bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium function and distribution during fertilization in angiosperms
Authors: Ge Li Li , Tian Hui Qiao , Russell Scott D.
Published: February 2008

Calcium has an essential signaling, physiological, and regulatory role during sexual reproduction in flowering plants; elevation of calcium amounts is an accurate predictor of plant fertility. Calcium is present in three forms: (1) covalently bound calcium, (2) loosely bound calcium typically associated with fixed and mobile anions (ionic bonding); and (3) cytosolic free calcium–an important secondary messenger in cell signaling. Pollen often requires calcium for germination. Pollen tube elongation typically relies on external calcium stores in the pistil. Calcium establishes polarity of the pollen tube and forms a basis for pulsatory growth. Applying calcium on the tip may alter the axis; thus calcium may have a role in determining the directionality of tube elongation. In the ovary and ovule, an abundance of calcium signals receptivity, provides essential mineral nutrition, and guides the pollen tube in some plants. Calcium patterns in the embryo sac also correspond to synergid receptivity, reflecting programmed cell death in one synergid cell that triggers degeneration and prepares this cell to receive the pollen tube. Male gametes are released in the synergid, and fusion of the gametes requires calcium, according to in vitro fertilization studies. Fusion of plant gametes in vitro triggers calcium oscillations evident in both the zygote and primary endosperm during double fertilization that are similar to those in animals.
Reaction tissue formation and stem tensile modulus properties in wild‐type and p‐coumarate‐3‐hydroxylase downregulated lines of alfalfa, Medicago sativa (Fabaceae)
Authors: Patten Ann M. , Jourdes Michaël , Brown Elvie E. , Laborie Marie‐Pierre , Davin Laurence B. , Lewis Norman G.
Published: February 2008

To our knowledge, xylary reaction tissue has never been reported in a forage crop species. Here we report the discovery of reaction tissue in a transgenic line of Medicago sativa (pC3H, for the gene for p‐coumarate‐3‐hydroxylase) with reduced lignin content and in the wild‐type (WT) line. Based on microscopy and biomechanical testing of internodal alfalfa branch sections, the transgenic (pC3H‐I) line, relative to the WT (1) apparently formed more reaction tissue containing gelatinous fibers with adjacent thick‐walled fibers (presumed to be “intermediate” tissue) more rapidly, (2) had more xylem tissue, and (3) had comparable tensile dynamic modulus properties. These findings thus establish the (limited) ability of this perennial angiosperm to form (inducible) reaction tissue in a manner somewhat analogous to that of woody arborescent angiosperms. The potential of effectuating reductions in lignin amounts in (woody) angiosperms with increased formation of reaction (tension wood) tissue is discussed because reaction tissues are often viewed as a deleterious trait in processing for many agronomic/industrial applications, especially with the current interest in biofuels.
Genealogy and fine mapping of obscuravenosa, a gene affecting the distribution of chloroplasts in leaf veins, and evidence of selection during breeding of tomatoes (Lycopersicon esculentum; Solanaceae)
Authors: Jones Carl M. , Rick Charles M. , Adams Dawn , Jernstedt Judy , Chetelat Roger T.
Published: February 2008

In the processes of plant domestication and variety development, some traits are under direct selection, while others may be introduced by indirect selection or linkage. In the cultivated tomato (Lycopersicon esculentum = Solanum lycopersicum), and all other Solanaceae examined, chloroplasts are normally absent from subepidermal and mesophyll cells surrounding the leaf veins, and thus, veins appear clear upon subillumination. The tomato mutant obscuravenosa (obv), in contrast, contains chloroplasts in cells around the vein, and thus, veins appear as dark as the surrounding leaf tissue. Among tomato cultivars, the obv allele is common in processing varieties bred for mechanical harvest, but is otherwise rare. We traced the source of obv in processing tomatoes to the cultivar Earliana, released in the 1920s. The obv locus was mapped to chromosome 5, bin 5G, using introgression lines containing single chromosome segments from the wild species L. pennellii. This region also contains a quantitative trait locus (QTL) for plant height, pht5.4, which cosegregated with SP5G, a paralog of self‐pruning (sp), the gene that controls the switch between determinate and indeterminate growth in tomato. The pht5.4 QTL was partially dominant and associated with a reduced percentage of red fruit at harvest. Our data suggest that the prevalence of obv in nearly all processing varieties may have resulted from its tight linkage to a QTL conferring a more compact, and horticulturally desirable, plant habit.
Differences in mechanical and structural properties of surface and aerial petioles of the aquatic plant Nymphaea odorata subsp. tuberosa (Nymphaeaceae)
Authors: Etnier Shelley A. , Villani Philip J.
Published: February 2008

Lily pads (Nymphaea odorata) exhibit heterophylly where a single plant may have leaves that are submerged, floating, or above (aerial) the surface of the water. Lily pads are placed in a unique situation because each leaf form is exposed to a distinctly different set of mechanical demands. While surface petioles may be loaded in tension under conditions of wind or waves, aerial petioles are loaded in compression because they must support the weight of the lamina. Using standard techniques, we compared the mechanical and morphological properties of both surface and aerial leaf petioles. Structural stiffness (EI) and the second moment of area (I) were higher in aerial petioles, although we detected no differences in other mechanical values (elastic modulus [E], extension ratio, and breaking strength). Morphologically, aerial petioles had a thicker rind, with increased collenchyma tissue and sclereid cell frequency. Aerial petioles also had a larger cross‐sectional area and were more elliptical. Thus, subtle changes in the distribution of materials, rather than differences in their makeup, differentiate petiole forms. We suggest that the growth of aerial petioles may be an adaptive response to shading, allowing aerial leaves to rise above a crowded water surface.
Morphology of Hydatellaceae, an anomalous aquatic family recently recognized as an early‐divergent angiosperm lineage
Authors: Rudall Paula J. , Sokoloff Dmitry D. , Remizowa Margarita V. , Conran John G. , Davis Jerrold I. , Macfarlane Terry D. , Stevenson Dennis W.
Published: February 2008

