C-bands and chiasma distribution inScilla amoena,S. ingridae,andS. mischtschenkoana (Hyacinthaceae)

An effect of C-band pattern and polymorphism on chiasma distribution in pollen meiosis was recently demonstrated inScilla siberica. A further meiotic banding study has been performed in the alliesS. amoena, S. ingridae, andS. mischtschenkoana in order to analyze the effect, if any, of their specific C-band patterns and cytochemically different heterochromatin types on recombination. No clear evidence for a preferential formation of chiasmata adjacent to homozygous intercalary heterochromatin and no consistent reduction of chiasma frequency near strongly heterozygous intercalary heterochromatin blocks, as observed inS. siberica, could be found. Terminal C-band heteromorphism is suspected to cause distal chiasma defaults. The results suggest once more that there is no uniform effect of heterochromatin on crossover distribution.     

Pollen morphology of the subtribe Cuspariinae (Rutaceae)

The neotropical subtribe Cuspariinae (Rutaceae) comprises as many as 26 genera and over 125 species. Pollen grains from 111 collections representing 71 species and 24 genera were examined by LM, SEM, and TEM. The pollen morphology of this subtribe is very diverse. Grains are mostly 3–6-aperturate and colporate, rarely porate (Spiranthera) or pantocolporate (Almeidea). Exine sculpturing is most commonly reticulate, sometimes perforate, foveolate-perforate, foveolate, foveolate-reticulate, reticulate, striate-reticulate, echinate, clavate, or baculate. The exine structure is columellate and tectate-perforate, columellate and semitectate, or intectate and is stratified into ektexine and endexine. The exine ofLeptothyrsa is distinctive in that the ektexine of the mesocolpium is longitudinally deeply ridged. The pollen ofHortia, characterized by a psilate exine with rare perforations, a very thick foot-layer, and reduced columellae, is unlike that of any member of the Cuspariinae and offers no support for the transfer of this genus from the Toddalioideae. The pollen data correlate with macromorphological characters and are taxonomically useful.     

The palynology of the genus Rondeletia L. (Rubiaceae-Cinchonoideae-Rondeletieae)

Pollen of 20 species of Rondeletia, covering three subgenera and seven sections or “species groups” of the genus, was studied using light and scanning microscopy. Rondeletia, characterized by binucleate mature pollen grains like numerous other Rubiaceae, was found to be eurypalynous. The pollen is isopolar and small-sized (average equatorial diameters 11.4–22.8 μm) and 3-colporate (rarely 4-colporate). In equatorial view, the pollen grains are mostly ± spheroidal (rarely suboblate); in polar view (ambitus), they are mainly circular or semiangular (intersemiangular in one species only). Three different exine types are distinguishable: exine with 1) tectum minutely perforate, perforations usually isodiametric, 2) tectum with comparatively large, not isodiametric perforations or 3) coarsely reticulate; supratectal sculpturing elements are lacking; the width of the perforations and lumina is either equal or different at the apo- and mesocolpia; in a few species rod-like luminal processes are present. Palynological features of most of the investigated taxa tend to overlap so that palynology is not very helpful in supporting the subgeneric division of Rondeletia. It was, however, noted that pollen morphology, to some extent, supports the sections of subgen. Arachnothrix. Palynologically, the subgen. Rogiera was found to be heterogeneous in that each of the three investigated species is characterized by a different exine type; one of these, R. strigosa, differs from all other Rondeletia species investigated in having a coarsely reticulate exine. R. odorata (subgen. Rondeletia) differs from all other investigated species in its intersemiangular pollen shape.     

