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1. Dryland riparian zones have steep spatial gradients of soil moisture and flood disturbance, and the component hydrogeomorphic surfaces support hydric to xeric plant species. These systems undergo extremes of flood and drought, a dynamic that may select for persistent soil seed banks. We asked if reliance on this strategy differed among plants in three moisture groups (hydric, mesic and xeric), and if patterns were related to diaspore traits. 2. We assessed the composition of soil and litter seed banks (emergence method) and extant vegetation along a riparian hydrogradient, and measured seed persistence (using an indirect method) and diaspore mass and shape variance of the component species. 3. Hydroriparian species had smaller diaspores than xeroriparian species, corresponding to differences in selective pressures on seedlings in their respective habitats, but the two groups formed persistent seed banks at approximately equal percentages. Persistent seeds were smaller than transient seeds, but within the persistent seed group there was separation between the smaller-diaspored hydrophytes and larger-diaspored xerophytes. 4. Distribution patterns of extant vegetation, in concert with diaspore trait differences among moisture-affinity groups, gave rise to divergent spatial patterns of diaspores within the soil: hydroriparian diaspores were abundant not only along wet channel bars but also in deep soils under floodplain forests and shrublands, presumably owing to dispersal by flood waters. Xeroriparian diaspores were largely restricted to the litter and upper soil layers of their drier, higher, floodplain habitats. With increasing depth in the soil of floodplain forests and shrublands, viable diaspores became smaller and rounder, and plant composition shifted from xeroriparian to hydroriparian species. 5. The wide distribution of hydroriparian diaspores in floodplain soils influences disturbance dynamics, increasing the probability that ephemeral wetland communities will develop wherever suitable conditions are stochastically created by floods. Persistent seed banks also allow many xeric annuals to be maintained in dryland riparian zones throughout extended drought, similar to processes that occur in desert uplands. [ABSTRACT FROM AUTHOR]

Abstract: We compared the ability of 33 plant species collected in forest to have their seeds dispersed by the wood red ant Myrmica ruginodis. The elaiosome-bearing seeds (species Chelidonium majus, Colchicum autumnale, Luzula forsteri, Viola reichenbachiana, Luzula multiflora, Melica uniflora) and the small and light caryopses of the grasses (Holcus mollis, Agrostis capillaris, Deschampsia flexuosa, Poa trivialis, Holcus lanatus) are the most efficiently collected by ants. The seed quantity removed by ants is correlated negatively with their length. No significant correlation is found between the rate of seed removal and the frequency of the plants in the field at the scale of the study. To cite this article: É. Delatte, O. Chabrerie, C. R. Biologies 331 (2008). [Copyright &y& Elsevier]

N, N-diethyl dodecyl amine(DEN12) was synthesized from dodecyl amine, formic acid and acetic aldehyde. The collecting property of DEN12 on diaspore, kaolinite and illite was investigated by flotation test and infrared spectrum. The results show that in the presence of 2.0×10−4 mol/L DEN12, the recoveries of kaolinite and illite are all higher than 78% and the recovery of diaspore is 50% in the pH range of 5.5–6.0. The mass ratio of Al2O3 to SiO2 in concentrate obtained from separation artificial mixture is higher than 10, suggesting that DEN12 can be used as a collector to separate the aluminosilicates from diaspore in bauxite ores at the pulp pH below 8. The measurements of the infrared spectrum approve that the action between aluminosilicates and tertiary amine collector is strong electrostatic adsorption and that of diaspore is weak electrostatic adsorption. [ABSTRACT FROM AUTHOR]

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Reduced dispersability of species living on islands relative to mainland has been documented in both plants and animals. One evolutionary scenario explains this trend by strong selection against dispersal, once the species has reached the island, to reduce dispersal out to sea. In this study, we compare the dispersal ability of three wind dispersed plant species ( Cirsium arvense, Epilobium angustifolium, and E. hirsutum) from populations on mainland and three islands. Dispersal ability was estimated directly as drop time of diaspores, and indirectly using a morphological measure relating the weight of the diaspore to the size of the pappus ( Cirsium) or seed hairs ( Epilobium). Positive correlation between the morphological measure of dispersal ability and drop time of diaspores were found for all study species. Dispersal ability varied significantly among mainland and islands, and among species. C. arvense showed a significant reduction in dispersal ability on islands compared to mainland, whereas the reverse was found for the two Epilobium species. Overall Epilobium diaspores had a 2–4 times higher dispersability than C. arvense, indicating that degree of isolation of islands vary among study species. Significant differences in dispersability among plants within populations were detected in all species suggesting that this trait may have a genetic component. [ABSTRACT FROM AUTHOR]

Bryophytes disperse by small unicellular spores between 7 μm und usually less than 100 μm. A large percentage of species is sterile and propagates vegetatively either by special brood bodies or fragments of whole plants. It is shown that there is no difference in the effectiveness between generative and vegetative propagation. Size and weight of the diaspores suggest that both must easily be dispersed and the species must therefore have wide ranges. This does, however, not result in ubiquitous occurrence. This is only true for part of the species. Many, even sterile species show wide transcontinental ranges. On the other hand, there are many examples of limited to very limited distribution in spite of a rich production of diaspores. These are explained by narrow ecological niches, age of taxa, local extinction or historical events such as ice ages. Conspicuously, species can loose the ability for dispersal for unknown (perhaps genetic) reasons, which may ultimately lead to extinction. [ABSTRACT FROM AUTHOR]

Techniques such as rewetting, topsoil removal, diaspore transfer or combinations of these are increasingly applied in fen meadow and flood meadow restoration in Western Europe. In this paper, we present a quantitative assessment of the effectiveness of the commonly used meadow restoration methods. We use the change in ‘saturation index’ to evaluate the degree of success. The index reflects the completeness of restored communities in comparison to regional target communities. Meadow restoration has limited success in most cases, with an average increase in species richness below 10% of the regional species pool. Restoration success was partly determinated by the starting situation. The more species-rich the starting situation, the higher the saturation index after restoration but, at the same time, the smaller the increase in the number of target species due to restoration. Top soil removal and diaspore transfer were found to contribute most to restoration success. A combination of top soil removal and diaspore transfer and a combination of all three techniques appeared to be the most effective measure and resulted in an increase in the saturation index of up to 16%. Rewetting alone had no measurable effect on restoration success. [Copyright &y& Elsevier]