The family Hydatellaceae was recently reassigned to the early‐divergent angiosperm order Nymphaeales rather than the monocot order Poales. This dramatic taxonomic adjustment allows comparison with other early‐divergent angiosperms, both extant and extinct. Hydatellaceae possess some monocot‐like features that could represent adaptations to an aquatic habit. Ecophysiological parallels can also be drawn from fossil taxa that are known from small achene‐like diaspores, as in Hydatellaceae. Reproductive units of Hydatellaceae consist of perianthlike bracts enclosing several pistils and/or stamens. In species with bisexual reproductive units, a single unit resembles an “inside‐out” flower, in which stamens are surrounded by carpels that are initiated centrifugally. Furthermore, involucre development in Trithuria submersa, with delayed growth of second whorl bracts, resembles similar delayed development of the second perianth whorl in Cabomba. Several hypotheses on the homologies of reproductive units in Hydatellaceae are explored. Currently, the most plausible interpretation is that each reproductive unit represents an aggregation of reduced unisexual apetalous flowers, which are thus very different from flowers of Nymphaeales. Each pistil in Hydatellaceae is morphologically and developmentally consistent with a solitary ascidiate carpel. However, ascidiate carpel development, consistent with placement in Nymphaeales, is closely similar to pseudomonomerous pistil development as in Poaes.
Introduction history and population genetics of the invasive grass Bromus tectorum (Poaceae) in Canada
Authors: Valliant Morgan T. , Mack Richard N. , Novak Stephen J.
Published: February 2008

The invasive annual Bromus tectorum (cheatgrass) is distributed in Canada primarily south of 52° N latitude in two diffuse ranges separated by the extensive coniferous forest in western Ontario. The grass was likely introduced independently to eastern and western Canada post‐1880. We detected regional variation in the grass's genetic diversity using starch gel electrophoresis to analyze genetic diversity at 25 allozyme loci in 60 populations collected across Canada. The Pgm‐1a & Pgm‐2a multilocus genotype, which occurs in the grass's native range in Eastern Europe, is prevalent in eastern Canada but occurs at low frequency in western Canada. In contrast, the Got‐4c multilocus genotype, found in the native range in Central Europe, is widespread in populations from western Canada. Overall genetic diversity of B. tectorum is much higher in eastern Canada than in the eastern U.S., while the genetic diversity in populations in western North America is similar between Canada and the U.S. The distribution of genetic diversity across Canada strongly suggests multiple introduction events. Heterozygous individuals, which are exceedingly rare in B. tectorum, were detected in three Canadian populations. Formation of novel genotypes through occasional outcrossing events could spark adaptive evolution and further range expansion across Canada of this exceedingly damaging grass.
Arbuscular mycorrhizal symbionts in Botrychium (Ophioglossaceae)
Authors: Winther Jennifer L. , Friedman William E.
Published: February 2008

Many plant species are characterized by a life cycle with a long‐lived, subterranean phase that is completely dependent on mycorrhizal fungal symbionts for fixed carbon. This type of life cycle is both phylogenetically and ecologically widespread and is found in diverse vascular plant lineages from the tropics to subalpine meadows. Here we report on the molecular identities of the arbuscular mycorrhizal fungi associated with the autotrophic and underground mycoheterotrophic life cycle phases of the ferns Botrychium crenulatum and B. lanceolatum. We show that the Glomus taxa found in the mycoheterotrophic life cycle phases of B. crenulatum and B. lanceolatum are also found in conspecific and heterospecific photosynthetic neighboring plants. From our DNA sequence data, we infer carbon flow from photosynthetic plants to mycoheterotrophic plants through shared glomalean fungal networks. Finally, our phylogenetic analyses identify a major Glomus clade that forms associations with mycoheterotrophic life cycle stages of B. crenulatum and B. lanceolatum.
Mycorrhizal benefit in two low arctic herbs increases with increasing temperature
Authors: Kytöviita Minna‐Maarit , Ruotsalainen Anna Liisa
Published: February 2008

Climate change may influence the relationship between arctic plants and their symbiotic mycorrhizal fungi. The benefit of the symbiosis for the host plant affects vegetation succession and may be a key parameter in predicting vegetation responses to warming. We investigated the mycorrhizal benefit in the low arctic perennial herbsPotentilla crantziiandRanunculus acrisin symbiosis with the arbuscular mycorrhizal fungusGlomus claroideum.Temperature response in the mycorrhiza‐mediated acquisition of nitrogen (N) and phosphorus (P), growth, and photosynthetic nutrient‐use efficiency were determined. Near the average natural soil temperature (12°C), mycorrhiza did not improve plant nutrient capture but significantly enhanced plant P capture at 17°C. Photosynthetic nitrogen‐use efficiency was higher at 17°C than at 12°C and was further increased by mycorrhiza at 17°C. Photosynthetic phosphorus‐use efficiency was not affected by temperature or mycorrhiza. Increasing the growing temperature by 5°C increased the relative shoot growth rate by 15%. Mycorrhizal symbiosis did not enhance plant growth rate, but the plants gained between 20% and 90% more mycorrhiza‐mediated P when grown at higher temperature. The results suggest that these low arctic species have good potential to respond positively to increasing temperatures.
Pollination patterns limit hybridization between two sympatric species ofNarcissus(Amaryllidaceae)
Authors: Marques Isabel , Rosselló‐Graell Antònia , Draper David , Iriondo José M.
Published: February 2008

