Number Of Pollen Sacs Research Articles

Neither Phoebe nor Cinnamomum – the tetrasporangiate species of Aiouea (Lauraceae)

AbstractCinnamomum is among the largest genera of the Lauraceae, including species from tropical to temperate Asia and from tropical to subtropical America. However, previous studies indicated that Cinnamomum might not be monophyletic in its current circumscription. We therefore re‐investigated the genus and possible relatives with an increased taxon sample, particularly of the Neotropical species. Our results, based on sequences of the nuclear ITS region and the chloroplast spacers psbA‐trnH and trnG‐trnS, show that the Neotropical Cinnamomum species indeed do not form a monophyletic group with the Paleotropical species. Instead, the American species form a clade in which most species of the Neotropical genus Aiouea are nested within several subclades. According to the ITS data the Aiouea/Cinnamomum clade is sister to the likewise predominantly Neotropical Ocoteacomplex, rather than the two Paleotropical Cinnamomum clades. Therefore, Cinnamomum cannot be upheld in its cur‐rent circumscription. As the type C. verum, is from Asia, the Neotropical species need to be placed in a different genus. We decided to transfer them to Aiouea here, because this is the oldest generic name in the Aiouea/Cinnamomum clade, and the only character separating Aiouea from Neotropical Cinnamomum is the number of pollen sacs per anther (di‐ vs. tetrasporangiate), a feature that is known to be variable within several other genera as well. This transfer requires 42 new combinations and two nomina nova. In addition, six species described in the unpublished Ph.D. thesis of one of the authors (FLH) are validated in Aioueahere, and the only species of the genus Mocinnodaphne is transferred to Aiouea as well.

Structure of anther heads in some Trifolium L. species

The species of the genus <i>Trifolium</i> differ by the number of pollen sacs in stamen heads. Some have only two, other four and in some species there arę two, three or four pollen sacs. The opinion of some authors (Schnarf 1931, Davis 1966) that from this point of view this genus is uniform is wrong. There is some dependence between the chromosome number (2n) and the number of pollen sacs. For two species - <i>T. carmeli</i> and <i>T. desvauxii</i> - the chromosome numbers 2n=14 were established for the first time.

Variability of male cones in Chamaecyparis as an example for Cupressaceae male cones

AbstractIn contrast to flowers of other seed plants, male cones in Cupressaceae show a high intraspecific variability regarding the number of scales per cone and the number of pollen sacs per scale. This is the first time a qualitative and quantitative analysis of this variability is given. The variability is shown in distinct patterns. A typical pattern or diagram can be gathered from the analyses of 30 cones, which illustrate the “normal” situation and the most frequent variability (average cone diagram). However, the overlapping intersections in the cone diagrams between the species do however not allow identifications based on single male cones. A detailed study of all five species of Chamaecyparis shows that all of them can be distinguished on the basis of their average male cone diagram. A principal component analysis shows that these five Chamaecyparis species form distinct clusters. Sample cones from different positions of the tree reveal no effect within the variability of the cone diagrams. In contrast, comparison between the species and its cultivars reveals a higher variability in cultivars. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Taxodiaceous Pollen Cones from the Early Tertiary of British Columbia, Canada

Two permineralized conifer pollen cones have been identified from the Appian Way locality on the east coast of Vancouver Island, British Columbia. These cones, found in marine calcareous nodules with invertebrates, are Eocene in age and have been studied with the cellulose acetate peel technique. Cones are small, terminal, and globose, with helically arranged subtending leaves, ensheathing leaves, microsporophylls, and pollen sacs with enclosed pollen grains. Peltate microsporophylls have a distal lamina with three abaxial pollen sacs. Pollen grains are small, subspherical, nonsaccate, and papillate, with a distal leptoma and proximal orbicules. Phyllotaxy of subtending leaves and microsporophylls, number of pollen sacs per microsporophyll, and ultrastructure of pollen grains are similar to those of the taxodiaceous Cupressaceae. These cones have closest similarities to Athrotaxis, Cunninghamia, Sequoia, Sequoiadendron, Taiwania, the extinct Sewardiodendron laxum (sensu Yao et al.), and Athrotaxites berryi. However, they have a combination of characters that make these cones unique among taxodiaceous conifers. Therefore, a new genus and species are described as Homalcoia littoralis Hernandez‐Castillo, Stockey et Beard. These cones show a novel combination of characters within the Cupressaceae that extends our understanding of the family and shows the presence of another extinct taxodiaceous genus in the North American Eocene.

