EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, initially ±globular, not motile, branched; showing gravitropism; glycolate oxidase +, glycolate metabolism in leaf peroxisomes [glyoxysomes], acquisition of phenylalanine lysase* [PAL], flavonoid synthesis*, microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, CYP73 and phenylpropanoid metabolism [development of phenolic network], xyloglucans in primary cell wall, side chains charged; plant poikilohydrous [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; thalloid, leafy, with single-celled apical meristem, tissues little differentiated, rhizoids +, unicellular; chloroplasts several per cell, pyrenoids 0; centrioles/centrosomes in vegetative cells 0, microtubules with γ-tubulin along their lengths [?here], interphase microtubules form hoop-like system; metaphase spindle anastral, predictive preprophase band + [with microtubules and F-actin; where new cell wall will form], phragmoplast + [cell wall deposition centrifugal, from around the anaphase spindle], plasmodesmata +; antheridia and archegonia +, jacketed*, surficial; blepharoplast +, centrioles develop de novo, bicentriole pair coaxial, separate at midpoint, centrioles rotate, associated with basal bodies of cilia, multilayered structure + [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] (0), 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, asymmetrical; oogamy; sporophyte +*, multicellular, growth 3-dimensional*, cuticle +*, plane of first cell division transverse [with respect to long axis of archegonium/embryo sac], sporangium and upper part of seta developing from epibasal cell [towards the archegonial neck, exoscopic], with at least transient apical cell [?level], initially surrounded by and dependent on gametophyte, placental transfer cells +, in both sporophyte and gametophyte, wall ingrowths develop early; suspensor/foot +, cells at foot tip somewhat haustorial; sporangium +, single, terminal, dehiscence longitudinal; meiosis sporic, monoplastidic, MTOC [= MicroTubule Organizing Centre] associated with plastid, sporocytes 4-lobed, cytokinesis simultaneous, preceding nuclear division, quadripolar microtubule system +; wall development both centripetal and centrifugal, 1000 spores/sporangium, sporopollenin in the spore wall* laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae]; plastid transmission maternal; nuclear genome [1C] <1.4 pg, main telomere sequence motif TTTAGGG, KNOX1 and KNOX2 [duplication] and LEAFY genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes [precursors for starch synthesis], tufA, minD, minE genes moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.
Many of the bolded characters in the characterization above are apomorphies of more or less inclusive clades 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.
Sporophyte well developed, branched, branching dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].
II. TRACHEOPHYTA / VASCULAR PLANTS
Sporophyte long lived, cells polyplastidic, photosynthetic red light response, stomata open in response to blue light; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; plant endohydrous [physiologically important free water inside plant]; PIN[auxin efflux facilitators]-mediated polar auxin transport; (condensed or nonhydrolyzable tannins/proanthocyanidins +); borate cross-linked rhamnogalactan II, xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; roots +, often ≤1 mm across, root hairs and root cap +; stem apex multicellular [several apical initials, no tunica], with cytohistochemical zonation, plasmodesmata formation based on cell lineage; vascular development acropetal, tracheids +, in both protoxylem and metaxylem, G- and S-types; sieve cells + [nucleus degenerating]; endodermis +; stomata numerous, involved in gas exchange; leaves +, vascularized, spirally arranged, blades with mean venation density ca 1.8 mm/mm2 [to 5 mm/mm2], all epidermal cells with chloroplasts; sporangia in strobili, sporangia adaxial, columella 0; tapetum glandular; sporophyte-gametophyte junction lacking dead gametophytic cells, mucilage, ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; archegonia embedded/sunken [only neck protruding]; embryo suspensor +, shoot apex developing away from micropyle/archegonial neck [from hypobasal cell, endoscopic], root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].[MONILOPHYTA + LIGNOPHYTA]
Sporophyte growth ± monopodial, branching spiral; roots endomycorrhizal [with Glomeromycota], lateral roots +, endogenous; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangium dehiscence by a single longitudinal slit; cells polyplastidic, MTOCs diffuse, perinuclear, migratory; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; nuclear genome [1C] 7.6-10 pg [mode]; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; mitochondrion with loss of 4 genes, absence of numerous group II introns; LITTLE ZIPPER proteins.
Sporophyte woody; stem branching axillary, buds exogenous; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
SEED PLANTS† / SPERMATOPHYTA†
Growth of plant bipolar [plumule/stem and radicle/root independent, roots positively geotropic]; 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, free-nuclear/syncytial to start with, walls then coming to surround the individual nuclei, process proceeding centripetally.
EXTANT SEED PLANTS
Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); microbial terpene synthase-like genes 0; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignin chains started by monolignol dimerization [resinols common], particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; roots often ≥1 mm across, stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated, gravitropism response fast; stem apical meristem complex [with quiescent centre, etc.], plasmodesma density in SAM 1.6-6.2[mean]/μm2 [interface-specific plasmodesmatal network]; eustele +, protoxylem endarch, endodermis 0; 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; leaf nodes 1:1, a single trace leaving the vascular sympodium; leaf vascular bundles amphicribral; guard cells the only epidermal cells with chloroplasts, stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; branching by axillary buds, exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, lamina simple; sporangia borne on sporophylls; spores not dormant; 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, exine alveolar/honeycomb; ovules with parietal tissue [= crassinucellate], megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte ± wholly dependent on sporophyte, development initially endosporic [apical cell 0, rhizoids 0, etc.]; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends], primary root/radicle produces taproot [= allorhizic], cotyledons 2; embryo ± dormant; chloroplast ycf2 gene in inverted repeat, trans splicing of five mitochondrial group II introns, rpl6 gene absent; ??whole nuclear genome duplication [ζ/zeta duplication event], 2C genome size (0.71-)1.99(-5.49) pg, two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.
