Psilate Pollen Research Articles

Does breeding system affect pollen morphology? A case study in Zygophylloideae (Zygophyllaceae).

We found a correlation between large pollens and selfing and between psilate pollen walls and cleistogamy. Flowering plants display extraordinary diversity in pollen morphology, yet the functional significance of this variation is not well understood. Zygophylloideae is a lineage characterized by high diversity of breeding systems, ranging from obligate selfing to facultative selfing and further to facultative outcrossing. This group is particularly suitable for testing hypotheses about the influence of breeding system on pollen morphology. We studied pollen morphology in 20 species of Zygophylloideae and one species of Tribuloideae as an outgroup. A phylogeny of Zygophylloideae was created based on available DNA sequences and used to trace the evolution of pollen characters. We performed a phylogenetic analysis of correlated evolution between breeding system and several pollen characters. Three types of pollen morphology were found in the studied species. Tricolporate pollen with a small apocolpium, microreticulate ornamentation and medium size was determined as the ancestral state in Zygophylloideae. The correlation analysis indicated an association between large pollens and selfing and between psilate pollen wall and cleistogamy. We hypothesize that large size of pollen in selfing species is mainly associated with the low number of produced pollen indicating a trade-off between pollen size and number. The independence from pollen vector in cleistogamous flowers accounts for the evolution of smooth pollen walls in these species.

Source-rock potential of the lowest coal seams of the Marcelina Formation at the Paso Diablo mine in the Venezuelan Guasare Basin: Evidence for the correlation of Amana oils with these Paleocene coals

The aims of this work were to carry out a combined petrographic, palynofacies, and organic geochemical study of twelve drill-core samples collected from the lowest coal seams in the Paleocene Marcelina Formation (Paso Diablo mine, Guasare Basin, northwestern Venezuela), to characterize crude oil samples from three wells in the nearby Amana Field and to evaluate oil-source correlations of these crude oils with the Paso Diablo coal extracts. The coals under study were classified as high volatile bituminous A or at the B-A boundary, and showed vitrinite contents between 50.0 and 89.4vol.%, liptinites ranging from 1.4 to 24.2vol.%, and inertinites in the 6.2–30.8vol.% range. Results from organic geochemical investigations indicate that the Guasare coals were generated in a limno-telmatic to telmatic zone under fluctuating oxygen conditions. A Type III kerogen with relatively high hydrogen content and a thermal maturity corresponding to the early oil window are proposed for these coals as supported by Rock-Eval and petrographic data, as well as biomarker interpretations. Oil generation potential from Marcelina Formation coals is probably due to the perhydrous nature of the vitrinite, high bitumen contents, and considerable liptinite concentrations, mainly oil-prone resinites and exsudatinites. Palynofacies observations denote a dominance of psilate pollen grains related to angiosperm plants and, as expected, Type III kerogens or humic coals in the studied seams, the parent material of which contained a significant contribution of algae. The non-detection of 18α(H)-oleanane does not preclude the fact that angiosperms are the dominant plants in the Guasare paleomire. On the other hand, the characterization of the Amana oils suggests that they all fall into a unique oil family; the presence of 25-norhopanes in them could indicate paleobiodegradation and mixing from various hydrocarbon charges in the reservoir. Thus, the crude oils from the Amana Field seem to be a mixture of one or more oil charges from the early mature marine carbonate source rocks of the La Luna Formation, deposited under anoxic reducing conditions, and a later pulse of hydrocarbon generation which originated from an unknown – so far – nonmarine source rock. In this regard, hydrocarbon liquid derived from the lowest Marcelina coal seams may be tentatively identified as the latter oil charge. Also, this work delineates some components of a currently subcommercial and hypothetical Tertiary petroleum system – identified and named as Marcelina/Misoa C5(.) – in the Lake Maracaibo region. Finally, the coalbed gas contents of sampled coals were determined.

