197 results on '"Pollen -- Research"'
Search Results
52. A tumor suppressor homolog, AtPTEN1, is essential for pollen development in Arabidopsis
- Author
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Gupta, Rajeev, Ting, Julie T.L., Sokolov, Lubomir N., Johnson, Sheila A., and Luan, Sheng
- Subjects
Arabidopsis -- Research ,Arabidopsis -- Genetic aspects ,Plant cells and tissues -- Research ,Pollen -- Research ,Biological sciences ,Science and technology - Published
- 2002
53. Silencing of the tapetum-specific zinc finger gene TAZ1 causes premature degeneration of tapetum and pollen abortion in petunia
- Author
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Kapoor, Sanjay, Kobayashi, Akira, and Takatsuji, Hiroshi
- Subjects
Plant cells and tissues -- Research ,Pollen -- Genetic aspects ,Pollen -- Research ,Biological sciences ,Science and technology - Published
- 2002
54. Effects of population size and pollen diversity on reproductive success and offspring size in the narrow endemic Cochlearia bavarica (Brassicaceae)
- Author
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Paschke, Melanie, Abs, Clemens, and Schmid, Bernhard
- Subjects
Plants -- Reproduction ,Plant populations -- Research ,Pollen -- Research ,Biological sciences - Abstract
In small, fragmented populations of self-incompatible plant species, genetic drift and increasingly close relationships between plants may restrict the number of genetically different pollen donors, the availability of compatible mates, and the opportunity for pollen competition and selection. These restrictions may reduce the siring success or increase the probability of inbreeding depression in the offspring. To test if this was the case, we hand-pollinated maternal plants in small and large populations of the rare, endemic plant Cochlearia bavarica (Brassicaceae) with pollen from one, three, or nine donors from the same population or with nine donors from a different population. In one additional population of intermediate size, maternal plants were hand-pollinated with ten donors located at a distance of 1, 10, 100, or 1000 m. We then recorded seed and offspring characters. On average, offspring from small populations were smaller than normal and fewer survived to maturity. Increasing the number of pollen donors had a positive effect on reproductive success in small and large populations, but at the highest pollen diversity this occurred at the expense of slightly reduced offspring fitness. Because the total amount of transferred pollen was held constant, these effects could not be attributed to increasing pollen load. Rather, the increasing pollen diversity may have increased the chances of selecting a particularly 'good' donor for fertilization--an example of a sampling effect of diversity. Pollen from outside a population or from 10-100 m away resulted in higher reproductive success and greater offspring size. Effects of population size and pollination treatments on reproductive success and offspring fitness were additive. Apparently, there is no obvious size threshold above which the potential of inbreeding depression can be ignored in C. bavarica. Key words: Brassicaceae; Cochlearia bavarica; endemic plant species; inbreeding depression; Munich, Germany; pollen competition; pollen diversity; pollination distance; population size; sampling effect.
- Published
- 2002
55. Widespread evidence of 1500 yr climate variability in North America during the past 14 000 yr
- Author
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Viau, Andre E., Gajewski, Konrad, Fines, Philippe, Atkinson, David E., and Sawada, Michael C.
- Subjects
North Atlantic Ocean -- Environmental aspects ,Geology -- Research ,Climatic changes -- Research ,Paleoclimatology -- Research ,Radiocarbon dating -- Usage ,Pollen -- Research ,Earth sciences - Abstract
There is debate concerning the spatial extent and magnitude of the recently identified 1500 yr climate oscillation. Existing evidence is largely restricted to the North Atlantic and adjacent landmasses. The spatial extent, magnitude, and effects of these climate variations within the terrestrial environment during the Holocene have not been established. We show that millennial-scale climate variability caused changes in vegetation communities across all of North America with a periodicity of 1650 [+ or -] 500 yr during the past 14 000 calendar years (cal yr). Times of major transitions identified in pollen records occurred at 600, 1650, 2850, 4030, 6700, 8100, 10 190, 12 900, and 13 800 cal yr B.P., consistent with ice and marine records. We suggest that North Atlantic millennial-scale climate variability is associated with rearrangements of the atmospheric circulation with far-reaching influences on the climate. Keywords: paleoclimatology, Holocene, Quaternary, pollen diagrams, radiocarbon dating.
- Published
- 2002
56. Tetrad pollen formation in Annona (Annonaceae): proexine formation and binding mechanism
- Author
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Tsou, Chih-Hua and Fu, Yu-Lan
- Subjects
Pollen -- Research ,Biological sciences - Abstract
Meiotic tetrads of Annona glabra and A. montana build up a well-developed proexine (protectum, probaculum, and pronexine) at the proximal side but only a thin pronexine at the distal side during the tetrad stage. The callosic envelope is only partially digested by the end of tetrad stage. The remaining, undigested part is composed of the intersporal mass and thin peripheral layers, and the latter is conjunct with the distal pronexine of the microspore. In this remaining callosic structure celluloses are also present. Later on, due to the continuous slow decomposition of this callose-cellulose structure and microspore expansion, microspores break up the callose-cellulose envelope. Because all the four microspores are bound together by the callose-cellulose structure, they move out of the chamber in rotation. Eventually the thin pronexine is pulled toward the center of the tetrad and the well-developed proexine becomes the distal wall. These descriptions of the partial digestion of callosic envelope, the transformation from a callose-cellulose structure to the binding system of tetrad pollen, and microspore rotation in Annona are unusual in the angiosperms. Key words: Annona; Annonaceae; callosic envelope; microspore rotation; pollen; proexine; tetrad.
- Published
- 2002
57. Evolution of microsporogenesis in angiosperms
- Author
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Furness, Carol A., Rudall, Paula J., and Sampson, F. Bruce
- Subjects
Botanical research -- Analysis ,Angiosperms -- Propagation ,Pollen -- Research ,Phylogeny -- Research - Published
- 2002
58. Scientist warns of pollination crisis
- Author
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Peters, Mark
- Published
- 2013
59. Pollen dispenser trial for kiwifruit pollination
- Author
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Goodwin, Mark and McBrydie, Heather
- Published
- 2013
60. Trialing the use of pollen dispensers
- Author
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Goodwin, Mark and McBrydie, Heather
- Published
- 2013
61. Pollination in the presence of Psa
- Author
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Holmes, Allister, Taylor, Rob, and Mowat, Alistair
- Published
- 2013
62. The southern conifer family Araucariaceae: history, status, and value for paleoenvironmental reconstruction
- Author
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Lucie-Smith, Edward and Wagstaff, Barbara
- Subjects
Southern Hemisphere -- Environmental aspects ,Ecological research -- Reports ,Biogeography -- Environmental aspects ,Vegetation and climate -- History ,Climatic changes -- Research ,Forests and forestry -- Environmental aspects ,Plants, Fossil -- Analysis ,Pollen -- Research ,Geology, Stratigraphic -- Quaternary ,Araucariaceae -- Environmental aspects ,Continental drift -- Environmental aspects ,Biological sciences ,Environmental issues - Abstract
The ancient southern conifer family Araucariaceae is discussed from the perspectives of history, status, and value for paleoenvironmental reconstruction with a review of current research. Ecology, phylogeny, and pollen and macrofossil assemblages are considered. Precise paleoclimatic estimates can be had from araucarians in late Quaternary pollen records and are particularly of value in giving evidence of climatic variability otherwise difficult to find. Focus is on research in Australia and dealing with tectonic and volcanic activity associated with Australia's collision with Southeast Asia.
