IAWA Journ al, Vol. 17 (2), 1996: 183-204 VESSELS IN ERIOCAULACEAE by Jennifer A. Thorsch & Vernon I. Cheadle I Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93 106, U.S.A. SUMMARY The occ urrence and level of specialization of vesse ls in 70 species representing 12 genera of Eriocaulaceae are presented. In alI species of Eriocaulaceae and in alI parts of the plant examined, vessels with simple perforations have been identified . Correlations between level of specia­ lization of vessel members and ecological conditi ons are reported for species from diverse habitats and species with distinct differences in habit. The pattern of origin and specialization of tracheary celIs in Erio­ caulaceae was compared to tracheary data for Xyridaceae , Rapateaceae, Restionaceae and Centrolepidaceae. The evolutionary position of these families has been regarded as close to Eriocaulaceae. Key words: Eriocaulaceae, vessels, perforation plates, phylogenetic posi­ tion. INTRODUCTION This paper provides detailed information about perforation plates of vessels in Erio­ caulaceae, the 29th family we have similarly examined in monocotyledons. The near­ ly complete list of families analyzed in detail is given in the literature cited in the paper on Commelinales (Cheadle & Kosakai 1980). Our studies on the tracheary elements in monocotyledons have included families and species from a broad range of habits, habitats and geographical sites around the world. Families for study were selected based on three criteria: I) presence of alI plant parts, 2) variety of habits and habitats, and 3) broad representation of the species within the family. The data on tracheids and vessels from these broadly based studies led to the folIowing brief conclusions. Vessels arose from a series of overlapping tracheids by loss of membranes from scalariformly arranged pits in long, oblique ends of tracheids (Cheadle 1953). Those vessel members that are most like tracheids are considered the most primitive: they are long and narrow, appear angular in transverse view, and have long oblique end walls with many perforations arranged scalariformly. Conversely, vessel members least like tracheids are most advanced: they have shorter lengths, greater diameters, are circular in transverse view, and have single perforations on transversely placed end walIs (simple perforation plates). All gradations between the types of ves­ sel members described as most primitive and the most advanced can be found in extant 1) Deceased. Downloaded from Brill.com09/28/2021 02:34:37AM via free access 184 IAWA Journal, Vol. 17 (2), 1996 monocotyledons. Indeed, such a range of tracheary elements throughout the plant in extant monocotyledons provides evidence for drawin g conclusions about probable evolutionary sequences. The evidence supports the view that vessels arose and subsequently became highly advanced in success ion in the roots, stems, infloresce nce axes, and leaves. Further­ more, within each organ, separately, the evolutionary sequence is identical, beginning in the late metaxylem and progressing successively into the early metaxylem and proto­ xylem (where the evidence is less obvious and less abundant). The evolutionary position of the Eriocaulaceae has been regarded as close to Xyri­ daceae (including Abolbodaceae), Rapateaceae, Restionaceae and Centrolepidaceae (Dahlgren et al. 1985). Specific features such as stylar appendages, vegetative char­ acteristics, compact inflorescences and floral and embryologica l charac ters indicate a somewhat close relatio nship between Eriocaulaceae and Xyridaceae.However, Erioca ulaceae does possess rather distinct characters that may sugges t placement in a separate order (as in Dahlgren 1975). Clasdistic analysis (Davis 1995) and morph o­ logical data (Linder & Kellogg 1995) have also shown a close relationship with Commelinaceae , Xyridaceae and Rapataceae. Exa mination of the tracheary cells and determination of degree of specialization of the perforation plates in the vessels of Eriocaulaceae will be compared with published studies on tracheary cells in Xyridaceae and Rapateaceae (Cheadle & Kosakai 1982) and Centrolepidaceae and Restionaceae (Chead le & Kosakai 1975). The tracheary elements of Eriocaulaceae have not rece ived much attention in the literature. This is particularly true of perforation plates ofvessel members. Van Tieghem (1887), Paulsen ( 1888), Malm anche (1919), Ruhland (1903) among others, mentioned vessels, but provide almost no crucial inform ation. Solereder and Meyer (1929) gave details of vesse ls in the vegetative axis and/or inflorescence axis in Paepalanthu s falcifolius, Syngo nanthus nivens and Tonina flu viatilis. Toml inson (1965, 1969) pro­ vided the most reliable general information on vesse l members in the family. Papers by Monteiro et al. on leaves of Eriocaulon (1984) and of Leiothrix (1985) included drawings of cross sections of tracheary elements but did not describe these elements. Sttitzel (1988), likewise, included little information on vessels in roots of the family. MATERIALS