Pollen morphology of the genus Gagea (Liliaceae) in Iran

Pollen grains of 26 species of the genus Gagea distributed in Iran were examined by light and scanning electron microscopy. Detailed pollen morphological characteristics are given for these species. Among the studied species, the newly described G. iranica together with G. olgae and G. graminifolia possess the smallest pollen grains, and the widely distributed G. lutea the largest ones. Our studies show that the sculpturing of exine provides valuable characters for separating the species, sometimes even for closely related ones, and delimitation of natural groups within the genus. The exine of the genus Gagea is in most cases perforated upon tectum or rarely tectate-columellate. The muri are solid or structured, compound, simpli-, dupli- or pluricolumellate. It seems that the structure of muri is very important in recognizing natural groups within the genus. Tectal perforations vary from <0.2 to 2.0 μm in diameter among the studied species. Regarding sculpturing of the exine in proximal face, four basic types of pollen grains can be distinguished: reticulate, microreticulate, foveolate and perforate. Within the reticulate type there is sufficient variation in exine structure at distal face to describe three subtypes: reticulate, microreticulate and perforate. A diagnostic key is given for all studied taxa based on palynomorphological characters. For a limited number of populations of selected Iranian species of Gagea, further aspects of pollen biology were studied. It seems that populations with ploidy levels other than diploidy, show a low percentage of pollen fertility. Moreover, the rate of pollen fertility is correlated with the manner of the reproduction in certain species.     

Le pollen de la tribu des Acalypheae (Acalyphoideae,Euphorbiaceae)

Le pollen de 2/730 genres et de 48/1300 espèces de la tribu des Acalypheae a été étudié en microscopie photonique et électronique à balayage. Les variations des caractères aperturaux et de la disposition des éléments ornementaux permettent de caractériser les onze sous-tribus. Le pollen est généralement colporé et présente presque toujours de petits épaississements de la nexine autour des apertures. Seuls deux genres font exception, Sampantaea p.p. et Dysopsis dont le pollen présente généralement trois simples sillons ectoaperturaux très étroits. Le tectum est perforé et porte en principe des microépines ou microverrues autour des perforations à l'exception de quelques rares espèces où l'ornementation est striée (Micrococca scariosa, Homonoia jaranensis) ou réticulée (Amyrea, Mareya longifolia, Seidelia). Le pollen des Acalypheae se répartit dans deux grands types: 1° le tectum est largement perforé et les grains sont en général plutôt longiaxes; 2° le tectum est à peine microperforé et les grains sont le plus souvent plutôt bréviaxes. Les variations des caractères du pollen: diminution des perforations tectales, réduction considérable de l'ectoaperture et/ou, de l'endoaperture qui peut disparaître même, sont corrélatives de celles de la fleur et du type de pollinisation. Le pollen des Acalypheae présente des rapports évidents avec celui des 3 tribus voisines appartenant aux Acalyphoideae, tandis que ses ressemblances avec celui des Crotonoideae et des Phyllanthoideae ne sont liées qu'à la disposition des éléments libres sur l'exine.

The pollen of 27/30 genera and 48/1300 species of the tribe Acalypheae have been studied by means of L.M. and S.E.M. Variations in the character of the apertures and in the sculpturing elements allow a characterization into eleven subtribes. The pollen is generally colporate and mostly has small nexine thickenings around the apertures. The genera Sampantaea and Dysopsis are the only exceptions to this having pollen with three very narrow ectoapertural simple furrows. The tectum is perforate and has microspines or micropapillae around the perforations, with the exception of some rare species in which the sculpturing is striate (Micrococca scariosa, Homonoia javanensis) or reticulate (Amyrea, Mareya longifolia, Seidelia). The pollen of the Acalypheae belong to two great types: 1° the tectum is widely perforate and the grains are generally longiaxe; 2° the tectum is scarcely microperforate and the grains are often breviaxe. The variations in the pollen characters: a decrease in the tectal perforations, and a great reduction in the ectoaperture and/or the endoaperture which can even disappear, are correlative with those of the flower and its type of pollination. The pollen of the Acalypheae clearly resembles that of the three nearest tribes of the Acalyphoideae. Similarities with the Crotonoideae and the Phyllanthoideae are evident except for the placement of the free elements on the exine.     

Pollen morphology of Diosma and Coleonema (Rutaceae: Diosminae) and its taxonomic implications

The pollen morphology of Diosma and Coleonema of the taxonomically problematic subtribe Diosminae (Rutaceae) was investigated to determine its taxonomic relevance. Pollen of 26 of the 28 species of Diosma and of each of the eight species of Coleonema was investigated by LM, SEM and TEM. In pollen of Diosma the exine sculpturing is uniform, and only one pollen type, reticulate, could be distinguished. In contrast, exine sculpturing shows interspecific variation in Coleonema and three distinct types, striate, reticulate and perforate, could be discerned. Species groupings indicated by the pollen types suggest possible relationships between species within Coleonema and with other genera that were not previously apparent. Pollen data support macromorphological evidence that suggests the generic re-classification of the Diosminae.     

