EMBRYOPSIDA Pirani & Prado

Gametophyte dominant, independent, multicellular, thalloid, with single-celled apical meristem, showing gravitropism; rhizoids +, unicellular; acquisition of phenylalanine lysase [PAL], phenylpropanoid metabolism [lignans +, flavonoids + (absorbtion of UV radiation)], xyloglucans +; plant [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; cuticle +; cell wall also with (1->3),(1->4)-ß-D-MLGs [Mixed-Linkage Glucans]; chloroplasts per cell, lacking pyrenoids; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles in vegetative cells 0, metaphase spindle anastral, predictive preprophase band of microtubules, phragmoplast + [cell wall deposition spreading from around the spindle fibres], plasmodesmata +; antheridia and archegonia jacketed, stalked; spermatogenous cells monoplastidic; blepharoplast, bicentriole pair develops de novo in spermatogenous cell, associated with basal bodies of cilia [= flagellum], multilayered structure [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] + spline [tubules from L1 encircling spermatid], basal body 200-250 nm long, associated with amorphous electron-dense material, microtubules in basal end lacking symmetry, stellate array of filaments in transition zone extended, axonemal cap 0 [microtubules disorganized at apex of cilium]; male gametes [spermatozoids] with a left-handed coil, cilia 2, lateral; oogamy; sporophyte dependent on gametophyte, embryo initially surrounded by haploid gametophytic tissue, plane of first division horizontal [with respect to long axis of archegonium/embryo sac], suspensor/foot +, cell walls with nacreous thickenings; sporophyte multicellular, with at least transient apical cell [?level], sporangium +, single, dehiscence longitudinal; meiosis sporic, monoplastidic, microtubule organizing centre associated with plastid, cytokinesis simultaneous, preceding nuclear division, sporocytes 4-lobed, with a quadripolar microtubule system; spores in tetrads, sporopollenin in the spore wall, initially laid down in association with several trilamellar layers [white-line centred layers, i.e. walls multilamellate]; nuclear genome size <1.4 pg, LEAFY gene present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes.

Many of the bolded characters in the characterization above are apomorphies of subsets of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.

All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group, [] contains explanatory material, () features common in clade, exact status unclear.

STOMATOPHYTES

Abscisic acid, ?D-methionine +; sporangium - tapetum +, columella + [developing from endothecial cells], seta developing from basal meristem [between epibasal and hypobasal cells]; stomata +, anomocytic, cell lineage that produces them with symmetric divisions [perigenous]; underlying similarities in the development of conducting tissue and in rhizoids/root hairs; spores trilete; polar transport of auxins and class 1 KNOX genes expressed in the sporangium alone; shoot meristem patterning gene families expressed; MIKC, MI*K*C* and class 1 and 2 KNOX genes, post-transcriptional editing of chloroplast genes; gain of three group II mitochondrial introns.

[Anthocerophyta + Polysporangiophyta]: archegonia embedded/sunken in the gametophyte; sporophyte long-lived, chlorophyllous; sporophyte-gametophyte junction interdigitate, sporophyte cells showing rhizoid-like behaviour.

POLYSPORANGIOPHYTA†

Sporophyte branched, branching apical, dichotomous; sporangia several, each opening independently; spore walls not multilamellate [?here].

EXTANT TRACHEOPHYTA / VASCULAR PLANTS

Photosynthetic red light response; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; (condensed or nonhydrolyzable tannins/proanthocyanidins +); sporophyte soon independent, dominant, with basipetal polar auxin transport; lignins +; vascular tissue +, G- and S-type tracheids, sieve cells + [nucleus degenerating], tracheids +, in both protoxylem and metaxylem, plant endohydrous [physiologically important free water inside plant]; endodermis +; leaves spirally arranged, blades with mean venation density 1.8 mm/mm2 [to 5 mm/mm2]; sporangia adaxial on the sporophyll, derived from periclinal divisions of several epidermal cells, wall multilayered [eusporangium]; columella 0; tapetum glandular; gametophytes exosporic, green, photosynthetic; basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; placenta with single layer of transfer cells in both sporophytic and gametophytic generations, root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].

[MONILOPHYTA + LIGNOPHYTA]

Sporophyte branching ± indeterminate; root apex multicellular, root cap +, lateral roots +, endogenous; endomycorrhizal associations + [with Glomeromycota]; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangia borne in pairs and grouped in terminal trusses, dehiscence longitudinal, a single slit; cells polyplastidic, microtubule organizing centres not associated with plastids, diffuse, perinuclear; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; LITTLE ZIPPER proteins.

LIGNOPHYTA†

Sporophyte woody; lateral root origin from the pericycle; branching lateral, meristems axillary; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].

SEED PLANTS†

Plants heterosporous; megasporangium surrounded by cupule [i.e. = unitegmic ovule, cupule = integument]; pollen lands on ovule; megaspore germination endosporic [female gametophyte initially retained on the plant].