AND METHODS Eriocaulaceae occur chiefly in the tropics and subtropics around the world, and are especially numerous in South America. Accordin g to Cro nquist (1981), the family consists of "about" 13 genera and some 1200 species, with most ofthe species belong­ ing to three genera, Paepalanthus (500), Eriocaulon (400), and Syngonanthus (200) . The plants generally grow in swampy, mucky or sandy (Moldenke 1957: 24) sites, but some are aquatic, and still others occur on borders of rocky, swiftly flowing creek s, or in places of moderate moisture or even in dryish areas. In habit, the plants vary from common rosette forms through spreading and erect types with aerial stems up to a meter or more in height. Downloaded from Brill.com09/28/2021 02:34:37AM via free access Thorsch & Cheadle - Vessels in Eriocaulaceae 185 The specimens were selected primarily from herbarium sheets that were on loan for our studies. From the over 900 herbarium sheets received, we were able to select ex­ amples representing a broad range of geographic sites, habits and habitats . In Table 1 (on the next page) the specimens examined are listed alphabetically and include our collection numbers (M or CA), as well as the abbreviation for the herbaria from which they were borrowed (if loaned specimens) and the accession numbers . All available plant parts of 70 species from 12 genera (20 spp. in Eriocaulon, 6 in Leiothrix, 21 in Paepalanthus, 9 in Syngonanthus) were examined. Dried specimens were rehydrated in several changes of warm water and preserved samples were rinsed thoroughly with water. The tissue was cut into .5 em segments and macerated in 40% glacial acetic acid, 50% distilled water and 10% hydrogen peroxide in pressure bottles at 65-75°C for 5-7 days. The tissue was rinsed in water, stained with Toluidine Blue and gently teased apart with fine needles in glycerine on a glass slide. Light microscope sections of all available plant parts were prepared from the chemi­ cally preserved specimens. The tissue was processed through a graded acetone series and embedded in Spurr 's resin (1969). Sections were cut at approximately 1-2 mil with a diamond knife and stained with Toluidine Blue. All the photomicrographs were taken with a Zeiss ultraphot equipped with a 35 mm camera attachment. To quantify the level of specialization of tracheary cells in the Eriocaulaceae a sys­ tem developed by V. Cheadle was employed. A value of 0 indicates only tracheids present; 1 only scalariform perforation plates; 2 mostly scalariform perforation plates; 3 approximately equal scalariform and simple perforation plates; 4 mostly simple per­ foration plates and 5 only simple perforation plates. RESULTS Photomicrographs of separated vessel members as well as of sectioned tissues of Erio­ caulaceae are presented to demonstrate the range of variation observed primarily in structure and position of perforation plates in each of the plant organs. Vessel members with simple perforation plates are described first, followed by those with clearly scalariform plates . A third category concerns plates intermediate in character between these two. Vessels with simple perforation plates have been identified in all parts of the plant in Eriocaulaceae. Simple perforations may have large (Fig. 1), intermediate (Fig. 2, 14,34) to small (Fig. 5, 6) diameters . The perforation plates may be transversely ori­ ented (Fig. 11, 13 upper, 29, 33), slightly oblique (Fig. 3, 16,30,39 profile view) or occur in a lateral position (Fig. 8 lower, 13 middle). In the short vessel members of rhizomes and caudices, simple plates generally occur on lateral walls (Fig. 7, 9, 10, 12). Simple perforation plates may occur on vessel members with little secondary wall thickening (Fig. 37, 38,43,47) as well as on those with more complete secondary wall thickening (Fig. 29, 30). The single perforation of simple perforation plates may oc­ cupy virtually the entire plate (Fig. 2, 6, 11, 37, 43) or only a portion of it leaving a small rim or border around the perforation (Fig. 1,3,29, and 64 at two arrows where part of a rim is visible). Downloaded from Brill.com09/28/2021 02:34:37AM via free access 186 IAWA Journal, Vol. 17 (2), 1996 Table 1. Eriocaulaceae. Key: genus/species with authority, VIC collection number and between brackets herbarium and herbarium accession number; if the latter is not available the collector's name and collection number is listed. Herbaria abbreviations as in the Index Herbariorum. B/astocau/on a/bidum (Koem.) Ruhl.: M /3/2 (UC 1397776) -B. prostratum Ruh!.: M / 4/8 (F 1770056), M / 488 (GH 27099). Comanthera kegeliana (Koern.) Moldenke: M /485 (US 1901897). Eriocau/on austra/e R. Br.: CA / 85; M /4 20 (F 473516) - E. dregei Hochst.: M /335 (MO 2688 157) - E. elichrysoides Bong.: M /358 (MO 2270471) - E. gilgianum Ruh!.: M /336 (MO 219905I) ­ E. humboldtii Kunth: M/ 370 (MO 2777459) - E.japonicum Koem .: M /334 (MO 2697885) - E. kunthii(= elichrysoidesi Koern.: M /4/6 (F 767669)- E.nilagirense Steud.: M /350 (MO 2582877); M /489 (Bembower 429, GH)- E.