Contagious seed dispersal beneath heterospecific fruiting trees and its consequences.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwit, Charles; Levey, Douglas, J.; Greenberg, Cathyrn, H.

2004-05-03

Kwit, Charles, D.J. Levey and Cathryn H. Greenberg. 2004. Contagious seed dispersal beneath heterospecific fruiting trees and its consequences. Oikos. 107:303-308 A n hypothesized advantage of seed dispersal is avoidance of high per capita mortality (i.e. density-dependent mortality) associated with dense populations of seeds and seedlings beneath parent trees. This hypothesis, inherent in nearly all seed dispersal studies, assumes that density effects are species-specific. Yet because many tree species exhibit overlapping fruiting phenologies and share dispersers, seeds may be deposited preferentially under synchronously fruiting heterospecific trees, another location where they may be particularly vulnerable to mortality, in this case bymore » generalist seed predators. We demonstrate that frugivores disperse higher densities of Cornus florida seeds under fruiting (female) I lex opaca trees than under non-fruiting (male) I lex trees in temperate hardwood forest settings in South Carolina, U SA . To determine if density of Cornus and/or I lex seeds influences survivorship of dispersed Cornus seeds, we followed the fates of experimentally dispersed Cornus seeds in neighborhoods of differing, manipulated background densities of Cornus and I lex seeds. We found that the probability of predation on dispersed Cornus seeds was a function of both Cornus and I lex background seed densities. H igher densities of I lex seeds negatively affected Cornus seed survivorship, and this was particularly evident as background densities of dispersed Cornus seeds increased. These results illustrate the importance of viewing seed dispersal and predation in a community context, as the pattern and intensity of density-dependent mortality may not be solely a function of conspecific densities.« less

Seed-predator satiation and Janzen-Connell effects vary with spatial scales for seed-feeding insects.

PubMed

Xiao, Zhishu; Mi, Xiangcheng; Holyoak, Marcel; Xie, Wenhua; Cao, Ke; Yang, Xifu; Huang, Xiaoqun; Krebs, Charles J

2017-01-01

The Janzen-Connell model predicts that common species suffer high seed predation from specialized natural enemies as a function of distance from parent trees, and consequently as a function of conspecific density, whereas the predator satiation hypothesis predicts that seed attack is reduced due to predator satiation at high seed densities. Pre-dispersal predation by insects was studied while seeds are still on parent trees, which represents a frequently overlooked stage in which seed predation occurs. Reproductive tree density and seed production were investigated from ten Quercus serrata populations located in south-west China, quantifying density-dependent pre-dispersal seed predation over two years by three insect groups. Acorn infestation was nearly twice as high in the low-seed year as that in the high-seed year, with considerable spatio-temporal variation in the direction and magnitude of density-dependent pre-dispersal seed predation evident. Across whole populations of trees, a high density of reproductive trees caused predator satiation and reduced insect attack in the high-seed year. Within individual trees, and consistent with the Janzen-Connell model, overall insect seed predation was positively correlated with seed production in the low-seed year. In addition, there was variation among insect taxa, with positive density-dependent seed predation by Curculio weevils in the high-seed year and moths in the low-seed year, but apparent density independence by Cyllorhynchites weevils in both years. The overall trend of negative density-dependent, pre-dispersal seed predation suggests that predator satiation limited the occurrence of Janzen-Connell effects across Q. serrata populations. Such effects may have large impacts on plant population dynamics and tree diversity, depending on the extent to which they are reduced by counteracting positive density-dependent predation for seeds on individual trees and other factors affecting successful recruitment. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice

PubMed Central

Adams, A.; Gore, J.; Musser, F.; Cook, D.; Catchot, A.; Walker, T.; Awuni, G. A.

2015-01-01

Two experiments were conducted at the Delta Research and Extension Center in Stoneville, MS, during 2011 and 2012 to determine the impact of water management practices on the efficacy of insecticidal seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel. Larval densities and yield were compared for plots treated with labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin and an untreated control. In the first experiment, plots were subjected to flood initiated at 6 and 8 wk after planting. Seed treatments significantly reduced larval densities with the 8-wk flood timing, but not the 6-wk flood timing. Overall, the treated plots yielded higher than the control plots. In the second experiment, the impact of multiple flushes on the efficacy of insecticidal seed treatments was evaluated. Plots were subjected to zero, one, or two flushes with water. All seed treatments reduced larval densities compared with the untreated control. Significantly fewer larvae were observed in plots that received one or two flushes compared with plots that did not receive a flush. All seed treatments resulted in higher yields compared to the untreated control in the zero and one flush treatments. When two flushes were applied, yield from the thiamethoxam and clothianidin treated plots was not significantly different from those of the control plots, while the chlorantraniliprole treated plots yielded significantly higher than the control. These data suggest that time from planting to flood did not impact the efficacy of seed treatments, but multiple flushes reduced the efficacy of thiamethoxam and clothianidin. PMID:26470232

[Effects of sowing date and planting density on the seed yield and oil content of winter oilseed rape].

