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92 R.L.B. de Borges et al. / Review of Palaeobotany and Palynology 154 (2009) 91–105 Table 1 Previous morphological pollen data of representatives of the Eriocaulaceae family Authors Taxa Method Subject Erdtman (1943) Eriocaulon septangulare Withering LM Pollen morphology and plant taxonomy - Angiosperms Kuprianova (1948) Eriocaulon benthamii Kunth and Paepalanthus blepharocnemis Mart. LM Pollen morphology of monocotyledons Erdtman (1952) Syngonanthus wahlbergii (Wikstr.) Ruhl and Tonina fluviatilis Aubl. LM Pollen morphology and plant taxonomy - Angiosperms Ikuse (1956) Eriocaulon miquelianum Körn., E. nipponicum Maxim., E. parvum Körn, E. senile Honda, and E. sielboldianum Sieb. et Zucc. (= E. cinereum R. Br.) LM Pollen flora of Japan Thanikaimoni (1965) Eriocaulon L. (46 spp.), Lachnocaulon Kunth (2 spp.), Leiothrix Ruhland (1 sp.), Paepalanthus Mart. (1 sp.), Philodice Mart. (1 sp.), Syngonanthus Ruhland (2 spp.), and Tonina Aubl. (1 sp.) LM Pollen morphology of the Eriocaulaceae family Huang (1972) Eriocaulon cinerum R. Br. Var. sieboldianum (Sieb. & Zucc.) T. Kayama, E. merrillii Ruhl., E. nantoense Hay., E. trisectum Satake, E. truncatum Buch.-Ham. LM Pollen flora of Taiwan Ybert (1979) Mesanthemum prescottianum (Bong.) Körn. LM Pollen flora of the Ivory Coast Furness (1988) Eriocaulon aquaticum (Hill) Druce. LM, SEM Eriocaulaceae in the Northwest European pollen flora Santos et al. (2000) Actinocephalus (8 spp.) and Paepalanthus (7 spp.) LM Pollen morphology of some Brazilian Eriocaulaceae Rull (2003) Paepalanthus perplexans Mold. LM Illustrated pollen key of some Venezuelan species Coan et al. (2007a) Syngonanthus caulescens (Poir.) Ruhland SEM Embryological study of the species, only SEM pictures of pollen grains were presented Coan et al. (2007b) Leiothrix fluitans (Mart.) Ruhland SEM Embryological study of the species, only SEM pictures of pollen grains were presented Method: LM — light microscopy, SEM — scanning electron microscopy. The first study of the Eriocaulaceae using scanning electron microscopy was undertaken by Furness (1988), who described the pollen grains of Eriocaulon aquaticum (Hill) Druce. Coan et al. (2007a,b) published electro-micrographs of the pollen grains of Syngonanthus caulescens (Poir.) Ruhland and Leiothrix fluitans (Mart.) Ruhland as a part of their study of the embryology of these taxa. Considering all the pollen morphological data related to the Eriocaulaceae to date, only 87 taxa have been described, of which 60 are species belonging to the genus Eriocaulon. Furthermore, the principal pollen study of the family (Thanikaimoni, 1965) was published 43 years ago and employed only light microscopy. For these reasons, the objective of the present work was to provide a more complete study of the family and to clarify the patterns of the pollen apertures exhibited by the different taxonomic groups, using both light and scanning electron microscopy. 2. Materials and methods In accordance with Ruhland's (1903) classification system for Eriocaulaceae, we studied the pollen grains of 55 species from the genera Actinocephalus, Blastocaulon, Eriocaulon, Lachnocaulon, Leiothrix, Paepalanthus, Philodice, Rondonanthus, Syngonanthus, andTonina. The genus Mesanthemum was not included in this work due to the lack of study material, but both of the subfamilies cited by Ruhland (1903), Eriocauloideae and Paepalanthoideae, were considered. Taxonomic arrangement of the group is: Order Poales Fam. Eriocaulaceae Subfam. Eriocauloideae Eriocaulon 400/4 1 Mesanthemum 12/0 Paepalanthoideae Actinocephalus 29/6 Blastocaulon 5/2 Lachnocaulon 7/2 Leiothrix 37/9 Paepalanthus 485/15 Philodice 2/1 Rondonanthus 6/1 Syngonanthus 200/14 Tonina 1/1 1 Total number of species/number of species included in present study. Pollen samples (the capitula) for our analyses were obtained from herbarium specimens that had been securely identified