Aperture Membrane Research Articles

Systematic implications of pollen morphology in Elsholtzia (Elsholtzieae–Lamiaceae)

Pollen morphology of 18 species (32 specimens) representing all three currently recognized sections of the genus Elsholtzia (Elsholtzieae–Lamiaceae) was investigated in detail using light, scanning electron and transmission electron microscopy. Elsholtzia pollen grains are small to medium in size (P=20–50 μm, E=16–45 μm), mostly prolate‐spheroidal to prolate, and rarely oblate‐spheroidal to subprolate in shape (P/E=0.95–1.46), hexacolpate (the amb more or less circular or ellipsoid) with granular aperture membranes. Three distinct types of sexine ornamentation are observed in Elsholtzia: perforate, rugulose‐bireticulate, and bireticulate. The bireticulate pattern is the most common, showing a wide range of morphological variation among species. The exine thickness varies from 1.2 to 2.5 μm. Among the present palynological data, the variability observed in sexine ornamentation of Elsholtzia could be of systematic significance. Current infrageneric classification of the genus Elsholtzia is partially congruent with pollen morphological data.

Distribution of extracellular polymeric substances in pilot-scale membrane bioreactor

The spatial distribution of extracellular polymeric substances (EPS) in a pilot-scale membrane bioreactor (MBR) was studied. The sampling points on top of and inside the membrane module were measured and analyzed by the experimental variant function. The content of EPS was spatially interpolated by ordinary Kriging method, and illustrated with SURFER software. A case study was carried out in an MBR with membrane aperture of 0.4 μm and handling capacity of 120 m3/d in Jizhuangzi sewage treatment plant, Tianjin. From the visualization of EPS distribution, it is seen that on the horizontal plane, the content of EPS was the lowest at the center; and on the vertical plane, the content of EPS decreased with the increase of depth. The shearing force caused by aeration of perforated pipe and the influent mode are the main influencing factors for this distribution.

Clinical and laboratory factors associated with shear-dependent platelet hyper-reactivity in patients on chronic aspirin therapy

The Platelet Function Analyzer-100® (PFA-100) assesses agonist-induced platelet aggregation under high shear by measuring the closure time (CT) of a membrane aperture by the formation of a platelet plug [ [1] Hayward C.P. Harrison P. Cattaneo M. Ortel T.L. Rao A.K. Platelet function analyzer (PFA)-100 closure time in the evaluation of platelet disorders and platelet function. J Thromb Haemost. 2006; 4: 312-319 Crossref PubMed Scopus (343) Google Scholar ]. The two agonist cartridges currently available are designed to screen patients for defects in primary hemostasis: The collagen/epinephrine (CEPI) agonist cartridge detects the antiplatelet effects of aspirin and the collagen/ADP (CADP) agonist cartridge, which is not influenced by aspirin, is useful in identifying patients with acquired and congenital platelet disorders such as von Willebrand disease [ [2] Favaloro E.J. Clinical application of the PFA-100. Curr Opin Hematol. 2002; 9: 407-415 Crossref PubMed Scopus (169) Google Scholar ]. With both agonist cartridges, prolongation of the CT beyond the normal range indicates inhibited or impaired platelet function. Recent evidence also suggests that the PFA-100 has utility in identifying patients with platelet hyper-reactivity, indicated by an abnormally low CT. In patients with cardiovascular disease, a CEPI CT in the normal range despite aspirin therapy has been associated with an increased risk of recurrent cardiovascular events [ 3 Reny J.L. de Moerloose P. Dauzat M. Fontana P. Use of the PFA-100 closure time to predict cardiovascular events in aspirin-treated cardiovascular patients: a systematic review and meta-analysis. J Thromb Haemost. 2008; 6: 444-450 Crossref PubMed Scopus (119) Google Scholar , 4 Crescente M. Di Castelnuovo A. Iacoviello L. De Gaetano G. Cerletti C. PFA-100 closure time to predict cardiovascular events in aspirin-treated cardiovascular patients: a meta-analysis of 19 studies comprising 3,003 patients. Thromb Haemost. 2008; 99: 1129-1131 PubMed Google Scholar ]. A CADP CT below the normal range, indicative of enhanced global platelet reactivity, has been observed in patients with acute coronary syndromes and found to correlate both with the degree of myocardial damage and with recurrent ischemic events [ 5 Frossard M. Fuchs I. Leitner J.M. Hsieh K. Vlcek M. Losert H. et al. Platelet function predicts myocardial damage in patients with acute myocardial infarction. Circulation. 2004; 110: 1392-1397 Crossref PubMed Scopus (223) Google Scholar , 6 Harrison P. Mackie I. Mathur A. Robinson M.S. Hong Y. Erusalimsky J.D. et al. Platelet hyper-function in acute coronary syndromes. Blood Coagul Fibrinolysis. 2005; 16: 557-562 Crossref PubMed Scopus (43) Google Scholar , 7 Fuchs I. Frossard M. Spiel A. Riedmuller E. Laggner A.N. Jilma B. Platelet function in patients with acute coronary syndrome (ACS) predicts recurrent ACS. J Thromb Haemost. 2006; 4: 2547-2552 Crossref PubMed Scopus (119) Google Scholar ].