PubMed

Zhang, Shu-Jie; Li, Ling; Zhang, Chun-Lei

2012-05-01

A field experiment was conducted to investigate the effects of different sowing date and planting density on the seed yield and seed oil content of winter oilseed rape (Brassica napus). Sowing date mainly affected the seed yield of branch raceme, while planting density affected the seed yields of both branch raceme and main raceme. The seed oil content was less affected by sowing date. The proportion of the seed yield of main raceme to the seed yield per plant increased with increasing planting density, and the seed oil content of main raceme was about 1% higher than that of branch raceme. Consequently, the seed oil production per plot increased significantly with increasing planting density. In the experimental region, the sowing date of winter oilseed rape should be earlier than mid-October. When sowing in late October, the seed yield would be decreased significantly. A planting density of 36-48 plants x m(-2) could improve the seed yield and oil content of winter oilseed rape.

Implications of seed banking for recruitment of Southern Appalachian woody species

Treesearch

Janneke Hille Ris Lambers; James S. Clark; Michael Lavine

2002-01-01

Seed dormancy is assumed to be unimportant for population dynamics of temperate woody species, because seeds occur at low densities and are short lived in forest soils. However, low soil seed densities may result from low seed production, and even modest seed longevity can buffer against fluctuating seed production, potentially limiting density-dependent mortality and...

Seed banks in a degraded desert shrubland: Influence of soil surface condition and harvester ant activity on seed abundance

USGS Publications Warehouse

DeFalco, L.A.; Esque, T.C.; Kane, J.M.; Nicklas, M.B.

2009-01-01

We compared seed banks between two contrasting anthropogenic surface disturbances (compacted, trenched) and adjacent undisturbed controls to determine whether site condition influences viable seed densities of perennial and annual Mojave Desert species. Viable seeds of perennials were rare in undisturbed areas (3-4 seeds/m2) and declined to <1 seed/m2 within disturbed sites. Annual seed densities were an order of magnitude greater than those of perennials, were one-third the undisturbed seed densities on compacted sites, but doubled on trenched sites relative to controls. On trenched sites, greater litter cover comprising the infructescences of the dominant spring annuals, and low gravel content, enhanced seed densities of both annuals and perennials. Litter cover and surface ruggedness were the best explanations for viable perennial seed densities on compacted sites, but litter cover and the presence of a common harvester ant explained annual seed densities better than any other surface characteristics that were examined. Surface disturbances can have a varied impact on the condition of the soil surface in arid lands. Nevertheless, the consistently positive relationship between ground cover of litter and viable seed density emphasizes the importance of litter as an indicator of site degradation and recovery potential in arid lands.

Natural seed fall in white pine (Pinus strobes L.) stands of varying density

Treesearch

Raymond E. Graber

1970-01-01

Seed fall was observed in three stands of mature white pines at stand basal-area densities of 80, 120, and 187 square feet per acre. It was found that the intermediate-density stand produced nearly 50 percent more seed than the stands of other densities. During a good seed year this stand produced 59 pounds of dry sound seed per acre. Most of the seeds were dispersed...

Precommercial thinning intensity in longleaf pine: effect on product volume and value

Treesearch

John S. Kush; William D. Boyer; Ralph S. Meldahl; George A. Ward

1998-01-01

The possible benefit of precommercial thinning in longleaf pine was evaluated from a spacing study initiated in 1967 on the Escambia Experimental Forest in Brewton, AL. The study was established in dense, naturally established, seedling stands 9 years from seed. Plots were thinned to densities of 300, 600, 900, 1200, and 1500 trees/acre. Later, the initial range of...

Analysis of plasma-mediated ablation in aqueous tissue

NASA Astrophysics Data System (ADS)

Jiao, Jian; Guo, Zhixiong

2012-06-01

Plasma-mediated ablation using ultrafast lasers in transparent media such as aqueous tissues is studied. It is postulated that a critical seed free electron density exists due to the multiphoton ionization in order to trigger the avalanche ionization which causes ablation and during the avalanche ionization process the contribution of laser-induced photon ionization is negligible. Based on this assumption, the ablation process can be treated as two separate processes - the multiphoton and avalanche ionizations - at different time stages; so that an analytical solution to the evolution of plasma formation is obtained for the first time. The analysis is applied to plasma-mediated ablation in corneal epithelium and validated via comparison with experimental data available in the literature. The critical seed free-electron density and the time to initiate the avalanche ionization for sub-picosecond laser pulses are analyzed. It is found that the critical seed free-electron density decreases as the pulse width increases, obeying a tp-5.65 rule. This model is further extended to the estimation of crater size in the ablation of tissue-mimic polydimethylsiloxane (PDMS). The results match well with the available experimental measurements.

Indirect interactions among tropical tree species through shared rodent seed predators: a novel mechanism of tree species coexistence.