IID. ANGIOSPERMAE / MAGNOLIOPHYTA
Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANA 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 cap meristem closed (open); pith relatively inconspicuous, lateral roots initiated immediately to the side of [when diarch] or opposite xylem poles; epidermis probably originating 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; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, multiseriate rays +, wood parenchyma +; sieve tubes enucleate, sieve plates with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, not occluding pores of plate, companion cell and sieve tube from same mother cell; ?phloem loading/sugar transport; nodes 1:?; dark reversal Pfr → Pr; protoplasm dessication tolerant [plant poikilohydric]; stomata randomly oriented, brachyparacytic [ends of subsidiary cells ± level with ends of guard cells], outer stomatal ledges producing vestibule, reduction in stomatal conductance with increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, secondary veins pinnate, fine venation hierarchical-reticulate, (1.7-)4.1(-5.7) mm/mm2, vein endings free; flowers perfect, pedicellate, ± haplomorphic, protogynous; parts free, numbers variable, development centripetal; P = T, petal-like, 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], each theca dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, cells elongated at right angles to long axis of anther; tapetal cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine restricted to the apertural regions, thin, compact, intine in apertural areas thick, orbicules +, pollenkitt +; nectary 0; carpels present, superior, free, several, spiral, ascidiate [postgenital occlusion by secretion], stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry; suprastylar 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, nucellar cap?; megasporocyte single, hypodermal, functional megaspore lacking cuticle; female gametophyte lacking chlorophyll, four-celled [one module, egg and polar nuclei sisters]; ovule not increasing in size between pollination and fertilization; pollen grains bicellular at dispersal, germinating in less than 3 hours, siphonogamy, pollen tube unbranched, growing towards the ovule, between cells, growth rate (ca 10-)80-20,000 µm h-1, tube 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 gametophytes tricellular, gametes 2, lacking cell walls, ciliae 0, double fertilization +, ovules aborting unless fertilized; fruit indehiscent, P deciduous; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, ?diploid [one polar nucleus + male gamete], cellular, development heteropolar [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 short [<¼ length of seed]; plastid and mitochondrial transmission maternal; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome [2C] (0.57-)1.45(-3.71) [1 pg = 109 base pairs], ??whole nuclear genome duplication [ε/epsilon event]; 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, palaeo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]]; chloroplast IR expansions, chlB, -L, -N, trnP-GGG genes 0.
[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. - Back to Main Tree
Age. Wikström et al. (2001) estimated that this node was (179-)171, 153(-145) Ma, in line with other early estimates (Magallón 2009); Soltis et al. (2008: a variety of estimates) give an age of 180-132 Ma. Magallón and Castillo (2009) offer an age of ca 229 Ma for relaxed and 127 Ma for constrained penalized likelihood datings, while Moore et al. (2010: 95% HPD) suggest an age of (162-)155(-145) Ma, Clarke et al. (2011: also other estimates) ages of (231-)197(-169) Ma, towards the upper end of the suggestions then, N. Zhang et al. (2012; see also Xue et al. 2012) ages of (211-)179(-158) Ma, and Magallón et al. (2013) an age of around 183.4 Ma. Ages around ca 139 Ma (Magallón et al. 2015) and 184.5-173 Ma are suggested in Naumann et al. (2013) and, the other extreme, (266, 233-)227, 195(-173)Ma by Zeng et al. (2014), ca 255 Ma by Z. Wu et al. (2014), and (297-)250(-207) Ma by Salomo et al. (2017). Y. Yang et al. (2020: Suppl. Fig. 22) suggested an age of around 189.6 Ma for this node, P.-L. Liu et al. (2020) an age of (251.5-)209.5(-177.1) Ma.
A fossil-based estimate for the age of this node is ca 113 Ma (Crepet et al. 2004).
Evolution: Divergence & Distribution. Magallón et al. (2018) suggested nested increases in diversification rates around here, one (139.4-)139.2(-139) Ma and another at the mesangiosperm node
For discussion as to where characters of pollen morphology and development are to be placed on the tree, see M. L. Taylor and Osborn (2006) and also Friis et al. (2009b); it partly depends on how the characters are defined and partly on the recent discovery of fossil Nymphaeales that do not have the pollen characteristics of extant members of the clade. For vessel evolution in angiosperms, including that in Nymphaeales, see the Amborellales page.
Genes & Genomes. For the possibility of a genome duplication at about this position, see Cui et al. (2006) and dePamphilis et al. (2009).
Chemistry, Morphology, etc.. For cell lineages in the embryo sac see Huang and Russel (1992) and Friedman (2006); identification of the pattern described above apparently goes back to Porsch (1907), although it has been observed for relatively few plants. For embryo sac evolution, see Friedman and Ryerson (2009).
Phylogeny. For discussion of the relationships of Nymphaeales, see the Magnoliophyta node.
NYMPHAEALES Dumortier - Main Tree.
Aquatic herbs, plant rhizomatous; mycorrhizae 0; starch grains compound; radicle aborts; root apex with secondary dermatogen, etc., epidermis derived from outer layer of cortex [?Hydatellaceae]; trichoblasts in vertical files, proximal cell smaller; root stele monarch; diaphragms in root aerenchyma; primary stem with ± scattered vascular bundles; protoxylem lacunae +; vascular cambium 0; nodes?; articulated laticifers +; vascular bundles lacking associated sclerenchyma; aerenchyma common; 4-celled uniseriate secretory trichomes with a large terminal cell [= hydropoten]; stomata anomocytic; leaves spiral, ?lamina margins, leaf base broad; bracts 0; pollen boat-shaped, tectum continuous, infratectal space large, columellae conspicuous; ovule with semi-annular [hood-shaped] outer integument; first division of endosperm transverse, chalazal cell undivided; P persistent; fruit maturation underwater; seed operculate, endotegmen below operculum, hilum outside; seed coat exotestal, palisade/?exotestal cells low, thin-walled; endosperm scanty, [develops from micropylar cell], chalazal endosperm haustorium +, single-celled, perisperm +, starchy, precocious, cells ± multinucleate, embryo broad, cotyledons connate; germination hypogeal; intergenic inversion in chloroplast inverted repeat. - 3 families, 6 genera, 74 species.
Includes Cabombaceae, Hydatellaceae, Nymphaeaceae.
Note: In all node characterizations, boldface denotes a possible apomorphy, (....) denotes a feature the exact status of which in the clade is uncertain, [....] includes explanatory material; other text lists features found pretty much throughout the clade. Note that the precise node to which many characters, particularly the more cryptic ones, should be assigned is unclear. This is partly because homoplasy is very common, in addition, basic information for all too many characters 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 are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed (see above).
Age. The age of crown-group Nymphaeales is around 125 Ma (Magallón et al. (2015), (133.2-)126.7(-120.6) Ma (Iles et al. 2014), (160-)132(-114 Ma (Salomo et al. 2017), as little as (176.6-)97.7(-42.8) Ma (Zhou et al. 2014), or as much as ca 164 (Z. Wu et al. 2014), ca 188 Ma (Tank et al. 2015), or ca 209 Ma (Foster et al. 2016a: q.v. for details).
The curious fossil Archaefructus, probably an aquatic plant and about 124 Ma old, has been linked with Hydatellaceae in morphological analyses (e.g. Doyle & Endress 2007, 2010; Doyle 2008b; Endress & Doyle 2009); see Sokoloff et al. (2011) for an evaluation. Although the two have very little in common in terms of overall appearance, Archaefructus may be another early aquatic angiosperm with very unconventional floral morphology. Hydatellaceae may be represented in the pollen record from the Isle of Wight in rocks some 130 Ma (Hoffmann & Zetter 2010).
Evolution: Divergence & Distribution. Cretaceous fossils assignable to Nymphaeaceae are quite common and these are discussed below under Cabombaceae and Nymphaeaceae. Indeed, it has been suggested that Nymphaeales were "the first globally diverse clade" (Borsch " Soltis 2008: p. 1051; see also Sender et al. 2010), however, looking only at extant taxa, their diversity is slight.