Anther wall and pollen development in Neotropical species-rich Miconia (Melastomataceae)

Miconia is one of the largest exclusively Neotropical genera, inserted in the tribe Miconieae. Although the monophyly of the tribe has recently been recognized, the delimitation of its genera is considered quite arbitrarily defined, mainly due to the great diversity combined with little morphological and genetic characterization of its members. Recent findings have associated this diversity with polyploidy, apomixis and hybridization, mechanisms commonly found in the group. The conventional delimitation of sections in Miconia, which has been largely based on stamen morphology, has proved to be undoubtedly artificial; nevertheless, the potential taxonomic significance of anther wall and pollen ontogenetic characters within the genera Miconia has been little explored. Hence, this study intended to fill that gap in our knowledge, by investigating the anther wall and pollen development in six closely related species of Miconia: M. albicans, M. fallax, M. latecrenata, M. paucidens, M. pepericarpa and M. stenostachya. Routine techniques for both light and electronic microscopy were used to examine anthers and pollen grains in several developmental stages. The species studied here share several character states, such as the remarkable monocotyledonous anther wall development, the persistent endothecium in the mature anthers with no cell wall thickenings, the bilocular dehiscent anther and the psilate pollen exine. This study also reports for the first time bisporangiate anthers, crystals and proteinoplasts in tapetal cells for Melastomataceae, and ultrastructural features of anther and pollen wall for Miconia.

A Review of the Fossil Record of the Genus Itea (Iteaceae, Saxifragales) with Comments on its Historical Biogeography

Itea is a genus of about 20 species of trees and shrubs that are today native to southeastern North America, eastern Asia, and eastern Africa. In this paper, I review the fossil record of Itea, which is based on four types of fossils: diporate, psilate pollen attributed to Itea or the dispersed pollen genus Iteapollis; carpofossils representing fruits and seeds attributed to Itea europaea; flowers preserved in amber and assigned to Adenanthemum iteoides; and leaf impressions attributed to Itea. The distributions of these fossils indicate that Itea was present in western North America from the early Eocene to Miocene, in eastern North America beginning no later than the early Miocene, and in western Eurasia from the late Eocene to Pliocene. Only one datapoint is known from eastern Asia; it is early Miocene in age. Based on the fossil record, it can be inferred that Itea crossed between continents over both the Bering Land Bridge and North American Land Bridge, and that it reached Africa from Europe via Anatolia. Thus, it is predicted that the sole extant North American species, I. virginica, may be most closely related to the sole extant African species, I. rhamnoides. The potential application of Itea fossils to calibrating phylogenetic trees generated from molecular sequence data is also discussed.

Palynological diversity in selected medicinal plant species of Asteraceae (Compositae) from flora of Kaghan Valley

Pollen morphology of seven species, belonging to seven Asteraceae genera from the flora of Kaghan Valley was investigated by light and scanning electron microscopy. The species named Achillea millefolium Linn., Chrysanthemum leucanthemum Linn., Gerbera gossypina (Royle) Beauv., Senecio chrysanthemoides DC. Prodr., Sonchus asper Linn.,Tagetes erecta Linn. and Xanthium strumarium Linn. were studied which showed considerable variation in pollen shape, size, length and number of spines, colpi and sculpturing in light as well as electron microscopy. The maximum pollen size was found inG. gossypina which was 38.3 µm in polar view and 57.75 in µm equatorial view whereas minimum pollen size in polar view that is, 23.65 µm was found in X. strumarium and 19 µm in equatorial view was found in A. millefolium. Psilate pollen sculpturing was observed in G. gossypina however the other species had spines on their pollen. The psilate sculpturing was considered as an advanced feature when compared to echinate sculpturing of pollen which was regarded as the primitive form. It was concluded that this research work has provided new dimensions towards further investigations in the field of palynology. Key words: Palynology, psilate, echinate.

Unraveling the Phylogeny of Heptacodium and Zabelia (Caprifoliaceae): An Interdisciplinary Approach

Abstract Recent molecular investigations place Heptacodium as sister to the Lonicera clade, whereas morphology suggests a close relationship with the Linnaea clade s. 1. (former tribe Linnaeeae). Zabelia has always been assumed to be closely related or even congeneric with Abelia. This study presents molecular and morphological data in an attempt to further clarify the systematic positions of Heptacodium and Zabelia as they are key genera to help us understand evolution in Dipsacales. Our molecular analyses strongly support a sister relationship between Heptacodium and the Lonicera clade. Zabelia, however, seems to be closer related to the Morina clade than to any other member of the Linnaea clade s. 1. None of our phylogenetic analyses suggest a close relationship between Abelia and Zabelia. Morphologically, Zabelia's relationship with the Morina clade is only supported by the shared presence of psilate pollen grains with an endocingulum. Fruit and seed morphology strongly indicate a close relationship b...