- Published
- 2001
63. WHAT GOVERNS PROTEIN CONTENT OF POLLEN: POLLINATOR PREFERENCES, POLLEN-PISTIL INTERACTIONS, OR PHYLOGENY?
- Author
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Roulston, T'ai H., Cane, James H., and Buchmann, Stephan L.
- Subjects
Pollen -- Research ,Pollination -- Research ,Fertilization of plants by insects -- Research ,Biological sciences ,Environmental issues - Abstract
Pollen ranges from 2.5% to 61% protein content. Most pollen proteins are likely to be enzymes that function during pollen tube growth and subsequent fertilization, but the vast range of protein quantity may not reflect only pollen-pistil interactions. Because numerous vertebrate and invertebrate floral visitors consume pollen for protein, protein content may influence floral host choice. Additionally, many floral visitors pollinate their host plants. If protein content influences pollinator visitation, then pollinators are hypothesized to select for increased protein content of host plants. We analyzed or gleaned from the literature crude pollen protein concentrations of 377 plant species from 93 plant families. Using this database, we compared pollen protein concentration with (1) pollination mode, (2) pollen collection by bees, and (3) distance from stigma to ovule, after accounting for phylogeny through paired phylogenetic comparisons and a nested ANOVA including taxonomic rank. We found that pollen protein concentrations were highly conserved within plant genera, families, and divisions. We found that bees did not collect pollen that was unusually rich in protein, whether they pollinated or merely robbed their host plant. Plant species with vibratile pollination systems, which require visitation by pollen-collecting bees in order to transfer pollen, tended to have very protein-rich pollen, but it was not clear whether this was due to plant enhancement of pollinator rewards or to the possession of very small pollen grains. We found that zoophilous species were not statistically richer in pollen protein than anemophilous species after accounting for phylogeny, although the three most species-rich anemophilous clades surveyed were generally poor in protein. Plant genera hosting specialist pollen-collecting bees did not have particularly protein-rich pollen. Both mass of protein per pollen grain and pollen grain volume were correlated with stigma-ovule distance. We suggest that the need for growing pollen tubes probably plays a more important role in determining pollen protein content than rewarding pollinators. Key words: anemophilous; pollen protein; pollen volume; pollination; pollinator reward; style length; zoophilous.
- Published
- 2000
64. Alterations in CER6, a gene identical to CUT1, differentially affect long-chain lipid content on the surface of pollen and stems
- Author
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Fiebig, Aretha, Mayfield, Jacob A., Miley, Natasha L., Chau, Samantha, Fischer, Robert L., and Preuss, Daphne
- Subjects
Arabidopsis -- Research ,Arabidopsis -- Physiological aspects ,Cruciferae -- Research ,Cruciferae -- Physiological aspects ,Mutation (Biology) -- Research ,Pollen -- Research ,Biological sciences ,Science and technology - Published
- 2000
65. CLONAL GROWTH OF LITHOSPERMUM CAROLINIENSE (BORAGINACEAE) IN CONTRASTING SAND DUNE HABITATS
- Author
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Weller, Stephen G., Keeler, Kathleen H., and Thomson, Barbara A.
- Subjects
Botanical research -- Analysis ,Fertility -- Research ,Pollen -- Research ,Growth (Plants) -- Research ,Cloning -- Analysis ,Flowers -- Morphology ,Biological sciences - Abstract
The occurrence of clonal growth of distylous Lithospermum caroliniense was investigated in a population in the Nebraska Sandhills, an area where sand dunes have been relatively stable for at least 1500-3000 yr, and compared to a population occurring at the Indiana Dunes, an area of active sand dune formation. Spatial autocorrelation analysis indicated the occurrence of significant clonal propagation of genetically based floral morphs at Arapaho Prairie, but not for the Indiana Dunes. Apparent clonal growth in the Sandhills population had no overall negative effect on pollen deposition or fecundity relative to the Indiana population, although in some large clones the proportion of compatible pollen grains on stigmas was lower. Clonal growth may have occurred in the Sandhills population because of the greater age and stability of the Nebraska Sandhills; infrequent establishment of seedlings permits detection of clonal growth using the spatial pattern of floral morphs. At the Indiana dunes, repeated cycles of dune formation provide conditions favoring establishment of seedlings, and sand dune succession results in disappearance of L. caroliniense before the development of clones. Key words: Boraginaceae; emergence; establishment; fecundity; heterostyly; Lithospermum caroliniense; pollen flow; spatial autocorrelation; self-incompatibility.
- Published
- 2000
66. MORPHOLOGICAL VARIATION AND FEMALE REPRODUCTIVE SUCCESS IN TWO SYMPATRIC TRILLIUM SPECIES: EVIDENCE FOR PHENOTYPIC SELECTION IN TRILLIUM ERECTUM AND TRILLIUM GRANDIFLORUM (LILIACEAE)
- Author
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Irwin, Rebecca E.
- Subjects
Botanical research -- Analysis ,Liliaceae -- Research ,Phenotype -- Research ,Pollen -- Research ,Sex-linkage (Genetics) -- Analysis ,Biological sciences - Abstract
I investigated the mating systems and phenotypic variation of two sympatric spring ephemerals, Trillium erectum and T. grandiflorum (Liliaceae), and phenotypic selection acting through female reproductive success for 11 morphological characters in five sympatric populations of the two species. I examined the degree of self-compatibility, pollinator-visitation rates, and pollen limitation of fruit and seed production in both species. Both Trillium species were self-compatible, but outcrossed flowers produced more successful fruits and seeds than self-pollinated flowers. Pollinator-visitation rates to the two species were low compared to other insect-pollinated spring ephemerals. In addition, both T. erectum and T. grandiflorum experienced pollen limitation in fruit and/or seed production; however, levels of fecundity in both species may be influenced by resource availability as well. I found significant phenotypic variation in 11 morphological characters within and among the five study populations. The sizes of all morphological characters were positively correlated. In general, larger T. erectum and T. grandiflorum produced more seeds. Phenotypic selection analysis revealed that direct and indirect selection acted on the size of morphological characters for both species. But there was no detectable selection acting on plant shape. This study reveals that variation in plant size exists within and among populations of both species, and this variation is associated with variance in female reproductive success. Spatial and temporal variation in pollinator and/or resource abundance may play a role in the phenotypic variation exhibited by both Trillium species. Key words: Liliaceae; mating system; phenotypic selection; pollen limitation; self-compatibility; spring ephemeral; Trillium erectum; Trillium grandiflorum.
- Published
- 2000
67. THE ABSENCE OF CRYPTIC SELF-INCOMPATIBILITY IN CLARKIA UNGUICULATA (ONAGRACEAE)
- Author
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Travers, Steven E. and Mazer, Susan J.