Saarela et al. (2007) suggest a few additional possible synapomorphies for Nymphaeales, and Zeng et al. (2014) thought that having protoxylem lacunae and vascular bundles lacking associated sclerenchyma might be apomorphies. For the development of root hairs, see e.g. Clowes (2000) and Sokoloff et al. (2008a). Borsch et al. (2007) discuss the evolution of a number of floral characters within the order, M. L. Taylor et al. (2015) outline palynological variation in the context of its phylogeny, and Endress and Doyle (2015) look at floral morphology. Understanding where some of these features should be placed on the tree is complicated by the highly autapomorphic nature of Hydatella and some uncertainty over the position of Nuphar.
The development of perisperm (2n, maternal, c.f. endosperm, 2n, maternal/paternal) is an apomorphy for the order. Povilus et al. (2018 - read the details carefully) examined seed development in Nymphaea thermarum and interpreted perisperm development there as a way for the female parent to control resource allocation to the offspring. In general, the endosperm is slight if quite persistent and it probably functions as transfer tissue between embryo and perisperm (Friedman et al. 2012).
As might be expected, endomycorrhizae are at most uncommon in Nymphaeales (e.g. de Marins et al. 2009).
Chemistry, Morphology, etc.. It is possible that there are epidermal oil cells in Nymphaeaceae (Wilkinson 2006); do they contain ethereal oils? Hydrolysable tannins in this group (e.g. in Nuphar) are different to those found elsewhere (Gottlieb et al. 1993; Ishimatsu et al. 1989), although the chemistry of Hydatellaceae is poorly known.
Hydatellaceae (Trithuria filamentosa) are reported to have vessel elements with scalariform perforation plates throughout the plant (Cheadle & Kosokai 19), however, Carlquist and Schneider (2009) could not find them when they examined the original sections. For micromorphological details of tracheids, see e.g. Carlquist and Schneider (2009), E. L. Schneider et al. (2009), Schneider and Carlquist (2009a, b); details of the wall structure of tracheids, at least, in Cabombaceae and Nymphaeaceae are very distinctive. Roots of Cabombaceae and Nymphaeaceae may have vessels of a sort (Carlquist & Schneider 2009; Schneider & Carlquist 2009). The distinctive uniseriate trichomes found in all groups may secrete nectar or mucilage, or they may be involved in ion exchange (Vogel 1998a); Wilkinson (2006) calls the trichomes on the leaves, hydropotes.
The inner bracts found in some Hydatellaceae and the inner petals of Cabomba are notably slow in developing (Rudall et al. 2007). If the corolla represents sterilised stamens, as some think, having external staminodes will probably be another synapomorphy at least for [Nymphaeaceae + Cabombaceae]. For discussion about the presence of a granular infratectum in Nymphaeales, see M. L. Taylor et al. (2013, 2015, also 2014 for other characters); the infractectum is generally columellate, how obviously so depending on the thickness of the infratectal space. Some genera in all families have exotestal cells that are neither very tall nor much thickened (Hamann et al. 1979; Collinson 1980). Rudall et al. (2009b) discuss the distinctive single-celled chalazal endosperm haustorium, the presence of which is sometimes suggested by a space between the embryo plus endosperm and the perisperm. Baskin and Baskin (2018) discuss embryo morphology and seed germination.
Phylogeny. Hydatellaceae are sister to Xyridaceae in Stevenson et al. (2000; see also Stevenson & Loconte 1995); both have latrorse anthers and seeds with an operculum "stopper" that is tegmic in origin. Trithuria and Xyris appear as sister taxa (weak support) and in turn are sister to Mayaca (still weaker support), although other Xyridaceae are not immediately related in the phylogeny of Michelangeli et al. (2003). However, although Bremer (2002) noted that Mayacaceae and Hydatellaceae might be weakly associated with Xyridaceae or Eriocaulaceae, depending on what taxa were included in the analysis, there were a number of long branches in this area and he excluded the first two families from his final analysis, while Janssen and Bremer (2004) suggested that the association of Hydatellaceae with Mayacaceae was probably an artefact (see also Chase et al. 2006). Subsequent studies (Saarela et al. 2006, esp. 2007: several genes from two compartments, morphology; Friis & Crane 2007: commentary) placed Hydatellaceae firmly with Nymphaeales, and sister to [Cabombaceae + Nymphaeaceae]; the sequence that placed Hydatellaceae in Poales was a chimaeric pcr recombinant involving a grass and a moss.
Hydatellaceae aside, for a morphological phylogeny of [Cabombaceae + Nymphaeaceae], see D. W. Taylor (2008). Y.-L. Liu et al. (2005) provide an ITS phylogeny focussing on Nymphaeaceae, but with some at first sight rather surprising relationships - [Nuphar [Cabomba + Brasenia] [Nymphaea [Euryale + Victoria]]]. Nelumbo, which was included in the analysis, did at least stay outside this clade... However, this position of Nuphar is recovered in other analyses, too (e.g. Borsch et al. 2008; Löne et al. 2007; D. W. Taylor & Gee 2014: some analyses; Gruenstaeudl et al. 2017) and so its position below as sister to Nymphaea, etc., may be provisional. He et al. (2018: chloroplast data) found that Nuphar was sister to Nymphaea and its associates, and with quite strong support; interestingly, a UPGMA dendrogram of RNA editing sites linked Nuphar with Cabombaceae. Moreover, in a renalaysis of the data in He et al. (2018), Gruenstaeudl (2019) found that how the data were partitioned affected the results, and individual gene trees also gave different results, thus almost as many supported a relationship of Cabombaceae with Nuphar as supported an association of Nuphar with Nymphaea and friends. H.-T. Li et al. (2019) found a [Nuphar + Nymphaea] association.
Previous Relationships. Many of the morphological features of Hydatellaceae that made it so different from other monocots are consistent with a position in Nymphaeales. Hamann (1998) had even noted that the antipodal cells were absent or degenerated early, and absence of these cells would be expected if Hydatellaceae were to be placed here - and Friedman (2008a) and Rudall et al. (2008) found that Hydatellaceae had the distinctive 4-celled embryo sac of other Nymphaeales and of Austrobaileyales.