Abstract: In the Oliete Sub-Basin, the Escucha Formation has been divided into three different lithologic intervals, from base to top: E1 (heterolithic with coal), E2 (mainly sandstones), and E3 (claystones). At the upper part of the interval E2, a grey-silty lithosome has been recognized, corresponding to a low-energy sedimentary environment related to a sandy shoal. In this lithosome, marchantiopsid-rich beds extending up to tens of square metres have been preserved. The plant association consists of well-developed mature gametophytes of complex thallose liverworts with thalli radial, dichotomous branched, rosette forming, prostrate and, in most cases, with gemmae cups located on their dorsal surface. The occurrence of scattered individuals forming distinct rosettes that, in many cases, are interlocked or interwoven and the loose arrangement of the association, along with sedimentological characteristics, allows us to interpret these liverworts-rich beds as monospecific colonization mats at early stages of colonization, in which marchantiopsids played the role of pioneers. In addition, the high proportion of gemmiferous individuals provides significant information on the environmental conditions and the effectiveness of colonization by asexual diaspores. Specimens have been assigned to family Marchantiaceae owing to their morphological features. Although liverworts colonization mats have been mentioned from the Albian of Antarctica, no fossil record of these existed at lower palaeolatitudes or in the Upper Aptian–Lower Albian. In addition, no previous record of clonal communities of plants derived from gemmae exists. Due to the latter, the occurrence of the studied colonization mats becomes of prime importance. [Copyright &y& Elsevier]

The article studies the effects of experimental restoration treatments on the diaspore bank of an upland British moor degraded by pteridium aquilinum. The experimental treatment included both the cutting and spraying of the pteridium and restoration treatments such as grazing and seeding, and the effects of these were studied. Soil depth was considered as to which type grass was replanted. The study concluded that the most successful combination of treatment was the combination of cutting twice per year with low grazing plus the planting of Calluna vulgaris.

The transport of diaspores on animal hairs depends on the ability of a diaspore to attach to the hair and to be retained in it over longer periods of time. Whereas several studies of diaspore retention on animal hairs have been conducted recently, the process of diaspore attachment to the hair has not yet been studied systematically. We describe a new method to quantify the attachment potential (AtP) of plant diaspores. Attachment potential was measured as the proportion of diaspores of a given species that attached to pieces of an animal coat in a standardised experiment. The experiment was conducted for 58 plant species (herbs and grasses) and three different coat types: sheep wool, cattle and roe deer hair. Attachment potentials differed widely between the three coat types, but also between plant species. We found diaspore surface structure (a quantitative measure of diaspore morphology) and diaspore exposition (describing the morphology of the infructescence) to be the most important plant traits regulating AtP. An influence of seed mass on attachment potential could not be detected. For sheep wool, a general linear model (with diaspore exposure as a factor and diaspore surface structure as covariate) explained 77% of the variation in AtPs. To validate this model, we predicted AtPs for 27 additional species and compared these to the measured Atps; the predicted and measured AtPscorrelated significantly with r s = 0.68. A comparison of attachment and retention potentials to sheep wool for 127 randomly selected plant species showed that attachment and retention are only very weakly correlated, indicating that both processes act rather independently of each other. Since many diaspores seem to perform well in only one of these processes, attachment can be considered to be as equally as decisive as retention in terms of epizoochorous dispersal. [ABSTRACT FROM AUTHOR]

Abstract: The Parnassos-Ghiona bauxite deposits of Greece are hosted within carbonate rocks and have been formed during different geological ages. The most economically important deposits occur in the B3 bauxite horizon, which is developed over long distance as a continuous layer of 1–10 m in thickness, within Cretaceous limestones. Due to intense tectonics, a significant (approximately 30 vol.%) bauxite ores along and near their contact with faults show a brittle deformation and change in the color from red to black-gray, in a distance of tens of meter. Commonly gray to whitish bauxites are aluminum-enriched (>65 wt.% Al2O3) and iron depleted. The most salient feature of bauxite ores of black-gray, grayish-brown or yellowish color along faults is the abundance of secondary pyrite of varying size (from less than 1 μm to a few hundreds μm) and form, which is closely associated with organic matter. Frambroidal pyrite and pyrite veins crosscutting sulfide-rich zones are occasionally present. Dismembered pyrrhotite and pentlandite crystals are only occasionally present. Pyrite is Co, Ni free, while Se varies from 0.7 to 0.9 wt.% Se. Pyrrhotite is Ni-bearing (up to 0.5 wt.% Ni) and pentlandite contains cobalt (average 1.5 wt.% Co). Textural relationships between Fe-sulfides/Fe-oxides, and the total organic carbon (TOC) content, ranging from 0.06 wt.% in red-color bauxite ores to 2.78 wt.% in gray-color ores, is consistent with a biological activity. Bacteria may play a significant role in the mineralogical and chemical composition of laterite ores, and in leaching and beneficiation of low-grade ores. Due to the behaviour of ferric iron as an electron acceptor for energy metabolism in a wide spectrum of bacteria the mobility of iron in the bauxite ores may be the result of an effective leaching by percolating pore waters, depending mostly on the pH–Eh conditions. [Copyright &y& Elsevier]

Paeonia officinalis L., a rare and protected species, mostly occurs in open and semi-open habitats and is often threatened by forest and shrubland spread. To explore the still undocumented dispersal features of this species, we address the following questions. What are the relative roles of ants, small rodents, and birds as diaspore removers in open habitat and woodland? Which animal groups constitute the potential disperser assemblage and how do they shape the spatial patterns of seed dispersal? Do diaspores fit the ornithochory syndrome or do they only mimic fleshy fruits? Two experiments were performed to quantify diaspore fall and diaspore removal by animal groups, above ground and on the ground. Ants did not contribute to dispersal. In open habitats, no seed removal was detected, either on follicles or once diaspores had fallen to the ground. In woodland, diaspores were weakly removed by vertebrates on follicles and were mainly removed by rodents on the ground. As a consequence, we suggest that long-distance dispersal events are very rare, weakening the possible escape into space of populations subject to forest spread. Several traits indicate that diaspores fit the ornithochory syndrome, but other traits are strongly reminiscent of mimetic diaspores deceiving bird dispersers. © 2007 CNRS. Journal compilation © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154, 13–25. [ABSTRACT FROM AUTHOR]