- Subjects
Botanical research -- Analysis ,Pollen -- Research ,Pollination -- Research ,Genetic markers -- Research ,Biological sciences - Abstract
Many species exhibit reduced siring success of self-relative to outcross-pollen donors. This can be attributed either to postfertilization abortion of selfed ovules or to cryptic self-incompatibility (CSI). CSI is a form of self-incompatibility whereby the advantage to outcross pollen is expressed only following pollinations where there is gametophytic competition between self and outcross pollen. Under the definition of CSI, this differential success is due to the superior prefertilization performance (pollen germination rate and pollen tube growth rate) of outcross pollen relative to self pollen. Although CSI has been demonstrated in several plant species, no studies have assessed among-population variation in the expression of CSI. We conducted a greenhouse study on Clarkia unguiculata (an annual species with a mixed-mating system) to detect CSI, and we compare our observations to previous reports of CSI in C. gracilis and another population of C. unguiculata. In contrast to these previous studies of CSI in Clarkia, we used genetic rather than phenotypic markers to measure the relative performance of selfed vs. outcross pollen. In this study, we measured the intensity of CSI in C. unguiculata from a large population in southern California and we determined whether the magnitude of pollen competition (manipulated by controlling the number of pollen grains deposited on a stigma) influenced the outcome of competition between self and outcross pollen. In contrast to previous investigations of Clarkia, we found no evidence for CSI. The mean number of seeds sired per fruit did not differ between self and outcross pollen following either single-donor or mixed pollinations. In addition, the relative success of selfed vs. outcross pollen was independent of the magnitude of pollen competition. These results suggest that: (1) one of the few nonheterostylous species previously thought to be cryptically self-incompatible is completely self-compatible (at least in the population studied here) or (2) phenotypic markers may be problematic for the detection of CSI. Key words: Clarkia; cryptic self-incompatibility; gametophytic competition; mating system; Onagraceae; outcrossing; pollen performance; selfing; siring success.
- Published
- 2000
68. THE CYTOSKLETON AND POLARIZATION DURING POLLEN DEVELOPMENT IN CAREX BLANDA (CYPERACEAE)
- Author
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Brown, Roy C. and Lemmon, Betty E.
- Subjects
Botanical research -- Analysis ,Cyperaceae -- Analysis ,Cytoskeleton -- Research ,Pollen -- Research ,Immunohistochemistry -- Analysis ,Electron microscopy -- Usage ,Biological sciences - Abstract
Patterns of cytoskeletal organization during distinct polarizations that characterize pollen development in the sedge Carex blanda (Cyperaceae) were studied by correlated methods of immunohistochemistry and confocal and transmission electron microscopy. As is typical of the family Cyperaceae, Carex produces a unique pollen type known as a pseudomonad in which all four microspores of the tetrad are enclosed within the wall of a single pollen grain. Only one member of the tetrad is functional and the other three abort. The pseudomonads are precisely oriented in the locule with the functional microspore in the wide abaxial portion of the wedge-shaped cytoplasm adjacent to the tapetum, and the degenerative microspores are packed tightly in the pointed adaxial portion. A unique sequence of post-meiotic developmental events reflects both intracellular and intercellular polarity. Development includes: (1) random placement of tetrad nuclei in the coenocytic sporocyte after meiosis, (2) interrupted cytokinesis resulting in a tetrad of nuclei that migrates as a unit into the narrow adaxial tip, (3) completion of unequal cytokinesis and centering of the functional nucleus in the wide abaxial portion of the microsporocyte via a radial array of microtubules and microfilaments, (4) unequal mitosis resulting in a small generative cell at the proximal surface of the functional microspore (adjacent to the abortive microspores), and (5) recentering of the vegetative nucleus in the abaxial cytoplasm via a radial cytoskeletal array. Key words: Cyperaceae; cytoskeleton; development; polarity; pollen.
- Published
- 2000
69. Trees for Profit and for bees too!
- Author
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McLean, John
- Published
- 2012
70. POLLEN AND ANTHER DEVELOPMENT IN NELUMBO (NELUMBONACEAE)
- Author
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Kreunen, Sarah S. and Osborn, Jeffrey M.
- Subjects
Botanical research -- Analysis ,Pollen -- Research ,Angiosperms -- Research ,Phylogeny -- Analysis ,Morphology -- Analysis ,Ultrastructure (Biology) -- Analysis ,Biological sciences - Abstract
The Nelumbonaceae are a small family of aquatic angiosperms comprising Nelumbo nucifera and Nelumbo lutea. Historically, the genus has been considered to be closely related to Nymphaeales, however new systematic work has allied Nelumbo with lower eudicots, particularly Platanus. In recent years, studies of pollen development have contributed greatly to the understanding of phylogenetic relationships, but little has been known about these events in Nelumbo. In this paper, pollen and anther development are morphologically described for the first time in N. lutea. A comprehensive ontogenetic sequence is documented, including the sporogenous tissue, microspore mother cell, tetrad, free spore, and mature pollen grain stages. The deposition of a microspore mother cell coat and callose wall, the co-occurrence of both tetrahedral and tetragonal tetrads, the formation of a primexine in tetrads, and primexine persistence into the late free spore stage are shown. The majority of exine development occurs during the free spore stage with the deposition of a tectate-columellate ectexine, a lamellate endexine, and an unusual granular layer below and intermixed with the endexine lamellae. A two-layered intine forms rapidly during the earliest mature pollen stage. Major events of anther development documented include the degradation of a secretory-type tapetum during the free spore stage and the rapid formation of U-shaped endothecial thickenings in the mature pollen grain stage. The majority of mature pollen grains are tricolpate, however less common monosulcate and diaperturate grains also develop. Co-occurring aperture types in Nelumbo have been suggested to be an important transition in angiosperm aperture number. However, aperture variability in Nelumbo may be correlated with the lateness of aperture ontogeny in the genus, which occurs in the early free spore stage. This character, as well as other details of pollen and anther ontogeny in Nelumbo, are compared to those of Nymphaeales and Platanus in an effort to provide additional insight into systematic and phylogenetic relationships. Although Nelumbo is similar to both groups in several characters, the ontogenetic sequence of the genus is different in many ways. Key words: anther; development; morphology; Nelumbo; Nelumbonaceae; pollen; ultrastructure.
- Published
- 1999
71. CYTOGEOGRAPHY AND CHROMOSOME EVOLUTION OF SUBGENUS TRIDENTATAE OF ARTEMISIA (ASTERACEAE)
- Author
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McArthur, E. Durant and Sanderson, Stewart C.
- Subjects
Botanical research -- Analysis ,Artemisia -- Research ,Hybridization -- Research ,Polyploidy -- Research ,Sagebrush -- Research ,Chromosomes -- Research ,Pollen -- Research ,Cells -- Analysis ,Biological sciences - Abstract
The subgenus Tridentatae of Artemisia (Asteraceae: Anthemideae) is composed of 11 species of various taxonomic and geographic complexities. It is centered on Artemisia tridentata with its three widespread common subspecies and two more geographically confined ones. Meiotic chromosome counts on pollen mother cells and mitotic chromosome counts on root tips were made on 364 populations (X = 3.1 plants per population). These population counts are approximately 60% of all Tridentatae counts. Some are first records for taxa. The Tridentatae are a polyploid complex (x = 9) with ploidy levels from 2x to 8x, but mostly 2x (48%) and 4x (46%). Polyploidy occurs in nine of the 11 species and in many subspecies as well. Supernumerary or b chromosomes are present only at a low frequency. In the principal species, A. tridentata, 2x plants are larger than 4x ones, which are adapted to drier conditions, probably in consequence of their slower growth rates. Gigas diploidy is a phenomenon shared by some other woody genera, but is in contrast to the gigas polyploid nature of many herbaceous genera. Polyploidy occurs within populations and is essentially autoploid. Hybridization sometimes occurs at taxa interfaces in stable hybrid zones. Stable Tridentatae hybrid zones coupled with the group's inherent propensity for polyploidization has led to the establishment of a geographically and numerically large and successful complex of species. Key words: Artemisia; Asteraceae; cytogeography; hybridization; polyploidy; sagebrush; Seriphidium; Tridentatae.