Use of the PFA-100 closure time to predict cardiovascular events in aspirin-treated cardiovascular patients: a systematic review and meta-analysis.

PFA-100 is a point-of-care assay that evaluates platelet reactivity in high-shear-stress conditions by measuring the closure time (CT) of a membrane aperture. When determined with a collagen/epinephrine cartridge (CEPI), the CT is usually prolonged by aspirin. Studies of the predictive value of a short PFA-100CT(CEPI) for ischemic events in aspirin-treated patients have given variable results. To conduct a systematic review and meta-analysis of studies on the clinical predictive value of a short PFA-100CT(CEPI) in aspirin-treated cardiovascular patients. Relevant studies were identified by scanning electronic databases. Studies were selected if they included aspirin-treated patients with symptomatic atherosclerosis, measured the PFA-100CT(CEPI), used a CT cut-off value to define aspirin 'responders' and 'non-responders', and reported ischemic events. We selected seven non-prospective studies (1466 patients) and eight prospective studies (1227 patients). In non-prospective studies, the PFA-100CT(CEPI) was performed after the ischemic clinical endpoint, and a publication bias was identified. In prospective studies, the global odds ratio (OR) for the recurrence of an ischemic event in 'aspirin non-responders' relative to 'aspirin responders' was 2.1 [95% confidence interval (CI) 1.4-3.4, P < 0.001]. Pooled analysis with a random effect model revealed no heterogeneity (Q Cochran P = 0.36 and I(2) = 9.4%). A short PFA-100CT(CEPI) is associated with increased recurrence of ischemic events in aspirin-treated cardiovascular patients. This finding needs to be confirmed in stable ischemic patients, and the PFA-100CT(CEPI) cut-off needs to be refined in these patients.

Pollen morphology and ultrastructure of Saururaceae

The fine details of pollen grains in Saururaceae have, until now, been relatively obscure and incomplete. The recent discovery of fossil saururaceous pollen led us to examine the six extant and one fossil species of Saururaceae for details of pollen morphology and ultrastructure. Pollen grains of Saururaceae are characterized as small to minute, boat‐shaped‐elliptic to globose, monosulcate with granulate sculpturing of the aperture membrane, with a punctate tectum. Pollen grains of Houttuynia are the largest. While pollen grains of Anemopsis, Houttuynia, and Saururus have papillae bordering the puncta, those of Gymnotheca are distinctive in lacking such papillae. Similarly, all genera have a smooth tectum, except for Gymnotheca, which has microstriate tectal sculpturing. Pollen grains of Gymnotheca and the fossil have a well‐defined columellar infratectum, while in modern Saururus, Anemopsis and Houttuynia the columellae are irregular in section. Endexine is clearly present in all taxa. This study is the first to characterize pollen from all the species in Saururaceae, using both scanning and transmission electron microscopy. Such knowledge will help recognize fossil pollen of Saururaceae, a family with a poor palynological record.