PubMed

Garzon-Lopez, Carol X; Ballesteros-Mejia, Liliana; Ordoñez, Alejandro; Bohlman, Stephanie A; Olff, Han; Jansen, Patrick A

2015-08-01

The coexistence of numerous tree species in tropical forests is commonly explained by negative dependence of recruitment on the conspecific seed and tree density due to specialist natural enemies that attack seeds and seedlings ('Janzen-Connell' effects). Less known is whether guilds of shared seed predators can induce a negative dependence of recruitment on the density of different species of the same plant functional group. We studied 54 plots in tropical forest on Barro Colorado Island, Panama, with contrasting mature tree densities of three coexisting large seeded tree species with shared seed predators. Levels of seed predation were far better explained by incorporating seed densities of all three focal species than by conspecific seed density alone. Both positive and negative density dependencies were observed for different species combinations. Thus, indirect interactions via shared seed predators can either promote or reduce the coexistence of different plant functional groups in tropical forest. © 2015 John Wiley & Sons Ltd/CNRS.

Direct seeding woody species for restoration of bottomlands

USGS Publications Warehouse

Twedt, D.J.; Connor, Kristina F

2006-01-01

I direct seeded (broadcast) seeds of 39 species of trees and shrubs using an ATV-mounted rotary spreader to initiate restoration of bottomland forest on retired agricultural sites. Four sites were planted during February, 2000, and 13 additional sites were planted during April and May, 2001. After two growing seasons, stem density of direct-seeded species varied greatly among study plots (range = 0 to 888 stems/ha) but averaged only 110 stems/ha. I recommend that future efforts at direct seeding focus on seven shrub species (Amorpha fruticosa L., Cephalanthus occidentalis L., Cornus spp., Crataegus spp., Ilex decidua Walt., Morus rubra L., and Prunus spp.) and seven tree species (Celtis laevigata Willd., Diospyros virginiana L., Fraxinus spp., Gleditsia triacanthos L., Robinia pseudoacacia L., Taxodium distichum (L.) Rich, and Ulmus spp.) that successfully established in these trials.

Seed harvesting is influenced by associational effects in mixed seed neighbourhoods, not just by seed density

USGS Publications Warehouse

Ostoja, Steven M.; Schupp, Eugene W.; Durham, Susan; Klinger, Robert C.

2013-01-01

Rodents frequently forage in a density-dependent manner, increasing harvesting in patches with greater seed densities. Although seldom considered, seed harvesting may also depend on the species identities of other individuals in the seed neighbourhood. When the seed harvest of a focal species increases in association with another seed species, the focal species suffers from Associational Susceptibility. In contrast, if seeds of the focal species are harvested less when in association with a second species, the focal species benefits from Associational Resistance.To evaluate density dependence and associational effects among seeds in mixtures, we conducted seed removal experiments using a completely additive design patterned after a two-species competition experiment using seeds of either Achnatherum hymenoides(Indian ricegrass), Leymus cinereus (basin wildrye) or Pseudoroegneria spicata (bluebunch wheatgrass), all native perennial grasses, combined with seeds of Bromus tectorum(cheatgrass), a non-native annual grass. The experiment involved placing five fixed quantities of the native seeds mixed with five fixed quantities of B. tectorum seeds in a factorial design, resulting in 35 seed mixture combinations. The seed-eating rodent community at our study sites, in order of abundance, is composed of Peromyscus maniculatus (North American deer mouse), Dipodomys ordii (Ord's kangaroo rat) and Perognathus parvus (Great Basin pocket mouse).Native seed harvesting was density dependent, with a greater proportion of seeds being harvested as density increased. In the mixed density model, the presence of B. tectorumdid not affect harvest of any of the native species' seeds when analysed individually. However, when all three native species were analysed together, increasing quantities of B. tectorum resulted in reduced harvest of native seeds, demonstrating weak but significant Associational Resistance. In contrast, harvest of B. tectorum seeds increased when in combination with any of the native seed species individually, indicating relatively strong Associational Susceptibility.These results demonstrate that seed harvest is determined not just by seed density, but also by the local seed neighbourhood and suggest that associational effects between native seeds and B. tectorum can occur in field conditions. The ecological implications of seed selection and associational effects on plant populations in natural and managed systems are also discussed.

Hypercarnivorous apex predator could provide ecosystem services by dispersing seeds

PubMed Central

Sarasola, José Hernán; Zanón-Martínez, Juan Ignacio; Costán, Andrea Silvina; Ripple, William J.