Lauraceous flowers from the Late Cretaceous of North Carolina, U.S.A.

Three new taxa with clear affinity to extant Lauraceae are described from the Santonian/Campanian (c.83 Myr, Late Cretaceous) Neuse River locality in North Carolina, U.S.A. A new lauraceous genus, Neusenia, is established to accommodate an excellently preserved flower with tetrasporangiate anthers and psilate pollen grains. Two additional lauraceous taxa are described but not named due to incomplete preservation. The fossil taxa described in this paper represent a variety of evolutionary lineages within Lauraceae with respect to inflorescence structure and anther morphology, including both distinctly pedicellate flowers and sessile, closely crowded flowers, as well as tetrasporangiate and disporangiate anthers. In light of the co-occurrence of both tetrasporangiate and disporangiate anthers in the Neuse River flora, the plesiomorphic state of lauraceous anthers is discussed. Mapped on a recent cladogram of Laurales, tetrasporangiate anthers appear to be primitive within Lauraceae. Thus, disporangiate 2-valvate anthers must have evolved independently at least three times in Laurales (in Lauraceae, Hernandiaceae, and Atherosperrnataceae/Gomortegaceae). In Hernandiaceae and Atherosperrnataceae/Gomortegaceae such anthers are interpreted to have originated from tetrasporangiate 2-valvate anthers through reduction of the septum in each theca, while in Lauraceae they may have originated in the same way and/or from reduction of two pollen sacs in a tetrasporangiate 4-valvate anther.

Lauraceous flowers from the Late Cretaceous of North Carolina, U.S.A.

Three new taxa with clear affinity to extant Lauraceae are described from the Santonian/Campanian (c. 83 Myr, Late Cretaceous) Neuse River locality in North Carolina, U.S.A. A new lauraceous genus, Neusenia, is established to accommodate an excellently preserved flower with tetrasporangiate anthers and psilate pollen grains. Two additional lauraceous taxa are described but not named due to incomplete preservation. The fossil taxa described in this paper represent a variety of evolutionary lineages within Lauraceae with respect to inflorescence structure and anther morphology, including both distinctly pedicellate flowers and sessile, closely crowded flowers, as well as tetrasporangiate and disporangiate anthers. In light of the co-occurrence of both tetrasporangiate and disporangiate anthers in the Neuse River flora, the plesiomorphic state of lauraceous anthers is discussed. Mapped on a recent cladogram of Laurales, tetrasporangiate anthers appear to be primitive within Lauraceae. Thus, disporangiate 2-valvate anthers must have evolved independently at least three times in Laurales (in Lauraceae, Hernandiaceae, and Atherospermataceae/Gomortegaceae). In Hernandiaceae and Atherospermataceae/Gomortegaceae such anthers are interpreted to have originated from tetrasporangiate 2-valvate anthers through reduction of the septum in each theca, while in Lauraceae they may have originated in the same way and/or from reduction of two pollen sacs in a tetrasporangiate 4-valvate anther.

Two New Species of Clusiella (Clusiaceae) with a Synopsis of the Genus

Two new species of Clusiella, one from Costa Rica and Panama (C. isthmensis) and one from Brazil (C. impressinervis), are described, one old species from Colombia (C. cordifolia Cuatrecasas) is newly placed in synonymy, and all eight species in the genus are brought together in a key. A description of the genus and brief descriptions of the species are given, specimens are cited, and distributions are mapped for all species. In view of its stipuliform structures, contorted petals, psilate pollen exine, baccate fruits, exarillate seeds, and embryos with well-developed cotyledons, Clusiella's presumed close relationship to Clusia is challenged.