POLLEN MORPHOLOGY OF AMPHIANTHUS,ARTANEMA, CURANGA,GLOSSOSTIGMA, AND PEPLIDIUM (SCROPHULARIACEAE-GRATIOLEAE)

Pollen of the scrophulariaceous genera Amphianthus, Artanema, Curanga, Glossostigma, and Peplidium was examined by light and scanning electron microscopy. All have single, isopolar, radially symmetrical pollen grains with equally spaced meridional colpi and columellate exines. Intergeneric differences are established mainly on the differential correlation of colpus number, colpus morphology, and sculpturing of the mesocolpium. The colpi vary in length and range in number from 3 to 6. The colpus membrane can be variously granular, verrucate, rugulate, or spinulose. The exine varies from semitectate and microreticulate or reticulate to tectate and sparsely perforate. It may be psilate or ornamented with supratectal processes ranging from small granules to relatively long spinules or bacules. All the genera examined, with the possible exception of Artanema vs. Amphianthus, are distinguished from one another by pollen morphology, and the grains of both Curanga and Glossostigma have morphotypes not previously reported in tribe Gratioleae. Final taxonomic assessment of the pollen data in the genera examined must await further comparative studies in the Gratioleae and other tribes, but the morphological diversity observed is clearly of potential significance in evaluating specialization levels and clarifying current conflicting interpretations of relationships in these taxa.     

Distyly in Polygonum jucundum Meisn. (Polygonaceae)

Pollen grains of tribe Sanguisorbeae (Rosaceae, Rosoideae) were examined using scanning electron microscopy to identify useful characters, test taxonomic and phylogenetic hypotheses among genera, and elucidate pollen character evolution based on a molecular phylogeny. Aperture number, aperture structure, pollen shape, and exine sculpturing were variable within Sanguisorbeae and were used to delineate six pollen types. Four types (I–IV) were observed only in subtribe Sanguisorbinae whereas two types (V–VI) were found only in subtribe Agrimoniinae. Pollen grains of tribe Sanguisorbeae were generally subprolate to spheroidal in shape, had operculate or pontoperculate apertures, and had three apertures, except for Margyricarpus (tetraperturate). Exine sculpturing within Sanguisorbinae represented variations of striate, verrucate, rugulate, and perforate patterns often with microechinate sculpturing. Striate exine patterns and prolate shapes characterized the pollen of the Agrimoniinae, except for the microechinate-verrucate pattern and subprolate to spheroidal shapes observed in Hagenia. Pollen characters are most useful at the generic level and, when mapped on to a molecular phylogenetic tree of the tribe, are concordant with a monophyletic Agrimoniinae and a clade comprising Margyricarpus + Acaena + Polylepis + Cliffortia + Sanguisorba in the Sanguisorbinae. Outgroup comparison indicated that operculate colpi, three apertures, and polymorphism for striate or microverrucate exines represented primitive states for tribe Sanguisorbeae.     

Pollen morphology and ultrastructure of Australian Monimiaceae ‐ Austromatthaea,Hedycarya, Kibara,Leviera, Steganthera and Tetrasynandra

The pollen morphology and ultrastructure of Austromatthaea elegans, Hedycarya angustifolia, H. loxocarya, Kibara rigidifolia, Leviera acuminata, Steganthera macooraia and Tetrasynandra laxiflora, are described. All are Australian members of the Monimiaceae sensu stricto of the order Laurales, subclass Magnoliidae. Except for Hedycarya angustifolia, which has pollen grains in permanent tetrads, all species have small, globose, apolar, inaperturate pollen. They can be identified under SEM by their surface ornamentation: Austromatthaea has fossulate sculpturing; Hedycarya angustifolia has tetrads with a warty configuration; H. loxocarya has echinate pollen; Kibara has spherical gemmae with nipple‐like projections; Leviera has stellate sculpturing; Steganthera has a verrucose surface with small spherical projections on each verruca, and Tetrasynandra is gemmate with one to several spiny projections on each gemma. The pollen grains of all genera of Australian Monimiaceae sensu stricto, some the results of previous studies, are summarized in tabular form. The exine has no columellae, foot layer or endexine, in contrast to the family Atherospermataceae (syn. subfamily Atherospermatoideae of the Monimiaceae, sensu lato). The most elaborate type of wall structure consists of radial elements ("radial processes") with white line‐centered regions extending from beyond the intine to the tectal region and a two‐layered intine with an outer channelled part (onciform zone). Trends of evolution from this type are discussed and comparisons are made with other Monimiaceae, Lauraceae, Amborellaceae and Trimeniaceae.     