2016-01-01

Large “hypercarnivorous” felids are recognized for their role as apex predators and hence as key elements in food webs and ecosystem functioning through competition and depredation. Here we show that cougars (Puma concolor), one of the largest and the most widely ranging apex felid predators with a strictly carnivorous diet, could also be effective secondary long distance seed dispersers, potentially establishing direct and non-herbivore mediated interactions with plant species at the bottom of the food web. Cougars accidently ingest and disseminate large amounts of seeds (31,678 seeds in 123 scats) of plant species initially consumed by their main prey, the Eared Dove Zenaida auriculata. The germination potential of seeds for the three plant species most abundantly found in cougar scats (19,570 seeds) was not significantly different from that observed in seeds obtained from dove gizzards, indicating that seed passage through cougar guts did not affect seed germination. Considering the estimated cougar density in our study area, dispersal of seeds by cougars could allow a mean, annual seed spread of ~5,000 seeds per km2. Our results demonstrate that strictly carnivorous, felid predators could have broad and overlooked ecological functions related to ecosystem structuring and functioning. PMID:26791932

Hypercarnivorous apex predator could provide ecosystem services by dispersing seeds.

PubMed

Sarasola, José Hernán; Zanón-Martínez, Juan Ignacio; Costán, Andrea Silvina; Ripple, William J

2016-01-21

Large "hypercarnivorous" felids are recognized for their role as apex predators and hence as key elements in food webs and ecosystem functioning through competition and depredation. Here we show that cougars (Puma concolor), one of the largest and the most widely ranging apex felid predators with a strictly carnivorous diet, could also be effective secondary long distance seed dispersers, potentially establishing direct and non-herbivore mediated interactions with plant species at the bottom of the food web. Cougars accidently ingest and disseminate large amounts of seeds (31,678 seeds in 123 scats) of plant species initially consumed by their main prey, the Eared Dove Zenaida auriculata. The germination potential of seeds for the three plant species most abundantly found in cougar scats (19,570 seeds) was not significantly different from that observed in seeds obtained from dove gizzards, indicating that seed passage through cougar guts did not affect seed germination. Considering the estimated cougar density in our study area, dispersal of seeds by cougars could allow a mean, annual seed spread of ~5,000 seeds per km(2). Our results demonstrate that strictly carnivorous, felid predators could have broad and overlooked ecological functions related to ecosystem structuring and functioning.

Seed viability detection using computerized false-color radiographic image enhancement

NASA Technical Reports Server (NTRS)

Vozzo, J. A.; Marko, Michael

1994-01-01

Seed radiographs are divided into density zones which are related to seed germination. The seeds which germinate have densities relating to false-color red. In turn, a seed sorter may be designed which rejects those seeds not having sufficient red to activate a gate along a moving belt containing the seed source. This results in separating only seeds with the preselected densities representing biological viability lending to germination. These selected seeds demand a higher market value. Actual false-coloring isn't required for a computer to distinguish the significant gray-zone range. This range can be predetermined and screened without the necessity of red imaging. Applying false-color enhancement is a means of emphasizing differences in densities of gray within any subject from photographic, radiographic, or video imaging. Within the 0-255 range of gray levels, colors can be assigned to any single level or group of gray levels. Densitometric values then become easily recognized colors which relate to the image density. Choosing a color to identify any given density allows separation by morphology or composition (form or function). Additionally, relative areas of each color are readily available for determining distribution of that density by comparison with other densities within the image.

Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation

PubMed Central

Rusli, Nurul Izni; Tanikawa, Masahiro; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2012-01-01

The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas was systematically investigated. The high-density growth of ZnO nanorods with (0002) orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnOx seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnOx seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnOx nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnOx clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnOx seed layer. The growth mechanism involved has been described by a combination of self-catalyzed vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism. The results suggest that for a more precise study on the growth of ZnO nanostructures involving the introduction of seeds, the initial seed structures must be taken into account given their significant effects.

ERRATUM: In vivo evaluation of a neural stem cell-seeded prosthesis In vivo evaluation of a neural stem cell-seeded prosthesis

NASA Astrophysics Data System (ADS)

Purcell, E. K.; Seymour, J. P.; Yandamuri, S.; Kipke, D. R.

2009-08-01

In the published article, an error was made in figure 5. Specifically, the three-month, NSC-seeded image is a duplicate of the six-week image, and the one-day, probe alone image is a duplicate of the three-month image. The corrected figure is reproduced below. Figure 5 Figure 5. Glial encapsulation of each probe condition over the 3 month time course. Ox-42 labeled microglia and GFAP labeled astrocytes are shown. Images are taken from probes implanted in the same animal at each time point. NSC seeding was associated with reduced non-neuronal density at 1 day post-implantation in comparison to alginate coated probes and at the 1 week time point in comparison to untreated probes (P < 0.001). Glial activation is at its overall peak 1 week after insertion. A thin encapsulation layer surrounds probes at the 6 week and 3 month time points, with NSC-seeded probes having the greatest surrounding non-neuronal density P < 0.001). Interestingly, microglia appeared to have a ramified, or `surveilling', morphology surrounding a neural stem cell-alginate probe initially, whereas activated cells with an amoeboid structure were found near an alginate probe in the same hemisphere of one animal (left panels).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meikle, T.; Ballek, L.; Briggs, B.