- Published
- 1999
72. POLLEN ULTRASTRUCTURE OF PANAX (THE GINSENG GENUS, ARALIACEAE), AN EASTERN ASIAN AND EASTERN NORTH AMERIPOLLEN ULTRASTRUCTURE OF PANAX (THE GINSENG GENUS, ARALIACEAE), AN EASTERN ASIAN AND EASTERN NORTH AMERICAN DISJUNCT GENUS CAN DISJUNCT GENUS
- Author
-
Wen, Jun and Nowicke, Joan W.
- Subjects
Botanical research -- Analysis ,Ginseng -- Analysis ,Transmission electron microscopes -- Usage ,Pollen -- Research ,Biological sciences - Abstract
Pollen of ten species of Panax and six species of Aralia was examined in light microscopy and scanning and transmission electron microscopy. Grains of both genera have similar complex apertures, short columellae, and overlapping tectal sculptures, suggesting a close relationship. Most species of Panax have pollen characterized by striato-reticulate tecta, short columellae, thick foot layers, costa ectocolpi, and lalongate endoapertures. The eastern North American P. trifolius, commonly known as the dwarf ginseng, has a distinctive pollen morphology and exine structure, supporting the hypothesis of its phylogenetically isolated position. Pollen of the eastern Asian P. ginseng (ginseng) can be distinguished from the eastern North American P. quinquefolius (American ginseng) by differences in ultrastructure. The monophyly of the three medicinally important species, P. ginseng, P. notoginseng, and P. quinquefolius, suggested by triterpenoid data, is not supported by pollen data. The results of the pollen study are generally congruent with those from the sequences of nuclear ribosomal DNA. Key words: Aralia; Araliaceae; ginseng; Panax; pollen ultrastructure.
- Published
- 1999
73. Wind pollination and reproductive assurance in Linanthus Parviflorus (Polemoniaceae), a self-incompatible annual
- Author
-
Goodwillie, Carol
- Subjects
Annuals (Plants) -- Research ,Pollen -- Research ,Plants -- Reproduction ,Pollination by insects -- Research ,Biological sciences - Abstract
Wind pollination was experimentally demonstrated in Linanthus parviflorus (Polemoniaceae), a predominantly beefly-pollinated, self-incompatible annual. Seed set in plants enclosed in mesh tents that excluded pollinators but allowed airborne pollen flow provided evidence for wind pollination, and the extent of seed set due to wind pollination was compared to that in open-pollinated controls and pollen-supplemented treatments. Additional controls were included to test for possible confounding effects of the mesh tent. Mean seed number in open-pollinated plants was 72.8-81.1% of that in pollen-supplemented plants, while wind pollination alone produced 49.5-52.2%, a smaller but substantial proportion of seed set with pollen supplementation. Further evidence for wind pollination was found in a comparison of sites differing in the extent of wind exposure in two populations of L. parviflorus. Airborne pollen counts were higher in exposed sites than in protected sites, and the difference was marginally significant. Seed set was significantly pollen limited in protected sites, but not in exposed sites. Taken together, the data suggest that wind pollination provides some reproductive assurance in this obligately outcrossing species. Wind pollination is hypothesized to represent an alternative to selfing as an evolutionary solution to the problem of temporal or spatial variation in pollination visitation. Key words: Linanthus parviflorus; Polemoniaceae; pollen limitation; reproductive assurance; self-incompatibility; wind pollination.
- Published
- 1999
74. MIcrotubule organization in germinated pollen of the conifer Picea abies (Norway spruce, Pinaceae)
- Author
-
Lazzaro, Mark D.
- Subjects
Microtubules -- Research ,Pollen -- Research ,Norway spruce -- Physiological aspects ,Biological sciences - Abstract
The organization of microtubules in germinated pollen of the conifer Picea abies (Norway spruce, Pinaceae) was examined using primarily confocal microscopy. Pollination in conifers differs from angiosperms in the number of mitotic divisions between the microspore and the sperm and in the growth rate of the pollen tube. These differences may be orchestrated by the cytoskeleton, and this study finds that there are important functional differences in microtubule organization within conifer pollen compared to the angiosperm model systems. Pollen from P. abies contains two degenerated prothallial cells, a body cell, a stalk cell, and a vegetative cell. The body cell produces the sperm. In the vegetative cell, microtubules form a continuous network from within the pollen grain, out through the aperture, and down the length of the tube to the elongating tip. Within the grain, this network extends from the pollen grain wall to the body and stalk cell complex. Microtubules within the body and stalk cells form a densely packed array that enmeshes amyloplasts and the nucleus. Microtubule bundles can be traced between the body and stalk cells from the cytoplasm of the body cell to the adjoining cell wall and into the cytoplasm of the stalk cell. Body and stalk cells are connected by plasmodesmata. The organization of microtubules and the presence of plasmodesmata suggest that microtubules form a path for intercellular communication by projecting from the cytoplasm to interconnecting plasmodesmata. Microtubules in the elongating tube form a net axial array that ensheathes the vegetative nucleus. Microtubules are enriched at the elongating tip, where they form an array beneath the plasma membrane that is perpendicular to the direction of tube growth. This enriched region extends back 20 [[micro]meter] from the tip. There is an abrupt transition from a net perpendicular to a net axial organization at the edge of the enriched region. In medial sections, microtubules are present in the core of the elongating tip. The organization of microtubules in the tip differs from that seen in angiosperm pollen tubes. Key words: conifer; cytoskeleton; microtubule; Picea abies; Pinaceae; pollen; pollen tube.
- Published
- 1999
75. White anther: a petunia mutant that abolishes pollen flavonol accumulation, induces male sterility, and is complemented by a chalcone synthase transgene (1)
- Author
-
Napoli, Carolyn A., Fahy, Deirdre, Wang, Huai-Yu, and Taylor, Loverine P.
- Subjects
Petunia -- Genetic aspects ,Pollen -- Research ,Biochemistry -- Research ,Biological sciences ,Science and technology - Published
- 1999
76. LeProt1, a transporter for proline, glycine betaine, and [gamma]-amino butyric acid in tomato pollen
- Author
-
Schwacke, Rainer, Grallath, Silke, Breitkreuz, Kevin E., Stransky, Elke, Stransky, Harald, Frommer, Wolf B., and Rentsch, Doris
- Subjects
Tomatoes -- Research ,Tomatoes -- Chemical properties ,Pollen -- Research ,Pollen -- Chemical properties ,Proline -- Chemical properties ,Glycine -- Chemical properties ,Phytochemistry -- Research ,Biological sciences ,Science and technology - Published
- 1999
77. The effects of pollen load size and donor diversity on pollen performance, selective abortion, and progeny vigor in Mirabilis jalapa (Nyctaginaceae)
- Author
-
Niesenbaum, Richard A.
- Subjects
Fruit -- Propagation ,Pollen -- Research ,Pollination -- Research ,Plants -- Reproduction ,Biological sciences - Abstract
The influence of pollen competitive environment on pollen performance (pollen germination, stigmatic penetration, and pollen tube growth rate), the maturation or abortion of initiated fruit, seed size, and seedling vigor was explored by manipulating the size and diversity of stigmatic pollen loads on Mirabilis jalapa. All aspects of pollen performance significantly increased with the number of pollen grains on a stigma or pollen tubes in a style, but was not influenced by the diversity of pollen donors. Plants tended to mature single-ovulate fruits that came from flowers where pollen load size and diversity were greatest and aborted those where these were lowest. No plants from seeds resulting from pollinations with a single pollen grain survived, but other fitness measures were mostly determined by maternal plant. The data suggest that pollen performance is influenced by pollen competitive environment, and both the genetic diversity of the pollen load and number of competing pollen tubes are important determinants of seed/fruit abortion. Key words: competition; fitness; fruit; fruit abortion; maternal effect; Mirabilis jalapa; Nyctaginaceae; pollen.