Synonymy: Barclayales Doweld, Cabombales Richard, Euryalales H. L. Li, Hydatellales Reveal & Doweld, Hydropeltidales Spenner - Hydatellanae Reveal, Nymphaeanae Reveal - Nymphaeidae Takhtajan - Hydropeltopsida Bartling, Nymphaeopsida Horaninow
HYDATELLACEAE U. Hamann, nom. cons. - Back to Nymphaeales
(Plant annual), growth sympodial, rhizome short, erect; chemistry?; mycorrhizae 0; cuticular waxes 0; leaves linear, with a single vein, margins entire; plant monoecious; inflorescence axillary, scapose (sessile), capitate, with involucral bracts; flowers very small, monosymmetric by reduction; P 0; staminate flowers: A 1, filament long, slender, ± articulated with the anther; endothecium 0; tapetal cells?; pollen with spinules; carpelate flowers: pedicel articulated; G 1, three vascular bundles equidistant (2, 1), stigma penicillate [hairs rows of plump cells]; extragynoecial compitum 0; ovule pendulous, anatropous, apotropous, micropyle bistomal, parietal tissue (?0), nucellar cap +/0; (two embryo sacs developing); fruit smooth to papillate, splitting into three valves, or achenial; exotestal cells with sinuous anticlinal walls, other layers ± collapsed, tanniniferous; embryo barely differentiated, suspensor unicellular; n = 7, x = 7 (?8), (chromosomes holocentric), nuclear genome [1 C] (0.064-)1.686(-44.679) pg/1335-1350 Mbp; seedling - see below.
1 [list]/10. India, New Zealand and Australia (map: from Cooke 1987; FloraBase 2004).
Age. It has been estimated that crown-group Hydatellaceae are (23.4-)19.1, 17.6(-14.7) Ma (Iles et al. 2014).
The pollen Monosulcites riparius in ca 75-70 Ma rocks from Eastern Siberia has been identified as Trithuria, but this must be a misidentification if the ages above hold.
Evolution: Divergence & Distribution. For the evolution and biogeography of the family - crown Hydatellaceae are certainly not Gondwanan in age - see Iles et al. (2014); Trithuria konkanensis (India) and T. lanterna (N. Australia) diverged (1.3-)0.76(-0.24) Ma and evolution in the genus seems in general to be pretty active (e.g. Marques et al. 2016 and references).
The flowers are much reduced, or they may be reduced inflorescences/pseudanthia, so interpretation of what the reproductive structures "are" is difficult, and Sauquet et al. (2017) reasonably elected not to include the family in their reconstruction of the morphology of the ancestral angiosperm flower.
Pollination Biology & Seed Dispersal. For reproductive ecology - wind-, self-, or hyphohydrous pollination - see M. L. Taylor et al. (2010); the pollen tubes grow down the multicellular hairs under the cuticle (Prychid et al. 2011).
Genes & Genomes. For chromosome numbers, see Marques et al. (2016). The genome of Trithuria submersa shows signs of polyploidy (n = 28), and meiosis during microsporogenesis has a number of odd features, and it is possible that (some of) the chromosomes, perhaps belonging to one of the genomes, are holocentric (Kynast et el. 2014).
Chemistry, Morphology, etc.. The sieve tube plastids were reported as having triangular proteinaceous inclusions, but the inclusions appear to be of the starchy type as are more to be expected in this part of the tree (Tratt et al. 2009). There is some variation in the epidermis of the root and whether or not root hairs are produced (Sokoloff et al. 2008a). Hairs with possible apical secretory cells are known only from the inflorescences.
The inflorescence is described as being cymose and capitate, although bractless and with highly reduced flowers, i.e., it is a sort of pseudanthium, although alternative interpretations are possible (Rudall et al. 2007a, 2009a; Rudall 2010), indeed, how the reproductive structures are to be interpreted, whether flowers or inflorescences, is unclear. The pedicels seem at least sometimes to be articulated. Early work suggested that the carpels might be initiated outside the stamens, and this has been confirmed (Rudall et al. 2007a); staminate flowers are the first to be initiated in the cymose inflorescence (see also Begoniaceae).
The fruit opens along three lines as the three vascular bundles separate from the rest of the pericarp (see also Sokoloff et al. 2013a). Both integuments have two cell layers; the operculum is formed from enlarged cells of the inner integument. Starch deposition in tissues that will become perisperm begins before fertilization (Friedman 2008a).
There is some disagreement over the interpretation of the embryo. Tuckett et al. (2010: discussion of "ancestral" embryo type for angiosperms must include Amborellaceae, at least; see also Sokoloff et al. 2014) found that the embryo differentiated and the shoot and root appeared only after germination began. Tillich et al. (2007) compared seedling morphology with that of a monocot, describing collar rhizoids, a coleoptile, two cotyledonary sheath lobes, and a haustorium. Sokoloff et al. (2008a) suggested that the sheathing structure with its bilobed apex that is found in some species could be interpreted as two more or less completely connate cotyledons; the rest of the embryo is attached to the sheathing structure. In some taxa there is apparently no sheathing structure at all, only a haustorial lateral outgrowth (cotyledonary) that goes into the rest of the seed, the rest of the cotyledon being photosynthetic, so the seedlings are simultaneously both phanero- and cryptocotylar - c.f. some monocots (Sokoloff et al. 2013b), and Sokoloff et al. (2008a, 2014) suggested that Hydatellaceae showed how monocot-like embryos/seedlings might have originated. Some species are phanerocotylar (Sokoloff et al. 2013b). Both Tillich et al. (2007) and Sokoloff et al. (2008a) examined largely the exterior morphology of the embryo, neither looked in any detail at anatomy (c.f. Friedman et al. 2012: superb micrographs; Sokoloff et al. 2014); for a discussion on germination, see Baskin and Baskin (2018).
Additional information is taken from Hamann (1998: general), Sokoloff et al. (2008b: family monograph, 2011: important literature review, 2019b: species limits), Cutler (1969: vegetative anatomy), Remizowa et al. (2008b: pollen), Hamann (1975) and Rudall et al. (2008), both embryology, Hamann et al. (1979), Cook (1983) and Rudall et al. (2009b), all seeds and germination, and Sokoloff et al. (2009a: growth patterns of perennial species).
Previous Relationships. Hydatellaceae had long been considered to be monocots, largely because of their superficial similarity to Centrolepidaceae (= Restionaceae). Both groups are very reduced morphologically, and indeed Hydatellaceae have been misidentified as Centrolepidaceae. It was unclear if the gynoecium of Hydatellaceae was 1- or 3-carpelate, and since the fruits of Trithuria (= Hydatella) opened by three valves, they looked rather monocot-like. The combination of characters in Hydatellaceae was recognised as being unique to that group, and it made them very distinctive within monocots as a whole (e.g. Hamann et al. 1979; Dahlgren et al. 1985).
[Cabombaceae + Nymphaeaceae]: plant monopodial, rhizome/stolon elongated; hydroyzable [ellagi]tannins +; vessel elements in roots [of sorts: pit membranes in end walls lyse], tracheids with pit membranes of end walls with two layers of large fibrils; astrosclereids [stellate parenchyma cells] with minute rhombic crystals; stomata perigenous; lamina vernation involute, secondary veins palmate, actinodromous, festoon brochidodromous, margin toothed/crenate/entire, (hydathodes +); flowers single, extra-axillary; receptacle with cortical vascular system; P whorled, outer members enclosing the rest of the bud; A whorled, (stamens in pairs opposite P members); tapetum (amoeboid), cells multinucleate; pollen tube growth moderately fast; carpel margins with postgenital fusion, placentation ± laminar; nucellar epidermal cells ± radially elongated, supra-chalazal tissue massive; mesocarp ± aerenchymatous; exotesta ± thin-walled and tabular, with sinuous anticlinal cell walls; endosperm bipolar, chalazal cell ± enlarged (and elongated), haustorial, embryo differentiated, suspensor often ± filamentous; seedling cryptocotylar, hypogeal, first leaf acicular.