Natural hybrids between rare and common sympatric species are commonly eradicated to avoid the potential extinction of the rare species, although there is currently no clear predictive framework to quantify this risk. As hybrids can have intrinsic value as new evolutionary pathways, further knowledge on the factors controlling hybridization is needed. In this study we evaluated the role of pollination patterns in hybridization events in two sympatric populations ofNarcissus cavanillesiiandN. serotinusin Portugal.Narcissus cavanillesiiis a rare species, whileN. serotinusis widely distributed across the Mediterranean. The hybrid,N.×perezlarae,is quite frequent in southeastern Spain but is scarce in Portugal. Reciprocal manual crossings confirmed compatibility between the two species, although hybridization was more successful whenN. cavanillesiiparticipated as female.Narcissus cavanillesiiandN. serotinusonly shared one pollinator,Megachilesp. (Hymenoptera), which had low visitation rates and high flower constancy. No single isolation mechanism was fully effective in preventing hybridization. Temporal displacement of flowering peaks, strong pollinator specificity, and high flower constancy in the shared pollinator all contributed to limiting hybridization in this site. In other sympatric occurrences, different phenological windows and pollination assemblages may allow greater frequency of the hybrid.
Aerodynamics of saccate pollen and its implications for wind pollination
Authors: Schwendemann Andrew B. , Wang George , Mertz Meredith L. , McWilliams Ryan T. , Thatcher Scott L. , Osborn Jeffrey M.
Published: February 2008

Pollen grains of many wind‐pollinated plants contain 1–3 air‐filled bladders, or sacci. Sacci are thought to help orient the pollen grain in the pollination droplet. Sacci also increase surface area of the pollen grain, yet add minimal mass, thereby increasing dispersal distance; however, this aerodynamic hypothesis has not been tested in a published study. Using scanning electron and transmission electron microscopy, mathematical modeling, and the saccate pollen of three extant conifers with structurally different pollen grains (Pinus, Falcatifolium, Dacrydium), we developed a computational model to investigate pollen flight. The model calculates terminal settling velocity based on structural characters of the pollen grain, including lengths, widths, and depths of the main body and sacci; angle of saccus rotation; and thicknesses of the saccus wall, endoreticulations, intine, and exine. The settling speeds predicted by the model were empirically validated by stroboscopic photography. This study is the first to quantitatively demonstrate the adaptive significance of sacci for the aerodynamics of wind pollination. Modeling pollen both with and without sacci indicated that sacci can reduce pollen settling speeds, thereby increasing dispersal distance, with the exception of pollen grains having robust endoreticulations and those with thick saccus walls. Furthermore, because the mathematical model is based on structural characters and error propagation methods show that the model yields valid results when sample sizes are small, the flight dynamics of fossil pollen can be investigated. Several fossils were studied, including bisaccate (Pinus, Pteruchus, Caytonanthus), monosaccate (Gothania), and nonsaccate (Monoletes) pollen types.
Bud and growth‐unit structure in seedlings and saplings of Nothofagus alpina (Nothofagaceae)
Authors: Puntieri Javier G. , Grosfeld Javier E. , Stecconi Marina , Brion Cecilia , Barthélémy Daniel
Published: February 2008

In temperate trees, axis length growth generally results from the differentiation of organs at the end of a growing season and the extension of such “preformed organs” in the next growing season. Neoformation, i.e., the simultaneous differentiation and extension of organs, has been studied for only a few species. Here we evaluated bud composition and growth unit (GU) size for seedlings and saplings of Nothofagus alpina, a valuable South American forest tree. Trunk GUs of seedlings and saplings included preformed and neoformed organs, whereas main‐branch GUs of saplings were entirely preformed. The size of a GU was more closely related to the number of preformed green leaves than to the number of cataphylls of its preceding bud. Proximal buds of a trunk GU had more cataphylls and less green‐leaf primordia than distal buds. Individual leaf area increased from proximal to distal positions on trunk GUs. For trunk and main‐branch GUs, the length/width ratio was maximum for leaves in intermediate positions. The development of large neoformed leaves at the end of the growing season could increase the photosynthetic capacity of this species in late summer, when the activity of preformed organs is likely to be decreasing.
Origin of Hawaiian Polystichum (Dryopteridaceae) in the context of a world phylogeny
Authors: Driscoll Heather E. , Barrington David S.
Published: February 2008