- Published
- 1999
78. Pollination of Picea orientalis (Pinaceae): saccus morphology governs pollen buoyancy
- Author
-
Runions, C. John, Rensing, Kim H., Takaso, Tokushiro, and Owens, John N.
- Subjects
Spruce -- Research ,Pinaceae -- Research ,Pollination -- Research ,Pollen -- Research ,Biological sciences - Abstract
Sacci of conifer pollen do not function primarily to increase the efficiency of wind pollination as is widely thought. Rather, they are bladders and cause pollen to float upwards in a liquid drop into the ovules. This observation is seemingly unsupported in the case of oriental spruce (Picea orientalis (L.) Link), which has saccate pollen. Ovulate cones are pendant at the time of pollination, which requires that pollen sink into the ovules. Pollen of oriental spruce floats at first but within 1-2 min sinks into the ovule. As sinking does not occur in saccate pollen of other Pinaceae, a variety of techniques was used to determine anatomical differences leading to this uncharacteristic tendency. Light, scanning electron, and confocal microscopy of the pollen surface yielded no significant appearing difference between pollen of oriental spruce and white spruce. However, transmission electron microscopy of freeze-fixed/freeze-substituted hydrated pollen revealed that the ektexine of oriental spruce pollen sacci is porous compared to that of white spruce. Confocal microscopy allowed examination of pollen hydration dynamics. Water enters pollen at the distal pole between sacci, and resulting rapid expansion of the tube cell forces air out of the saccate space. White spruce pollen remains buoyant because of enclosed air pockets in the saccus ektexine. Evolutionary change in pollen wall anatomy with resultant loss of saccus function is correlated with a change in ovulate strobilus orientation at pollination in oriental spruce. A suite of characters interact in the conifer pollination mechanism, and concerted change in these characters may lead to speciation. Key words: Picea; Pinaceae; pollen; pollination; sacci.
- Published
- 1999
79. Cost of mutualism: competition, tree morphology, and pollen production in limber pine clusters
- Author
-
Feldman, Ronald, Tomback, Diana F., and Koehler, James
- Subjects
Mutualism (Biology) -- Research ,Trees (Plants) -- Research ,Competition (Biology) -- Research ,Pollen -- Research ,Biological sciences ,Environmental issues ,Research - Abstract
All aspects of a mutualism may not be optimal for the participating species. We examined possible consequences to limber pine (Pinus flexilis) from competition within reproductive multi-genet tree clusters, which come from multi-seed caches stored by Clark's Nutcracker (Nucifraga columbiana). Limber pine occurs in three different tree growth forms. We predicted that genets within the tree-cluster growth form would have both reduced radial growth rates and lower pollen-cone whorl production relative to single-trunk and multitrunk growth forms. We tested these predictions with three populations in the Front Range of the Colorado Rocky Mountains (USA), using ANCOVA models. Genets in clusters had reduced diameters, but similar heights and lower pollen-cone whorl production relative to same-aged genets in the other growth forms. Because seeds stored in clusters represent potential direct fitness loss to parent trees in comparison to seeds stored singly, nutcracker caching behavior may be suboptimal for limber pine at late life-history stages, thus generating a 'cost of mutualism.' Key words: Clark's Nutcracker; competition; female cones; limber pine; mutualism, cost of; Nucifraga columbiana; Pinus flexilis; pollen cones; seed caching; tree clusters; tree growth form; tree morphology., INTRODUCTION Thompson (1982, 1994) has argued that many mutualisms result from the amelioration over evolutionary time of an antagonistic relationship between two species. An important consequence of this origin may [...]
- Published
- 1999
80. Detection of Pseudomonas syringae pv. acinidiae in kiwifruit pollen samples
- Author
-
New Zealand Plant Protection Conference and Vanneste, Joël L
- Published
- 2011
81. Target identification in Ory S1 pollen protein allergen from Oryza sativa in the course of construction of hypoallergenic vaccines
- Author
-
Sharma, Ruchi and Singh, A.K.
- Subjects
Allergens -- Identification and classification ,Allergens -- Health aspects ,Allergens -- Structure ,Allergens -- Research ,Allergic reaction -- Risk factors ,Allergic reaction -- Diagnosis ,Allergic reaction -- Research ,Allergy -- Risk factors ,Allergy -- Diagnosis ,Allergy -- Research ,Pollen -- Health aspects ,Pollen -- Research ,Biological sciences - Abstract
Problem statement: Recombinant-based approaches are mostly focused on genetic modification of allergens to produce molecules with reduced allergenic activity and conserved antigenicity, such as hypoallergens. Recombinant allergens represent promising tools for diagnosis and therapy of type I allergy. This approach was probably feasible with every allergen with known amino acid sequence. Approach: The primary aim of this study was to determine the consensus epitope from twenty homologous protein sequences of Ory S1 allergenic protein sequence from Oryza sativa (indica group) pollen. Molecular modeling calculations had been used to investigate the allergenic protein models for the epitope. Results: Oryza sativa (japonica), Phleum pratense, Poa pratensis, Holcus lanatus, Lolium perenne, Triticum aestivum, Dactylis glomerata and Zea mays were found more closely related (alignment score 1145-812) among all the homologs and investigated further. The major binding pocket comprised an area of 604.5 [[Angstrom].sup.2] and 970 [[Angstrom].sup.3] volume and another key binding pocket had 425.6 [[Angstrom].sup.2] area and 658.8 [[Angstrom].sup.3] volume. The residues found in the key site included ile2, lys13, cys14, ser15, lys16, pro17, ala25, leu26, ile27, tyr40, his41, phe42, asp43, leu44, ser45, gly46, leu47, ala48, met49, ala50, asp55, leu58, arg59, ala61, gly62, ile63, ile64, asp65, gln67, phe68; corresponding to the allergen binding site and the IgE binding epitope given in the title. Conclusion: These are the functional sites on the allergenic proteins that can be mutated to develop hypoallergenic vaccine. These sites can be rationalized on the basis of simple arguments that lead to vaccine development, by predicting the structure of the allergenic epitopes and comparative analysis. Key words: Homology modeling, allergen binding epitope, allergenic proteins, INTRODUCTION An allergen simply means a harmful immune response elicited by an antigen that is not itself intrinsically harmful. Grass pollens are well known among the health hazardous bio aerosols [...]
- Published
- 2009
82. Fungi and pollen exposure in the first months of life and risk of early childhood wheezing
- Author
-
Harley, K.G., Macher, J.M., Lipsett, M., Duramad, P., Holland, N.T., Prager, S.S., Ferber, J., Bradman, A., Eskenazi, B., and Tager, I.B.