Abstract  The structural compression mechanism and compressibility of diaspore, AlO(OH), were investigated by in situ single-crystal synchrotron X-ray diffraction at pressures up to 7 GPa using the diamond-anvil cell technique. Complementary density functional theory based model calculations at pressures up to 40 GPa revealed additional information on the pressure-dependence of the hydrogen-bond geometry and the vibrational properties of diaspore. A fit of a second-order Birch–Murnaghan equation of state to thep–Vdata resulted in the bulk modulusB 0 = 150(3) GPa andB 0 = 150.9(4) GPa for the experimental and theoretical data, respectively, while a fit of a third-order Birch–Murnaghan equation of state resulted inB 0 = 143.7(9) GPa with its pressure derivativeB′ = 4.4(6) for the theoretical data. The compression is anisotropic, with thea-axis being most compressible. The compression of the crystal structure proceeds mainly by bond shortening, and particularly by compression of the hydrogen bond, which crosses the channels of the crystal structure in the (001) plane, in a direction nearly parallel to thea-axis, and hence is responsible for the pronounced compression of this axis. While the hydrogen bond strength increases with pressure, a symmetrisation is not reached in the investigated pressure range up to 40 GPa and does not seem likely to occur in diaspore even at higher pressures. The stretching frequencies of the O–H bond decrease approximately linearly with increasing pressure, and therefore also with increasing O–H bond length and decreasing hydrogen bond length. [ABSTRACT FROM AUTHOR]

Several studies on endozoochory have established large herbivores as important for seed dispersal, yet no studies have evaluated how endozoochory is dependent on ecological scale and context. Here we address effects of reindeer density on endozoochory in a hierarchical, multi-scale study, encompassing several ecological contexts. We found reindeer density effects on endozoochory to vary with spatial scale. Higher reindeer densities at the level of landscape areas, as indexed through faeces abundance, were related to both less species and lower abundance of emerging plants from faeces. In contrast, there was no effect of higher reindeer densities at the level of herding districts (i.e. large scale assemblages of landscapes). Lack of consistency between scales reflects ecological hierarchy, indicating that reindeer density effects on endozoochory best matches at the scale of landscapes. Pasture seed plant composition was only partly an important ecological factor. That is, ericoid species, the dominating plants in the pastures, were also the most abundant seed plants found to emerge from the faeces. However, most herbaceous seed plant species in the pastures were not emerging from the faeces and the few that emerged were positively related to the site fertility and altitude of the pasture. Studies addressing endozoochory of ruminants are typically concerned with seed plants, whereas in this study we also found indications of that diaspores of ferns are viable after passing the digestive tract of large herbivores. Vascular spore plants were even more abundant in the faeces than were vascular seed plants. Results from this study demonstrate that reindeer may counteract a potentially negative impact on seed limitation from their grazing by returning viable seeds in their faeces. However, in Finnmark, northern Norway, this effect is only marginal, relates only to a very few species and individuals and shows ecological scale and context dependence. [ABSTRACT FROM AUTHOR]

1 Variation in diversity with habitat productivity has long been a central ecological topic. Plant diversity is mostly highest at intermediate productivity, exhibiting the unimodal (so-called ‘hump-back’) relationship. This relationship has been explained by both evolutionary and ecological processes, but the potential role of dispersal limitation has not been considered. 2 We used European flora data to show that dispersal limitation may contribute to the unimodal productivity-diversity relationship. Species were characterized by their habitat productivity preference and dispersal probability (determined by the number of seeds and the presence of a dispersal syndrome). We calculated average relative dispersal probabilities for species assemblages occurring preferentially in different habitat productivity levels. 3 At low productivity levels, species without dispersal syndromes predominate ( R2 = 0.89), but at high productivity levels, species with a low number of seeds are common ( R2 = 0.89). The total relative dispersal probability, combining both the dispersal probabilities attributable to the number of seeds and to the presence of dispersal syndrome, had a unimodal relationship with habitat productivity ( R2 = 0.86). Thus, the unimodal productivity-diversity relationship may arise due to the minimal dispersal limitation of local richness in conditions of moderately low productivity. At very low productivity, the lack of dispersal syndromes may limit dispersal. At high productivity, the low number of seeds may limit dispersal. 4 Consequently, in conditions where species pool size and biotic interactions do not vary along productivity gradients, the variation in dispersal probabilities with productivity alone can produce unimodal relationships between diversity and productivity. Thus, dispersal limitation may contribute to the observed diversity pattern and ecosystem functioning to a greater extent than usually assumed. [ABSTRACT FROM AUTHOR]

Question: What is the relative ability of four species of Sphagnum (S. fuscum, S. rubellum, S. magellanicum and S. angustifolium) to establish on bare peat substratum in the field when re-introduced as single or multi-species re-introductions and in relation to interannual variations in climate? Location: Continental southeastern Canada. Methods: Diaspores (fragments) of four Sphagnum species alone or in combination were re-introduced onto residual peat surfaces and were monitored to follow the development of the moss carpet over four growing seasons. In order to compare results under a variety of climatic conditions, this whole experimental setting was repeated four times (trials), with a four-year follow-up for each trial. Conclusions: The establishment rate of the moss carpet varied among years, in response to climatic variations between growing seasons. The relative success of different moss species and combinations of species, however, did not vary within or between trials. Thus, the species and combinations of species resulting in the highest short-term or long-term establishment rates remained the same for all trials, independent of the climatic conditions at the time of re-introduction. Our results showed no link between the number of species in the diaspore mixture and successful establishment of the moss carpet. Yet successful regeneration was clearly influenced by the identity of species chosen for re-introduction. S. fuscum, alone or in combination, was the species found to lead to the most extensive development of the moss carpet under the current test conditions. [ABSTRACT FROM AUTHOR]

Questions: What is the mechanism of bog ground layer colonization post-fire? Is species colonization stochastic or does facilitation occur? Location: Boreal bog peatland near Crow Lake, Alberta, Canada. Methods: Diaspore-addition treatments were applied in 2003 to autoclaved peat samples from high and low microtopographic positions within a recently burned bog. Colonization was assessed within the plots in 2005 and compared to control plots to determine treatment success and patterns of colonization. Results: A significant degree of ground layer colonization was found two years after fire, with Polytrichum stricture dominating the site. Colonization was greater in low (wet) plots, although only P. stricture and Sphagnum angustifolium had significant colonization. No effect of diaspore addition was observed and Sphagnum was only found in conjunction with P. stricture. Conclusions: Environmental conditions and species life history strategy are more important than diaspore availability for post-fire colonization. True mosses (e.g. P. strictum) appear to facilitate Sphagnum colonization. [ABSTRACT FROM AUTHOR]

