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Pollen Ultrastructure of the Philydraceae

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Grana 24: 23-3 1, 1985 Pollen ultrastructure of the Philydraceae MICHAEL G. SIhlPSON Simpson, M. G. 1985. Pollen ultrastructure of the Philydraceae. - Grana 24: 23-31, 1985. Uppsala 8 May 1985. ISSN 0017-3134. Pollen morphology, sculpturing, and wll ultrastructure of the five species in the monocot family Philydraceae were investigated in order to assess phylogenetic relationships. All members of the Philydraceae have monosulcate, heteropolar pollen grains with a tectate- columellate exine having distinctive lamellae inner to the foot-layer. Histochemical tests of Pliilpdrrim lanirgiriosrirn indicate an ektexinous exine composition. The aperture uall of all members of the family consists of a thick, 2-layered intine with exine absent or composed of scattered deposits. The inner intine layer is infused with numerous vesicular or channel- like structures. Histochemical tests of Philpdriirn laniiginosirrri suggest that the outer intine layer is primarily cellulosic and the inner intine layer is pectic-rich, a trend opposite from that noted in pollen of other monocot taxa. Palynological similarities between the Philydra- ceae and related families, including monosulcate apertures and a tectate-columellate exine, are hypothesized to represent ancestral features which are of no value in assessing phylogenetic relationships. hficlinel G. Simpson, Depnrfrtient of Bornrip, Dirke Uiiiversirp, Dirrhnrn, Norzh Cnrolinn 27706, USA (Current address: Depnrttnent of Biology, Albrighr College, Rending, Penn- sylvonia 19603, USA) (hfanuscript receiwd 2 September 1983. revised version accepted 7 hinrch 1981) The Philydraceae (sensu Hamann 1966) are a small to either the Haemodoraceae or Pontederiaceae. monocot family of four genera and five species: For example, Engler & Prantl (1930) placed the Helriilioltzio (2 species; eastern Australia, New Philydraceae adjacent to the Pontederiineae (Ponte- Guinea). Orrhorhjl~x(monotypic; eastern Austra- deriaceae and Cyanastraceae), whereas Hutchinson lia); Pliilydrella (monotypic; western Australia), (1934, 1959, 1973) classified the Philydraceae with and Philydririn (monotypic; Australia, Malaysia, five other families (Taccaceae, Apostasiaceae, Vel- and eastern Asia). All family members are peren- loziaceae, Hypoxidaceae, and Haemodoraceae) in nial, rhizomatous or cormose herbs having disti- his order Haemodorales. Hamann (1966) suggested chous, ensiform (equitant, unifacial) leaves and a close affinities between the Philydraceae and Pon- simple to branched spicate, bracteate inflores- tederiaceae and possibly also to the Haemodora- cence. The Philydraceae probably constitute a ceae and Hypoxidaceae. The Philydraceae was monophyletic taxon as evidenced by the occur- classified by Dahlgren (1980) and Dahlgren & Clif- rence of a distinctive and apparently derived floral ford (1982) as the order Philydrales, closely related Downloaded by [SDSU San Diego State University] at 10:35 25 February 2015 structure, consisting of: fusion of the two outer to the Haemodorales, Pontederiales, Velloziales, latero-posterior tepals with the inner posterior tepal and Commelinales. Thorne (1976) grouped the Phi- and presence of a single, anteriorly positioned sta- lydraceae with the Pontederiaceae in the suborder men (Hutchinson 1973, Hamann 1966). Pontederiineae (Commeliniflorae), to which Thorne Because of the morphological homogeneity of the (1981), based on chemical evidence (Hams & Hart- Philydraceae, taxonomists have encountered few ley 1980) added the Haemodoraceae. The Philydra- differences as to the circumscription and intrafamil- ceae were thought to share common ancestry with ial classification of the family (see Hamann 1966). the Pontederiaceae by Takhtajan (1980) because of Interfamilial classifications of the Philydraceae similarities in anatomy and embryology. Finally, have varied; most systems place the family "near" Cronquist (1981) placed the Philydraceae adjacent Griina 24 24 M. G. Sitlipsoti Downloaded by [SDSU San Diego State University] at 10:35 25 February 2015 Fig. 1. Heltnholrziu. A-E: If. acorvolio. (A) Whole grain, Apertunl wall, showing thick, 2-layered intine (11 with aperture above. SEM ~2700.(B) Close-up; note reticu- numerous vesicles (arrow) of inner intine layer. Note late non-apertunl \mil and verrucate apertunl elements. exine (e) composed of a continuous thin layer and larger SEM XS 100. (C) Interface between apertural wall (lower irregular exine elements. ~20000.