- Subjects
Wheeze -- Risk factors ,Wheeze -- Environmental aspects ,Wheeze -- Research ,Fungi, Pathogenic -- Health aspects ,Fungi, Pathogenic -- Research ,Pollen -- Health aspects ,Pollen -- Research ,Allergens -- Research ,Health - Published
- 2009
83. Is relative pollen production or removal a good predictor of relative male fitness? An experimental exploration with a wild strawberry (Fragaria virginiana, Rosaceae)
- Author
-
Ashman, Tia-Lynn
- Subjects
Rosaceae -- Physiological aspects ,Pollen -- Research ,Biological sciences - Abstract
Understanding plant reproduction requires knowledge of genetic contributions through pollen and seeds. Since direct genetic assessments of fitness through pollen are often intractable, reproductive ecologists use components of male fitness such as pollen production and pollen removal as surrogates for paternity. However, we know little of the strength of the relationship between these components and actual paternity. Here, I report on a study undertaken to examine the relationship of pollen production and removal with paternity in Fragaria virginiana, a wild strawberry. A morphological marker was used to track paternity in experimental arrays exposed to native pollinators. Relative pollen production proved to be a poor predictor of relative paternity in most arrays, and over all arrays there was no significant correlation between relative paternity and relative pollen production. In contrast, relative pollen removed correlated significantly and positively with proportion of seeds sired, suggesting that a plant's contribution to the pool of removed pollen is a good predictor of its male reproductive success. Deviations from expected paternity based on relative pollen removal suggest a systematic overestimation of the siring success of plants with low pollen removal. And, in at least one specific case, low pollen removal may be explained by delayed anther dehiscence, which could lower the effectiveness of the removed pollen. Key words: Fragaria virginiana; male fitness; paternity; pollen; pollen removal; reproduction; Rosaceae; siring success; strawberry.
- Published
- 1998
84. Molecular characterization of S locus genes, SLG and SRK, in a pollen-recessive self-incompatibility haplotype of Brassica rapa L
- Author
-
Hatakeyama, Katsunori, Takasaki, Takeshi, Watanabe, Masao, and Hinata, Kokichi
- Subjects
Brassica -- Genetic aspects ,Pollen -- Research ,Amino acids -- Research ,Biological sciences - Abstract
In Brassica species that exhibit self-incompatibility, two genes, SLG and SRK, at the S locus are involved in the recognition reaction with self and non-self pollen. From a pollen-recessive [S.sup.29] haplotype of Brassica rapa, both cDNA and genomic DNA clones for these two genes were isolated and characterized. The nucleotide sequence for the S domain of [SRK.sup.29] showed a high degree of similarity with that of [SLG.sup.29], and they belong to Class II type. RNA gel blot analysis showed that the transcript of [SLG.sup.29] consisted of the first and second exons, and no other transcript containing any part of the intron sequence was detected. Because no transmembrane domain was encoded by the second exon of [SLG.sup.29], [SLG.sup.29] was designated a secreted type glycoprotein. SLGs of two other pollen-recessive haplotypes, [S.sup.40] and [S.sup.44], of B. rapa also had a similar structure to that of [SLG.sup.29]. Previously, [SLG.sup.2] from a pollen-recessive haplotype, [S.sup.2], of Brassica oleracea was found to produce two different transcripts, one for the secreted type glycoprotein and the other for a putative membrane-anchored form of SLG. Therefore, the nature of these SLGs from pollen-recessive haplotypes of B. rapa is different from that of [SLG.sup.2] of B. oleracea.
- Published
- 1998
85. Mentor effects in wild species of Helianthus (Asteraceae)
- Author
-
Desrochers, Andree M. and Rieseberg, Loren H.
- Subjects
Sunflowers -- Research ,Origin of species -- Research ,Pollen -- Research ,Hybridization -- Research ,Plants -- Self-incompatibility ,Biological sciences - Abstract
Self-incompatibility (SI) is an effective method for limiting self-fertilization in flowering plant species, but there are circumstances in which an otherwise functional SI system may fail. One of the most intriguing of these is the induction of selfing by mixed loads of self and heterospecific pollen (the mentor effect) because it is likely to occur under natural conditions, such as in hybrid zones. Here we conducted a series of controlled crosses to determine whether mentor effects operate in two SI annual species, Helianthus annuus and H. petiolaris, and whether the failure of SI results in a decrease in the frequency of hybridization between these two species. Of the 1396 achenes examined from pollen mixtures that included varying ratios of self, intraspecific compatible, and interspecific pollen, 71 (5.1%) were selfed. Selfing frequencies were significantly less than expected based on pollen ratios, except when the proportion of intraspecific compatible pollen was low. Hybridization frequencies from these same pollen ratios averaged 41.8% with H. annuus as the maternal species and 13.3% with H. petiolaris as the mother. Analysis of 1404 achenes from pollen mixtures that excluded self pollen resulted in hybridization frequencies for H. annuus (42.2%) and H. petiolaris (18.2%) that do not differ significantly from those including self pollen. Thus, mentor effects do not appear to play an important role in reproductive isolation between these species. On the other hand, even a modest increase in self-fertilization in hybrid populations, such as that due to mentor effects, could enhance the probability of hybrid species establishment. Key words: Asteraceae; Helianthus; hybrid speciation; introgression; mentor effect; pollen competition; reproductive isolation.
- Published
- 1998
86. The effect of Microbotryum violaceum spores on pollen germination in Silene acaulis
- Author
-
Marr, Deborah L.
- Subjects
Smut fungi -- Research ,Fungi -- Spores ,Fungi, Phytopathogenic -- Host plants ,Pollen -- Research - Published
- 1998
87. Susceptibility of pollen to UV-B radiation: an assay of 34 taxa
- Author
-
Torabinejad, Javad, Caldwell, Martyn M., Flint, Stephan D., and Durham, Susan
- Subjects
Ultraviolet radiation -- Physiological aspects ,Pollen -- Research ,Germination -- Research ,Biological sciences - Abstract
Much of the ultraviolet-B radiation (UV-B) research on plants has concentrated on vegetative plant parts, and only a small fraction has dealt with the reproductive system. The present study analyzed pollen grains of 34 taxa germinated and grown under two levels of UV-B radiation (187 and 460 mW/[m.sup.2]) or no UV-B (control group). Visible radiation at 260 [[micro]molar] [multiplied by] [m.sup.-2] [multiplied by] [s.sup.-1] was present in all treatments. Taxa included those with binucleate and trinucleate pollen types. We detected differences among species. A significant reduction in pollen germination occurred in only five species. Pollen tubes of >50% of the species showed significant reduction in length. Trinucleate pollen types were more likely to exhibit tube length reduction than the binucleate types. Proportionately more monocotyledonpus species were sensitive to UV-B treatment than dicotyledonous species, and proportionately more wild species were sensitive than cultivated species and pollen collected from plants growing in the field were somewhat more sensitive than pollen collected from plants grown in the greenhouse. Species in which pollination occurred earlier in the season were more likely to be susceptible to UV-B radiation than those for which anthesis took place later in the season, suggesting a possible adaptation to UV-B radiation. Key words: binucleate; pollen germination; pollen tube growth; trinucleate; UV-B radiation.
- Published
- 1998
88. Pollen parent effects on oil, protein, and starch concentration in maize kernels
- Author
-
Letchworth, M.B. and Lambert, R.J.
