarities with these alkaloids. This is perhaps the best place to put triploid endosperm on the tree; the other would be as a synapomorphy for all angiosperms, but in that case it would subsequently be lost twice or lost once and then regained.

Relationships between the lineages immediately above the basal pectinations in the main tree, the ANITA grade (Amborellales, Nymphaeales and Austrobaileyales here), have only recently been clarified. The topology of the main tree in this area thus differs somewhat from that in A.P.G. II (2003). The optimisation of benzylisoquinoline alkaloids on the tree is unclear. They appear to occur in Chloranthaceae, the magnoliids, and eudicots, so if there is a clade [Chloranthaceae + magnoliids] [monocots [Ceratophyllaceae + eudicots]], as is provisionally recognized in this site, they may be best optimised here. For further information, see especially the discussion immediately preceding the Magnoliales, i.e. the magnoliid clade; Ceratophyllales, eudicots, and monocots are the other clades involved.

CHLORANTHALES + MAGNOLIIDS: sesquiterpenes +.

CHLORANTHALES J. F. Leroy  Main Tree, Synapomorphies.

Branching from the current flush; neolignans ?+; nodes often swollen, ?type; leaves opposite, toothed, teeth with lateral vein and others; stipules +; flowers very small, monosymmetric, parts whorled; P 0 (3), A 1, G 1, ± inferior, ascidiate, postgenital fusion by secretion, 1 apical straight [atropous] ovule/carpel; fruit fleshy; endotesta palisade, lignified, crystalliferous; (endosperm starchy, grains clustered). - 1 family, 4 genera, 75 species.

Includes Chloranthaceae.

Synonymy: Chloranthineae Thorne & Reveal - Chloranthanae Doweld - Chloranthidae C. Y. Wu

CHLORANTHACEAE Lindley, nom. cons.   Back to Chloranthales

Evergreen; wood storied; (vessels 0); primary stem with vascular cylinder; rays 6-10-seriate; nodes 1:1, 1:2, or ± 3:3, 2 traces from the central or all gaps, or split laterals; (sclereids - Hedyosmum); cuticle wax crystalloids 0; stomata variable; branching from current flush; leaves conduplicate [Chloranthus], teeth with clear persistent swollen cap, into which proceed higher order veins as well as secondaries or tertiaries, stipules small, paired, interpetiolar, usually on rim of sheath; (plants dioecious; flowers monosymmetric), staminate flowers: P 0, A 1 [abaxial], ± latrorse, lobed or connective produced or not, pistillode 0; carpellate flowers: (P + - Hedyosmum), staminode 0, outer integument 4-8 (2 - Ascarina) and inner integument (3-)7-10 cells thick, (micropyle bistomal), nucellar cap +, antipodal cells multiply, stigma ± expanded or not, dry ?or wet; fruit baccate or drupaceous (bracts accrescent and succulent); (mesotesta lignified - Chloranthus) tegmen ± crushed (exo- and mesotegmen fibrous), endotegmen initially subpalisade; n = 8, 14, 15, chromosomes (1-4(-10: Hedyosmum) µm long.

Chloranthaceae

4[list]/75: Hedyosmum (45). Tropics and subtropics, not Africa (Madagascar - Ascarina only) (Map: from Verdcourt 1986; Todzia 1988). [Photo - Leaf, Flower.]

Chloranthaceous fossils are common, diverse, and world-wide in distribution in the early fossil record. Fossil pollen grains, Asteropollis, are first known from the Barremian-Aptian of the early Cretaceous by 125 million years before present (Friis et al. 1997; Doyle 1999; Eklund 1999); these grains are assignable to Hedyosmum (see also Eklund et al. 2003; Friis et al. 2005 - see also Doyle & Endress 2007 for other palynomorphs that have been assigned to Chloranthaceae).

Endress (2001) has emphasized what he considered to be the plesiomorphic floral morphology of the family, although there is no evidence that it is a member of the ANITA grade; a number of aspects of floral development, including the loss of the perianth, are clearly derived (e.g. Li et al. 2005). Within Chloranthaceae, morphological analyses, including details of wood anatomy, suggested the genus pairs Ascarina + Hedyosmum, mainly woody, plant monoecious to dioecious, and Chloranthus + Sarcandra, herbaceous to semi-shrubby, flowers perfect. In molecular work (Qiu et al. 1999), on the other hand, the relationships Hedyosmum [Ascarina [Chloranthus + Sarcandra]] were found. Although they had strong support, the sampling was rather minimal, but these relationships were confirmed by Zhang and Renner (2003b) with a much improved sampling. They were also found in recent morphological analyses with constrained outgroups (Doyle et al. 2003; Eklund et al. 2004).

Although benzylisoquinoline alkaloids apparently have not been detected in Chloranthaceae, (S)norcolaurine synthase activity is high, suggesting that they may be found here (Liscombe et al. 2005). Eklund et al. (1997) and Eklund (1999) discuss the nature of the androecium in the family. In Chloranthus it has been suggested that the androecium is lobed, with 2 or 4 dithecal stamens(!!?), and that staminate flowers of Hedyosmum have hundreds of anthers, however, staminate flowers in general seem to have but a single dithecal stamen (Kong et al. 2002, and references). The style is filled with secretion.

Roots - presumably those of the seedlings and young plants - apparently do not have any secondary thickening (Blanc 1986). Endress and Igersheim (1997) describe the stigma as being wet (cf. Todzia 1988). The ovules in Chloranthus is only subatropous (Yamada et al. 2001a). For variation in micropyle type, see Heo and Tobe (1995). Johri et al. (1992) noted that the endosperm stores oil, but there may also be starch.

For general information, see Swamy (1953), Todzia (1988, 1993) and Eklund (1999), for chemistry, see Hegnauer (1964, 1989), young plants, see Blanc (1986), general vegetative anaomy, see Metcalfe (1987), for wood anatomy, see Carlquist (1992), for morphological evolution, living and fossil Chloranthaceae integrated, see Eklund et al. (2004), and for floral development, see G. S. Li et al. (2005).

Synonymy: Hedyosmaceae Caruel