EXTANT SEED PLANTS

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 rich in guaiacyl units; true roots present, apex multicellular, xylem exarch, 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 +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; stem cork cambium superficial, root cork cambium deep seated; nodes ?; stomata ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral, veins -5 mm/mm2 [mean for all non-angiosperms 1.8]; 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, 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 duplication [N/O//A/C and P//BE lines], 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 in ANITA grade?], 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 a sieve plate and cytoplasm with P-proteins, companion cells from same mother cell that gave rise to the sieve tube; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm2, endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable; P not sharply differentiated, outer members not enclosing the rest of the bud, smaller than inner members; A many, 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, walls developing by centripetal furrowing; pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous or microperforate, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; nectary 0; G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, [outer integument often largely subdermal in origin, inner integument dermal], micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte four-celled [one-modular, nucleus of egg cell sister to one of the polar nuclei], stylulus short, hollow, stigma ± decurrent, dry [not secretory]; P deciduous in fruit; seed exotestal; pollen germinating in less than 3 hours, tube elongated, growing at 80-600 µm/hour, with callose plugs and callose-based walls, penetrating between cells, siphonogamy, penetration of ovules within ca 18 hours, distance to first ovule 1.1.-2.1 mm; 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, minute; 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 + C/PHYB + E gene pairs.

Evolution. Possible apomorphies for flowering plants 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, there is considerable variation between families in particular for several of these characters, and also because details of relationships among gymnosperms will affect the level at which some of these characters are pegged. For example, if reticulate-perforate pollen is optimized to the next node on the tree (see Friis et al. 2009 for a discussion), it effectively makes the pollen morphology of the common ancestor of all angiosperms ambiguous....

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates, axial parenchyma diffuse or diffuse-in-aggregate; tectum reticulate-perforate [here?]; ?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; tectum reticulate-perforate [here?], nucellar cap + [character lost where in eudicots?]; 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, antipodal cells persisting; endosperm triploid; ?germination.  Back to Main Tree

Chemistry, Morphology, etc. 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.

Phylogeny. 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 +.

Evolution. Although Soltis et al. (2008) suggest ages for a number of branching points in this clade, they are based on the topology [monocots [Chloranthaceae, magnoliids [Ceratophyllaceae + eudicots]]].

CHLORANTHALES J. F. Leroy  Main Tree, Synapomorphies.

Branching from the current flush; neolignans ?+; nodes often swollen, 2:2; leaves opposite, joined by sheath, 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 ovule/carpel, antipodal cells proliferating; 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, ± connate); staminode 0; stigma ± expanded or not, dry ?or wet; ovules with outer integument 4-8 (2 - Ascarina) and inner integument (3-)7-10 cells thick, (micropyle bistomal), nucellar cap +, antipodal cells multiply; fruit baccate or drupaceous, (bracts accrescent and succulent; P persistent); (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.]

Evolution. Chloranthaceous fossils are common, diverse, and world-wide in distribution in the early fossil record. Distinctive fossil pollen grains, Asteropollis are first known from the Barremian-Aptian of the early Cretaceous, some 125 million years before present (Friis et al. 1997; Doyle 1999; Eklund 1999); these grains have been identified as belonging 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). Estimates of the time of divergence of Chloranthaceae are 168-131(-126) million years before present, however, estimates of the age of crown group diversification are much more recent, being within the last 60-29 million years (Zhang & Renner 2003b; Soltis et al. 2008).

Endress (2001) emphasized what he considered to be the plesiomorphic floral morphology of the family. However, there is no evidence that it is a member of the ANITA grade, and several aspects of its floral morphology and development, including the loss of any perianth, are clearly derived (e.g. Li et al. 2005). For morphological evolution, living and fossil Chloranthaceae integrated, see Eklund et al. (2004).

Chemistry, Morphology, etc. 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). Roots - presumably those of the seedlings and young plants - apparently do not have any secondary thickening (Blanc 1986). Eklund et al. (1997) and Eklund (1999) discuss the nature of the androecium in the family, a matter over which there has been considerable controversy. 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, here as elsewhere staminate flowers seem to have but a single dithecal stamen (Kong et al. 2002, and references). The stylulus is filled with secretion. Endress and Igersheim (1997) describe the stigma as being wet (cf. Todzia 1988). The ovule 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. The cotyledonary nodes has split laterals (Bailey 1956).

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), and for floral development, see G. S. Li et al. (2005).

Phylogeny. 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).

Synonymy: Hedyosmaceae Caruel