A genus‐wide molecular phylogeny for Polystichum and allied genera (Dryopteridaceae) was reconstructed to address the biogeographic origin and evolution of the three Hawaiian Polystichum species, all endemic there. The analysis was based on the cpDNA sequences rbcL and the trnL‐F spacer from a taxonomically and geographically diverse sample. Parsimony and Bayesian phylogenetic analyses of the combined data support a monophyletic Polystichum and corroborate recent hypotheses as to membership and sequence of origin of the major groups within the genus. The Hawaiian Polystichum species are polyphyletic; two separate lineages appear to have arrived independently from the Old World. The provenance of the diploid Polystichum hillebrandii is continental eastern Asia, while the source of the polyploid lineage comprising tetraploid P. haleakalense and octoploid P. bonseyi is likely continental Asia. From our results, the origin of the Hawaiian species of Polystichum, like many Hawaiian fern genera with several species, is the result of multiple migrations to the islands, rather than single migrations yielding nearly all the local diversity as in the angiosperms. This emerging pattern provides a modern test of the premise that propagule vagility has a central role in determining pattern of evolution.
Functional diversity of carbon‐gain, water‐use, and leaf‐allocation traits in trees of a threatened lowland dry forest in Hawaii
Authors: Sandquist Darren R. , Cordell Susan
Published: February 2008

We examined carbon‐gain, water‐use, and leaf‐allocation traits for six tree species of a Hawaiian dry forest to better understand the functional diversity within this threatened ecosystem. Tropical dry forests are among the most endangered ecosystems on Earth, and in Hawaii, as elsewhere, declining biodiversity threatens ecosystem processes that may depend on forest functional diversity. We found broad variation among species including a two‐fold difference for mean photosynthetic rate, a greater than three‐fold difference for predawn water potential, and a nearly three‐fold difference for leaf life span. Principal component analysis showed a clear separation of species based on carbon‐gain vs. water‐use related axes, and δ13C analysis revealed differing limitations (supply vs. demand) on carbon assimilation. The broad functional variation not only spanned traditional classifications (avoiders vs. tolerators), but also included unusual strategies (e.g., fast growth with drought tolerance). Correlations among traits, including leaf life span, leaf mass per area, and %N, followed typical global patterns, but some exceptions appeared as a result of unique life‐history characteristics, such as latex‐rich sap and root parasitism. Elucidating functional variation provides important information that can be used to link plant biodiversity with ecosystem processes and also facilitate the management and preservation of tropical dry forests and other threatened communities.
Impact of global warming on a group of related species and their hybrids: cherry tree (Rosaceae) flowering at Mt. Takao, Japan
Authors: Miller‐Rushing Abraham J. , Katsuki Toshio , Primack Richard B. , Ishii Yukio , Lee Sang Don , Higuchi Hiroyoshi
Published: February 2008

Climate change is affecting plant phenology worldwide. Phenological responses vary among species, but it is not clear how responses differ among closely related species. We examined a 25‐yr record (1981–2005) of flowering times for 97 trees, representing 17 species and hybrids of cherry (Cerasus sp. or Prunus sp.) grown at Mt. Takao, in Tokyo, Japan. The cherry trees flowered earlier over time, by an average of 5.5 d over the 25‐yr study. Earlier flowering was explained largely by a 1.8°C increase in February–March mean monthly temperatures. Most species and hybrids flowered 3–5 d earlier for each 1°C increase in temperature, but early‐flowering taxa flowered as much as 9 d earlier for each 1°C increase in temperature. Flowering durations and differences in flowering times among species were greater in warm years than in cold years. Species and individual trees also flowered longer in warm years. These results show that the flowering times of closely related species may change similarly in response to climate change, but that early‐flowering species may diverge from the overall trend in a predictable way. Such changes in flowering may affect gene flow and pollination as the length of the flowering season increases.
Seed morphology of modern and fossilAmpelocissus(Vitaceae) and implications for phytogeography
Authors: Chen Iju , Manchester Steven R.
Published: February 2008

Seeds are useful in distinguishing among extant genera of Vitaceae and provide a good basis for interpretation of fossil remains in reconstructing the evolutionary and phytogeographic history of this putatively basal Rosid family. Seeds ofAmpelocissuss.l. includingPterisanthesandNothocissusare distinguished from those of all other vitaceous genera by long, parallel ventral infolds and a centrally positioned oval chalazal scar. Principal component analysis facilitates recognition of fourAmpelocissuss.l. seed morphotypes differentiated by dorsiventral thickness, width of ventral infolds, chalazal depth, and degree of dorsal surface rugosity. While these intergrade, their end‐member morphologies are distinctive and coincide well with inflorescence morphology, extant geographic distribution, and ecology. Seven fossil morphospecies are recognized.Ampelocissus parviseminasp. n. (Paleocene of North Dakota; Eocene of Oregon) andA. auriformaManchester (Eocene of Oregon) resemble extant Central American species;A. bravoiBerry (Eocene of Peru) is similar to one group of Old World extant species; andA. parachandlerisp. n. (Eocene of Oregon) and the three European fossil speciesA. chandleri(Kirchheimer) comb. n.,A. lobatum(Chandler) comb. n., andA. wildeisp. n. (Eocene to Miocene) resemble another group of extant Old WorldAmpelocissus. All these fossils occur outside the present geographic range of the genus, reflecting warmer climates and former intercontinental links.
Phylogeny of the tribe Aveneae (Pooideae, Poaceae) inferred from plastid trnT‐F and nuclear ITS sequences
Authors: Quintanar Alejandro , Castroviejo Santiago , Catalán Pilar
Published: February 2008