Anatomical Peculiarities of Reproductive Organs of «Lycopersicon esculentum» Infected with a Severe Strain of Tobacco Mosaic Virus

The histopathology of tomato sepals, petals, anthers, ovaries and fruit pericarps infected with a highly heat resistant strain of TMV showed many peculiarities. Among these were: undulation and wrinkling of the lower epidermis of sepals and petals, presence of isthmus and failure of xylem and phloem to differentiate. The epidermal cells of the anthers were hooked, the number of pollen sacs was reduced and the vascular elements of the lower region of the fruits appeared thicker than normal, ruptured or disintegrated, and the cortical region appeared small with a wavy or ruptured layers.

A Note on the Evolution of the Stamens in the Laurales, with Emphasis on the Lauraceae

AbstractThe number of pollen sacs per anther and their position have traditionally been among the most important systematic characters in the Lauraceae. Opinions differ, however, about the evolutionary direction in these characters. This paper is intended to draw attention to little known morphological features of the stamens, in particular to transitions between disporangiate and tetrasporangiate anthers. In addition, the phylogenetic derivation of the stamen appendages is discussed. It is hypothesized that branched androecial structures may be primitive within the Laurales, if not in the angiosperms as a whole.

Taxodiaceous pollen cones from the Upper Cretaceous (Horseshoe Canyon Formation) of Drumheller, Alberta, Canada

One hundred permineralized cones, 1.0–1.2 mm × 1.5-2.0 mm, some attached to branching systems, have been examined from the Upper Cretaceous ironstones in the Horseshoe Canyon Formation near Drumheller, Alberta. Cones are borne laterally and terminally on specialized shoots. Microsporophylls are helically arranged on the cone axis with one large resin canal and two pollen sacs per microsporophyll. Pollen is 12–16 μm in diameter with one exit papilla that forms a low protuberance on the grain. External surfaces of grains are scabrate with numerous orbicules and macrogranules while the nexine is laminated. Arrangement of cones on branches is similar to those of Taxodium whereas the number of pollen sacs per microsporophyll is similar to Sequoia and Sequoiadendron. Pollen morphology is similar to Metasequoia and Taxodium, while ultrastructurally it most closely resembles that of Metasequoia. This combination of morphological features is unlike that found in any living taxodiaceous genus. These remains are therefore described as Drumhellera kurmanniae gen. et sp. nov. This study reveals the importance of whole plant reconstructions of other fossil Taxodiaceae due to the scarcity of distinctive morphological characters in isolated organs. Furthermore, the large number of fossil plant specimens associated with these taxodiaceous remains in the Horseshoe Canyon Formation show enormous potential for reconstructions of several types of seed plants.

Studies of Floral Morphology in the Ericales VI. The Diapensiaceae

1. Organography and vascular anatomy of the flower and certain aspects of embryology are reported for eight members of the family Diapensiaceae: Diapensia lapponica, D. lapponica subsp. obovata, Galax aphylla, Pyxidanthera barbulata, P. brevifolia, Schizocodon soldanelloides, Shortia galacifolia, and S. uniflora. 2. The flowers are actinomorphic, essentially hypogynous, and pentamerous except for the tricarpellate pistil. There are five fertile stamens opposite the sepals, and, in all but Diapensia and Pyxidanthera, five staminodes opposite the petals. The stamens and, to a varying extent, the staminodes are epipetalous except in Galax in which the petals are almost completely free and the stamens and staminodes monadelphous. Differences occur in length, orientation and number of pollen sacs, plane of dehiscence, and occurrence of appendages. Placentation is basically axile but may approach parietal in the top of the ovary. Ovules are few to many. 3. The sepals receive three traces in most species, but in...