EXTANT SEED PLANTS / SPERMATOPHYTA

Plant 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 particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; root stele with xylem and phloem originating on alternate radii, cork cambium deep seated; mitochondrial density in whole SAM 1.6-6.2[mean]/μm2 [interface-specific mitochondrial network]; stem with vascular cylinder around central pith [eustele], phloem abaxial [ectophloic], endodermis 0, xylem endarch [development centrifugal]; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaves with single trace from vascular sympodium [nodes 1:1]; stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; axillary buds exogenous, (none; not associated with all leaves); prophylls two, lateral; leaves with petiole and lamina, development basipetal, blade simple; plant heterosporous, sporangia borne on sporophylls, sporophylls spiral; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation with deposition of sporopollenin from tapetum there], exine and intine homogeneous; megasporangium indehiscent; ovules with parietal tissue 2+ cells across, megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte development initially endosporic, lacking chlorophyll, not photsynthesising, dependent on sporophyte, apical cell 0, rhizoids 0, development continuing outside the spore; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; female gametophyte initially syncytial, walls then surrounding individual nuclei; embryo cellular ab initio, endoscopic, plane of first cleavage of zygote transverse, suspensor +, short-minute, embryonic axis straight [shoot and root at opposite ends; plant allorhizic], cotyledons 2; plastid transmission maternal; ycf2 gene in inverted repeat, whole nuclear genome duplication [ζ - zeta - duplication], 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 trans- nad2i542g2 and coxIIi3 introns present.

ANGIOSPERMAE / MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], lignin also with syringyl units common [G + S lignin, positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], 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, hypodermis suberised and with Casparian strip [= exodermis +]; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, associated gelatinous fibres [g-fibres] with innermost layer of secondary cell wall rich in cellulose and poor in lignin; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, cytoplasm not occluding pores of sieve plate, companion cell and sieve tube from same mother cell; sugar transport in phloem passive; nodes 1:?; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule, reduction in stomatal conductance to increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, venation hierarchical-reticulate, secondary veins pinnate, veins (1.7-)4.1(-5.7) mm/mm2, endings free; most/all leaves with axillary buds; flowers perfect, pedicellate, ± haplomorphic; protogynous; parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P +, members each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], sporangium pairs dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, endothecial cells elongated at right angles to long axis of anther; (tapetum glandular), cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine lamellate only in the apertural regions, thin, compact; nectary 0; carpels present, superior, free, several, ascidiate, with postgenital occlusion by secretion, stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, stigma wet, extragynoecial compitum +; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across [crassinucellate], nucellar cap?; megasporocyte single, hypodermal, functional megaspore, chalazal, lacking cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; ovule not increasing in size between pollination and fertilization; pollen grains land on stigma, bicellular at dispersal, mature male gametophyte tricellular, germinating in less than 3 hours, pollen tube elongated, unbranched, growing between cells, growth rate (20-)80-20,000 µm/hour, apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametes lacking cell walls, cilia 0, siphonogamy; double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; mature seed much larger than ovule when fertilized, small [], dry [no sarcotesta], exotestal; endosperm diploid, cellular, heteropolar [micropylar and chalazal domains develop differently, first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous; dark reversal Pfr → Pr; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome size <1.4 pg [1 pg = 109 base pairs], whole nuclear genome duplication [ε - epsilon - duplication]; protoplasm dessication tolerant [plant poikilohydric]; ndhB gene 21 codons enlarged at the 5' end, 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 three copies of the PHY gene, [PHYB [PHYA + PHYC]].

[NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]]: wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood +; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; carpels plicate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.

[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [possible position]; pollen tube growth intra-gynoecial [extragynoecial compitum 0]; embryo sac bipolar, 8 nucleate, antipodal cells persisting; endosperm triploid.

[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (extra-floral nectaries +); (veins in lamina often 7-17 mm/mm2 or more [mean for eudicots 8.0]); (stamens opposite [two whorls of] P); (pollen tube growth fast).

[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0.

EUDICOTS: (Myricetin, delphinidin +), asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; (vessel elements with simple perforation plates in primary xylem); nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic; protandry common; K/outer P members with three traces, ("C" +, with a single trace); A few, (polyandry widespread, initial primordia 5, 10, or ring, ± centrifugal), filaments fairly slender, anthers basifixed; microsporogenesis simultaneous, pollen tricolpate, apertures in pairs at six points of the young tetrad [Fischer's rule], cleavage centripetal, wall with endexine; G with complete postgenital fusion, stylulus/style solid [?here]; seed coat?

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

Evolution. Estimates of the age of divergence within this clade (but as [Proteales [Sabiales [Buxales [Trochodendrales....]) range from (138-)125, 121(-110) m.y. (see Bell et al. 2010 for details), while Magallón and Castillo (2009) suggest ages of ca 122.8 and 123.6 (relaxed and constrained penalized likelihood ages) m.y. for the clade.

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 temporarily adopted here. For further discussion see the Ranuculales page, and for an updated discussion on Sabiaceae and its relationships, see the Proteales page - I think that is where Sabiaceae will end up.

SABIALES Takhtajan  Main Tree.

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

Note: (....) denotes a feature common in the clade, exact status uncertain, [....] includes explanatory material. Possible apomorphies are in bold. However, the actual level at which many of these features, particularly the more cryptic ones, should be assigned is unclear. This is partly because many characters show considerable homoplasy, in addition, basic information for all too many is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there is the not-so-trivial issue of how ancestral states are reconstructed (see above).

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.

Sabiaceae

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

Evolution. Fossils of Sabiaceae are known from the Cretaceous-Cenomanian (ca 98 m.y. 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 m.y. before present, crown group Sabiaceae 119-91 m.y. before present, and Magallón and Castillo (2009: Sabiaceae part od the eudicot pectination) offer the figure of ca 123.2 m.y. for the stem age.

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