(E) Nonapertural wall. left) and non-apertural wall; note, in apertural region, Note 2-layered intine (9, with vesicular inner layer, and expansion of the 2-layered intine. TEM X 11 0oO. (D) tectate-colurnellate exine (e), with lamellate inner foot- Grana 24 Exine iiltrastriictiire of Philydraceae 25 to the Pontederiaceae and Haemodoraceae in the pollen morphology and wall ultrastructure. A tec- Liliales. tate-columellate exine wall architecture is found in All four genera and five species of the family investigated members of the Cyanastraceae (Cyan- have been investigated palynologically with bright- astrrim), Hypoxidaceae (Hypoxis, Curculigo), Pon- field microscopy (Erdtman 1966, Hamann 1966 and tederiaceae (flereranthera, Pontederia), Taccaceae references cited therein). Pollen grains of Phily- (Tacca), and Velloziaceae (Barbecmia, Vellozia). drum are distinct in the family in being united as In contrast, fourteen genera of the Haemodoraceae tetragonal tetrads at maturity; grains of the other have a 1- to 3-layered, non-tectate-columellate ex- four species are shed as monads (Erdtman 1966, ine architecture (see Simpson, 1983a). Therefore, a Hamann 1966). Erdtman (1966) described Orrhothy- primary goal of the present study is to determine lax glaberrima, Philydrella pygmaea, and Phily- what similarities and differences of pollen sculptur- drum laniiginosirm as monosulcate; Ilelmholrzia ing or wall architecture occur between members of acorifolia was described by Erdtman as “probably the Philydraceae and these presumed related fam- 3-Or zonisulcate.” Hamann (1966), however, disa- ilies. In addition, the determination of whether greed with Erdtman, and described both H. acori- these palynological features are ancestral or de- folia and H. nouo-griineensis as monosulcate. (Ha- rived within this complex of families is vital in mann reported that the “3-sulculate” condition de- order to assess their value in recognizing monophy- scribed by Erdtman was possibly the result of a letic taxa (sensu Hennig 1966). shrinkage effect from acetolysis.) With regard to sculpturing, Erdtman (1966) described Orrhothylux MATERIAL AND METHODS and Philydrella as “reticulate (polybrochate),” and Philydriim as “reticulate (slightly heterobrochate; Pollen samples were obtained either from herbarium sheets (“DRIED”) or were fixed in formalidacetic ac- muri +I- duplibaculate).” Both species of Helm- idalcohol (“FAA”). Dried anthers were re-hydrated in holtzia are reported to have a tine, unresolvable Aerosol OT for 1-4 days, followed by several water (with light microscopy) exine sculpturing (Hamann rinses. The following species were examined (parentheses 1966). The sexine of all genera in the family is indicate herbaria where vouchers are deposited): Helm- holrziu acorifoliu F. v. Mueller ‘‘FAA’’ - M. G.Simpson described as thicker than or as thick as the nexine 81-16A (DUKE); H. now-girineensis(Krause) Skottsberg (Erdtman 1966). Erdtman summarizes the Philydra- “DRIED” - L. J. Brass 12859 (A); Ortho1hylaxgloberri- ceae as “pollenomorphologically a +/- heteroge- miis (Hooker fil.) Skottsberg “FAA” - cult. Hod. Bot. nous family.” Kew (Herb. U. Hamann, Bochum 1183); Philydrellu pyg- The purpose of the present study is to describe moea (R. Brown) Caruel “FAA” - M. G. Simpson 28IX81A (DUKE); Pbilydrum lunirginosum Banks & So- and characterize, using SEM and TEM, the pollen lander ex Gaertner “FAA” - E. F. Constable 4128 sculpturing and ultrastructure of the Philydraceae in (Herb. U. Hamann, Bochum 959, ex. Herb. NSW 58993). order to assess phylogenetic relationships of the fa- For SEM studies, whole, dehisced anthers containing mily, particularly with reference to other monocoty- mature pollen were placed in a modified capsule between two 5 pm Nucleopore filters. Anthers or free pollen were ledonous taxa. Of the families cited by the above progressively dehydrated to 100% ethanol, then infiltrat- authors to be closely related to the Philydraceae, ed with 100% Freon I13 (intermediate fluid). The material the Cyanastraceae (Simpson, in press, Haemo- was critical-point dried in a BOMAR SPC W/EX drier doraceae (Simpson 1983 a), Velloziaceae (Ayensu using COz as the transition fluid. Pollen grains were & tapped onto a stub covered by double-stick Scotch tape, Skvarla 1974), and selected members of the Hy- sputter coated (ca. 200 A thickness) with goldpalladium poxidaceae, Pontederiaceae and Taccaceae (Simp- (60/40),and viewed with a Jeol TZO SEM. Downloaded by [SDSU San Diego State University] at 10:35 25 February 2015 son 19836) have been investigated with respect to For TEM analysis of wall architecture, pollen samples were fixed in 4.2% buffered gluteraldehyde for 2 hours, rinsed in 0.1 M Sorensen’s phosphate buffer, and post- layer (arrow). TEM X21 OOO. F-J: 11. now-guineensis.(0 fixed in 2% Os04for 1 hour, After two rapid hater rinses Whole grain, sulcate aperture above. SEM x3 100. (G) and progressive dehydration to 100% ethanol, the materi- Close-up, nonapertural wall. SEM ~4700.(H) Close-up, al was infiltrated in a series of increasing concentrations
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