Abstract: There are more than fifteen bauxite outcrops in the study area located in the southern part of the Central Taurides. The bauxites are developed in the Upper Permian Cebireis Formation (carbonate rocks interbedded with schist) and Lower Triassic Asmaca Formation (limestone, dolomite, quartzite and schist). The bauxite outcrops are observed as parts of two or three independent bauxite blocks that were broken apart by faulting and an erosional surface. Based on outcrop appearances, four ore types can be defined; black, earthy, clayey, and Fe- and Mn-bearing bauxites. Oolitic textures are common in all ore types, except the earthy ones. Bauxites are represented by a mixture of diaspore and clay in varying proportions. Diaspore, boehmite, gibbsite, corundum, hematite, goethite, amorphous iron hydroxide, magnetite, chamosite, pyrite, marcasite, psilomelane, rutile, kaolinite, illite, muscovite, hydro-muscovite, chlorite, chloritoid, rectorite, ephesite, albite, microcline, quartz, K–Mg–Al silicate, hydrated K–Al silicate, and dolomite are present in the ore paragenesis. Bauxites, which are observed at or near the contact between the Cebireis and Asmaca formations, are thought to be fillings of cavities within and/or on Late Triassic—early Cretaceous carbonate rocks. [Copyright &y& Elsevier]

The experimental study of the relationship between biodiversity and ecosystem function has mainly addressed the effect of species and number of functional groups. In theory, this approach has mainly focused on how extinction affects function, whereas dispersal limitation of ecosystem function has been rarely discussed. A handful of seed introduction experiments, as well as numerous observations of the effects of long-distance dispersal of alien species, indicate that ecosystem function may be strongly determined by dispersal limitation at the local, regional and/or global scales. We suggest that it is time to replace biodiversity manipulation experiments, based on random draw of species, with those addressing realistic scenarios of either extinction or dispersal. Experiments disentangling the dispersal limitation of ecosystem function should have to take into account the probability of arrival. The latter is defined as the probability that a propagule of a particular species will arrive at a particular community. Arrival probability depends on the dispersal ability and the number of propagules of a species, the distance a species needs to travel, and the permeability of the matrix landscape. Current databases, in particular those in northwestern and central Europe now enable robust estimation of arrival probability in plant communities. We suggest a general hypothesis claiming that dispersal limitation according to arrival probability will have ecosystem-level effects different from those arising due to random arrival. This hypothesis may be rendered more region-, landscape- or ecosystem-specific by estimating arrival probabilities for different background conditions. [ABSTRACT FROM AUTHOR]

The mutual solubility in the system corundum–hematite [α-(Al, Fe3+)2O3] was investigated experimentally using both synthetic and natural materials. Mixtures of γ-Al2O3 and α-Fe2O3 (weight ratios of 8:2 and 10:1) were used as starting materials for synthesis experiments in air at 800–1300°C with run times of 7–34 days. Experiments at 8–40 kbar and 490–1100°C were performed in a piston-cylinder apparatus (run times of 0·8–7·4 days) using a natural diasporite consisting of 60–70 vol. % diaspore and 20–30 vol. % Ti-hematite. During the diasporite–corundite transformation, the FeTiO3 component (12–18 mol %) of Ti-hematite only slightly increased, implying that oxygen fugacity was maintained at high values. Run products were studied by electron microprobe and X-ray diffraction (Rietveld) techniques. An essentially linear volume of mixing exists in the solid solution with a slight positive deviation at the hematite side. Up to 1000°C, corundum contains <4 mol % Fe2O3 and hematite <10 mol % Al2O3; at 1200°C these amounts increase to 9·3 and 17·0 mol %, respectively. At 1300°C hematite was no longer stable and α-(Al0·88Fe0·123+O3) coexists with the orthorhombic phase Fe0·533+Al0·47O3. The present results agree with corundum (solvus) compositions obtained in previous studies but indicate a larger solubility of Al in hematite. The miscibility gap in the solution can be modelled with an asymmetric Margules equation with interaction parameters (2σ uncertainties): WHCor = 89 ± 10 kJ/mol; WSCor = 23 ± 8 J/(Kmol); WHHem = 91 ± 14 kJ/mol; WSHem = 14 ± 10 J/(Kmol). Application of the corundum–hematite solution as a solvus geothermometer is limited because of the scarcity of suitable rock compositions. [ABSTRACT FROM AUTHOR]

1. Deliberate breaching of sea defences is frequently practised with the aim of restoring salt-marsh vegetation on previously embanked land. However, experience so far has shown that it may take several years before salt-marsh vegetation is fully established, and it is possible that limited diaspore dispersal plays a role in this. In order to ascertain whether salt-marsh development may be constrained by limited diaspore dispersal, we studied the dispersal of salt-marsh species by tidal water. 2. From October 2001 to the end of March 2002 a total of 38 species, of which 18 were salt-marsh species, was trapped in a restoration site and adjacent marsh. Aster tripolium, Limonium vulgare, Puccinellia maritima, Salicornia spp., Spergularia media and Suaeda maritima were the most abundant salt-marsh species, with more than 3 diaspores m−2 trapped during the study period. 3. For most species, the number of diaspores trapped was representative of their abundance in nearby vegetation. Hence, despite the potential for long-distance transport by tidal water, our results indicate a predominantly local dispersal of salt-marsh species. 4. Synthesis and applications. For the restoration of salt-marsh vegetation after de-embankment, relatively rapid colonization may be expected from pioneer and low-marsh species, provided they are present in a nearby source area and the restoration site is at the appropriate altitude. The establishment of species absent from the adjacent marsh may be dependent on the presence of birds or humans as the main dispersal agents. Breaching of sea defences should preferably take place before or during September, in order to take advantage of the peak in dispersal of salt-marsh species in the first year after breaching. Journal of Applied Ecology (2005) doi: 10.1111/j.1365-2664.2005.01051.x [ABSTRACT FROM AUTHOR]

Biological force microscopy (BFM) was combined with two-dimensional gel electrophoresis and mass spectrometry to search for evidence of putative mineral-specific outer membrane proteins (OM) synthesized by Shewanella oneidensis for Fe-oxide binding and/or anaerobic Fe(III) reduction. BFM shows that S. oneidensis possess an affinity towards goethite (FeOOH) but not diaspore (AIOOH) under anaerobic conditions, despite the fact that diaspore is isostructural with goethite and has essentially the same surface charge. The worm-like chain model was used to identify force-signatures indicative of putative OM polypeptides that bind to goethite. Two-dimensional protein expression patterns show that over 100 OM proteins are differentially expressed under aerobic versus anaerobic Fe(III) reducing conditions. Peptide mass fingerprinting and tandem mass spectrometry were used to identify several of the protein spots predominately detected when Fe(III) was the terminal electron acceptor. Among those identified were proteins involved in metal reduction, protein transport and secretion, polysaccharide biosynthesis and export, and hypothetical proteins with unknown functions. A comparison of the BFM and proteomic data suggest that a few specific OM proteins are synthesized by S. oneidensis under anaerobic conditions to function in iron oxide binding and/or Fe(III) reduction. This suggests the intriguing possibility that metal reducing bacteria contain the genetic repertoire to make proteins directed at specific inorganic phases. [ABSTRACT FROM AUTHOR]