Pollen morphology of endemic species of the Horton Plains National Park,Sri Lanka

The pollen morphology of 27 endemic and palaeoecologically-important species belonging to 16 families and 20 genera from the mountain rain forests of Sri Lanka was studied using both light (LM) and scanning electron microscopy (SEM). The pollen grains exhibit a wide range of morphological characters. Their sizes (P and E) are in the range 10-53 2 9-60 mum, and they are distributed among seven shape classes. All the taxa have radially-symmetrical pollen grains except for Impatiens (bilateral). The amb varies from rounded to triangular, with intermediate shapes possible. The pollen grains of all the Lauraceae species studied are inaperturate and microspinose, with a thin, fragile, perforated exine. Sarcococca zeylanica (Buxaceae) has pantoporate pollen grains and a Croton -pattern consisting of faintly striate pegs of various shapes attached or enveloping the smooth rings. Colp(or)ate, syncolpate to parasyncolp(or)ate pollen grains with rugulate to perforate exine patterns occur in Eugenia mabaeoides ssp. mabaeoides and Syzygium ssp. (Myrtaceae). Osbeckia walkeri (Melastomataceae) has heterocolpate pollen with fossulate, foveolate to perforate exine pattern. 3-colporate, microreticulate pollen grains are met with in Euonymus revolutus (Celastraceae), and scabrate-microreticulate ones in Calophyllum walkeri (Clusiaceae). Hedyotis lawsoniae (Rubiaceae) pollen is microreticulate to perforate, while pollen of the Elaeocarpus (Elaeocarpaceae) species is 3-colporate, smooth to scabrate-perforate. Casearia thwaitesii (Flacourtiaceae) has 3-colporoidate pollen grains with a smooth, imperforate to occasionally sparsely perforate exine. Mastixia spp (Cornaceae) have a granular-perforate exine pattern, while Adinandra lasiopetala (Theaceae) has a smooth-perforate exine pattern. Triangular 3 (4)-colporate, and indistinctly faintly microreticulate-perforate pollen was found in Rhamnus arnottianus (Rhamnaceae), rugulate-perforate in Isonandra montana (Sapotaceae) and verrucate-perforate in Symplocos elegans (Symplocaceae). Glochidion coriaceum (Euphorbiaceae) has a 5-colporate grain with a coarsely reticulate exine pattern. Pollen grains of Impatiens walkeri and I. thwaitesii (Balsaminaceae) are bilateral, 4-colpate, reticulate and granular. A pollen key based on light microscope is constructed for all the taxa studied.     

The pollen morphology ofOdontites (Scrophulariaceae) and its taxonomic significance

The pollen morphology of 29 species ofOdontites and related genera was examined by light and scanning electron microscopy. Three major pollen types differing fundamentally in exine sculpturing were found. In the parasitic tribePedicularieae retipilate sculpturing is the most widespread type representing a plesiomorphic character state from which the two other types are derived. Of these, reticulate sculpturing is confined toOdontites, whereas a complex retirugulate pattern was found only in the monotypic Near East genusBornmuellerantha. Within the retipilate and the reticulate major types eight minor types were distinguished based on the differential correlation of exine surface morphology, size, shape and amb form. The pollen data are generally well correlated with macromorphological features and furnish important taxonomic characters at the genus—as well as at the specieslevel.     