and incorporated into the Herbário da Universidade Estadual de Feira de Santana — HUEFS, Herbarium of the Miami University — MU, and Herbário do Departamento de Botânica, Instituto de Biociências (Universidad de São Paulo) — SPF. All of the specimens examined are listed in the Appendix A. The acetolysis method (Erdtman, 1960) was used for the light microscope (LM) analysis of the pollen grains of 36 species. For each species, at least 20 pollen grains were used (except when not possible) in the morphometric analyses of the principal pollen parameters: diameter, width of the interapertural exine strip, thickness of the exine layers, and length of the spines. For the scanning electron microscopy (SEM) studies, 41 species of the above-mentioned genera were examined. Due to the fragile nature of the pollen grains and their low production, the anthers were removed from the flowers and opened directly over a stub covered by doublefaced self-adhesive carbon tape. The material was subsequently coated with gold and analyzed (LEO 1430 VP — Carl Zeiss). Photographs of the pollen characteristics were obtained under both LM and SEM techniques. The palynological nomenclature used follows Punt et al. (2007), and that of the type of aperture follows Pozhidaev (2000). All of the prepared material is deposited in the palynotheca of the Laboratory of Plant Micromorphology (LAMIV) at the Universidade Estadual de Feira de Santana, Bahia State, Brazil. 3. Results 3.1. General pollen morphology All species of Eriocaulaceae studied here had pollen grains that were monads, generally spherical, and varied in size from small (up to 25 µm) to medium (N25 µm) (Table 2). The smallest pollen grains are observed in Blastocaulon albidum, Lachnocaulon minus, Paepalanthus tortilis, and P. subtilis, while the largest grains are seen in Paepalanthus comans, P. planifolius (both P. subg. Platycaulon) and Rondonanthus duidae. Variations among the sizes of the pollen grains of the same specimen are relatively large: up to 14 µm as recorded for Syngonanthus schwackei (T. B. Cavalcanti et al. 2906) and 15 µm for Paepalanthus pulvinatus (M. J. G. Andrade 106). This fact may be due to rupturing of the aperture during chemical treatment (acetolysis), which increases the size of the pollen grains. Constant features among the pollen grains of the species of Eriocaulaceae that were analyzed are the spiral apertures and that the
Table 2 Morphometric data and apertural type of pollen grains of studied Eriocaulaceae species through light microscopy Species Diameter⁎ Interapertural strips⁎ surface of the exine is composed of (micro)spinose and granulose supratectal processes (Tables 2–3, Plates I–VII). 3.2. Apertures The pollen grains of Eriocaulaceae are spirapeturate. They have one or more spiral apertures. Apertures isolate strips of exine between the spirals (Plate I, 3;Plate IV, 9;Plate VI, 1;Plate VII, 5). Here, these strips are considered to be “interapertural exine”. The R.L.B. de Borges et al. / Review of Palaeobotany and Palynology 154 (2009) 91–105 Exine thickness⁎ Apertural type Actinocephalus Actinocephalus bongardii (A. St.-Hill.) Sano (21) 24 (26) (7) 9 (12) (1) 1 (1) Spiraperturate (helicoidal) Actinocephalus denudatus (Körn.) Sano (25) 28 (31) (9) 11 (14) (1) 1 (2) Spiraperturate (helicoidal) Actinocephalus divaricatus (Bong.) Sano (24) 27 (33) (8) 10 (15) (1) 1 (1) Spiraperturate (helicoidal, other arrangements) Actinocephalus ramosus (Wikstr.) Sano (24) 27 (33) (9) 10 (13) (1) 1 (1) Spiraperturate (helicoidal, other arrangements) Blastocaulon Blastocaulon albidum Ruhland (19) 22 (25) (6) 7 (9) (1) 1 (1) Spiraperturate (helicoidal) Eriocaulon Eriocaulon elichrysoides Bong. (30) 33 (38) (6) 8 (11) (2) 2 (2) Spiraperturate (interapertural exine in a crosshatch pattern, other arrangements) Eriocaulon humboldtii Kunth (28) 32 (38) (6) 8 (10) (2) 2 (2) Spiraperturate (interapertural exine in a crosshatch pattern, other arrangements) Eriocaulon