Establishing a fossil record for the perianthless Piperales: Saururus tuckerae sp. nov. (Saururaceae) from the Middle Eocene Princeton Chert

Investigations of small permineralized flowers from the Middle Eocene Princeton Chert, British Columbia, Canada have revealed that they represent an extinct species of Saururus. Over 100 flowers and one partial inflorescence were studied, and numerous minute perianthless flowers are borne in an indeterminate raceme. Each flower is subtended by a bract, and flowers and bracts are borne at the end of a common stalk. Five stamens are basally adnate to the carpels. Pollen is frequently found in situ in the anthers. Examined under SEM and TEM, pollen grains are minute (6-11 μm), monosulcate, boat-shaped-elliptic, with punctate sculpturing and a granulate aperture membrane. The gynoecium is composed of four basally connate, lobed carpels with recurved styles and a single ovule per carpel. Flower structure and pollen are indicative of Saururaceae (Piperales), and in phylogenetic analyses using morphological characters, the fossils are sister to extant Saururus. The fossil flowers are described here as Saururus tuckerae sp. nov. These fossil specimens add to the otherwise sparse fossil record of Piperales, represent the oldest fossils of Saururaceae as well as the first North American fossil specimens of this family, and provide the first evidence of saururaceous pollen in the fossil record.

Comparative exine ontogeny in some members of the family Zygophyllaceae sensu lato

Exine ontogeny is studied in five taxa of the family Zygophyllaceae sensu lato (Peganum harmala L., Zygophyllum album L., Fagonia cretica L., Tribulus terrestris L., and Nitraria retusa [Forsk.] Asch.). In the beginning of the tetrad stage, the plasmalemma is attached to the callose wall, except in T. terrestris, where it describes crests and hollows. The primexine matrix is fibrillar, bilayered in T. terrestris and unilayered in the other taxa. In all species except P. harmala, the procolumellae are heterogeneous with clear zones and they become compact later. In T. terrestris, they are built on the crests. In Z. album and T. terrestris, a primordial nexinic lamella is set up. It is tripartite with a white line seen at some levels; on its external leaflet, the foot layer is observed, and on its internal leaflet, there is the endexine with numerous lamellae. This white line disappears often in the mature exine. In T. terrestris, there is a thick nexine that is coarsely lamellate inside. In the aperture zone, the columellae are lacking, the tectum and the foot layer get thinner; they unite and form the apertural membrane with the external part of the endexine. There is a granulolamellar endexinic zone well developed in P. harmala, whereas it is threelayered and weakly developed in T. terrestris.

Morfologia polínica de espécies do gênero Merremia Dennst. (Convolvulaceae) ocorrentes no Estado da Bahia, Brasil

O gênero Merremia (Convolvulaceae) teve as espécies nativas na Bahia inventariadas e estudadas sob o ponto de vista palinológico. Foram registrados nove táxons do gênero: M. aegyptia (L.) Urb., M. cissoides (Lam.) Hallier f., M. digitata (Spreng.) Hall. f. var. digitata, M. digitata var. ericoides (Meissn.) Austin &amp; Staples, M. dissecta (Jacq.) Hall. f. var. edentata (Meisn.) O'Donell, M. flagellaris (Choisy) O'Donell, M. macrocalyx (Ruiz et Pav.) O'Donell, M. tomentosa (Choisy) Hall. f. e M. umbellata (L.) Hall. f. Em M. digitata var. digitata e M. flagellaris os grãos de pólen apresentavam-se irregularmente e com três e seis colpos; membrana apertural espessa em M. aegyptia, M. cissoides, M. digitata var. ericoides; a exina é espessa e granulada em todas as espécies, o teto é fino; sexina mais espessa que nexina. Os grãos de pólen com 6 aberturas são zonocolpados (M. umbellata) ou pantocolpados (M. digitata var. digitata, M. digitata var. ericoides, e M. flagellaris), podendo ocorrer em um mesmo espécime mais de um tipo apertural de grão de pólen. Os dados palinológicos observados vêm fortalecer a união das espécies M. aegyptia, M. dissecta var. edentata e M. macrocalyx em M. sect. Schizips, M. umbellata em M. sect. Xanthips e as demais em M. sect. Cissoides. Nesta última seção, com exceção de M. tomentosa, as espécies restantes pertencem ao complexo M. digitata. No referido complexo as espécies não estão bem delimitadas sendo necessário que estudos mais profundos sejam realizados afim de melhor delimitá-las.