This study investigates the cost effectiveness of three separate reclamation methods utilized in the long-term establishment of Big Sage (Artemisia tridentata va. wyomingensis). Direct seeding and planting with four cubic inch and ten cubic inch containerized stock were compared using five 36 square meter plots per treatment within a fenced randomized block. Seed plots were hand broadcast at a rate of 2 kilograms per hectare and mulched with certified weed-free wheat straw. Containerized stock plots were planted at a density of one per square meter. Controls with no seeding or planting were established to differentiate actual plant production/reproduction from seedmore » bank recruitment and migration from replaced topsoil and surrounding native areas. Stem density (stem/m{sup 2}), plant height (cm), and plant reproduction (seedlings/m{sup 2}) data will be gathered every spring and fall for three years (1994-1997). Final analysis of the data will relate establishment success to cost efficiency. This initial report on the study reviews only seedling establishment based on first year data.« less

Dense understory dwarf bamboo alters the retention of canopy tree seeds

NASA Astrophysics Data System (ADS)

Qian, Feng; Zhang, Tengda; Guo, Qinxue; Tao, Jianping

2016-05-01

Tree seed retention is thought to be an important factor in the process of forest community regeneration. Although dense understory dwarf bamboo has been considered to have serious negative effects on the regeneration of forest community species, little attention has been paid to the relationship between dwarf bamboo and seed retention. In a field experiment we manipulated the density of Fargesia decurvata, a common understory dwarf bamboo, to investigate the retention of seeds from five canopy tree species in an evergreen and deciduous broad-leaved mixed forest in Jinfoshan National Nature Reserve, SW China. We found that the median survival time and retention ratio of seeds increased with the increase in bamboo density. Fauna discriminately altered seed retention in bamboo groves of different densities. Arthropods reduced seed survival the most, and seeds removed decreased with increasing bamboo density. Birds removed or ate more seeds in groves of medium bamboo density and consumed fewer seeds in dense or sparse bamboo habitats. Rodents removed a greater number of large and highly profitable seeds in dense bamboo groves but more small and thin-husked seeds in sparse bamboo groves. Seed characteristics, including seed size, seed mass and seed profitability, were important factors affecting seed retention. The results suggested that dense understory dwarf bamboo not only increased seeds concealment and reduced the probability and speed of seed removal but also influenced the trade-off between predation and risk of animal predatory strategies, thereby impacting the quantity and composition of surviving seeds. Our results also indicated that dense understory dwarf bamboo and various seed characteristics can provide good opportunities for seed storage and seed germination and has a potential positive effect on canopy tree regeneration.

High-Energy-Density Shear Flow and Instability Experiments

NASA Astrophysics Data System (ADS)

Doss, F. W.; Flippo, K. A.; Merritt, E. C.; di Stefano, C. A.; Devolder, B. G.; Kurien, S.; Kline, J. L.

2017-10-01

High-energy-density shear experiments have been performed by LANL at the OMEGA Laser Facility and National Ignition Facility (NIF). The experiments have been simulated using the LANL radiation-hydrocode RAGE and have been used to assess turbulence models ability to function in the high-energy-density, inertial- fusion-relevant regime. Beginning with the basic configuration of two counter-oriented shock-driven flows of >= 100 km/s, which initiate a strong shear instability across an initially solid-density, 20 μm thick Al plate, variations of the experiment to details of the initial conditions have been performed. These variations have included increasing the fluid densities (by modifying the plate material from Al to Ti and Cu), imposing sinusoidal seed perturbations on the plate, and directly modifying the plate's intrinsic surface roughness. Radiography of the unseeded layer has revealed the presence of emergent Kelvin-Helmholtz structures which may be analyzed to infer fluid-mechanical properties including turbulent energy density. This work is conducted by the US DOE by LANL under contract DE-0AC52-06NA25396. This abstract is LA-UR-16-24930.

Do cacti form soil seed banks? An evaluation using species from the Southern Central Andes.

PubMed

Lindow-López, Lucía; Galíndez, Guadalupe; Sühring, Silvia; Pastrana-Ignes, Valeria; Gorostiague, Pablo; Gutiérrez, Angela; Ortega-Baes, Pablo

2018-06-22

There is controversy over whether cactus species form soil seed banks. Although it is commonly assumed that cacti do not form seed banks, very few studies have evaluated them. In this work, we analyzed whether cactus species form soil seed banks, studying seed distribution, seed density and seed longevity in the Southern Central Andes. Soil samples were collected in two microhabitats (under nurse plants and in bare areas) at 12 selected sites. We determined seed presence-absence, density and distribution for 32 native cactus species. Seed longevity for six of these species was determined through a burial experiment. We recorded viable seeds for 62.5% of the 32 evaluated species, finding variation in seed density between microenvironments and among populations. In some species, the greatest seed density was found under potential nurse plants. Seed germination and seed viability decreased with burial time, with seed longevity always being less than 24 months after burial. Our results show strong evidence that cactus species do form seed banks. Seed density can vary between microenvironments and among populations, suggesting that cactus-nurse plant associations can also be explained by differential seed dispersal and not only by differential establishment. We found that Echinopsis and Gymnocalycium species form short-term seed banks. Our results will help to better understand the population dynamics of cactus species, a focal species group for conservation actions because many of them are threatened by human activities. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Modeling the Effect of Density-Dependent Chemical Interference Upon Seed Germination

