LIGNOPHYTA

True roots +; lateral meristems: cork cambium producing cork abaxially, vascular cambium producing phloem abaxially and xylem adaxially.

EXTANT SEED PLANTS/SPERMATOPHYTA

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 derived from (some) sinapyl and particularly coniferyl alcohols, thus containing p-hydroxyphenyl and guaiacyl lignin units, (lignins derived from p-coumaryl alcohol, i.e. S [syringyl] lignin units); true roots present, apex multicellular, xylem exarch, and 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 and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, plastids with starch grains; phloem fibres +; stem cork cambium superficial, root cork cambium deep seated; leaves with single trace from sympodium ["nodes 1:1"]; stomata ?; leaf vascular bundles collateral; leaves megaphyllous [determinancy evolved first, then ad/abaxial symmetry], spiral, simple, lamina with vein density up to 5 mm/mm² [mean for all non-angiosperms 1.8]; axillary buds associated with at most some leaves; prophylls [including bracteoles] two, lateral; 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, developing after pollination, 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 duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.

MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], S [syringyl] lignin units common, positive Maüle reaction [syringyl:guaiacyl ratio more 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; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, with gelatinous fibres; 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 cells from same mother cell that gave rise to the sieve tube; sugar transport in phloem passive; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves petiolate, lamina [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; most/all leaves with axillary buds; flowers perfect, pedicellate, polysymmetric, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P not sharply differentiated, with a single trace, outer members not enclosing the rest of the bud, often smaller than inner members; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], ± embedded in the filament, 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, 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, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, dry [not secretory]; 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, megaspore tetrad linear, functional megaspore chalazal, lacking sporopollenin and cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; P deciduous in fruit; seed exotestal; pollen binucleate at dispersal, trinucleate eventually, germinating in less than 3 hours, pollination siphonogamous, tube elongated, growing at 80-600 µm/hour, with pectic outer wall, callose inner wall and callose plugs, growing between cells, penetration of ovules via micropyle [porogamous] within ca 18 hours, distance to first ovule 1.1.-2.1 mm, tube moves between nucellar cells; double fertilisation +, endosperm diploid, cellular [micropylar and chalazal domains develop diffently, 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, embryo cellular ab initio, minute; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, 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]].

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. This is because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied, there is considerable homoplasy as well as variation within and between families of the ANITA grade 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... For other features such as details of sugar transport in the phloem, their placement on the tree is frankly speculative. Finally, for features such as parietal tissue/a nucellus only one (Nymphaeales) to three cells thick above the embryo sac and a stylar canal lacking an epidermal layer, although plesiomorphous for basal grade angiosperms (Williams 2009), I am unsure where on the tree a thicker nucellus and a stylar epidermal layer are acquired.

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

[PETROSAVIALES [[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]]: cyanogenic glycosides uncommon; starch grains simple, amylophobic; stomata anomocytic, (cuticular waxes as parallel platelets); colleters 0.

Evolution. Divergence & Distribution. The stem-group age of this whole group ("core monocots") is ca 131 million years before present, the crown group age ca 126 million years before present (Janssen & Bremer 2004). Magallón and Castillo (2009) suggest ca 150 million years for relaxed and 124 million years for constrained penalized likelihood datings of the divergence of Petrosaviales from other monocots.

Subsequent branching in this general part of the tree - i.e. the Petrosaviales, Dioscoreales + Pandanales, and Liliales clades, and including crown group Petrosaviales, may be somewhere around 125-120 million years before present (ca 111 million years before present in Bremer 2000b), and the stem groups of all other orders, including those in the commelinid group, diverge by ca 115 million years before present or soon afterwards (Janssen & Bremer 2004). These and also many clades within all these orders may have originated in Southern Gondwana, i.e. Antarctica, Australasia, and southern South America (Bremer & Janssen 2006).

Phylogeny. The relationships between commelinids, Asparagales, Dioscoreales, Liliales, and Pandanales remained unclear for some time. A three-gene (rbcL, atpB, 18S RNA) study (Chase et al. 2000a) showed a polytomy of Petrosaviaceae, Dioscoreales, Pandanales, Liliales, Asparagales and commelinids, although a single shortest tree showed a pectinate structure with the taxa in the sequence of the list above; another analysis with placeholders for taxa missing some sequences gave a similar structure, except that Pandanales and Liliales were sister taxa. (Note that a combined morphological plus molecular tree in the same volume [Stevenson et al. 2000] suggested a substantially different set of relationships; bootstraps were not given.) Fay et al. (2000a) also suggested a sister relationship between Asparagales and commelinids, although sampling outside Asparagales was sketchy since it was outside their immediate interest. Hilu et al. (2003: matK) i.a. suggested that Orchidaceae might be separate from other Asparagales (the latter being sister to commelinids) and that Dioscoreales and Pandanales formed a clade.