- Subjects
Corn -- Research ,Pollen -- Research ,Agricultural industry ,Business ,Research - Abstract
The ability to evaluate maize (Zea mays L.) hybrids and inbreds for grain quality traits is important. Twelve maize hybrids were grown in research plots under open-pollinated (OP) and self-pollinated (SP) conditions to determine pollen source effects on kernel oil, protein, and starch concentrations. Self-pollinated kernels were higher in protein concentration than OP kernels but hybrid rank did not change within pollination treatments. Evaluation of reciprocal crosses indicated a strong maternal effect for protein concentration and no pollen effect. Field evaluations of hybrids for protein concentration are feasible under OP small plot conditions. Oil concentration was significantly higher in OP kernels than in SP kernels. Significant differences among hybrids for oil concentration indicated a maternal effect, and data from reciprocal crosses indicated a pollen effect. Although the range in oil concentration for the hybrids was relatively narrow (41-55 g [kg.sup.-1]), rankings of the three highest and three lowest hybrids for oil concentration did not change within pollination treatments. Field evaluations with OP will separate genotypes with extreme oil concentrations, but accurate determinations of oil concentration should be conducted under SP or sib-pollinated conditions. Open-pollinated kernels were higher in starch concentration than SP kernels, Reciprocal crosses indicated a maternal effect for starch concentration and no pollen effect. Field evaluations for starch concentration are feasible under OP research plot conditions. Significant differences existed for kernel weight, kernel size, and kernel density among the maize hybrids within pollination treatments., Maize is one of the most important cereal crops in the USA for livestock feeding, commercial products, and human consumption. Increasing kernel protein, oil, and starch concentrations, as well as [...]
- Published
- 1998
89. Direct and indirect estimates of seed versus pollen movement within a population of ponderosa pine
- Author
-
Latta, Robert G., Linhart, Yan B., Fleck, David, and Elliot, Michael
- Subjects
Seeds -- Dispersal ,Dispersal (Ecology) -- Research ,Mitochondrial DNA -- Research ,Ponderosa pine -- Research ,Pollen -- Research ,Biological sciences ,Research - Abstract
The distances traveled by plant seeds and pollen have been difficult to measure (Levin 1981). It is evident that some propagules can travel very great distances, but that these represent [...]
- Published
- 1998
90. Study Data from Chinese Academy of Sciences Provide New Insights into Paleobotany (Pollen Development In Three Selected Species of Rubiaceae Provides Ontogenetic Evidence for Pollen Evolution)
- Subjects
Plants -- Reproduction ,Botanical research ,Rubiaceae -- Physiological aspects -- Varieties ,Pollen -- Research ,Health ,Science and technology - Abstract
2021 JUL 16 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- A new study on Paleobotany is now available. According to news reporting out of Guangzhou, [...]
- Published
- 2021
91. New Aerobiology Study Findings Recently Were Reported by Researchers at Jagiellonian University [Unusually High Birch (Betula Spp.) Pollen Concentrations In Poland In 2016 Related To Long-range Transport (Lrt) and the Regional Pollen Occurrence]
- Subjects
Birch -- Research ,Environment -- Research ,Pollen -- Research ,Biological sciences ,Health - Abstract
2021 MAY 25 (NewsRx) -- By a News Reporter-Staff News Editor at Life Science Weekly -- Investigators discuss new findings in Life Science Research - Aerobiology. According to news reporting [...]
- Published
- 2021
92. Recent Findings from University of Abdelmalek Essaadi Has Provided New Information about Aerobiology [Airborne Pollen Trends In Tetouan (Nw of Morocco)]
- Subjects
Botanical research ,Aerobiology ,Pollen -- Research ,Biological sciences ,Health - Abstract
2021 MAY 4 (NewsRx) -- By a News Reporter-Staff News Editor at Life Science Weekly -- Investigators discuss new findings in Life Science Research - Aerobiology. According to news reporting [...]
- Published
- 2021
93. Comparison of flagellated and nonflagellated sperm in plants
- Author
-
Southworth, Darlene and Cresti, Mauro
- Subjects
Cytoskeleton -- Research ,Pollen -- Research ,Plant cells and tissues -- Research ,Microtubules -- Research ,Plants -- Reproduction ,Biological sciences - Abstract
Differences among flagellated and nonflagellated sperm in land plants are striking, but close examination reveals similarities in pattern of cytoskeleton and in nuclear structure. The microtubular cytoskeleton of flowering plant sperm consists of microtubule bundles arranged obliquely around the nucleus, terminating in cellular extensions. Microtubules are linked into bundles that branch and rejoin along the axis of the sperm cell, forming a cytoskeleton that determines cell shape but does not actively participate in cell movement. Generative cells and sperm share a pattern of microtubules not found in somatic cells. This pattern is initiated in the generative cell, one division before sperm formation, a situation parallel to spermatogenous cell development in vascular plants with flagellated sperm. Chromatin in flagellated and nonflagellated sperm is condensed by specialized histones. Key words: cytoskeleton; generative cell; microtubules; pollen; sperm (plant).
- Published
- 1997
94. Reproductive and vegetative morphology of Polyptera (Juglandaceae) from the Paleocene of Wyoming and Montana
- Author
-
Manchester, Steven R. and Dilcher, David L.
- Subjects
Wyoming -- Natural history ,Montana -- Natural history ,Paleobotany -- Paleocene ,Pollen -- Research ,Biological sciences - Abstract
The morphology, systematics, and ecology of the extinct juglandaceous genus Polyptera are interpreted on the basis of infructescences, fruits, staminate catkins, pollen, and compound leaves from the Paleocene of Wyoming and Montana. The elongate infructescences of Polyptera manningii bear numerous helically arranged sessile fruits. The fruit is a pyramidal nut with a vascularized husk and a multilobed disk-like wing adaptive for wind dispersal. Associated staminate catkins bear numerous helically arranged florets, each with six or more stamens. Pollen from the anthers is triporate and isopolar, with ultrastructure diagnostic of Juglandaceae, but with a pattern of exinous thinning characteristic of the extinct dispersed pollen type Maceopolipollenites anellus (Nichols et Ott) comb. nov. The correlated leaves, Juglandiphyllites glabra (Brown ex Watt) comb. nov., are deciduous, pinnately compound, and have five to seven petiolulate finely serrate leaflets. Systematically, Polyptera shows relationships both with the Hicorieae and the Juglandeae. Occurrences in the Torrejonian and Tiffanian stages of the Paleocene place Polyptera as the oldest unequivocal record of Juglandaceae. Polyptera manningii typically occurs in low-diversity assemblages of 8-15 species, and usually is a dominant or subdominant constituent of floodplain assemblages. It may have been an early-successional colonizer. Key words: fruits; Juglandaceae; leaves; Maceopolipollenites; pollen; paleobotany; Paleocene; Polyptera.
- Published
- 1997
95. Microspectrophotometric evaluation of digestibility of pollen grains
- Author
-
Franchi, G. G., Franchi, G., Corti, P., and Pompella, A.