Age. There has been much discussion over the timing of diversification within the Cabombaceae-Nymphaeaceae clade (e.g. Nixon 2008), however, the disagreement is not a simple morphology vs molecules dichotomy. Wikström et al. (2001) suggested that divergence of the two families occurred (152-)144, 111(-103) Ma and the figure in Salomo et al. (2017) is (117-)110(-106) Ma, while the age in Magallón and Castillo (2009) is ca 112 Ma (see also Tank et al. 2015: ca 112.5 My), that in Magallón et al. (2013) is around 122.7 Ma, and that in Iles et al. (2014) (107.1-)102.1(-98.8) Ma. However, Löhne et al. (2008: molecules) thought that divergence was only Palaeocene in age, (75-)56.4(-38) Ma, while Bell et al. (2010) offered a still younger date of (56-)42, 38(-25) Ma; Yoo et al. (2005) pegged the crown group age to 44.6 ± 7.9 Ma, while in Naumann et al. (2013), at around 94.75 Ma, the age was intermediate. A recent estimate, as high as they go, is 185-147 Ma (L. Zhang et al. 2019).
Early fossil-based estimates for the age of this group were only ca 90 Ma (Crepet et al. 2004), but substantially earlier dates are likely (Friis et al. 2009b). There are fossils of stem-group Nymphaeaceae, Cabombaceae and/or [Nymphaeaceae + Cabombaceae] from several parts of the world in the Lower Cretaceous (e.g. D. W. Taylor et al. 2001, 2008; Friis et al. 2011; see Taylor & Gee 2014: ca 113 Ma). Indeed, a dozen or more genera based on fossil seeds have been described that belong around here, and exotestal seeds, e.g., having tall exotestal cells with sinuous antinclinal walls, were diverse in the Middle Albian-Middle Aptian some 115-105 Ma, and their limited occurrence now seems to reflect extensive extinction at around this time (Friis et al. 2017b, 2018b, c). Silvestro et al. (2020) estimate the time-of-origin of Cabombaceae to be ca 120 Ma and that of Nymphaeaceae to be ca 112.5 Ma.
Although other fossils possibly of this group (to a certain extent characters of the two families are combined) are known from the Barremian-Aptian deposits 125-113 Ma in Portugal (Friis et al. 2001), they may also be from a member of Austrobaileyales (Gandolfo et al. 2004). See also von Balthazar et al. (2008) for another fossil perhaps assignable to this general [Nymphaeales-Austrobaileyales] area.
Pluricarpellatia, probably to be placed in or near Cabombaceae (Doyle & Endress 2014), is known from the Early Cretaceous (Mohr et al. 2008). The Early Cretaceous Monetianthus was embedded within crown Nymphaeaceae in morphological analyses (Friis et al. 2009b, but c.f. 2011; see also Doyle & Upchurch 2014/; Doyle 2016), and this may be true for the mid-Albian Carpestella, from Virginia (Doyle & Endress 2014); both these genera have very small flowers. The distinctive reticulate-perforate pollen of Monetianthus would then be independently derived within Nymphaeales, but other analyses also placed the genus at the node above Nymphaeales along the spine of the angiosperm tree (Friis et al. 2009b). Yoo et al. (2005) thought that the ca 90 Ma fossil Microvictoria was stem group Nymphaeales, although other studies had suggested it was crown-group Nymphaeaceae (Gandolfo et al. 2004 [its initial description]; Endress 2006; Friis et al. 2011), while in a recent general phylogenetic analysis it ended up in a number of positions in the ANA grade, also in Laurales-Calycanthaceae, although not in the [Cabombaceae + Nymphaeaceae] clade itself... (Schönenberger et al. 2020).
Evolution: Divergence & Distribution. D. W. Taylor et al. (2008, see also Taylor 2008) looked at vegetative evolution in [Cabombaceae + Nymphaeaceae]; the inclusion of different fossils in analyses of morphological variation affected the relationships they obtained, and hence evolutionary interpretations. Friis et al. (2011: fig. 20.2) discussed diversification here in some detail, also assigning many Palaeogene fossils to the two families. Carlquist and Schneider (2009) suggest a number of distinctive features of the xylem in this clade.
Carpenter (2005) described the stomata as being largely variants of the actino/stephanocytic types; only one member of Cabombaceae was studied. Rudall and Knowles (2013) looked at stomatal development in some detail, observing that it was perigenous, the subsidiary cells being members of different cell lineages than the guard cells (other members of the ANA grade are more or less mesogenous); there is a similarity here to other aquatic lineages such as Callitriche (Doll et al. 2021). Rudall and Knowles (2013) noted that other taxa with anomocytic stomata had mesogeneous stomatal development.
Ecology & Physiology. Members of this clade, along with other angiosperms, may have come to dominate aquatic habitats in Europe by the Albian ca 105 Ma (Sender et al. 2010).
Pollination Biology & Seed Dispersal. Generalist pollination is common here (Gotttsberger 2016); see also Luo et al. (2018) for a summary and references.
Genes & Genomes. L. Zhang et al. (2019) note that there is a genome duplication around here, certainly in Nymphaeaceae, but perhaps also including Cabombaceae.
For the chloroplast inverted repeat, see Graham and Olmstead (2000).
Chemistry, Morphology, etc.. Warner et al. (2008, 2009) discuss perianth evolution, and in Warner et al. (2008) there is a useful summary of the literature on perianth morphology. Zini et al. (2016) described the distinctive nucellar epidermis of the ovules as being an epistase.
For information on anatomy, see Gwynne-Vaughan (1897), for root epidermis, see Voronkina (1974: ordinal characterisation above), for root anatomy, see Seago (2002), for peduncular/floral anatomy, see Moseley et al. (1993), for perianth venation, Hiepko (1965b), for pollen morphology, Osborn et al. (1991), for embryo sac development, Orban and Bouharmont (1998), for endosperm evolution, Floyd and Friedman (2001), for ovule development, Yamada et al. (2001b), for pericarp anatomy, Yatzenko et al. (2012), for seed anatomy, see Collinson (1980) and Chen et al. (2004), for seedlings, see Ito (1982), and for general information, Raciborski (1894a, b), Les et al. (1999) and E. L. Schneider et al. (2003).
Phylogeny. See above.