The aerodynamic constraints operating on the wind-dispersed, drag-producing diaspores of several species of the tropical family Bombacaceae were examined. Kapok (the drag-promoting appendage) was best characterized as a moderately flattened hemisphere impervious to air movement. The kapok shape was not isometric: kapok planform area was proportional to the kapok mass raised to the power 0.52 rather than to the 0.67 expected from isometry. Thus, necessarily, terminal velocity rises with seed mass much faster in this group than among taxa with winged seeds. Further, we derived the optimality argument to show that the kapok mass ought to be about 50% of the total diaspore mass (seed plus kapok). While seven of eight species had a lower kapok investment than this, and none were especially close to the theoretically optimal value, nonetheless the kapok investment values were hardly draws from a random distribution. Finally, the kapok fibers of these Bombacaceae species begin to bend at a drag of about 0.005 N, and this sets an upper limit on the efficient diaspore size of about 250 mg for the seed mass. This latter value is similar to the mass of the largest seed we know of in this family. [ABSTRACT FROM AUTHOR]

Abstract: Empirical force field and quantum mechanical calculations were completed to investigate the interaction between azotobactin and iron/aluminum oxide surfaces, and to further evaluate force measurements made on the same systems using an atomic force microscope (AFM). The increased force affinity for goethite over diaspore, characteristic of the experimental force signatures, was also observed in the simulated siderophore interaction with these minerals. Ab initio calculations on siderophore fragment analogs confirm previous findings and suggest that the iron affinity can, in part, be attributed to greater electron density associated with the Fe–O bond compared to the Al–O bond. This observation correlates with iron''s larger electronegativity compared to aluminum leading to a more covalent Fegoethite–Osiderophore bond. Calculations with hydrated fragment analog Al3+/Fe3+ complexes suggest the lowered siderophore force affinity observed experimentally for diaspore could also reflect the extra energy required to remove water coordinated to the Al in the surface. In the molecular mechanics simulations, chelating ligand pairs, which consisted of both backbone and amino acid side chain oxygen atoms, coordinated with neighboring iron and aluminum atoms to form a binuclear geometry. Upon retraction of azotobactin from each surface, simulated Fe–Osiderophore bonds persisted into a higher force regime than Al–Osiderophore bonds, and surface metals were removed from both minerals. Extrapolation of the model to more realistic hydrated conditions using a polarizable continuum model (PCM) (e.g., solvent is modeled as a continuum of uniform dielectric constant) and water coordination shells in quantum mechanical calculations and water clusters in the molecular mechanics model demonstrated that the presence of water energetically favors and enhances metal extraction. In this way, our system may be a good model to understand the forces of the azotobactin–mineral interaction and how they relate to siderophore-mediated dissolution of Fe from goethite in a natural system. [Copyright &y& Elsevier]

Abstract: Thermogravimetric data for the decomposition of diaspore have been obtained under nonisothermal conditions. A model-free isoconversional method is used to yield dependency of the activation energy on the extent of conversion for experiments. Reaction model of the Sestak–Berggren equation is identified by Malek and Mitsuhashi method. The parameter of the model SB(m, n) and the pre-exponential factor (A) are calculated. [Copyright &y& Elsevier]

Dispersal limitation was studied in a species-rich meadow (53-65 species of vascular plants per 1.1 m²) to which a mixture of weeds was accidentally sown. Even if none of the sown species belonged to the local species pool, five species successfully established. Of them one persisted for 7 years, however declined from 41 individuals in 1995 to 1 individual recorded in 2001. These results can be interpreted as an evidence for short-term diaspore limitation. In contrast, long-term data indicate no diaspore limitation. Establishment of weeds in subplots with a lower number of species and individuals was higher than in other subplots, indicating that plant establishment in the studied open-canopy grassland is affected by the spatial pattern of present plants. [ABSTRACT FROM AUTHOR]

It has been hypothesized that the relative role of species dispersal in determining plant community composition and species richness changes along primary productivity and disturbance intensity gradients. Manipulative experiments with either diaspore addition or prevention are needed to validate this hypothesis. Due to methodological constraints, diaspore prevention experiments are rarely used. In the case of diaspore addition experiments, there are some potential sources of error. (1) Experiments may be confounded since patchiness of microbial communities is not considered and techniques equalizing microbial communities over study plots are not used. (2) The length of the period of observation may not be sufficient to understand whether the establishment of sown individuals was really successful. (3) The effect of the sowing treatment and the theoretical context of the whole experiment depends on the number and identity of species sown. When addressing the role of long-distance dispersal, it is almost impossible to say what the appropriate number and composition of species to be used for the experiment should be. (4) Until now, most of the attention has been on dispersal in space, while the role of "dispersal in time" (seed bank) has rarely been addressed. We conclude that stepwise accumulation of experimental studies, addressing the role of dispersal in shaping plant communities, will sooner or later reveal general patterns, given the experiments are well planned and aim to avoid the sources of errors described above. [ABSTRACT FROM AUTHOR]

Species pool theory claims that diaspore and microsite availability limit species richness in plant communities. Wet meadows (Calthion) and litter meadows (Molinion, Caricion davallianae) belonging to the most species-rich meadows in the foothills of the Alps have suffered from a strong decrease since the 1970s. Restoration efforts including nutrient impoverishment and rewetting management after drainage and fertilization did not result in the re-establishment of the former species richness although the abiotic filter would have been appropriate for the re-colonization of many locally extinct species. In our experiment at four sites in the largest fen of Southwest-Germany we tested if the restoration success was seed- and gap-limited. We applied sowing and hay spreading (hay seed) as treatments to make seeds available and harrowing to increase gap availability. Sowing seeds or hay seed of species of the former meadow types increased species richness immediately. The proportion of re-established species was higher when additional harrowing was applied. Species richness could be increased not only in vascular plants but also in bryophytes when hay spreading was applied. The strongest re-development towards the target communities (defined through the abiotic filter and the species richness before drainage and fertilization) took place on those sites where hay spreading and harrowing were applied. Sowing seeds and hay seed were traditional techniques to establish e.g. litter meadows, both techniques have been applied for centuries. Even harrowing was described as early as the 19th century to increase the chance of establishing certain species. Therefore, the "application of the knowledge coming from the species pool theory" (although not named during this time) has been common practice since at least the 19th century. [ABSTRACT FROM AUTHOR]