New insights into evolutionary trends in the economically important oat tribe (Aveneae) are presented. Plastid trnT‐F and nuclear ribosomal ITS sequences were used to reconstruct the phylogeny of the Aveneae–Poeae–Seslerieae complex (Pooideae, Poaceae) through Bayesian‐ and maximum parsimony‐based analyses, separately and in combination. The plastid data identified a strongly supported core Aveneae lineage that separated from other former Aveneae and Poeae groups. Koeleriinae, Aveninae, and Agrostidinae emerged as the main groups of this core Aveneae, which also included other minor subgroups with uncertain relationships and a few former Poeae members. Several former Aveneae representatives were also placed in independent sublineages in Poeae. Seslerieae resolved as close allies of Poeae or Aveneae in the plastid and nuclear topologies, respectively. Because of the intermingling of some Aveneae and Seslerieae lineages in Poeae and vice versa, we propose to expand Poeae to include all the aforementioned lineages. This best reflects our current understanding of the phylogeny of these important temperate grasses and sheds light on their evolutionary history.
Vivipary in coastal cacti: a potential reproductive strategy in halophytic environments
Authors: Cota‐Sánchez J. Hugo , Reyes‐Olivas Álvaro , Sánchez‐Soto Bardo
Published: February 2008

Vivipary, the germination of seeds within the fruit prior to abscission from the maternal plant, is an important event in plants. Two main types of vivipary are known in vascular plants: true vivipary and pseudovivipary. In crop grasses, pseudovivipary is an undesirable character as it results in lower yields. To date, vivipary in the Cactaceae has been reported for less than 20 species, most of which are cultivated. Here, we report viviparous (cryptoviviparous—a subcategory of true vivipary) cacti in nature in members of the tribes Cacteae and Pachycereeae (subfamily Cactoideae). We present four species inhabiting coastal plains in areas subject to periodic flooding, namely, Ferocactus herrerae, Stenocereus alamosensis, S. thurberi, and Pachycereus schottii. These species from localities in northwestern Mexico had viviparous fruits and offspring in different stages of development. A potential trend in the data indicates that the overall proportion of viviparous plants is higher in coastal flooding areas relative to halophytic, nonflooding areas. In our view, vivipary is a reproductive strategy that has evolved to provide a more efficient mechanism favoring germination and new avenues for survival by contributing to population maintenance and short‐distance dispersal on halophytic substrates.
Hormone interactions and regulation of PsPK2::GUS compared with DR5::GUS and PID::GUS in Arabidopsis thaliana
Authors: Bai Fang , DeMason Darleen A.
Published: February 2008

The putative pea PINOID homolog, PsPK2, is expressed in all growing plant parts and is positively regulated by auxin, gibberellin, and cytokinin. Here, we studied hormonal regulation of PsPK2::GUS expression compared with DR5::GUS and PID::GUS in Arabidopsis. PsPK2::GUS, DR5::GUS, and PID::GUS expression in Arabidopsis shoots is mainly localized in the stipules, hydathodes, veins, developing leaves, and cotyledons. Unlike DR5::GUS, PsPK2::GUS, and PID::GUS are weakly expressed in root tips. Both DR5::GUS and PsPK2::GUS are induced by different auxins and are more sensitive to methyl indole acetic acid, 4‐chloro‐indole acetic acid, and α‐naphthalene acetic acid than others. GA3 has no significant effect on GUS activity in DR5::GUS‐transformed seedlings compared to the control, but induction by auxin and gibberellin in combination is synergistic. Cytokinin increases auxin transport in Arabidopsis seedlings. Auxin, gibberellin, and cytokinin all increase GUS activity in shoots of PsPK2::GUS transformed plants compared to the control. However, only auxin and gibberellin increase GUS activity in PID::GUS shoots. In conclusion, auxin, gibberellin, and cytokinin positively regulate PsPK2 expression in shoots, but not in roots. Auxin and gibberellin also upregulate AtPIN1 and LEAFY expression, which is similar to PsPIN1 and Uni in pea. With minor exceptions, the orthologous genes from both species are regulated similarly.
Morphology and biogeography of Apiaceae subfamily Saniculoideae as inferred by phylogenetic analysis of molecular data
Authors: Calviño Carolina I. , Martínez Susana G. , Downie Stephen R.
Published: February 2008

The phylogenetic placements of several African endemic genera at the base of Apiaceae subfamilies Saniculoideae and Apioideae have revolutionized ideas of relationships that affect hypotheses of character evolution and biogeography. Using an explicit phylogeny of subfamily Saniculoideae, we reconstructed the evolutionary history of phenotypic characters traditionally important in classification, identified those characters most useful in supporting relationships, and inferred historical biogeography. The 23 characters examined include those of life history, vegetative morphology, inflorescences, and fruit morphology and anatomy. These characters were optimized over trees derived from maximum parsimony analysis of chloroplast DNA trnQ‐trnK sequences from 94 accessions of Apiaceae. The results revealed that many of these characters have undergone considerable modification and that traditional assumptions regarding character‐state polarity are often incorrect. Infrasubfamilial relationships inferred by molecular data are supported by one to five morphological characters. However, none of these morphological characters support the monophyly of subfamilies Saniculoideae or Apioideae, the clade of Petagnaea, Eryngium and Sanicula, or the sister‐group relationship between Eryngium and Sanicula. Southern African origins of Saniculoideae and of its tribes Steganotaenieae and Saniculeae are supported based on dispersal–vicariance analysis.
Phylogenetics and reticulate evolution in Pistacia (Anacardiaceae)
Authors: Yi Tingshuang , Wen Jun , Golan‐Goldhirsh Avi , Parfitt Dan E.
Published: February 2008