CABOMBACEAE A. Richard - Back to Nymphaeales
Rhizomes monopodial; alkaloids 0; stem with two pairs of vascular bundles, protoxylem lacunae + [see below]; internodes long; petiole with one bundle pair; lamina peltate; inflorescences sympodial (in part); pedicel with 3 bundle pairs; flowers rather small, parts whorled, (2)3(4)-merous, polysymmetric [hexamerous]; P = two whorls of T, C-like, members with single trace; filaments moderately slender; tapetum more or less amoeboid; pollen endexine lamellate when young, not when mature; pollen tube growth intra-gynoecial; when G 3 or more, inner whorl of three ± opposite inner P, three vascular bundles equidistant, stylulus +, short, stigma papillate; extragynoecial compitum at least initially 0; ovules 1-3(-5)/carpel, attached variously, outer integument semi-annular [hood-shaped], hypostase +; hilum and micropyle sharing same opening in center of operculum; micropylar endosperm cell with free-nuclear divisions [endosperm helobial]; x = 7 (?8, ?6), nuclear genome [1 C] (0.036-)1.989(-109.219) pg; seedling erect, internodes short [= short shoot of sorts].
2 [list]/6. World-wide, rather scattered, Brasenia schreberi subfossil remains show it to be far more widespread in Europe than at present (map: from Raymond & Dansereau 1949; Fassett 1953; Ørgaard et al. 1992; Hultén 1961; Fl. N. Am. III 1997; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003, 6. 2011; Löhne et al. 2008). [Photo - Brasenia Habit] [Photo - Flower.]
Age. Bell et al. (2010) suggested that the two genera diverged (31-)21, 20(-10) Ma; other estimates are (109-)101(-93) and (75-)67, 60(-52) Ma (Wikström et al. 2001).
Pluricarpellatia, probably Cabombaceae, is known from rocks 115 Ma in northeast Brazil (Mohr et al. 2008).
1. Cabomba Aublet
Rhizomes from erect short shoots or other rhizomes; vascular plexus at nodes, stomata [on floating leaves] parallel to the veins; short shoots with cataphylls, submerged leaves opposite or 3-whorled, lamina deeply palmately (subdichotomously) dissected, lobes linear; flowering shoots long shoots, from erect shoots or rhizomes, monopodial (becoming sympodial); flowers initially axillary; T ± in a single whorl, inner T somewhat delayed in development, nectaries +, trichomatous; A 3 [opposite inner T], 6 [alternating with T], extrorse; pollen trichotomocolpate, tectum continuous, striate; G 1-4(-7), (basally connate), style becoming hollow [lysigenous], stigma capitate; fruit follicular; seeds 2-3, spiny; n = 13.
1/5. New World; warmer areas.
2. Brasenia Schreber
Rhizomes from seedling-derived short shoots; root stele 6-8-arch; glandular hairs 2-celled; stems encased in thick layer of mucilage, paired, glandular patches at nodes; flowering shoots short shoots, from rhizomes, sympodial; pedicel often with 3 bundles; T whorls somewhat different in size; A many, outer ± alternating with T, inner with variable position; pollen scabrate; G 4-18, stigma elongate; seed achenial, 1-2-seeded; testa cells tall, thick-walled; n = 40.
1/1: Brasenia schreberi. Scattered, tropical and (warm) temperate, but also southeast Australia and southeast Siberia.
Evolution: Pollination Biology & Seed Dispersal. Brasenia is wind pollinated, while Cabomba has paired nectaries (trichome patches) on its inner tepals and is pollinated by flies. M. L. Taylor and Williams (2009) describe details of reproduction of Cabomba from pollination to fertilization, while E. L. Schneider and Jeter (1982) discuss its pollination. For more details, see Erbar (2014) and Gottsberger (2016)
Chemistry, Morphology, etc.. The root endodermis has a Casparian strip and suberin lamellae. The two bundles that share protoxylem lacunae are adjacent vascular bundles in Cabomba but members of opposite pairs in Brasenia (Moseley et al. 1984). The "vessels" in the roots and rhizomes of Cabomba have helical thickenings that are not developed away from the end plate (E. L. Schneider & Carlquist 1996). It is unclear how to interpret nodal anatomy. In Cambomba a trace leaves from each member of a vascular bundle pair which shortly thereafter fuse commissurally, creating a nodal plexus; the foliar traces fuse and then divide, providing two petiolar bundles (Moseley et al. 1984). The peltate leaves are spirally arranged, although in some taxa they are uncommon, while the more or less dichotomously-divided submerged leaves are opposite; for leaf morphology, see Rutishauser and Sattler (1987).
There are often five vascular bundles in the sepals and three vascular bundles in the petals of Cambomba, in both cases a single trace leaves the floral axis (Moseley et al. 1984). Stamens are sometimes physically close to each nectary and then they appear paired (Ørgaard et al. 1992). Pollen of Cabomba has striate exine; although the endexine of mature pollen of Brasenia schreberi is not lamellate, it is laid down in plates (M. L. Taylor & Osborn 2006).
The granular infratectum of the pollen of Podostemaceae has been compared with that of Cabombaceae; both are aquatics (Passarelli et al. 2002).
Some information is taken from Raciborski (1894a, b), Moseley et al. (1984: esp. tables 4, 5) and Williamson and Schneider (1993), both general, Richardson (1969: development of Brasenia flowers), Ito (1986a: floral morphology/anatomy), Erbar (2014) and Tölke et al. (2019), both nectaries, Khanna (1965) and Batygina et al. (1982), both embryology, Floyd and Friedman (2000: endosperm development), and M. L. Taylor et al. (2008: esp. pollen).
Synonymy: Hydropeltidaceae Dumortier
NYMPHAEACEAE Salisbury - Back to Nymphaeales
Perennials (annuals); myricetin, sesquiterpene [pseud]alkaloids; roots arise at the base of each leaf; root stele polyarch; stem bundles (in concentric rings), axial bundles collateral/concentric, pith with vascular tissue; peduncle bundles radially arranged; astrosclereids +; nodes 3 traces; lamina cordate; flowers lateral, replace leaf in spiral/not, large [>3 cm across], haplomorphic; P members usu. with K- and C-like areas; A many, often whorled, laminar, the staminal bundle branched from near base in thecal region, (filaments stout), connective produced or not, staminodes +, next to G; tapetum both glandular and amoeboid; microsporogenesis simultaneous; pollen (tricellular), (no exine), membranous granular layer + [innermost endexine]; G laterally connate, whorled, postgenital margin fusion complete, placentation laminar, residual receptacle apex + [?level], stylulus 0, stigma dry, radiate; ovules many/carpel (-3), not filling the locule, outer integument also cap-shaped [annular]; embryo sac ± 8-shaped [?level]; fruit baccate [sort of], dehiscence irregular; testa between micropyle and hilum; endosperm scanty, embryo chlorophyllous or white, broad and plug-like, (large); x = 7 (?8, ?6), nuclear genome [1 C] (0.053-)1.666(-52.735) pg; cotyledons, etc., 1-trace.
3 [list]/58 - two groups below. World-wide (map: from Vester 1940; Wickens 1976; Hultén 1961; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003; Heywood 2007; Löhne et al. 2008). [Photo - Leaf, Flower.]