Characterization of heterochromatin in different species of the Scilla siberica group (Liliaceae) by in situ hybridization of satellite DNAs and fluorochrome banding

Satellite DNAs have been isolated from the monocotyledonous plants Scilla siberica, S. amoena, S. ingridae (all are highly GC-rich), and S. mischtschenkoana by using the Ag⁺ –Cs₂SO₄ density centrifugation technique. Hybridization in situ has been performed with ₃H-cRNA to these satellite DNAs in all four species. In each species, the endogenous satellite DNA is located mainly in intercalary and major heterochromatin bands associated with terminal regions and nucleolar organizer regions (NORs) but not in centromeric regions. Patterns observed after cross-species hybridization show a high degree of satellite DNA homology between S. siberica, S. amoena, and S. ingridae. By contrast, satellite DNA of S. mischtschenkoana consists largely of different, non homologous DNA sequences, with two exceptions: (i) the NORs of all four species contain similar satellite sequences, and (ii) a strong homology exists between the satellite DNA of S. mischtschenkoana and centromeric DNA of S. siberica but not with those of S. amoena and S. ingridae. — Heterochromatin has also been characterized by the AT-specific fluorochromes quinacrine (Q) and DAPI and the GC-specific agent chromomycin A₃ (CMA₃), in combination with two counterstaining techniques. While CMA₃-fluorescence is largely in agreement with data on base composition and location of the specific satellite DNAs, the results with Q and DAPI are conflicting. Prolonged fixation has been found to change the fluorescence character in certain instances, indicating that other factors than the base sequence of the DNA also play a role in fluorochrome staining of chromosomes. The results are discussed in relation to the taxonomy and phylogeny of the four species.     

Quantitative analyses of C-banded karyotypes,and systematics in the cultivated species of theScilla siberica group (Liliaceae)

Quantified C-band karyograms are presented for the related speciesScilla siberica, S. mordakiae, S. ingridae, S. amoena, andS. mischtschenkoana. Chromosome structure, banding style, and heterochromatin characters suggest a systematic grouping of two more closely related species pairs:S. siberica andS. mordakiae, S. ingridae andS. amoena; they are part of a larger aggregate, well separated fromS. mischtschenkoana. Four different heterochromatin fractions can be recognized inS. siberica and its relatives, but only two inS. mischtschenkoana. C-bands do not replace, but they are added to euchromatin. The particular origin and history of the cultivatedS. amoena and the triploidS. siberica cv. Spring Beauty appear to be responsible for their karyotype constancy, but chromosome conservatism obviously is genuine inS. mischtschenkoana. The banding data support the systematic grouping proposed on a morphological basis, and provide additional evolutionary evidence.Evolution ofScilla and Related Genera, IV.     

Pollen morphology in relation to pollinators in Papilionoideae (Leguminosae)

The surface sculpturing of the pollen of some species of the taxonomically widely separated genera Harpalyce (tribe Brongniartieae), Camoensia (tribe Sophoreae), Millettia (tribe Tephrosieae), and of the monotypic Dahlstedtia (tribe Tephrosieae) which have large red or white flowers adapted for pollination by birds or bats, is coarsely rugulate or verrucate. Related taxa with small insect pollinated flowers have pollen with simple reticulate or perforate surface sculpturing. The exine stratification of Alexa and Castanospermum (tribe Sophoreae), genera with large red bird-flowers, is complex with a layer of tectal columellae and differs from that of other genera in the tribe Sophoreae which have a normal pollen wall structure. These modifications of pollen structure and sculpture appear to be the result of convergent evolution and a secondary adaptation to pollination. The taxonomic and functional significance of the observations are briefly discussed.     

Taxonomic implications of pollen exine morphology in infrageneric classification of Scutellaria (Lamiaceae)