The systematic position and intrageneric relationships of the economically important Pistacia species (Anacardiaceae) are controversial. The phylogeny of Pistacia was assessed using five data sets: sequences of nuclear ribosomal ITS, the third intron of the nuclear nitrate reductase gene (NIA‐i3), and the plastid ndhF, trnL‐F and trnC‐trnD. Significant discordance was detected among ITS, NIA‐i3, and the combined plastid DNA data sets. ITS, NIA‐i3, and the combined plastid data sets were analyzed separately using Bayesian and parsimony methods. Both the ITS and the NIA‐i3 data sets resolved the relationships among Pistacia species well; however, these two data sets had significant discordance. The ITS phylogeny best reflects the evolutionary relationships among Pistacia species. Lineage sorting of the NIA‐i3 alleles may explain the conflicts between the NIA‐i3 and the ITS data sets. The combined analysis of three plastid DNA data sets resolved Pistacia species into three major clades, within which only a few subclades were supported. Pistacia was shown to be monophyletic in all three analyses. The previous intrageneric classification was largely inconsistent with the molecular data. Some Pistacia species appear not to be genealogical species, and evidence for reticulate evolution is presented. Pistacia saportae was shown to be a hybrid with P. lentiscus (maternal) and P. terebinthus (paternal) as the parental taxa.
DNA from herbarium specimens settles a controversy about origins of the European potato
Authors: Ames Mercedes , Spooner David M.
Published: February 2008

Landrace potato cultivars are native to two areas in South America: the high Andes from eastern Venezuela to northern Argentina and the lowlands of south‐central Chile. Potato first appeared outside of South America in Europe in 1567 and rapidly diffused worldwide. Two competing hypotheses suggested the origin of the “European” potato from the Andes or from lowland Chile, but the Andean origin has been widely accepted over the last 60 years. All modern potato cultivars predominantly have Chilean germplasm, explained as originating from breeding with Chilean landraces subsequent to the late blight epidemics beginning in 1845 in the UK. The Andean origin has been questioned recently through examination of landraces in India and the Canary Islands, but this evidence is inferential. Through a plastid DNA deletion marker from historical herbarium specimens, we report that the Andean potato predominated in the 1700s, but the Chilean potato was introduced into Europe as early as 1811 and became predominant long before the late blight epidemics in the UK. Our results provide the first direct evidence of these events and change the history of introduction of the European potato. They shed new light on the value of past breeding efforts to recreate the European potato from Andean forms and highlight the value of herbarium specimens in investigating origins of crop plants.
Life span correlates with population dynamics in perennial herbaceous plants
Authors: García María B. , Picó F. Xavier , Ehrlén Johan
Published: February 2008

Survival and fecundity are basic components of demography and therefore have a strong influence on population dynamics. These two key parameters and their relationship are crucial to understand the evolution of life histories. It remains, however, to be empirically established how life span, fecundity, and population dynamics are linked in different organism groups. We conducted a comparative study based on demographic data sets of 55 populations of 23 perennial herbs for which structured demographic models and among‐year natural variation in demographic attributes were available. Life span (from 4 to 128 yr old), estimated by using an algorithm, was inversely correlated with the deviance of the population growth rate from equilibrium as well as with among‐year population fluctuations. Temporal variability was greater for short‐lived species than for the long‐lived ones because fecundity was more variable than survival and relatively more important for population dynamics for the short‐lived species. The relationship between life span and population stability suggests that selection for longevity may have played an important role in the life history evolution of plants because of its ability to buffer temporal fluctuations in population size.
Embryology of Manekia naranjoana (Piperaceae) and the origin of tetrasporic, 16‐nucleate female gametophytes in Piperales
Authors: Arias Tatiana , Williams Joseph H.
Published: February 2008

The vast majority of flowering plant seeds contain a triploid endosperm formed by fertilization of a monosporic, Polygonum‐type female gametophyte. However, evolutionary transitions to six other genetic constructs of endosperm are widespread, and six of seven known patterns are found in the order Piperales. Within Piperaceae, Manekia has not been described, and we report its female gametophyte to be tetrasporic and 16‐nucleate at maturity. Manekia ontogeny is generally characterized by early establishment of a bipolar or weakly bipolar body plan and a binucleate central cell at maturity (Drusa‐type pattern); however, ca. 16% of early stages had distinctly tetrapolar organization, and ca. 21% of mature specimens had a tetranucleate central cell (Penaea‐type pattern, not previously reported in Piperaceae). An evolutionary developmental analysis indicates heterochrony, heterotopy, novelties, and sequence deletions have each played roles in modulating variation within Piperales. Our data suggest the common ancestor of Piperaceae was tetrasporic and retained a plesiomorphic bipolar body plan, producing a “functionally bisporic” form of triploid endosperm derived from the lineal descendants of two megaspores and a sperm. Developmental modifications of this tetrasporic, bipolar ontogeny can account for the origin of all three other known “true” tetrasporic endosperm genetic constructs, formed from derivatives of all four megaspores and a sperm. These derived endosperms in turn have higher ploidy, higher potential heterozygosity, and reduced genetic conflicts.
Hydraulic traits are influenced by phylogenetic history in the drought‐resistant, invasive genus Juniperus (Cupressaceae)
Authors: Willson Cynthia J. , Manos Paul S. , Jackson Robert B.
Published: February 2008