Age. E. L. Schneider et al. (2004) suggested an age for the family of ca 121 Ma, Magallón et al. (2013) an age of around 100.1 Ma, while Iles et al. (2014) suggested an age of (99.6-)95.5(-92.9) Ma. However, estimates in Bell et al. (2010) are only (49-)32, 29(-15) Ma and those in Zhou et al. (2014) (60.6-)28.2(-3.8) Ma, while those in Naumann et al. (2013) are around 51.8 or 40.8 Ma, somewhat intermediate.
The Late Aptian/Early Albian Cretaceous Monetianthus, from Portugal, is embedded in Nymphaeaceae in morphological analyses (Friis et al. 2009b). Microvictoria, a somewhat later fossil from the Turonian ca 90 Ma old and found in New Jersey, U.S.A., is very like Victoria (= Nymphaea). Victoria has paracarpels (= ) immediately surrounding the gynoecium, and these are also found in Microvictoria; indeed, flowers of this latter are like those of Victoria in almost all respects, although they are less than 1/10th their size (Gandolfo et al. 2004). Jaguariba is assignable to crown group Nymphaeaceae; it is from the Aptian Crato flora of northeast Brazil and is some 115 Ma (Coiffard et al. 2013a). For Cecilanthus, from early Cenomanian Maryland ca 100 Ma, see Herendeen et al. (2016) and above).
1. Nupharoideae Ito
Rhizomes stout, horizontal, creeping; indolizidine alkaloids +; roots with 10-18 xylem poles, pith broad; lamina margin entire; peduncle at base with several vascular bundles, one outer satellite bundle, with subbasal abaxial leaf ["bract"]; P dimorphic, first member initiated sublaterally, outer members 5-6(-14), spiral, with 3 traces, initially green, often becoming ± completely yellow, inner members many, smaller, C-like, with 1 trace, somewhat delayed in development; nectary on abaxial surface of inner members; no intermediates between A and C; anthers (longer than filament), valvate [H-dehiscence], connective strongly produced; pollen grains tricellular, spiny, tectum continuous, anasulcate, aperture operculate; G 5-23(-36); outer integument 4-6 cells across, parietal tissue ca 2 cells across, nucellar cap ca 4 cells across, hypostase, postament +; fruit emergent, outer P turn green, persistent; endocarp and funicle becoming aerenchymatous, surrounding seeds, seeds hairy, operculate, micropyle and hilum very close; exotestal cells with straight anticlinal walls; n = 17.
1/1-15 - ca 11? North Temperate.
Age. Friis et al. (2017b) were inclined to link Notonuphar, fossil seeds perhaps some 37 Ma found commonly in mid to upper Eocene deposits from Seymour Island, Antarctica, to those of Nuphar, which has low exotestal cells (but the two have a similar micropyle-hilum area), although they have tall, thick-walled exotestal cells like those of Brasenia (Cabombaceae).
Synonymy: Nupharaceae A. Kerner
2. Nymphaeoideae Arnott
(Mycorrhizae +); (rhizome +, short, erect); phloem loading active, cell walls smooth, no plasmodesmata; roots with 5-9 xylem poles, pith at most small; stomata parallel [?to what]; vegetative buds not axillary; lamina (peltate/base truncate), (margin serrate), (spines on lower surface, pedicel, etc.); stipules +, adaxial and bicarinate or lateral; peduncle at base with one bundle, inner satellite bundle +; bracts 0; hypanthium ± developed; P members 3-veined, "K" 4-5, spiral, first member initiated is abaxial, (long aristate - Barclaya), "C" (0 - some Nymphaea ondinea), (basally connate - Barclaya); intermediates between A and "C"; A (adnate to "C"), (outer staminodes +, showy, inner staminodes + - Victoria); (staminal bundle unbranched, esp. in smaller inner A); pollen (in tetrads), (bicellular), with encircling sulcus [zonasulcate], (inaperturate), surface various, inc. tectum continuous, infratectal space usu. small, columellae inconspicuous; G 3-many, ± inferior [A alone on top of G; K and C also often on top], with inter-carpellary septal slits, marginal appendages + (0), central pool of stigmatic fluid, floral axis projecting in the middle [not Barclaya], stigmatic surface continuous; ovules (straight - Barclaya), (micropyle bistomal), (outer integument 4-5, ca 20 cells across [Euryale]), (parietal tissue 3-4 cells across - Victoria ); fruit maturing submerged; seeds arillate (not, but spiny - Barclaya); exotesta mucilaginous [?level], (cells cuboid, anticlinal walls straight - Euryale); (embryo suspensor 0); n = 10, 12, 14-18, nuclear genome [1 C] 450-4557 Mbp.
2/48: Nymphaea (46). World-wide.
Synonymy: Barclayaceae H.-L. Li, Euryalaceae J. Agardh
Evolution: Divergence & Distribution. The family is thought to have been much more diverse in earlier epochs, distinctive seeds with a micropylar and palisade exotesta with sinuous anticlinal walls that can be assigned here being common in the Cretaceous (Friis et al. 2009b, 2011, 2017b; see also above). Recently, fossils assigned to crown group Nymphaeaceae (as Jaguariba) have been found in the Aptian Crato flora, some 115 Ma in northeast Brazil (Coiffard et al. 2013a) and the first seeds from the Southern Hemisphere have been described in Eocene deposits from Seymour Island, Antarctica (Friis et al. 2017b).
Although the family is widespread and probably very old, individual clades within it are relatively localized, and it has even been suggested that crown group diversification may have occurred in the northern hemisphere in the early Caenozoic (Löhne et al. 2008; see also Friis et al. 2011).
Although there are separate cauline vascular bundles, the basic stem structure is unlike that of monocotyledons (Weidlich 1976, 1980 and references).
Ecology & Physiology. Barclaya rotundifolia is a terrestrial plant of wet forests in western Malesia.
Pollination Biology & Seed Dispersal. Thermogenesis has been detected in the flowers of some Nymphaeaceae (Seymour 2001; Seymour & Matthews 2006). Beetles and a variety of other insects, including bees and flies, are pollinators (e.g. Gandolfo et al. 2004; Padgett 2007; Thien et al. 2009; Zini et al. 2019). Scarab beetles (Cyclocephalini) may have pollinated night-flowering water lilies for some 100 My; they pollinate species both in America, where the beetles are common, and in Africa, where the beetles are otherwise very uncommon (Ervik & Knudsen 2003; Moore & Jameson 2013); beetle pollination may have occurred even in the early small-flowered members of the family (M. L. Taylor et al. 2013 and references). The distinctive flowers of Ondinea (= Nymphaea ondinea), wind pollinated, are derived from Nymphaea-type flowers (Löhne et al. 2009). Zini et al. (2019) examined the marginal carpellary appendages common in flowers of Nymphaea and Barclaya and found that they often provided visual and/or olofactory cues for the pollinator, be it bee or beetle. E. L. Schneider (1979) summarized information about the pollination biology of the family; see also Erbar (2014), Gottsberger (2016: Table 2, much detail), Luo et al. (2018) and Coiro and Barone Lumaga (2018: floral epidermal micromorphology).