Pollen Diversity and Evolution in Myristicaceae (Magnoliales)

Myristicaceae consist of 21 genera and nearly 500 species of lowland rainforest trees with a pantropical distribution. This article presents new scanning electron microscopy observations on pollen of 13 genera, including all Asian genera, which had previously received very little attention from palynologists. While confirming that all Myristicaceae have monoaperturate pollen shed as monads with a sculptured aperture membrane, this study increases our knowledge of the diversity of pollen shapes, aperture shapes, tectal sculpture and microsculpture, and infratectal structure across the family. It also clarifies a few characters in previously investigated Afro‐Malagasy taxa. These results are discussed in the context of a recent phylogenetic study. While several pollen characters appear to be homoplastic, aperture shape, tectal sculpture, and infratectal structure seem to be of great phylogenetic value in Myristicaceae and clearly distinguish an Afro‐Malagasy clade of five genera (including Mauloutchia) from the rest of the family. Contrary to previous assumptions on character polarity, the ulceroid aperture shape and mixed (to granular) infratectum of most species in this clade both appear to be derived features, whereas the common ancestor of Myristicaceae likely was characterized by sulcate pollen with a columellar infratectum. A continuous tectum also clearly sets apart the members of this Afro‐Malagasy clade from the rest of the family, which has a reticulate to rugulate tectum. However, the status of this character in the ancestor of Myristicaceae remains equivocal.

Androdecidua endressiigen. et sp. nov., from the Late Cretaceous of Georgia (United States): Further Floral Diversity in Hamamelidoideae (Hamamelidaceae)

The early history of Hamamelidaceae is currently documented by several reproductive structures from Late Cretaceous sediments of the Northern Hemisphere. Recently discovered floral remains from the late Santonian (Late Cretaceous) Allon locality, in central Georgia (United States), represent an additional extinct taxon, Androdecidua endressii gen. et sp. nov., which documents further floral diversity within Hamamelidaceae. The remains of A. endressii comprise the androecium and corolla of a whorled, pentamerous, and actinomorphic flower. Calyx and gynoecium are unknown. The androecium consists of 10 stamens arranged in two alternating whorls of five, with the stamen filaments fused at their bases. The five petals are fusiform and slightly dorsiventrally flattened. They are opposite and basally fused to the filament bases of the inner whorl of stamens. The stamens and petals detach as a unit from the floral receptacle. The stamens have distinct filament and anther and a prominent apical extension of the anther connective. Filaments are massive, broad, and nearly parallel‐sided. Anthers are short and abaxially rounded, but radially elongate. The long apical extension of the connective is flattened and directed toward the center of the flower, where the connective extensions of the 10 stamens converge to form a low conical peak. Stamens of the outer whorl have bithecal and bisporangiate anthers in which the adaxial pollen sac of each theca is missing. Thecal dehiscence is through a single valve. Stamens of the inner whorl have bithecal and tetrasporangiate anthers that dehisce through two valves. Pollen grains are spheroidal and tricolpate, with a coarse and moderately heterobrochate exine reticulum and a line of gemmae on the aperture membrane. The presence of a long apical extension of the connective and the valvate anther dehiscence indicate the affinity of A. endressii with the genera of subtribe Loropetalinae (Hamamelideae; Hamamelidaceae). The level of synorganization of the corolla and androecium and the presence of two structural types of anthers are characters previously unknown among Hamamelidaceae.