PubMed Central

Sinkkonen, Aki

2005-01-01

A mathematical model is presented to estimate the effects of phytochemicals on seed germination. According to the model, phytochemicals tend to prevent germination at low seed densities. The model predicts that at high seed densities they may increase the probability of seed germination and the number of germinating seeds. Hence, the effects are reminiscent of the density-dependent effects of allelochemicals on plant growth, but the involved variables are germination probability and seedling number. The results imply that it should be possible to bypass inhibitory effects of allelopathy in certain agricultural practices and to increase the efficiency of nature conservation in several plant communities. PMID:19330163

Modeling the Effect of Density-Dependent Chemical Interference upon Seed Germination

PubMed Central

Sinkkonen, Aki

2006-01-01

A mathematical model is presented to estimate the effects of phytochemicals on seed germination. According to the model, phytochemicals tend to prevent germination at low seed densities. The model predicts that at high seed densities they may increase the probability of seed germination and the number of germinating seeds. Hence, the effects are reminiscent of the density-dependent effects of allelochemicals on plant growth, but the involved variables are germination probability and seedling number. The results imply that it should be possible to bypass inhibitory effects of allelopathy in certain agricultural practices and to increase the efficiency of nature conservation in several plant communities. PMID:18648596

[Soil seed bank in Keerqin meadow grassland under grazing and harvesting].

PubMed

Jiang, Deming; Li, Rongping; Liu, Zhimin; Yan, Qiaoling

2004-10-01

This study on the size and composition of seed bank and its relationship with vegetation showed in Keerqin meadow grassland, the density of soil seed bank was 6158 +/- 1647 grains x m(-2) under grazing and 8312 +/- 2540 grains m(-2) under harvesting. Under grazing, the seed bank was mainly composed of some dwarf and short-life annuals. The seeds of the annuals and biennials accounted for 81.66% of the seeds in seed bank. The four species with largest proportion of seed bank were Chloris virgata, Chenopodium glaucum, Digitaria cilliaris and Setaria viridis, and the proportions were 38.55%, 15.42%, 14.95%, and 9.83%, respectively. The density of perennials in soil seed bank was 1129 +/- 302 grains x m(-2). Under harvesting, the seeds of annuals and biennials accounted for 68.08% of the seed in seed bank, and the proportion of Setaria viridis was 52.7%. In the harvesting meadow grassland, the seed density of perennials was 2653 +/- 811 grains x m(-2). There was no significant correlation between the seed density in soil and the vegetation under grazing, but a significant correlation between the seed density in soil and the species abundance of vegetation under harvesting (r = 0.76, P < 0.01). The index of Shannon-Wiener and richness of grazing meadow grassland were 2.96 and 2.98, respectively, distinctly smaller than 3.10 and 5.09 of harvesting meadow, which showed that free grazing made the diversity of seed bank decrease easily.

Effects of dispersal, shrubs, and density-dependent morality on seed and seedling distributions in temperate forests

Treesearch

Janneke Hille Ris Lambers; James S. Clark

2003-01-01

Processes limiting recruitment of trees may have large impacts on forest dynamics. In this paper, we determined the effects of dispersal, shrubs (Rhododendron maximum), and density-dependent mortality on seed and seedling distributions of Southern Appalachian trees. We quantified the spatial distribution of seed rain, seed bank densities, first-year...

Spatio-temporal variation in a seed bank of a semi-arid region in northeastern Brazil

NASA Astrophysics Data System (ADS)

da Silva, Kleber A.; dos Santos, Danielle M.; dos Santos, Josiene M. F. F.; de Albuquerque, Ulysses P.; Ferraz, Elba M. N.; Araújo, Elcida de L.

2013-01-01

This study aimed to evaluate variations in the seed bank within a 3-year temporal series in order to answer the following questions: 1) Does the seed bank's species richness and seed density differ among climatic seasons and between years? 2) Are there differences in the richness and density of seed banks between the litter and mineral soil? 3) Can the seed bank's species richness and seed density be explained by characteristics such as the previous year's precipitation and soil depth (litter or mineral soil)? The samples were collected from litter and mineral soil (0-5 cm), in 210 sub-plots, during the dry and rainy seasons of each year (August 2005 through February 2008). Overall, 79 species were recorded. On average, 1 168, 304 and 302 seeds.m-2 were recorded in the seed bank during years I, II and III, respectively. This study showed that the Caatinga's seed bank is rich in herbaceous species, yet species' density and richness are low in the litter. Furthermore, about 43% of the variation in species richness and density was explained by soil depth (litter and mineral soil) and previous years' rainfall.