In the conifer genus Juniperus (Cupressaceae), many species are increasing rapidly in distribution, abundance, and dominance in arid and semiarid regions. To help understand the success of junipers in drier habitats, we studied hydraulic traits associated with their water stress resistance, including vulnerability to xylem cavitation, specific conductivity (KS), tracheid diameter, conduit reinforcement, and wood density in stems and roots, as well as specific leaf area (SLA) of 14 species from the United States and the Caribbean. A new phylogeny based on DNA sequences tested the relationships between vulnerability to cavitation and other traits using both traditional cross‐species correlations and independent contrast correlations. All species were moderately to highly resistant to water‐stress‐induced cavitation in both roots and shoots. We found strong phylogenetic support for two clades previously based on leaf margin serration (serrate and smooth). Species in the serrate clade were 34–39% more resistant to xylem cavitation in stems and roots than were species in the smooth clade and had ∼35% lower KS and 39% lower SLA. Root and stem resistance to cavitation and SLA were all highly conserved traits. A high degree of conservation within clades suggests that hydraulic traits of Juniperus species strongly reflect phylogenetic history. The high resistance to cavitation observed may help explain the survival of junipers during recent extreme droughts in the southwestern United States and their expansion into arid habitats across the western and central United States.
Pollinator foraging modifies nectar sugar composition in Helleborus foetidus (Ranunculaceae):An experimental test
Authors: Canto Azucena , Herrera Carlos M. , Medrano Mónica , Pérez Ricardo , García Isabel M.
Published: February 2008

We experimentally tested the hypothesis that the extensive within‐plant variation of nectar sugar composition in Helleborus foetidus (Ranunculaceae) and other species results from differences between flowers and nectaries in pollinator visitation history. Experiments were conducted to mimic single‐nectary visits by wild‐caught individuals of the main bee pollinators of H. foetidus, which were assayed for their capacity to modify the sugar composition of natural and artificial nectar. Experimental nectar probing with bee mouthparts induced extensive changes in proportional sugar composition 48 h after treatment, and bee taxa differed widely in their effects. Nectar probing by Andrena, medium‐sized Anthophoridae, Apis mellifera, and Lasioglossum had no subsequent effects on nectar sugar composition, while probing by Bombus terrestris and B. pratorum induced an extensive reduction in percentage sucrose, a marked increase in percentage fructose, and a slight increase in percentage glucose. Results support the hypothesis that stochastic variations among flowers or nectaries in the taxonomic identity of recent visitors and their relative visitation frequencies may eventually generate very small‐scale mosaics in nectar sugar composition. Changes in nectar sugar composition following bumblebee probing may be the consequence of nectar contamination with pollinator‐borne nectarivorous yeasts.
Interpreting claims in offender profiles: the role of probability phrases, base‐rates and perceived dangerousness
Authors: Villejoubert Gaëlle , Almond Louise , Alison Laurence
Published: March 2008

Offender profilers use verbal and numerical probability expressions to convey uncertainty surrounding claims made about offender's characteristics. No previous research has examined how these expressions might affect the recipient's interpretation of the information. Seventy participants completed an online questionnaire and results showed a diverse range of interpretations of these uncertainty expressions. Moreover, characteristic base‐rates and dangerousness affected the perceived likelihood of the profiling claim, such that increased base‐rates and perceived dangerousness resulted in an increased perception of the claim being likely. Perceived likelihoods also depended on the framing of characteristics as well as the framing of the claim itself. Finally, where claims involved presenting a characteristic qualified by a low probability these claims were interpreted as more likely than not to be present. These findings have practical implications for profilers and more general theoretical implications for the study of risk perception. Copyright © 2008 John Wiley & Sons, Ltd.
Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide
Authors: Walker T. A. , Frankowski D. J. , Spontak R. J.
Published: February 2008

Environmentally‐responsible materials processing is becoming an important global consideration in a wide variety of technologies, especially those wherein volatile and/or residual organic solvents cannot be tolerated. In this context, polymer processing has benefited tremendously from advances achieved using high‐pressure CO2 as a viscosity modifier, plasticizing agent, foaming agent, and reaction medium. Pressurized CO2 is environmentally benign, inexpensive, sustainable, and versatile owing to its gas‐like viscosity and liquid‐like solubility, which can be tuned through judicious choice of temperature and pressure. The addition of high‐pressure CO2 to homopolymer blends and block copolymers can have a profound impact on polymer thermodynamics and kinetic processes since the number of interacting species increases. As a result, the compressibility as well as plasticization and intermolecular screening effects become non‐negligible. In this work, we review how these factors influence such polymeric systems, and discuss commercial polymer processes and applications that benefit from the use of high‐pressure CO2.
Pyrotechnik mit dem “Ökosiegel”: eine chemische Herausforderung
Authors: Steinhauser Georg , Klapötke Thomas M.
Published: February 2008