Relacionamentos entre as espécies autógamas de Cuphea P. Browne seção Brachyandra koehne (Lythraceae)

A seção Brachyandra, uma das 13 seções de Cuphea, é excepcional por compreender a maioria das espécies autógamas do gênero. A maior parte das outras espécies de Cuphea, embora autocompatíveis, são alógamas protândricas. A seção Brachyandra é definida pela presença de estames com filetes curtos e profundamente inseridos no tubo floral, caracteres diretamente relacionados à autogamia. Entre as espécies da seção, existem poucas diferenças na morfologia floral e os caracteres vegetativos são variáveis e sobrepostos. As similaridades poderiam ser atribuídas à recente especiação dentro de um grupo monofilético, definido pela aquisição do modo autógamo de reprodução, ou a seção poderia ser polifilética, com similaridades resultantes de convergência, dirigidas pela mudança de alógamas para autógamas. A morfologia do pólen e da semente, descrita agora para este grupo, sugere que a seção Brachyandra não seja monofilética, mas sim que compreenda um mínimo de três diferentes linhas evolutivas, representadas por: 1) quatro espécies com sementes aladas e pólen oblato, sincolporado e estriado, com poros proeminentes; 2) duas espécies com sementes grandes e não aladas e pólen psilado, sem poros proeminentes e leves espessamentos interaperturados; 3) oito espécies com sementes pequenas, não aladas e quase esferoidais, pólen não sincolpado, psilado a rugulado. A variação neste último grupo sugere que o mesmo seja derivado de mais do que um ancestral. Na análise cladística, as espécies da seção Brachyandra ocorrem dentro de ciados de espécies das seções Euandra, Pseudochvaea, Trispernuun e Amazoniana. Os resultados indicam que não existe base filogenética sólida para o reconhecimento da seção Brachyandra como presentemente definida.

Pollen Morphology of the Genera Panurea and Bowdichia (Leguminosae: Papilionoideae: Sophoreae)

Abstract Bowdichia and Panurea are the only genera in the tribe Sophoreae with psilate pollen. The pollen of the four species recognised in the two genera can be divided into three distinct types: (1) Spheroidal in shape, tricolporate with long colpi (Bowdichia); (2) Oblate in shape with three very short colpi or pori (Panurea bowdichioides); (3) Cuboid in shape, tetracolpate (Panurea longifolia). The exine stratification of Bowdichia is very distinctive with a thick tectum, short columellae and thick foot layer. The two species of Panurea have a similar exine stratification with long columellae and much thinner tectum and foot layer. Exine stratification provides additional evidence to support the generic relationships of P. bowdichioides, a new species, which has some floral characters similar to Bowdichia and simple leaves of Panurea. Pollen morphology provides additional evidence to support the view that Bowdichia and Panurea have no very close relatives in the Sophoreae.

A PERMINERALIZED FLOWER FROM THE MIDDLE EOCENE OF BRITISH COLUMBIA

A permineralized flower bud, two stamen clusters and one isolated stamen of similar morphology have been found in the black cherts of the Middle Eocene Allenby Formation of Princeton, British Columbia. Specimens were studied using a modified cellulose acetate peel technique and hydrofluoric acid. The single flower specimen, 4.5 mm long and 4.0 mm in diameter, represents half of a relatively mature bud of a bisexual flower with a superior ovary. The two‐loculate pistil is 2.5 mm long with a solid style and a lobed stigmatic surface. No ovules have been observed in attachment. Twenty‐two to 24 stamens are borne in three whorls or a tight helix. Pollen sacs of the anther are elongate with a thin connective while filaments are laminar. Anther walls contain rectangular cells with dark contents that also can be identified in isolated stamens or stamen clusters. Abundant stephanocolpate (pentacolpate), psilate pollen grains 20 μm in diameter have been isolated and examined using scanning and transmission electron microscopy. Grains are tectate, columellate with a broad foot layer that thins near the apertures, and an endexine of small platelets. The remains of four petals are surrounded by one large sepal, suggesting two in the whole flower. Morphological features of this flower are comparable to taxa of the Flacourtiaceae and Papaveraceae, but show closest similarities to the Eschscholziaeae of the Papaveraceae. Difficulties with reconciling the placement of this flower in the Eschscholziaeae and the known environment of deposition of the Princeton chert are discussed. The fossil material represents a new angiospermous taxon: Princetonia allenbyensis Stockey gen. et sp. nov., family Incertae sedis.

The fine structure of the pollen of Eupomatiaceae

Pollen of Eupomatia laurina R. Br. and of Eupomatia bennertii F. Muell. are described. The pollen of both species is subspheroidal with a zonizonasulculus (a band-like, encircling aperture at the equator). E. laurina has a less dense and more vacuolated pollen containing lipids. E. bennettii has a dense pollen with many starch granules. Differences occur in their wall layers, especially in the aperture, but basically both species have an atectate, psilate pollen of medium size.