Many lichen species produce both sexual and asexual propagules, but, aside from being minute, these diaspores lack special adaptations for long-distance dispersal. So far, molecular studies have not directly addressed isolation and genetic differentiation of lichen populations, both being affected by gene flow, at a regional scale. We used six mycobiont-specific microsatellite loci to investigate the population genetic structure of the epiphytic lichenLobaria pulmonariain two regions that strongly differed with respect to anthropogenic impact. In British Columbia,L. pulmonariagrows in continuous old-growth forests, while its populations in the old cultural landscape of Switzerland are comparably small and fragmented. Populations from both British Columbia and Switzerland were genetically diverse at the loci. Geographically restricted alleles, low historical gene flow, and analyses of genetic distance (upgmatree) and of differentiation (amova) indicated that populations from Vancouver Island and from the Canadian mainland were separated from each other, except for one, geographically intermediate population. This differentiation was attributed to different glacial and postglacial histories of coastal and inland populations in British Columbia. In contrast to expectations, the three investigated Swiss populations were genetically neither isolated nor differentiated from each other despite the long-lasting negative human impact on the lichen's range size in Central Europe. We propose that detailed studies integrating local landscape and regional scales are now needed to understand the processes of dispersal and gene flow in lichens. [ABSTRACT FROM AUTHOR]

A series of abrasives with various hardness values including monocrystalline and polycrystalline diamond, α- and γ-alumina, zirconia, ceria, and silica were used to examine the concept of chemical-assisted polishing for finishing the (0001), c-plane (basal plane), of sapphire. Diaspore, a monohydrate of alumina, was also evaluated. Atomic force microscopy suggested that the hydrated layer of the c-plane surface was about 1 nm thick. Polishing experiments were designed to determine whether the chemically modified surface hydration layer forms on the basal plane in water. The results indicate that harder abrasives do not necessarily cause faster material removal and better surface finish for similar abrasive particle size. Abrasives with hardness equal to or less than sapphire such as α-Al2O3 and γ-Al2O3 achieved the best surface finish and greatest efficiency of material removal. It is proposed that the (0001) c-plane sapphire surface was modified by water to form a thin hydration layer with structure and hardness close to diaspore. This reaction layer can be removed by an abrasive that is softer than sapphire but harder than the reaction layer, α-Al2O3 was particularly effective. This result is attributed to adhesion between identical reaction layers on the basal planes of the alumina abrasive and the sapphire. This demonstrates that high removal rates and good surface finish can be achieved without costly diamond polishing. [ABSTRACT FROM AUTHOR]

Seasonal changes in the diaspore bank of bryophytes and background processes were investigated in two open grasslands on dolomite rock in Hungary by means of soil samples. To test the longevity of propagules and to collect information about their potential dormancy, a part of each sample was stored air-dried in the laboratory for periods of half a year and 1 year. In contrast to results of earlier studies, temporal variation was detected in the number of propagules stored in the soil of three species (Bryum argenteum, Bryum erythrocarpum agg. and Weissia controversa). There is evidence of dormancy in vegetative gemmae of species of the Bryum erythrocarpum complex and Weissia controversa. Dormancy is also hypothesized in spores of Phascum cuspidatum. We suggest that dormancy in bryophyte propagules is less rare than had hitherto been assumed. Probably this is due mainly to the relatively small number of investigations of species living in habitats with periodically unfavourable moisture and temperature conditions. [ABSTRACT FROM AUTHOR]

Question: Which restoration measures (introduction of donor diaspore material, application of straw mulch, alteration of residual peat depths) contribute to the establishment of a fen plant community on minerotrophic surfaces after peat mining? Location: Rivière-du-Loup peatland, southern Québec, Canada at 100 m a.s.l. Methods: The effectiveness of introducing fen plants with the application of donor diaspore material was tested. The donor diaspore material, containing seeds, rhizomes, moss fragments, and other plant propagules, was collected from two different types of natural fens. We tested whether the application of straw mulch would increase fen species cover and biodiversity compared to control plots without straw mulch. Terrace levels of different peat depths (15 cm, 40 cm, and 56 cm) were created to test the effects of different environmental site conditions on the success of re-vegetation. Results: Applying donor seed bank from natural fens was found to significantly increase fen plant cover and richness after the two growing seasons. Straw mulch proved to significantly increase fen plant richness.The intermediate terrace level (40 cm) had the highest fen plant establishment. Compared to reference sites, the low terrace level (15 cm) was richer in base cations, whereas the high terrace level (56 cm) was much drier. Conclusions: The application of donor diaspore material was demonstrated as an effective technique for establishing vascular fen plants. Further rewetting measures are considered necessary at the restoration site to create a fen ecosystem rather than simply restoring some fen species. [ABSTRACT FROM AUTHOR]

Juvenile development has been investigated for the first time in an Antarctic lichen species—Usnea antarctica—in the northern maritime Antarctic, Livingston Island (South Shetland Islands, 62°27′–62°48′S, 59°45′–61°15′W). Here, U. antarctica grows on rocks and forms the dominant vegetation on this site together with a few other macrolichens. This species reproduces mainly by vegetative diaspores (soredia), which include both the photobiont and the mycobiont. To understand the early ontogenetic strategies in U. antarctica, culture experiments were performed in an Antarctic field site where the species occurs naturally. This paper focuses on the different developmental steps seen between the initial colonization of soredia to the formation of a small well-developed thallus, and also on the growth rate of the respective juvenile stages. Compared with growth rates of lichens from temperate European regions the early development of U. amarctica is extraordinarily slow, taking 5–6 years until an adult thallus has been formed. The low photobiont content in the juvenile stages probably limits the growth rate. It is suggested that juvenile development of U. antarctica is controlled by a combination of ecophysiological and morphological adaptations that are required for success in extreme environments such as the terrestrial habitats of the Antarctic. [ABSTRACT FROM AUTHOR]

1 Restored floodplains and backwaters lacking a viable propagule bank, may need flood pulses to facilitate inward dispersal of diaspores. Temporal patterns of hydrochorous plant dispersal are, however, not well known.2 Diversity and abundance of diaspores dispersed in a water body over 12 months were quantified using a 200 µm net in order to: (i) test for a relationship between discharge and the number of species and diaspores dispersed; (ii) examine the effect of seed buoyancy and seed release period on the length of the dispersal period; and (iii) test whether diaspores of species that disperse during a similar period of the year are characterized by similar dispersal and dormancy traits.3 A total 359 188 individuals of 174 vascular species developed from 144 samples, with most (90%) from vegetative diaspores and only 10% from seeds. Mean number of species and diaspores varied between months in parallel with discharge levels. Stepwise multiple regression analysis showed that both seed buoyancy and seed release influenced dispersal periods.4 In general, species that dispersed most diaspores in spring and summer had non-dormant seeds, a shorter seed release period and a shorter seed dispersal period than species whose dormant seeds dispersed in autumn and winter. Vegetative diaspores were dispersed on average over 8 months, indicating their importance to long-distance dispersal. Several species dispersed both generative and vegetative diaspores, often in different seasons.5 Our results may assist the planning of regenerative processes in riverine wetlands at landscape scales, as dispersal phenology, and discharge rates must be taken into consideration. Vegetative diaspores may be more important than seeds, although the latter may extend the species dispersal period into other seasons. Temporal heterogeneity in diaspore dispersal influences the identity of diaspores reaching restored habitats.Journal of Ecology(2004)92, 786 –796 [ABSTRACT FROM AUTHOR]