Pollen morphology and wood anatomy of the Crudia group (Leguminosae, Caesalpinioideae, Detarieae)

Pollen from all 12 and wood from 11 genera in the Crudia group have been examined using light, scanning electron and transmission electron microscopy. This group is currently of systematic interest because it is part of a tribe undergoing taxonomic revision. The pollen grains fall into four groups: (1) Oxystigma, Kingiodendron, Gossweilerodendron, Bathiaea, Neoapaloxylon, Stemonocoleus, Guibourtia and Prioria have pollen of a widespread and generalized caesalpinioid type that are small to medium sized, spheroidal to prolate, tricolporate and with a perforate exine, with some variation in surface ornamentation, aperture margins and ultrastructure. (2) Crudia pollen is tricolporate, coarsely striate with a coarsely scabrate to vermiculate aperture membrane. (3) Augouardia is tricolporate and coarsely reticulate. (4) Hardwickia and Colophospermum are pantoporate and reticulate or microreticulate-rugulate. The wood of Prioria, Oxystigma, Kingiodendron and Gossweilerodendron has diffusely arranged axial canals, and these are four genera that have recently been merged into Prioria. Bathiaea has tangentially arranged axial canals. The other genera lack normal axial canals. Crudia is distinct, with banded parenchyma and variably storied short rays, Augouardia has much less abundant axial parenchyma that is mainly scanty paratracheal and vasicentric, Guibourtia has mainly aliform parenchyma and rays variable in height and width, and Colophospermum and Hardwickia have similar paratracheal parenchyma patterns, although the rays tend to be wider in the latter. Our conclusion is that the Crudia group is not monophyletic.

Pollen morphology and wood anatomy of the Crudia group (Leguminosae, Caesalpinioideae, Detarieae)

Pollen from all 12 and wood from 11 genera in the Crudia group have been examined using light, scanning electron and transmission electron microscopy. This group is currently of systematic interest because it is part of a tribe undergoing taxonomic revision. The pollen grains fall into four groups: (1) Oxystigma, Kingiodendmn, Gossweilerodendron, Bathiaea,. Neoapaloxylon, Stemonocoleus, Guibourlia and Prioria have pollen of a widespread and generalized cacsalpinioid type that are small to medium sized, spheroidal to prolate, tricolporate and with a perforate exine, with some variation in surface ornamentation, aperture margins and ultrastructure. (2) Crudia pollen is tricolporate, coarsely striate with a coarsely scabrate to vcrmiculate aperture membrane. (3) Augouardia is tricolporate and coarsely reticulate. (4) Hardwickia and Colophosperrnum are pantoporate and reticulate or microreticulate-rugulate. The wood of Prioria, Oxystigma, Kingiodendmn and Gossweilerodendron has diffusely arranged axial canals, and these are four genera that have recently been merged into Prioria. Bathiaea has tangentially arranged axial canals. The other genera lack normal axial canals. Crudia is distinct, with banded parenchyma and variably storied short rays, Augouardia has much less abundant axial parenchyma that is mainly scanty paratracheal and vasiccntric, Guibourtia has mainly aliform parenchyma and rays variable in height and width, and Colophosperrnum and Hardwickia have similar paratracheal parenchyma patterns, although the rays tend to be wider in the latter. Our conclusion is that the Crudia group is not monophyletic.

Caractères ultrastructuraux du pollen de quelques Podostémales. Affinités avec les Rosidae évoluées

The order Podostemales are two pantropical families of aquatic plants living in running water: Tristichaceae (five genera, ten species) and Podostemaceae (35 genera, 200 species). Pollen of the 26 genera and 62 species studied is characterized by: a granular infratectum in which the granules are sometimes organized as columellae like units, and a lamellar and/or granular endexine in all pollen types, single or in dyads. Most of the apertural characters and the ornamentation of the exine allow us to distinguish the previously established taxonomic groups: Weddellinoideae have tricolporate rugulo-areolate, pollen with a smooth apertural membrane; in Tristichoideae, pollen is periporate and the microspines of the tectum and of the apertural membrane are massive; in Podostemaceae, the tectal spines with their broad bulbous base are formed from numerous masses of sporopollenin, the endexine is microfibrillar at the base, the apertural membrane is constituted of structured ectexinous masses, and the endexine is granular at the aperture. Presence of the tricolporate pollen type associates the Podostemales with the higher eudicotyledons. Most of the pollen characters of Podostemales and their variations are found among advanced Rosidae (Hamamelidales, Polygalales, Santalales, Violales, Euphorbiaceae).