Scutellaria L. in Lamiaceae subfamily Scutellarioideae is a subcosmopolitan genus with about 360 species. According to the latest subgeneric classification, two subgenera are recognized: S. subgen. Scutellaria and S. subgen. Apeltanthus. We studied pollen grains from 29 species of Scutellaria belonging to both subgenera and from both the Old and the New World to evaluate their taxonomic importance for the infrageneric classification of the genus. Pollen grains were acetolysed and studied by scanning electron microscope (SEM) and light microscope (LM). All examined pollen grains are isopolar, tricolpate, suboblate, oblate spheroidal, prolate spheroidal to subprolate. The exine is mainly bireticulate perforate, but with variations in lumina shape and size as well as perforation size and uniformity. Based on the exine sculpturing, two subtypes are recognized within the bireticulate pollen type. In subtype I the primary reticulum of the exine consists of angular muri; the lumen has an irregular polygonal shape and the perforations of the secondary reticulum are more or less uniform and of the same size. This pollen subtype was observed in species of subgenus Scutellaria, sectt. Scutellaria p.p., Anaspis, Perilomia and Salazaria. In subtype II the primary reticulum of the exine consists of a more or less curved murus; the lumen is rounded or obtusely angular and the secondary reticulum consists of one or more large central perforations surrounded by some smaller ones. This pollen subtype was observed in species of subgenus Scutellaria sectt. Scutellaria p.p., Salviifoliae and in all members of subgenus Apeltanthus. The results of this study reveal that the exine ornamentation is a diagnostic character useful for the infrageneric classification of Scutellaria.     

Some evidence for infrageneric classification in Ziziphora L. (Lamiaceae:Mentheae)

The genus Ziziphora L. (Lamiaceae) consists of annual herbs, except Ziziphora clinopodioides, and is represented by six taxa in the flora of Turkey: Z. clinopodioides, Z. capitata, Z. persica, Z. tenuior, Z. taurica subsp. taurica and Z. taurica subsp. cleonioides. They are strong aromatic herbs and important medicinal plants. This study has been conducted to determine the palynological and karyological features of these taxa. The pollen morphology and exine structure of Ziziphora species were investigated by light microscope and scanning electron microscope. Pollen grains were determined as hexacolpate, medium in size and a circular or elliptic amb. The shape of pollen grains varies from oblate to prolate spheroidal. Ornamentation types of pollen grains are bireticulate, microreticulate or perforate. Somatic chromosome number has been determined and counted as 2n = 16, 18. Results indicate that the pollen characters and chromosome numbers of the genus are valuable for taxonomic applications and may be useful for infrageneric classification.     

Sputtering,a New Method for Coating Pollen Grains in Scanning Electron Microscopy

Sputtering is an easy, rapid and effective method for metal coating of pollen grains for examination in the scanning electron microscope. A very thin, regular and stable metal layer is obtained by bombarding a metal target with ions under a low vacuum, so that it ejects atoms on to the specimen. This allows of the observation of exine sculpturing which would be completely masked by a coating resulting from evaporation of carbon and metal. The sputtering method was tested on pollen of Deschampsia flexuosa, Molinia caerulea and Betula pubescens. Very narrow perforations could be discerned in the exine, similar to those seen in the images of carbon replicas obtained by many authors with the transmission electron microscope.     

FINE STRUCTURE OF MISTLETOE POLLEN. III. LARGE-FLOWERED NEOTROPICAL LORANTHACEAE AND THEIR AUSTRALIAN RELATIVES

Pollen of all large-flowered neotropical loranthaceous genera and related Australian taxa (Nuytsia, Atkinsonia) were examined in the light, scanning, and transmission electron microscopes. Trilobate, deeply concave, peroblate or oblate pollen shapes are basic within the complex; triangular, slight convex, suboblate shapes are more derived features. The non-fixiform pollen of Atkinsonia is unique within the family. Most of the large-flowered genera possess exclusively syncolpate aperture types. However, among Psittacanthus species tricolpate, diplosynrugate and diplorugate apertures are also present, representing derived types for the complex. The inaperturate pollen of Atkinsonia appears to have developed independently within the family. Pollen sculpturing is typically non-uniform, i.e., there are pronounced sculpturing differences in polar and equatorial regions. Uniformly sculptured pollen is restricted to Atkinsonia, Ligaria and some species of Psittacanthus. Ultrastructurally, most exine modifications have occurred in the equatoral ektexine. Here the basic organization ranges from essentially columellaless to columellate, the latter the more derived condition. Endexine is typically thick and stratified in polar areas, thin and lamellate in peripheral and apertural regions. Similar pollen morphologies of Nuytsia and Gaiadendron support the idea of a transoceanic evolutionary connection between the Old and New Worlds. Pollen characters show Gaiadendron to be the most primitive and Psittacanthus the most advanced among the large-flowered neotropical genera.