Kaum eine andere Anwendung aus dem Bereich der Chemie weckt in der Allgemeinbevölkerung so positive Assoziationen wie die Feuerwerkerei. Dabei wird das Umweltverschmutzungspotenzial von Feuerwerken sowie zivilen und militärischen pyrotechnischen Anwendungen häufig außer Acht gelassen. Moderne Entwicklungen in der Pyrotechnik konzentrieren sich verstärkt auf die Implementierung stickstoffreicher, energetischer Verbindungen wie Tetrazol‐ und Tetrazinderivate, um der längst fälligen Ökologisierung Rechnung zu tragen. Der vorliegende Aufsatz widmet sich den Umweltaspekten der Pyrotechnik und den aktuellen Bestrebungen, ihr ein neues, umweltverträglicheres Gesicht zu verleihen.
“Green” Pyrotechnics: A Chemists' Challenge
Authors: Steinhauser Georg , Klapötke Thomas M.
Published: February 2008

Fireworks are probably the application of chemistry which resonates best with the general public. However, fireworks and (civil and military) pyrotechnic applications cause environmental pollution and thus have given rise to the development of new, environmentally friendly pyrotechnic compounds and formulations. Nitrogen‐rich energetic materials, such as the derivatives of tetrazoles and tetrazines, are about to revolutionize traditional pyrotechnic compositions. This Review summarizes the sources of pollution in current formulations and recent efforts toward “green” pyrotechnics.
Effects of the diluent mixing ratio and conditions of the thermally induced phase‐separation process on the pore size of microporous polyethylene membranes
Authors: Yoo S. H. , Kim C. K.
Published: February 2008

Microporous polyethylene (PE) membranes having a controlled pore size were produced via the thermally induced phase separation process by manipulation of the phase boundary of the PE/diluent blend and process conditions. The phase boundary of the PE blend, caused by upper critical solution temperature type phase behavior, was controlled by the use of a diluent mixture, that is, an isoparaffin/soybean oil mixture. The phase‐separation temperature of the PE/soybean oil blend was always higher than that of the PE/isoparaffin blend. In PE/(isoparaffin/soybean oil) ternary blends, the phase‐separation temperature of the ternary blend rapidly increased with increasing soybean oil content in the diluent mixture. Furthermore, the phase‐separation temperatures of ternary blends were always higher than that of the PE/soybean oil blend, regardless of the blend compositions, when the diluent mixture contained more than 50 wt % soybean oil. The observed phase behavior of the ternary blends was analyzed with interaction energy densities calculated with the Flory–Huggins theory and ternary stability conditions. The growth of droplets caused by both coalescence and the Oswald ripening process was observed after the onset of phase separation. As the blends became less stable, the droplet growth rate increased, and larger equilibrium droplets were formed. Microporous membranes with the desired pore structure could be prepared by control of the phase boundary and the variation of processing conditions such as the quenching depth, annealing time, and cooling rate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Microstructural investigation of long‐term degradation mechanisms in GFRP dowel bars for jointed concrete pavement
Authors: Park Chan‐Gi , Jang Chang‐Il , Lee Si‐Won , Won Jong‐Pil
Published: February 2008

Steel dowel bar is used to transfer loads in concrete pavement slab. However, once the steel dowel bar corrodes, it may cause faults, such as joint freezing in concrete pavement, level differences resulting from spalling or decreased efficiency of load transfer, etc., which are the same problems experienced by typical reinforcing steel. This study evaluated the applicability of glass fiber‐reinforced polymer (GFRP) dowel bar as a substitute for steel dowel bar. A microstructural analysis was conducted to examine the decrease in durability of GFRP dowel bar exposed to deterioration environments. To analyze the deterioration mechanism of GFRP dowel bar, scanning electron microscopy was employed and the porosity was measured by the gas absorption method. It was concluded that the longer the GFRP dowel bar was exposed to deterioration environments, the more the interlaminar shear stress decreased. This result was validated by the microstructural analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Neuropsychological development of children born to patients with antiphospholipid syndrome
Authors: Nacinovich R. , Galli J. , Bomba M. , Filippini E. , Parrinello G. , Nuzzo M. , Lojacono A. , Motta M. , Tincani A.
Published: February 2008

Objective

To verify the occurrence of learning disabilities (LDs) in the offspring of women with primary antiphospholipid syndrome (APS) as a consequence of fetal exposure to maternal antiphospholipid antibodies (aPL), and to evaluate the impact of maternal chronic disease on children's development.

Methods

We studied 17 children of mothers with primary APS using a standardized intelligence test (Wechsler Intelligence Scale for Children, Revised), a specific LD battery of tests (Sartori, MT groups' test for reading ability, MT groups' test for math skills), and a questionnaire on behavioral and social characteristics (Child Behavior Checklist [CBCL]). Mothers were interviewed about their pregnancy and motherhood experience.

Results

All children had a normal intelligence level (full‐scale intelligence quotient >85); 15 pregnancies occurred in mothers with IgG aPL. LDs were diagnosed in 4 children (26.7%), 2 boys and 2 girls. One of these children was born premature, with a brother also affected. Four children (26.7%) showed a higher risk to present problems on the CBCL total competence scale and 2 children (13.3%) on the CBCL total behavior scale. Two children were described as hyperactive (1 had an LD). All families had a good socioeconomic status and educational level.

Conclusion

Besides prematurity and genetic and environmental factors, the genesis of LDs may also include in utero exposure to aPL, in agreement with described experimental models and patients with systemic lupus erythematosus. Socioeconomic status does not seem to influence the occurrence of LDs. A long‐term multidisciplinary followup may improve quality of life in patients with primary APS and their children.