ligulatum (Vell.) L. B. Sm. (25) 29 (34) (5) 8 (9) (2) 2 (3) Spiraperturate (interapertural exine in a crosshatch pattern, other arrangements) Lachnocaulon Lachnocaulon minus Small (19) 22 (29) (6) 9 (13) (1) 1 (2) Spiraperturate (as the seams of a tennis ball) Leiothrix Leiothrix subgen. Leiothrix Leiothrix angustifolia (Körn.) Ruhland (25) 26 (31) (9) 11 (13) (1) 1 (1) Spiraperturate (helicoidal, other arrangements) Leiothrix distichoclada Herzog (25) 26 (30) (8) 11 (13) (1) 1 (2) Spiraperturate (helicoidal) Leiothrix flavescens (Bong.) Ruhland (25) 30 (34) (8) 12 (15) (1) 1 (2) Spiraperturate (as the seams of a tennis ball) Leiothrix hirsuta (Wikstr.) Ruhland (24) 26 (29) (8) 9 (11) (1) 1 (1) Spiraperturate (as the seams of a tennis ball) Leiothrix plantago (Mart.) Giul. (29) 32 (35) (9) 11 (13) (1) 1 (2) Spiraperturate (many arrangements) Leiothrix subgen. Rheocaulon Leiothrix fluitans (Mart.) Ruhland (28) 33 (39) (13) 15 (16) (1) 1 (2) Spiraperturate (as the seams of a tennis ball) Paepalanthus Paepalanthus subgen. Paepalanthus Paepalanthus applanatus Ruhland (29) 34 (40) (12) 13 (16) (1) 1 (2) Spiraperturate (helicoidal, other arrangements) Paepalanthus giganteus Sano (26) 29 (34) (10) 11 (13) (1) 1 (2) Spiraperturate (many arrangements) Paepalanthus pulvinathus N. E. Br. (20) 26 (35) (8) 11 (14) (1) 1 (1) Spiraperturate (helicoidal) Paepalanthus subtilis Miq. (19) 21 (24) (6) 7 (9) (1) 1 (1) Spiraperturate (helicoidal) Paepalanthus tortilis (Bong.) Mart. (19) 22 (25) (6) 9 (13) (1) 1 (1) Spiraperturate (helicoidal) Paepalanthus subgen. Platycaulon Paepalanthus bromelioides Silveira (26) 32 (39) (8) 12 (15) (1) 1 (1) Spiraperturate (helicoidal) Paepalanthus planifolius (Bong.) Körn. (30) 35 (40) (11) 13 (16) (1) 1 (2) Spiraperturate (many arrangements) Paepalanthus subgen. Xeractis Paepalanthus comans Silveira (31) 37 (43) (10) 13 (18) (1) 1 (2) Spiraperturate (many arrangements) Philodice Philodice hoffmannseggii Mart. (20) 25 (29) (6) 8 (13) (1) 1 (2) Spiraperturate (different arrangements) Rondonanthus Rondonanthus duidae (Gleason) Hensold & Giul. (31) 36 (41) (11) 13 (15) (2) 2 (2) Spiraperturate (helicoidal) Syngonanthus Syngonanthus sect. Syngonanthus Syngonanthus fuscescens Ruhland (25) 28 (31) (10) 13 (18) (1) 1 (2) Spiraperturate (many arrangements) Syngonanthus schwackei Ruhland Syngonanthus sect. Carphocephalus (26) 32 (40) (9) 11 (15) (1) 1 (2) Spiraperturate (many arrangements) Syngonanthus caulescens (Poir.) Ruhland Syngonanthus sect. Eulepis (23) 25 (28) (6) 7 (9) (1) 1 (2) Spiraperturate (many arrangements) Syngonanthus bisulcatus (Körn.) Ruhland (19) 24 (31) (9) 12 (15) (1) 1 (2) 2-zonasulcate Syngonanthus elegans var. elegans (Körn.) Ruhland (25) 27 (33) (10) 12 (14) (1) 1 (1) 2-zonasulcate Syngonanthus euschemus Ruhland (25) 28 (30) (11) 13 (15) (1) 1 (2) 2-zonasulcate Syngonanthus giuliettiae L. R. Parra (23) 25 (29) (11) 13 (18) (1) 1 (2) 2-zonasulcate Syngonanthus mucugensis Giul. Syngonanthus sect. Thysanocephalus (25) 32 (39) (13) 15 (18) (1) 1 (2) 2-zonasulcate Syngonanthus cipoensis Ruhland (29) 32 (38) (9) 12 (14) (1) 1 (2) Spiraperturate (many arrangements) Syngonanthus imbricatus (Körn.) Ruhland (26) 30 (35) (13) 17 (23) (1) 1 (2) 2-zonasulcate Syngonanthus vernonioides (Kunth) Ruhland ⁎Average (range), in µm. (28) 34 (39) (9) 11 (13) (1) 1 (2) Spiraperturate (many arrangements) spiral pattern of the apertures varies according to the group of species being examined (Plate I,1;Plate II, 9;Plate IV, 7). There are pollen grains with only one spiraperture, as seen in Actinocephalus (Plate I, 7–9), Blastocaulon (Plate II, 7–9), Lachnocaulon (Plate III, 1–3), Leiothrix (Plate IV, 4–6), and Rondonanthus (Plate VI, 1–3). On occasion, the apertures have an arrangement reminiscent of the pattern on a tennis ball, such as that observed in Lachnocaulon (Plate III, 1–3) and Leiothrix (Plate III, 7–9, 12). 93
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