Repeated landscape-scale treatments following fire suppress a non-native annual grass and promote recovery of native perennial vegetation

USGS Publications Warehouse

Munson, Seth M.; Long, A. Lexine; Decker, Cheryl E.; Johnson, Katie A.; Walsh, Kathleen; Miller, Mark E.

2015-01-01

Invasive non-native species pose a large threat to restoration efforts following large-scale disturbances. Bromus tectorum (cheatgrass) is a non-native annual grass in the western U.S. that both spreads quickly following fire and accelerates the fire cycle. Herbicide and seeding applications are common restoration practices to break the positive fire-invasion feedback loop and recover native perennial species, but their interactive effects have infrequently been tested at the landscape-scale and repeated in time to encourage long-lasting effects. We determined the efficacy of repeated post-fire application of the herbicide imazapic and seeding treatments to suppressBromus abundance and promote perennial vegetation recovery. We found that the selective herbicide reduced Bromus cover by ~30 % and density by >50 % across our study sites, but had a strong initial negative effect on seeded species. The most effective treatment to promote perennial seeded species cover was seeding them alone followed by herbicide application 3 years later when the seeded species had established. The efficacy of the treatments was strongly influenced by water availability, as precipitation positively affected the density and cover of Bromus; soil texture and aspect secondarily influenced Bromus abundance and seeded species cover by modifying water retention in this semi-arid region. Warmer temperatures positively affected the non-native annual grass in the cool-season, but negatively affected seeded perennial species in the warm-season, suggesting an important role of seasonality in a region projected to experience large increases in warming in the future. Our results highlight the importance of environmental interactions and repeated treatments in influencing restoration outcomes at the landscape-scale.

Effects of seed density and proximity to refuge habitat on seed predation rates for a rare and a common Lupinus species.

PubMed

Pardini, Eleanor A; Patten, Melissa V; Knight, Tiffany M

2017-03-01

Biotic interactions such as seed predation can play a role in explaining patterns of abundance among plant species. The effect of seed predation will depend on how the strength of predation differs across species and environments, and on the degree to which seed loss at one life-cycle phase increases fitness at another phase. Few studies have simultaneously quantified predispersal and postdispersal predation in co-occurring rare and common congeners, despite the value of estimating both for understanding causes of rarity. We quantified predispersal seed predation on the rare, herbaceous species Lupinus tidestromii (Fabaceae) and its common, shrubby congener L. chamissonis across multiple years in the same community. We experimentally measured postdispersal seed predation at two seed densities and locations near or far from an exotic grass housing high densities of deer mice ( Peromyscus maniculatus ), their primary, native seed predator. The common L. chamissonis had the lowest predispersal seed predation of the two lupine species, potentially because of its height: its high racemes received less predation than those low to the ground. By contrast, the same species experienced higher postdispersal seed predation, and at predators traveled long distances away from refuge habitat to consume their seeds. Across both plant species, mice preferentially predated high-density seed sources. Our results show differences in the magnitude and direction of seed predation between the species across different life-cycle phases. We demonstrated possible roles of proximity to refuge habitat, seed density, and seed size in these patterns. Congeneric comparisons would benefit from a comprehensive framework that considers seed predation across different life-cycle phases and the environmental context of predation. © 2017 Botanical Society of America.

Primordial black holes as seeds of magnetic fields in the universe

NASA Astrophysics Data System (ADS)

Safarzadeh, Mohammadtaher

2018-06-01

Although it is assumed that magnetic fields in accretion disks are dragged from the interstellar medium, the idea is likely not applicable to primordial black holes (PBHs) formed in the early universe. Here we show that magnetic fields can be generated in initially unmagnetized accretion disks around PBHs through the Biermann battery mechanism, and therefore provide the small scale seeds of magnetic field in the universe. The radial temperature and vertical density profiles of these disks provide the necessary conditions for the battery to operate naturally. The generated seed fields have a toroidal structure with opposite sign in the upper and lower half of the disk. In the case of a thin accretion disk around a rotating PBH, the field generation rate increases with increasing PBH spin. At a fixed r/risco, where r is the radial distance from the PBH and risco is the radius of the innermost stable circular orbit, the battery scales as M-9/4, where M is the PBH's mass. The very weak dependency of the battery on accretion rate, makes this mechanism a viable candidate to provide seed fields in an initially unmagnetized accretion disk, following which the magnetorotational instability could take over.