The services provided within a community can change as the species composition of that community changes. For example, ant-seed dispersal mutualisms can be disrupted in habitats dominated by invasive ants. We propose that this disruption is related to changes in mean ant body size, given that invasive ants are smaller than most native seed-dispersing ants. We demonstrate that the mean and maximum distances that ants transport seeds adapted for ant dispersal increase with worker body size, and that this relationship is an accelerating power function. This pattern is consistent among three ant subfamilies that include most seed-dispersing ants as well as most invasive ant species, is generalizable across ant species and communities, and is independent of diaspore mass. Using a case study, we demonstrate that both the mean body size of seed-collecting ants and seed dispersal distances are decreased in sites invaded by Solenopsis invicta, the im- ported red fire ant. Furthermore, we demonstrate that the mean size of seed-collecting ants at a seed depot or within a community is a useful predictor of mean seed dispersal distances at those sites. Last, we show that small seed-collecting ants and decreased seed dispersal distances are common features of sites occupied by invasive ants. The link between ant body size and seed dispersal distance, combined with the dominance of invaded communities by typically small ants, predicts the disruption of native ant-seed dispersal mutualisms in invaded habitats. [ABSTRACT FROM AUTHOR]

High-grade gneisses from the Pulur complex in NE Turkey bear evidence for biotite-dehydration melting at ≥820 °C and 0.7-0.8GPa, melt segregation and near-isothermal decompression to 0.4-0.5GPa. During further exhumation, the rocks underwent secondary pervasive rehydration at temperatures between ∼400 and 230 °C and fluid pressures between ∼0.3 and 0.1 GPa. Metamorphic peak conditions are dated at 331-327 Ma, while hydrothermal retrogression occurred significantly later at 315-310Ma under static conditions. During the rehydration event, primary high-grade mineral assemblages including garnet, cordierite, sillimanite, spinel, biotite, plagioclase and ilmenite were extensively replaced by muscovite, paragonite, margarite, corundum, diaspore, chlorite, kaolinite, pumpellyite, prehnite, epidote, titanite, anatase, pyrite and chalcopyrite. Secondary mineral assemblages indicate that the infiltrating fluids were characterized by low fO2, very low XCO2 (<0.002), variable activities of Ca2+, K+, Na+ and H+ and relatively high activities of H2S and CH4. Quartz veins that might have acted as pathways for the fluids are rare. Ubiquitous veinlets consisting of (i) albite, (ii) chlorite + calcite + quartz or (iii) K-feldspar + calcite + quartz were formed after the pervasive rehydraton event by precipitation from aqueous solutions that were somewhat richer in CO2. [ABSTRACT FROM AUTHOR]

Functional Ecology (2004) 18, 141–147 [ABSTRACT FROM AUTHOR]

Seed predation by animals has been shown to be an important factor in the evolution of dispersal mechanisms and diaspore morphology of plants. We studied seed production and predation of the perennial tussock-grass Stipa tenacissima L. in “El Desierto”, a semi-desert area in south-eastern Spain. As almost all other species in the genus, this plant produces diaspores with a long awn capable of hygroscopic movements that may lead to a drilling of the basal part of the diaspore into the soil substrate, to inserting into crevices or to lodging under rock fragments (trypanocarpy). Three species of granivorous ants (Messor barbarus, M. timidus, M. bouvieri) consume a substantial proportion of the seed production of S. tenacissima. We show in detail that the presence of the awn and the drilling mechanism of S. tenacissima reduce the intake rate of diaspores by Messor spp. dramatically. The long awn (mean overall length 56.8 mm) makes the diaspore cumbersome and heavier, so that it can only be retrieved much more slowly than a diaspore without the awn. Cutting of the awn by an ant requires a long time (mean 9.35 min) and small workers (head width < 1.3 mm) are incapable of it altogether. Diaspores drilled into the ground can still be excavated by workers. However, once the awn breaks off by weathering at the distinct preformed breaking point at the base of the awn, diaspores have practically escaped predation because ants cannot locate them underneath the soil surface. These results are consistent with the hypothesis that trypanocarpy is a very effective mechanism against seed predation in S. tenacissima. We also evaluate how seed predation by Messor spp. affects the population structure of S. tenacissima and caution against categorizing this grass as a mast species as previously suggested. Finally, we discuss the implications of pre-dispersal seed predation by Messor spp. for the interaction with S. tenacissima and other plants. [Copyright &y& Elsevier]

In previous studies, limited dispersal was revealed to be the main obstacle to restoration of species-rich flood-meadows along the northern Upper Rhine in Germany. To overcome dispersal limitation we transferred freshly mown plant material from species-rich sources to a restoration site on a former arable field. Before plant material application, topsoil was removed to accelerate nutrient impoverishment and create favourable conditions for seedling recruitment. Topsoil removal led to a drastic reduction in organic matter and essential mineral nutrients to the level of target communities (P) or even below (N, K). At a removal depth of 30 cm content of the soil seed bank that comprised exclusively of annual arable weeds, ruderals and some common grassland species, declined by 60-80%,while at a removal depth of 50 cm the seed bank was almost completely eliminated. With few exceptions, all species recorded in source plant material were found established at the restoration site. However, the overall correlation between seed content in plant material and establishment success was not very high. Vegetation development at the restoration site was characterized by a rapid decline in arable weeds and ruderals, while resident grassland species and species transferred with plant material increased rapidly from the third year onwards. After four years as many as 102 species were established that could be exclusively attributed to plant material transfer, among them many rare and highly endangered plants. Establishment of species from plant material was most successful in regularly flooded plots, due to the suppression of competitors as well as the creation of favourable moisture conditions for seedling emergence. Diaspore transfer with plant material proved to be an extremely successful method in restoring species-rich grass-land. However, high quality of plant material and suitable site conditions with low competition in early stages of succession seem to be essential... [ABSTRACT FROM AUTHOR]

