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.

VITALES + ROSIDS: anthers articulated [± dorsifixed, transition to filament narrow, connective thin].

ROSIDS: (nectary receptacular); embryo long; genome duplication; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.

MALVIDAE = [GERANIALES + MYRTALES] [CROSSOSOMATALES [PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]]]: ?

CROSSOSOMATALES [PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]]: ?

PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]: 2 apical pendulous ovules/carpel.

Chemistry, Morphology, etc. The position of the character of ovule number on the tree is unclear. However, taxa with one or two usually apical ovules/carpel are common in the rosid II clade.

Phylogeny. See the Dilleniales and the Saxifragales pages for further discussion on the relationships of the malvids in general and of Picramniales in particular.

PICRAMNIALES Hutchinson  Main Tree, Synapomorphies.

C₁₈ acetylenic tariric acid, petroselenic acid [both in seed oils], anthraquinones, anthracenone moieties linked to C₅-sugar derivatives +; vessel elements with simple perforations; staminate flowers: stamens = and opposite petals; ?seed coat; ?endosperm, ?embryo. - 1 family, 2 genera, 46 species.

PICRAMNIACEAE Fernando & Quinn

Trees; bark bitter or very bitter; leaves spiral, odd-pinnate, leaflets conduplicate, often ± alternate, extrafloral nectaries +, stipules 0; plant dioecious, inflorescence racemose, flowers 3-5(-6)-merous, small, K connate basally (free); staminate flowers: pollen?, disc, pistillode minute; carpellate flowers: staminodes [?nectariferous] +; G [2-3], micropyle ?bistomal, styles recurved, pointed; endosperm ?development; n = ?

2[list]/46. Neotropical.

1. Picramnioideae Engler

Ovules epitropous; fruit a berry; seed coat ca 6 cells across, vascularised, unlignified, or two subepidermal layers lignified, inner layers crushed; embryo minute.

1/41. S.E. USA, Central and South America, Caribbean (map: from Pirani 1990). [Photo - Fruit]

2. Alvaradoideae Liebm.

Vascular tracheids +; staminate flowers: C usu. 0; carpellate flowers: staminodes opposite sepals, only 1 G fertile, ovules apotropous, basal; fruit a samaroid capsule; exotesta resinous, endotegmen as a resinous membrane; endosperm 0, cotyledons large.

1/5. Florida, Central America, Bahama, esp. the Greater Antilles, Bolivia to Argentina (map: from Thomas 1990). [Photo - Fruit]

• Picramniaceae are often rather small trees with bitter-tasting bark and spirally-arranged, compound leaves; the leaflets alternate along the rachis. The small flowers are born in a raceme, and the stamens are equal to and opposite the petals.

Chemistry, Morphology, etc. The bitter taste in the bark is probably caused by the presence of sugar-linked anthracenone derivatives (Jacobs 2003). Indeed, Jacobs (2003) emphasizes the distinctive nature of their secondary metabolites, these anthracenone moieties linked to C₅-sugar derivatives apparently being unknown in any other plants and the C₁₈acetylenic acid, tariric acid, is also unknown from other flowering plants (see also Bohlmann et al. 1973; Badami & Patil 1981). For some chemistry of Alvaradoa, see Villatoro et al. (1974).

The family is very poorly known; I have seen only Picramnia in the field. Xylem parenchyma is rather scanty to absent. Fiber tracheids dominate, but Alvaradoideae commonly have vascular tracheids (Webber 1936). Picramnia may have unilacunar nodes with three or more traces; the hairs are unicellular and have distinctive golden contents (M. Ogburn, pers. comm.).

For general information, see Fernando and Quinn (1995) and Kubitzki (2006b), and for chemistry, see Hegnauer (1973, 1990) and Stuhlfauth et al. (1985), both as Simaroubaceae, and especially Jacobs (2003). Rao (1970) briefly mentions the seed coat of Alvaradoa. Additional data are taken from seeds of Alvaradoa (Núñez et al. 83), Picramna sellowiana (Vásquez & Jaramillo 11419) and P. latifolia (Aguilar 5020).

Previous Relationships. Picramniaceae were placed between Rosid I, which includes Surianaceae and Irvingiaceae (ex Simaroubaceae), and Rosid II, which includes Simaroubaceae themselves, by Fernando et al. (1995), but in the past they have usually been placed within Simaroubaceae (e.g. Cronquist 1981; Takhtajan 1997) with which they agree in their bitter bark, compound leaves and small flowers.