- Subjects
Corn poppy -- Health aspects ,Corn poppy -- Physiological aspects ,Corn poppy -- Research ,Digestion -- Health aspects ,Digestion -- Research ,Filbert -- Physiological aspects ,Filbert -- Health aspects ,Filbert -- Research ,Pollen -- Health aspects ,Pollen -- Research ,Health - Abstract
Byline: G. G. Franchi (1), G. Franchi (1), P. Corti (1), A. Pompella (2) Keywords: Corylus avellana L.; Dietetic foods; Digestion; Microspectrophotometry; Papaver rhoeas L.; Pollen Abstract: Digestibility of pollen grains of poppy (Papaver rhoeas) and hazelnut (Corylus avellana) subjected to a human-like in vitro digestion with pancreatic enzymes was evaluated. Pollens showed different types of walls. Digestibility was determined for total protein and insoluble carbohydrate contents by means of a new application of microspectrophotometry. Results demonstrated that pollen grains of both species were only partly digested after 24h treatment, only 26% of carbohydrates and 48% of proteins were digested in poppy and only 3% and 59% in hazelnut. This is probably due to the difficulty of enzymes to penetrate the intine of pollen grains. The degree of digestion of insoluble carbohydrates varied in the studied species according to their chemical nature and their storage sites. Author Affiliation: (1) Dept. Farmaco Chimico Tecnologico, University of Siena, Banchi di Sotto 55, 53100, Siena, Italy (2) Institute of General Pathology, University of Siena, Via A. Moro, 53100, Siena, (Italy) Article History: Registration Date: 26/05/2006 Received Date: 28/06/1995 Accepted Date: 28/10/1996
- Published
- 1997
96. Systematic significance of pollen arrangement in microsporangia of Poaceae and Cyperaceae: review and observations on representative taxa
- Author
-
Kirpes, Christine C., Clark, Lynn G., and Lersten, Nels R.
- Subjects
Pollen -- Research ,Grasses -- Research ,Cyperaceae -- Research ,Biological sciences - Abstract
An anatomical survey of anthers of the Poaceae and Cyperaceae and two related families, the Restionaceae and Flagellariaceae, was conducted to determine the taxonomic distribution and possible phylogenetic significance of pollen arrangement. An unusual pollen arrangement was known from a small number of taxa in the Poaceae and Cyperaceae, in which a single, uniseriate cylinder of pollen grains is arranged in the anther locule such that each grain is in contact with the tapetum (termed here 'peripheral' pollen). This contrasts with the prevailing arrangement in other angiosperms in which the locule contains a relatively large number of pollen grains in no special configuration, with many interior grains that never touch the tapetum (termed here 'central' pollen). A total of 48 species in these four families was examined in this study, and observations on pollen arrangement for numerous additional species in these families were gleaned from the literature. We confirm that the peripheral arrangement is predominant in Poaceae and Cyperaceae, although both families also include species with central pollen, whereas only central pollen is found in Restionaceae and Flagellariaceae. In the peripheral arrangement, the pore of the pollen grain or pseudomonad, when observed, is in contact with the tapetum, but it has not been definitively demonstrated that this is always the case. Peripheral pollen in the Poaceae and Cyperaceae is nonhomologous because of the presence of pseudomonads in the latter family. It remains unexplained why peripherally arranged pollen or pseudomonads, with the attendant reduction in the number of pollen grains, should be associated with anemophily in these two families. Key words: anatomy; anther; Centrolepidaceae; Cyperaceae; Juncaceae; Poaceae; pollen; Restionaceae.
- Published
- 1996
97. Pollinator behavior and postpollination reproductive success in alternative floral phenotypes of Clarkia gracilis (onagraceae)
- Author
-
Jones, Kristina Niovi
- Subjects
Genetic polymorphisms -- Research ,Plants -- Reproduction ,Pollen -- Research - Published
- 1996
98. The timetable for development of maternal tissues sets the stage for male genomic selection in Betula pendula (Betulaceae)
- Author
-
Dahl, Aslog E. and Fredrikson, Margit
- Subjects
Plants -- Reproduction ,Flowers -- Anatomy ,Pollen -- Research ,Biological sciences - Abstract
The influence of the sequence of maternal tissue development in Betula pendula upon the potential for male gamete selection was investigated, and the timing of the fixed abortion of one of the two ovules was determined. We used scanning electronic microscopy, confocal laser scanning microscopy, and blue light microscopy. The stigmas remain fresh throughout male anthesis, and may also last after its end, depending on ambient temperatures. The presence of germinated pollen does not induce stigmatic necrotization, and grains may arrive at different times. The pollen tube tips remain within the stigma base until the end of female anthesis. The ovules will not develop until after necrotization of the stigmas. The pollen tubes thus have a fair start to the ovules, regardless of their different arrival times and of the original positions of the pollen grains at the stigma surface. Therefore, competition among different microgametophytes is possible, in spite of low pollination intensity. Our results indicate that when the first pollen tube penetrates an ovule, this ovule starts to outgrow the other one, and even if the other is also penetrated, its vascular support soon atrophies and the megagametophyte will shrivel. Fertilization of both ovules was never seen in this study. Key words: abortion; anemophily; Betula; Betulaceae; brood size; confocal laser scanning microscopy; floral longevity; pollen competition; pollen load.
- Published
- 1996
99. Effect of enhanced UV-B (Ultraviolet Beta) radiation on pollen quantity, quality, and seed yield in Brassica rapa (Brassicaceae)
- Author
-
Demchik, Sophie M. and Day, Thomas A.
- Subjects
Growth (Plants) -- Research ,Pollen -- Research ,Plants, Effect of radiation on -- Research ,Chinese cabbage -- Growth ,Biological sciences - Abstract
We conducted three experiments to examine the influence of ultraviolet-B radiation (UV-B; 280-320 nm) exposure on reproduction in Brassica rapa (Brassicaceae). Plants were grown in a greenhouse under three biologically effective UV-B levels that simulated either an ambient stratospheric ozone level (control), 16% ('low enhanced'), or 32% ('high enhanced') ozone depletion levels at Morgantown, WV, USA in mid-March. In the first experiment, we examined whether UV-B level during plant growth influenced in vivo pollen production and viability, and flower production. Pollen production and viability per flower were reduced by [approximately equal to]50% under both enhanced UV-B levels relative to ambient controls. While plants under high-enhanced UV-B produced over 40% more flowers than plants under the two lower UV-B treatments, whole-plant production of viable pollen was reduced under high-enhanced UV-B to 17% of that of ambient controls. Whole-plant production of viable pollen was reduced under low-enhanced UV-B to 34% of ambient controls. In the second experiment, we collected pollen from plants under the three UV-B levels and examined whether source-plant UV-B exposure influenced in vitro pollen germination and viability. Pollen from plants under both enhanced-UV-B treatments had initially lower germination and viability than pollen from the ambient level. After in vitro exposure to the high-enhanced UV-B levels for 6 h, viability of the pollen from plants grown under ambient UV-B was reduced from 65 to 18%. In contrast, viability of the pollen from plants grown under both enhanced UV-B treatments was reduced to a much lesser extent: only from [approximately equal to]43 to 22%. Thus, ambient source-plant pollen was more sensitive to enhanced UV-B exposure. In the third experiment, we used pollen collected from source plants under the three UV-B levels to fertilize plants growing under ambient-UV-B levels, and assessed subsequent seed production and germination. Seed abortion rates were higher in plants pollinated with pollen from the enhanced UV-B treatments, than from ambient UV-B. Despite this, seed yield (number and mass) per plant was similar, regardless of the UV-B exposure of their pollen source. Our findings demonstrate that enhanced UV-B levels associated with springtime ozone depletion events have the capacity to substantially reduce viable pollen production, and could ultimately reduce reproductive success of B. rapa. Key words: Brassica rapa; ozone depletion; pollen; seed yield; UV-B radiation.
- Published
- 1996
100. Pollen germination and tube growth in selfing and outcrossing populations of Clarkia tembloriensis (onagraceae)
- Author
-
Smith-Huerta, Nancy L.
- Subjects
Pollen -- Research ,Germination -- Research ,Plants -- Reproduction - Published
- 1996
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