Pollen types in the Amaranthaceae. Morphology and evolutionary significance

The Amaranthaceae is a family within the order Caryophyllales and comprises approx. 800 species in about 70 genera. A representative selection of 130 species from 67 genera was studied. The pollen was found to be generally pantoporate. High resolution scanning electron microscopy and additional light microscopy revealed many new characters of the apertures, in particular of the ektexinous bodies on the aperture membrane, of the exine microsculpture, of the wall ultrastructure, and information on pollenkitt. The subsequent analysis of the resulting large data set led to the recognition of 17 well defined pollen types. The taxonomic distribution of pollen characters in the Amaranthaceae indicates that pollen morphology is informative at different taxonomic levels. Certain pollen characters can be used to circumscribe genera or groups of genera, and often also to distinguish species. Unique within the angiosperms are the hook‐shaped, stellately arranged ektexinous bodies covering the pore membranes in pollen of nine genera. Palynological data support the basic subdivision of the Amaranthaceae into the Amaranthoideae and Gomphrenoideae, but indicate that the commonly accepted tribes and subtribes in the classification of Schinz are largely polyphyletic. Pollen characters further provide evidence that a previously described pollination syndrome involving betalains as optical attractants is derived within the Amaranthaceae.

Fabrication Process of Character Projection Mask for EB Lithography

A new structure for a character projection (CP) mask has been developed for the electron-beam (EB) lithography system, EX-8D. The mask comprises an electroplated Au membrane on which apertures are formed and a (110) oriented Si substrate. The Au membrane is 4 µm thick, which is thick enough to stop 50 keV electrons. The aspect ratio of the Au aperture is much less than that of the conventional Si aperture, so that the size of the apertures can be well controlled. By a repair process using a focused ion beam (FIB), the edge roughness and the curvature radius at the corner of the aperture are reduced to less than 0.2 µm. Since the demagnification ratio of EX-8D is 1/36, these errors are 0.006 µm on the wafer and sufficiently small for 0.15 µm lithography. On the CP mask, we arranged a 7×7 array of apertures in a 1650×1650 µm2 area with a small amount of dead space. This arrangement can be realized by the use of a Si (110) substrate on which back-etched holes with ve rtical sidewalls were formed. In addition, this CP mask has sufficient mechanical rigidity and heat conductivity, because the aperture membrane is supported by Si struts.

Pollen grain and Ubisch body development in Platanus acerifolia

Different stages of development of pollen wall, aperture and Ubisch bodies of Platanus acerifolia (Aiton) Willdenow, have been examined with transmission electron microscopy. Different histochemical techniques for glycoprotein, unsaturated lipids and neutral and acid polysaccharides have been used. At the post-meiotic stage a polysaccharide primexine or glycocalyx is formed around the young microspores. The lipidic, glycoprotein and polysaccharide pro-Ubisch bodies are located between the tapetum plasmalemma and glycocalyx. At the liberation of microspores, glycocalyx increases in conjunction with the pro-columella and the pro-foot layer; elements of the discontinuous proectexine are located in the apertural membrane; pro-sporopollenin-like material is located on the pro-Ubisch bodies. At a more advanced microspore stage, the glycocalyx is fibrillar and the pro-endexine layer is formed under a white line; the pro-Ubisch bodies show a strong lipidic and scanty glycoprotein and polysaccharide central body; the glycocalyx envelope is formed by a thin neutral polysaccharide layer. At the vacuolate stage, a fibrillar polysaccharide glycocalyx is observed on the tapetum and microspore, the ectexine and endexine are consolidated and the Ubisch bodies have the same pattern as the reticulate and spinulate exine. In ripe pollen, the intine is located, the glycocalyx is faintly contrasted and the veil of lucent pollenkitt is present on the exine. At this stage the staining for lipids, glycoprotein, acid and neutral polysaccharide in the central part of the Ubisch bodies is still marked.