The protonemal system of Discelium nudum produces a sward of unicellular, colourless, starch-filled rhizoidal tubers ca 1 cm below the surface of unstable clay banks. These short-lived and desiccation-intolerant diaspores are exposed on new clay surfaces following winter exfoliation of the original substratum. Their abundance and rapid germination appears to be a reproductive strategy giving Discelium a competitive advantage in this highly unstable habitat. The rounded, thin-walled, non-gemmiferous chloronemal filaments and colourless rhizoids of Discelium suggest affinities with the Funariaceae and the Gigaspermaceae. An early report of multicellular tubers in Discelium is most probably due to misinterpretion of the large starch grains, up to 20 µm in diameter, as cells within the unicellular tubers. [ABSTRACT FROM AUTHOR]

The effect of chemical composition of diaspores on their electrokinetics was studied. Increasing SiO2 content in a diaspore sample was found to decrease its isoelectric point. The X-ray diffraction and SEM microanalysis showed the absence of distinct SiO2 phases. A linear correlation was found to exist between the measured isoelectric point and alumina to silica mass ratio in diaspore samples. The linear regression analysis of the experimental data suggests a more significant impact of silicon content than aluminum content, indicating a preferential adsorption of dissolved silicon on diaspore samples and/or preferential dissolution of aluminum from diaspore samples. [Copyright &y& Elsevier]

The possibilities of mechanical activation for extraction of alumina from low-grade bauxites are investigated on the example of the Bokson deposit ores. It is established that the effective acid opening results from combination of mechanical activation and acid processing of activated product. The two-stage method of bauxite decomposition is considered. [ABSTRACT FROM AUTHOR]

Mn&z.sbnd;Ga mixed oxides have been prepared by coprecipitation of the corresponding oxo-hydroxides as powders and have been characterized in relation to their structural and optical properties. The materials have been characterized by XRD, TG-DTA, skeletal IR and UV–visible–NIR spectroscopies. Large solubility of Mn in the diaspore type α-GaOOH oxo-hydroxide has been found. The spinel related structures of hausmannite Mn3O4 and of β-gallia present large reciprocal solubilities at least in a metastable form. At high temperature also bixbyite-type α-Mn2O3 solid solutions containing up to 20% at. Ga have been observed. [Copyright &y& Elsevier]

The forces of interaction were measured between the siderophore azotobactin and the minerals goethite (α-FeOOH) and diaspore (α-AlOOH) in aqueous solution using force microscopy. Azotobactin, a pyoverdin-type siderophore, was covalently linked to a hydrazide terminated atomic force microscope tip using a standard active ester protein coupling technique. Upon contact with each mineral surface, the adhesion force between azotobactin and goethite was two to three times the value observed for the isostructural Al-equivalent diaspore. The affinity for the solid iron oxide surface reflected in the force measurements correlates with the specificity of azotobactin for aqueous ferric iron. Further, the adhesion force between azotobactin and goethite significantly decreases (4 nN to 2 nN) when small amounts of soluble iron (0.1 μM FeCl3 · 6H2O) are added to the system at pH 3.5 suggesting a significant specific interaction between the chelating reactive center of azotobactin and the mineral surface. Changes in the force signature with pH and ionic strength were fairly predictable when considering mineral solubility, the charge character of the mineral surfaces, the molecular structure of azotobactin, and the intervening solution. For example, azotobactin–goethite adhesion values were consistently smaller at pH 3.5 relative to the forces at pH 7. At the lower pH, the large number of protons and the increase in the mineral solubility provides additional electron acceptors (e.g., H+ and Fe3+(aq)) that are free to compete for the basic oxygen chelating sites in the azotobactin structure. It is believed that this competition disrupts siderophore affinity for the surface resulting in decreased adhesion values. [Copyright &y& Elsevier]

Presents a study which focused on lithium-rich zincostaurolite and its decompression-related breakdown products in a diaspore-bearing metabauxite from East Samos in Greece. Occurrences of zinc-rich staurolite; Geological setting and metamorphic evolution of Samos; Petrographic description; Discussion.

Rain forests at Los Tuxtlas are islands surrounded by anthropogenic vegetation containing invasive species. Epizoochory is an important dispersal syndrome among invasive species but ecological studies are scant. In order to evaluate the movement of epizoochore diaspores into the mature forest, we selected two abundant secondary herbs with contrasting diaspore morphology, and five dispersers with different pelage type. We used stuffed mammals as a dummy and passed them through patches of these two plant species, counting the number of adhered diaspores. For dispersal into the forest, diaspores were manually adhered to dispersers, these were pulled along 100-m forest transects, counting the number of diaspores remaining at distance intervals. We observed the highest amount of detachment in the first 20 m of the forest edge. For Desmodium incanum diaspores with sticky hairs, adhesion to dispersers showed no differences among pelage types, therefore dispersal is determined mainly by diaspore detachment. Dispersers with long pelage (Didelphis marsupialis, Nasua narica and Procyon lotor) move diaspores for shorter distances, while dispersers with short pelage (Silvilagus floridanus and Philander opossum) are more likely to move diaspores for longer distances. In Pavonia schiedeana more diaspores (seeds with spines and hooks) were attached and remained attached on dispersers with long and thick pelage. Mean distance travelled for P. schiedeana diaspores varied between 11 and 2700 m. In D. incanum the distance travelled did not exceed 500 m. Based on comparisons between dispersal patterns and on ecological data of these two plant species and their potential dispersers, P. schiedeana has a higher probability of invading the forest and finding suitable habitats for establishment than D. incanum. [ABSTRACT FROM PUBLISHER]

The dehydration of diaspore to corundum was investigated by means of X-ray powder diffraction at reaction temperatures (400° and 600°C) as well as by transmission electron microscopy (TEM). The TEM studies were performed at the reaction interface of partially dehydrated natural diaspore crystals. The corundum produced consisted of thin dense regions which were separated by nanometer-sized pores forming lamellae with a periodicity of 3.7 nm. At the reaction front a transition phase (D') could be detected in electron diffraction patterns. The phase D' is isotypic to diaspore, but with a larger spacing of the close-packed (100) oxygen planes (a[sub D], from 0.475 to 0.480 nm). The expansion with respect to diaspore is explained by breaking of the hydrogen bonds of diaspore, considered to be the initial step of the transformation. The spacing of the !amellar pore system in corundum is explained by the misfit of the (100) planes of D' and the (0003) planes of corundum. We conclude that at well-fitting regions of the closed-packed planes at the D'/C interface, dense corundum is formed, while at misfitting regions, the formation of corundum is not favored and the pores are produced. Hence, the transformation of the solid phases takes place as a two-step process, i.e., D → D' → C. [ABSTRACT FROM AUTHOR]