Elaborate petals and staminodes in eudicots: Diversity, function, and evolution

Petals, a characteristic feature of eudicots, have evolved elaborations in various ways and across diverse clades. In this survey of petal and staminode elaborations throughout the eudicots, based on both new studies and a review of the literature, the diversity of such structures and their functions is discussed. Petal elaborations are primarily present as marginal lobes and ventral lobes of various shapes. Lobation patterns can be loosely classified as pinnate, binate, or ternate. One of these patterns may be dominant within a family (e.g. pinnate in Anisophylleaceae, binate in Caryophyllaceae, ternate in Elaeocarpaceae); transitional forms also occur (e.g. between binate and ternate in Onagraceae). Coronas between the corolla and androecium are found in several groups, for example in several families of Malpighiales or in Apocynaceae. In some clades, petal elaborations are especially prominent and can be used as approximate systematic markers (Anisophylleaceae, Elaeocarpaceae, Rhizophoraceae). Petal elaborations are especially diverse in rosids. In asterids, which are characterized by sympetaly, elaborations are more conspicuous at the level of the architecture of the entire corolla, rather than at the level of individual petals. Evolutionary trends in petal elaboration in certain larger clades are shown and their involvement in floral biological functions is discussed.     

The effects of cognitive and behavioral control on coping with an aversive health examination.

The effects of cognitive and behavioral control on coping with an aversive health examination were tested in a 2 x 2 factorial design. Cognitive control was represented by sensory or health-education information; instruction or no instruction in abdominal relaxation constituted the levels of behavioral control. The study was conducted in the natural setting of a family-planning clinic with 24 young women who were undergoing a routine pelvic examination. Subjects who received sensory information prior to the examination showed less distress, as indicated by overt distress behaviors and pulse rates, than did subjects who received health-education information. Cognitive control did not show a significant effect on self-report of fear. No significant effects were demonstrated for the factor of behavioral control. The results suggested that cognitive control information, which emphasizes the sensory experiences typically accompanying an aversive event, limits reactivity to aversive stimuli. The reduction in reactivity is thought to result in an increased ability to cope with aversive events.     

Rate of succession in restored wetlands and the role of site context

Question: Are changes in plant species composition, functional group composition and rates of species turnover consistent among early successional wetlands, and what is the role of landscape context in determining the rate of succession? Location: Twenty‐four restored wetlands in Illinois, USA. Methods: We use 4 years of vegetation sampling data from each site to describe successional trends and rates of species turnover in wetlands. We quantify: (1) the rate at which composition changes from early‐successional to late‐successional species and functional groups, as indicated by site movement in ordination space over time, and (2) the rate of change in the colonization and local extinction of individual species. We correlate the pace of succession to site area, isolation and surrounding land cover. Results: Some commonalities in successional trends were evident among sites. Annual species were replaced by clonal perennials, and colonization rates declined over time. However, differences among sites outweighed site age in determining species composition, and the pace of succession was influenced by a site's landscape setting. Rates of species turnover were higher in smaller wetlands. In addition, wetlands in agricultural landscapes underwent succession more rapidly, as indicated by a rapid increase in dominance by late‐successional plants. Conclusions: Although the outcome of plant community succession in restored wetlands was somewhat predictable, species composition and the pace of succession varied among sites. The ability of restoration practitioners to accelerate succession through active manipulation may be contingent upon landscape context.     

Ecology and ecosystem impacts of common buckthorn (<Emphasis Type="Italic">Rhamnus cathartica</Emphasis>): a review

In this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions, unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be able to use it for food or habitat.     

A revision of asterogyne (Arecaceae: Arecoideae: Geonomeae)

A taxonomic revision of the neotropical genusAsterogyne Hook. (Arecaceae: Arecoideae: Geonomeae) is presented. The genus is characterized by one autoapomorphic character, the separation of anther thecae by a bifid connective, and the combination of small to medium-sized stems, bifid simple leaf blades, floral pits in bud covered by a rounded upper lip that overlaps a lower lip, and pistillate flowers with staminodial lobes that are displayed in a starlike shape. Five species are recognized in this treatment: one of them (Asterogyne martiana) is widely distributed from Belize in Central America to northern Ecuador, three species (A. ramosa, A. spicata, andA. yaracuyense) are endemic to small areas in the Venezuelan Coastal Range, and one species (A. guianensis) is endemic to eastern French Guiana. The taxonomic history, morphology, reproductive biology, distribution and ecology, intrageneric relationships, and conservation status are reviewed.     

Floral structure and evolution of primitive angiosperms: Recent advances

Concepts of primitive angiosperm flowers have changed in recent years due to new studies on relic archaic groups, new paleobotanical finds and the addition of molecular biological techniques to the study of angiosperm systematics and evolution.Magnoliidae are still the hot group, but emphasis is now on small primitive flowers with few organs and also on the great lability of organ number. Of the extant groups, a potential basal position of the paleoherbs has been discussed by some authors. Although some paleoherbs have a simple gynoecium with a single orthotropous ovule, anatropous ovules may still be seen as plesiomorphic in angiosperms. Anatropy is not necessarily a consequence of the advent of closed carpels. It may also exhibit biological advantages under other circumstances as is the case in podocarps among gymnosperms. Valvate anthers have now been found in most larger subgroups of theMagnoliidae (recently also in paleoherbs) and in some Cretaceous fossils. Nevertheless, as seen from its systematic distribution, valvate dehiscence is not necessarily plesiomorphic for the angiosperms, but may be a facultative by-product of the thick connectives and comparatively undifferentiated anther shape inMagnoliidae and lowerHamamelididae. A perianth is relatively simple in extantMagnoliidae or even wanting in some families. In groups with naked flowers the perianth may have been easily lost because integration in the floral architecture was less pronounced than in more advanced angiosperm groups. Problems with the comparison of paleoherb flowers with those ofGnetales are discussed. The rapid growth of information from paleobotany and molecular systematics requires an especially open attitude towards the evaluation of various hypotheses on early flower evolution in the coming years.     

Synthesis of rhamnogalacturonan I fragments by a modular design principle

The improved syntheses of methyl 2-O-acetyl-3-O-benzyl-alpha-L-rhamnopyranoside (12) and 1,2-di-O-acetyl-3-O-benzyl-alpha-L-rhamnopyranose (15), which were used as glycosyl acceptor and donor, respectively, are described. Glycosylation of the O-4 position of both rhamnose derivatives with 2,3,4,6-tetra-O-benzoyl-alpha-D-galactopyranosyl bromide (26) provided disaccharides 27 and 29. After partial deprotection of 27 and coupling of the resulting 28 with disaccharide 19, tetrasaccharide 31 was obtained. Furthermore, transforming of 29 into the corresponding bromide 30 and coupling with galacturonates 16 and 32 provided trisaccharides 33 and 34, respectively, which could be regarded as building blocks of ramified rhamnogalacturonan fragments. The preparation of tetra- (21) and hexasaccharide (25) of rhamnogalacturonan I is reported to demonstrate the feasibility of the synthesis of larger pectin fragments using the modular design principle with this type of building blocks.