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.

[SABIACEAE + PROTEALES] [TROCHODENDRALES [BUXALES + CORE EUDICOTS]]]: (axial/receptacular nectary +).

Chemistry, Morphology, etc. For the distinction between gynoecial (supposedly asterids only) and receptacular nectaries, see Smets (1988) and Smets et al. (2003); for a general survey of nectaries, see Bernadello (2007).

Phylogeny. The position of Sabiaceae has been unclear. Worberg et al. (2007: Ophiocaryon not included) found Sabiaceae to be sister to all other [eudicots minus Ranunculaceae], although with little more than 80% jacknife support; this position is adopted here. For further discussion see the Ranuculales page.

SABIALES Takhtajan  Main Tree, Synapomorphies.

P = K + C, pollen colporate, nectary a thin ± lobed disc; G connate, 1 or 2 pendulous campylotropous ovules/carpel, micropyle 0; seed with condyle [placental intrusion]; endosperm helobial, embryo long, curved. - 1 family, 3 genera, 100 species.

Includes Sabiaceae.

Synonymy: Meliosmales C. Y. Wu et al.

SABIACEAE Blume, nom. cons.   Back to Main Tree

Evergreen (deciduous) trees or lianes; pentacyclic triterpenoids +, tanniniferous, benzylisoquinoline alkaloids?; vessel elements with simple to scalariform perforation plates, bars few (-30); wood with broad rays (0 - Sabia), (true tracheids +; pits vestured - Meliosma); secondary phloem with broad or flaring rays; nodes complex unilacunar [Meliosma]; (sieve tube plastids also with protein crystalloids); cuticle wax crystalloids 0; stomata also paracytic; buds perulate or not; leaves spiral or two-ranked, simple to odd-pinnately compound, conduplicate [Meliosma], teeth ± spiny or 0; flowers poly- or obliquely monosymmetric, (3-)5-merous, K C A opposite each other, latter basally adnate to C, (2 A fertile, with 2 basal processes and opposing C small, 2-3 A staminodial - Meliosma, Ophiocaryon); A 5 (Sabia), disporangiate [?Ophioocaryon], dehiscence transverse or valvular; G [2-3], completely closed (also secretory canal), when 2, oblique or median, ovules apotropous, (Sabia - unitegmic, integument 6 cells across), styluli (marginal - Ophiocaryon) short, stigmas punctate, wet; fruit a (bilobed) ± drupelet to ± dry, dehiscent, (styluli excentric); seed coat ?; chalazal endosperm haustoria +, (embryo ± spiral or coiled), cotyledons usually folded; n = 12, 16.

3[list]/100: Meliosma (70). South East Asia to Malesia, tropical America (map: from van Beusekom 1973). [Photo - Flower] [Photo - Fruit]

• Sabiaceae are evergreen trees or lianes that may be recognised by the brochidodromous venation of their leaves or leaflets, their small flowers with the perianth whorls and stamens all opposite, and the more or less flattened and distinctly curved drupes; the surface of the latter is often distinctly venose.

Evolution. Fossils of Sabiaceae are known from the Cretaceous-Cenomanian (ca 98 million years before present, Insitiocarpus, c.f. Meliosma) and -Turonian (Sabia) of Europe (Knobloch & Mai 1986). Anderson et al. (2005) date stem group Sabiaceae to 122-118 million years before present, crown group Sabiaceae 119-91 million years before present.

Sabiaceae are distinctive among members of the eudicot grade in that the perianth is differentiated into a calyx and corolla (Drinnan et al. 1994; Hoot et al. 1999) and there is a nectary that appears to be axial/receptacular. Meliosma has explosively dehiscent anthers that are held under tension by the complex staminodes, but there is also a kind of secondary pollination presentation in which pollen collects on the broad connective between the anthers sacs (Ronse De Craene & Wanntorp 2008 for discussion).

Chemistry, Morphology, etc. There have been arguments over the interpretation of the flower of Meliosma, especially of the nature of the perianth members; two sepals are smaller than the others and have been called bracteoles. According to Baillon (1874), the two carpels of Sabia are median; Wanntorp and Ronse de Craene (2007) illustrate those of Meliosma as being more or less collateral. Warburg (1896) drew the two carpels of Meliosma as being oblique to the vertical axis of the flowers, but median to the plane between the two bracteoles; van Beusekom and van der Water (1989) show the carpels as being oblique both to the vertical axis and to the plane between the bracteoles, and the flower could be called obliquely monosymmetric (for a careful study, see Wanntorp & Ronse de Craene 2007).

In Meliosma the integument does not grow over the apical part of the nucellus so there is no micropyle. Ophiocaryon paradoxum has a coiled embryo; it is known as the snake nut. For chemistry, see Hegnauer (1973, 1990), and for a general account, see Kubitzki (2006b).

Classification. For a revision of Sabia, see van de Water (1980).

Synonymy: Meliosmaceae Endlicher, Wellingtoniaceae Meisner