However, a two-gene (matK, rbcL) study (Tamura et al. 2004a) began to clarify the situation considerably. Petrosaviaceae (both genera were studied) were sister to a clade including [Dioscoreaceae + Pandanaceae], then Liliales diverged, while Asparagales were sister to the commelinids (i.e. a topology rather like that in the most parsimonious tree mentioned above in Chase et al. 2000a). Support was quite high (³85% bootstrap) for all order and family branches, although rather lower for [Asparagales + commelinids] (68%) (see also Tamura et al. 2004b, a smaller study). The topology in Janssen and Bremer (2004) was broadly similar, except that the all orders just mentioned were successive branches of the tree. Davis et al. (2004) also found Petrosaviales to be sister to the same monocots, but with moderate to weak (>72%) support. Graham et al. (2006) in a study analysing considerable amounts of data also recovered relationships similar to those suggested by Tamura et al. (2004a), all sister taxon relationships in this area having 94% or more support, although that for [Liliales [commelinids + Asparagales]] was only 70% (see also Givnish et al. 2006b; Chase et al. 2006). Dioscoreales and Pandanales are sister taxa in several studies (e.g. Hilu et al. 2003; Tamura et al. 2004a, b; see also Graham et al. 2006; Chase et al. 2006; Qiu et al. 2010, support strong). In other trees they have been found to be adjacent along the spine when the major polytomy in the monocots (inc. Asparagales, Liliales) is resolved (e.g. Janssen & Bremer 2004; Bremer & Janssen 2006; Givnish et al. 2006b, not a strongly supported position), or are parts of adjacent branches (for the latter, see Davis et al. 2004, who also summarize earlier literature on relationships of the two). Although a recent four-gene mitochondrial tree suggests relationships [Asparagales [[Dioscoreales + Pandales} [Liliales + Commelinids]]], support is not strong (Qiu et al. 2010).

Classification. Since no firm association of Petrosaviaceae with any other order has been supported, and its phylogenetic position, as in the tree here, seems well supported, a monofamilial Petrosaviales is appropriate.

PETROSAVIALES Takhtajan  Main Tree, Synapomorphies.

Stem with a ring of bundles; sieve tube plastids also with polygonal protein crystalloids; microsporogenesis simultaneous; pollen surface gemmate; septal nectaries +; styluli +; fruit a follicle; seed endotestal. - 1 family, 2 genera, 4 species.

Evolution. Divergence & Distribution. Stem-group Petrosaviales are dated to ca 126 million years before present (Janssen & Bremer 2004), while Magallón and Castillo (2009) suggest ca 150 million years for relaxed and 124 million years for constrained penalized likelihood ages.

Includes Petrosaviaceae.

Synonymy: Miyoshiales Nakai - Petrosaviineae Shipunov

PETROSAVIACEAE Hutchinson

(Plant echlorophyllous, myco-heterotrophic, vascular bundles in stem forming a cylinder, vessels 0 - Petrosavia); hairs 0; leaves spiral, scaly on rhizome, base?; bracteoles sublateral or 0; T members with a single trace, whorls slightly differentiated [outer somewhat smaller], tube at most short; A inserted at base of T or free; ovary superior to semi-inferior, partly connate, plicate, fusion (congenital and) postgenital, stigma subcapitate or decurrent; ovules 4-many/carpel, ana-campylotropous, integumentary obturator +; fruit also septicidal [Japonolirion], T persistent [?Petrosavia]; seeds obliquely arranged, winged or not, endotegmen crushed, contents persist; embryo small; n = 12, 13, 15; seedling?

2[list]/4. Japan and China, W. Malesia (map: from Jessop 1979).

Evolution. Divergence & Distribution. Crown group Petrosaviaceae date to ca 123 million years before present (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The roots of Petrosavia have an unmedullated, four-radiate stele. Remizowa (2011) sugests that the position of the septal nectaries in both the ascidiate and plicate zone of the gynoecium might be unique and so a synapomorphy for this tiny but heterogeneous clade.

For general information, see Tamura (1998, in Nartheciaceae) and especially Cameron et al. (2003), for anatomy, see Stant (1970), for sieve tube plastids, see Behnke (2003), for floral and inflorescence morphology, see Remizowa et al. (2006a, b) and Tobe (2008), and for the embryology of Petrosavia, see Tobe and Takahashi (2009: nice comparative table).

Previous Relationships. Petrosaviaceae have often been included in other families, thus Dahgren et al. (1985) placed them - along with representatives here placed in Nartheciaceae and Tofieldiaceae - in Melianthaceae, and while Tamura (1998) recognised a Petrosaviaceae, he also included members of Tofieldiaceae and Nartheciaceae in them. Petrosaviaceae s. str. (i.e. Petrosavia alone) were placed in Triuridales by Cronquist (1981) and in Triurididae by Takhtajan (1997); the latter included a monogeneric Japonoliriaceae in Melanthiales-Liliidae.

Synonymy: Japonoliriaceae Takhtajan, Miyoshiaceae Nakai