The progamic phase, the time between pollination and fertilization, is notably short, up to a mere 8 hours, as in at least some other aquatic angiosperms (including Nelumbo: see Williams et al. 2010).
Dehiscence of the fruit of Nymphaeoideae is by swelling of the mucilage inside it whereupon the wall splits irregularly.
Plant-Animal Interactions. Nymphaeaceae are host plants of reed beetles, Chrysomelidae-Donaciinae (see also Poales: Kölsch & Pedersen 2008: much discussion on the age and evolution of the group). Enterobacteriaceae near Buchnera are thought to produce the material that makes up the cocoon that characterises Donaciinae, a group that is also noted for the ability of the larvae to grow under water (Kölsch & Pedersen 2010).
Genes & Genomes. A genome duplication in Nuphar is estimated to have occurred (76.8-)72.8(-67.9) Ma (Vanneste et al. 2014b) and one in Euryale ferox at 106-94 Ma (Y. Yang et al. 2020); it is pegged at the level of [Nymphaea + Nuphar] and dated to around 106.3 Ma (Landis et al. 2018: App. S1), so its extent depends on confirmation of the position of Nuphar... See also L. Zhang et al. (2019) for this/another duplication.
For chloroplast organisation, etc., see He et al. (2018). Interestingly, Nuphar has the highest number of short tandem repeats (>50), followed by Barclaya (>30), and Nymphaea as few as 19 (He et al. 2018).
Economic Importance. Nymphaeaceae include a disproportionally high number of serious and widespread weeds (Daehler 1997).
Chemistry, Morphology, etc.. The root endodermis has a Casparian strip. There are sometimes sclerenchymatous diaphragms in the pith. The vasculature of the stem is exceedingly complex, especially at the node, with the peduncular complex and a root trace forming from the same axial bundles that supply the leaf (Weidlich 1976, 1980 and references); the vascular bundles were mesarch, the central xylem being mixed with phloem or not and there may be vascular tissue in the pith. E. L. Schneider et al. (2008, 2009) and Schneider and Carlquist (2009) discuss stem tracheids and root vessels, emphasizing the rather arbitrary distinction between vessels and tracheids; Carlquist (2012c) suggested that there were no vessels. The astrosclereids of Nuphar and Nymphaea, at least, have calcium oxalate crystals in the walls (Fink 1991).
In both Nuphar and Nymphaea flowers and even branches may replace leaves in the genetic spiral, and they are certainly not simply axillary (e.g. Cutter 1957a, b; Groß et al. 2006). Cutter (1957b) noted that the leaf apparently subtending the flower of Nuphar was in fact borne on the flower stalk; if a prophyll, it should be noted that it is abaxial in position; for more discussion as to whether or not Nuphar has bracts, see E. L. Schneider et al. (2003).
Flower parts are generally whorled (see Endress & Doyle 2015 and references). Yoo et al. (2010) discuss the evolutionary/developmental relationship between sepals and petals; see also Doyle and Endress (2011), who suggest that Nuphar has both tepals and petals, the latter being the smaller, inner, petal-like structures. E. L. Schneider (1976) and Moseley and Uhl (1985) note that the vascular supply to perianth and androecial members consists of two radially associated bundles. Zini et al. (2017) looked at the epidermal micromorphology in particular of these tepal whorls, noting that the outer "series" were sepal-like, the innermost corolla-like, and the middle either a mixture of traits or corolla-like. In Euryale the filaments are quite slender and are basally adnate to the staminodes; it is unclear if it has free nuclear endosperm (Floyd & Friedman 2001 - see also Kanna 1964, 1967 for endosperm development in the family). Weberling (1989) suggested that in at least some Nymphaeaceae the individual carpels were free laterally but adnate to the central axis inside and to hypanthial tissue outside (see also Moseley 1965; von Balthazar et al. 2008). The ovules of Victoria and Euryale are massive affairs (Zini et al. 2016). Zhou and Fu (2008) found that at anthesis, but not before or after, the micropyle of Nuphar was bistomal, not endostomal. Weberling (1989) also described how in Nuphar axial tissue separates from the gynoecium when the fruits are ripe, so exposing the basically free carpels. However, Moseley (1965) seems more accurate, and he described the fruit as eventually being irregularly circumscissile, the seeds being in groups surrounded by aerenchyma that developed from the endocarp and funicle; Padgett (2007) described dehiscence as being along lines in the septal and ovarian walls where aerenchymatous tissue had developed. For embryo development and germination in Nymphaea, see Baskin and Baskin (2007b), the embryo may be fully developed before germination begins. The seedling axis in some species of Nymphaea has a lateral projection.
Some information is taken from Raciborski (1894a, b), E. L. Schneider and Williamson (1993) and Padgett (2007: Nuphar), all general; see Schneider and Carlquist (1995) for root xylem of Barclaya, Moseley (1958) for stamen morphology, Yao et al. (2004), M. L. Taylor et al. (2012, 2013) and Coiro and Barone Lumaga (2013), all pollen morphology, Zini et al. (2014b) and Shamrov (1998: Nuphar) for ovules, Takhtajan (1988) and Losada et al. (2014) ovules and seeds, Cook (1909), Khanna (1964, 1967: 8-nucleate embryo sacs...), Floyd and Friedman (2001) and Povilus et al. (2015, 2018), all embryology, Valtzeva and Savich (1965), embryo development, and Wheeler Haines and Lye (1975: evolutionary stories) and Tillich (1990), both seedling morphology.
Phylogeny. Nymphaea s. str. was monophyletic in a phylogenetic analysis of vegetative characters, but without much support (D. W. Taylor 2008); see also Borsch et al. (2007, 2012) - the genus definitely includes the wind-pollinated and usually apetalous Ondinea, but some relationships lacked much support, e.g. the position of [Euryale + Victoria] as sister to Nymphaea s.l. (see also Gruenstaeudl et al. 2017: support also not that strong). An increasing number of studies are finding that the spiny Victoria and Euryale are well embedded in Nymphaea s.l. (Löhne et al. 2007, 2009; Borsch et al. 2008; He et al. 2018; Laczkó et al. 2019; c.f. Friis et al. 2011). See also D. W. Taylor and Gee (2014) and Coiro and Barone Lumaga (2018) for relationships, the former integrating data from fossils and the latter floral epidermal micromorphology in their analyses. Padgett et al. (1999) discuss relationships/species numbers in Nuphar.
Classification. The inclusion of Nuphar in Nymphaeaceae needs to be confirmed (see above ). In any event, a broad circumscription for Nymphaea, including genera like Victoria, etc., seems best.