The morphology and ultrastructure of Caytonanthus

The morphology and ultrastructure of Caytonanthus arberi pollen organs and pollen, collected from the Middle Jurassic, Cayton Bay locality of England, are described. Pollen organs consist of flattened rachises with suboppositely branched pinnae, which bear terminal synangia. The synangium is covered with a two-zoned (fibrillar and amorphous) cuticle. The locule of each pollen sac is lined with a lamellated tapetal membrane and contains numerous pollen grains and orbicules. Grains are small, monosulcate, and bisaccate. Exine ornamentation of the proximal wall is psilate, while distally the apertural membrane is scabrate. The exine is composed of a thick, lightly staining sexine and a thin, darkly staining nexine. The sexine is tectate-alveolate laterally, becoming nearly homogeneous medially. The infratectal alveolae are robust and are continuous with the endoreticular units of the sacci. Sacci are eusaccate, with endoreticulations attached only to the outer walls. Several immature grains have also been identified and indicate that the nexine is lamellate throughout and that infratectal alveolae and nexine lamellae are well developed prior to complete tectum synthesis. Saccus size and ultrastructure of Caytonanthus pollen are compared with those of other Late Paleozoic and Mesozoic seed ferns that produced saccate pollen (Callistophytales, Glossopteridales, Corystospermales) and found to be smaller and more extensively filled with thicker endoreticulations. Documentation of the eusaccate character state in Caytonanthus is also discussed regarding its phylogenetic implications. Key words: Caytonanthus, Caytoniales, Mesozoic, pollen, seed fern, ultrastructure.

A New Section and Two New Species of Tragia (Euphorbiaceae) from the Venezuelan Guayana and French Guiana

A New Section and Two New Species of Tragia (Euphorbiaceae) from the Venezuelan Guayana and French Guiana

Pollen apertures, exine sculpturing and phylogeny in Iridaceae subfamily Iridoideae

Specialization from the basic monosulcate and semitectate-reticulate pollen grains of Iridaceae subfamily Iridoideae occurs in all of its four tribes. Disulcate apertures characterize Tigridieae subtribe Tigridiinae (4 genera). Zonasulculate grains occur in two derived species of Cipura (Tigridieae subtribe Cipurinae) and Dietes iridoides (Irideae subtribe Iridinae), all three autogamous. Aperture membranes are typically smooth, but are verrucate in Alophia (Cipurinae), a condition evidently apomorphic for the genus. Operculate apertures occur in Hermodactylis and Iris reticulata (subgenus Hermodactyloides) and there appears to be a gradation in the subgenus to a zonasulculate condition as found in I. danfordiae. While a fairly uniformly reticulate exine predominates in Iridoideae, a trend towards microreticulate or reticulo-rugulate exine is evident. This is accomplished in Gelasine by elongation of the muri and narrowing of the lumina, and by thickening of the muri in Ennealophus and Herbertia. Notable increase in lumina size characterizes some species of Moraea, and the species of Cipura and Dietes in which the grains are zonasulculate. Lumina of sharply different sizes are a notable feature of the exine of Isophysis (Isophysidioideae) and the species of Cypella sometimes segregated as Hesperoxiphium. We conclude that variability in both apertures and exine sculpturing is sufficiently great in the larger genera of Tigridieae and Irideae, and in some smaller ones as well, that palynological data should be sought routinely in systematic and phylogenetic studies in the two tribes. A smaller degree of variation in Mariceae makes it seem less useful to include such studies here. Data from this and other palynological investigations of the Iridoideae indicate that at least at the tribal level for Tigridiinae, and at the generic level for Alophia (and possibly Ennealophus and Gelasine), pollen characters provide valuable synapomorphies for taxon delimitation.

Pollen morphology of spanishlithospermums.l. (boraginaceae) and its taxonomic significance

Abstract The pollen morphology of 12 taxa belonging to four genera of Boraginaceae have been investigated by LM and SEM. The pollen grains vary from genus to genus, and even in some species. In general, the pollen grains are small, isopolar, sometimes subisopolar, colporate with four, five or more apertures; apertural membrane granular. Exine tectate, tectum psilate. The taxonomic implications of the pollen morphological features are discussed.