Seed population dynamics on abandoned slopes in the hill and gully Loess Plateau region of China

NASA Astrophysics Data System (ADS)

Yu, Weijie; Jiao, Juying

2017-04-01

Recovery of natural vegetation is an effective but slow approach to control the soil erosion in the Chinese hill and gully Loess Plateau region. As seed stage is particularly vulnerable to environmental conditions, characteristics of seed population should be needed to study for determining whether the recovery of natural vegetation is limited during this stage on the abandoned slopes in this region. The study was performed on three abandoned slopes in a watershed with an area of 8.27 km2in the Shaanxi province of China. The differences in soil seed banks were investigated in two different points in time, late March2011 and early April 2013. Main factors of seed population dynamics, such as seed yield of dominant species, seed inputs by seed rain as well as seed outputs through seed loss by overland flow and seedling emergence, were monitored from late March 2011 to early April 2013. In this study, seed rain densities of the main later successional species, i.e., Lespedeza davurica, Stipa bungeana and Artemisia gmelinii accounted for 51.5-71.6% of their own seed yields. The soil seed bank density in early April 2013 was larger than that in late March 2011. The density of seed inputs by seed rain was 10186 seeds•m-2, and the total seed bank, including seed rain and seeds present in the soil seed bank in late March 2011, reached a density of 15018 seeds•m-2 during the study period. Seed densities of loss due to overland flow and seedling emergence were 79 seeds•m-2 from 20 species and 938 seedlings•m-2 that belonged to 38 species during a study period, and the seed output through them accounted for 0.5% and 6.3% of the total seed bank, respectively. The study concluded that overland flow could not result in large numbers of seeds loss and seeds were accumulating in the soil seed bank due to seed rain, and vegetation succession might be limited by curbed spatial seed dispersal and seedling establishment.

Two-stage Raman compression of laser pulses with controllable phase fronts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balakin, A. A.; Fraiman, G. M.; State University of Nizhny Novgorod, Nizhny Novgorod

2015-05-15

The phase front of an ultrashort laser pulse undergoing Raman amplification and compression in inhomogeneous plasma can be controlled such that it is unaffected by density gradients and thus remains focusable. This is achieved by performing the Raman backscattering in two stages. At the first stage, the standard nonlinear Raman compression of a seed wave takes place and produces a short ultraintense pulse, which yet may be poorly focusable. At the second stage, this amplified pulse is scattered again, now serving as a pump, off a second copy of the initial seed. This stage, which utilizes a denser and shortermore » plasma, is intended not for compression but rather for passing a significant fraction of the energy to the second seed quickly. Then, the output pulse that is produced is not just short and ultraintense, but also has the smooth phase front of the original seed.« less

A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana, USA)

USGS Publications Warehouse

Leicht-Young, S. A.; Pavlovic, N.B.; Grundel, R.; Frohnapple, K.J.

2009-01-01

In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m-2, but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone. ?? 2008 Springer Science+Business Media B.V.

Effect of variation in self-incompatibility on pollen limitation and inbreeding depression in Flourensia cernua (Asteraceae) scrubs of contrasting density

PubMed Central

Ferrer, Miriam M.; Good-Avila, Sara V.; Montaña, Carlos; Domínguez, César A.; Eguiarte, Luis E.

2009-01-01

Background and Aims Selection may favour a partial or complete loss of self-incompatibility (SI) if it increases the reproductive output of individuals in the presence of low mate availability. The reproductive output of individuals varying in their strength of SI may also be affected by population density via its affect on the spatial structuring and number of S-alleles in populations. Modifiers increasing levels of self-compatibility can be selected when self-compatible individuals receive reproductive compensation by, for example, increasing seed set and/or when they become associated with high fitness genotypes. Methods The effect of variation in the strength of SI and scrub density (low versus high) on seed set, seed germination and inbreeding depression in seed germination (δgerm) was investigated in the partially self-incompatible species Flourensia cernua by analysing data from self-, cross- and open-pollinated florets. Key Results Examination of 100 plants in both high and low scrub densities revealed that 51% of plants were strongly self-incompatible and 49 % varied from being self-incompatible to self-compatible. Seed set after hand cross-pollination was higher than after open-pollination for self-incompatible, partially self-incompatible and self-compatible plants but was uniformly low for strongly self-incompatible plants. Strongly self-incompatible and self-incompatible plants exhibited lower seed set, seed germination and multiplicative female fitness (floral display × seed set × seed germination) in open-pollinated florets compared with partially self-incompatible and self-compatible plants. Scrub density also had an effect on seed set and inbreeding depression: in low-density scrubs seed set was higher after open-pollination and δgerm was lower. Conclusions These data suggest that (a) plants suffered outcross pollen limitation, (b) female fitness in partially self-incompatible and self-compatible plants is enhanced by increased mate-compatibility and (c) plants in low-density scrubs received higher quality pollen via open-pollination than plants in high-density scrubs. PMID:19218580

High seeding density of human chondrocytes in agarose produces tissue-engineered cartilage approaching native mechanical and biochemical properties.

PubMed

Cigan, Alexander D; Roach, Brendan L; Nims, Robert J; Tan, Andrea R; Albro, Michael B; Stoker, Aaron M; Cook, James L; Vunjak-Novakovic, Gordana; Hung, Clark T; Ateshian, Gerard A

2016-06-14

Animal cells have served as highly controllable model systems for furthering cartilage tissue engineering practices in pursuit of treating osteoarthritis. Although successful strategies for animal cells must ultimately be adapted to human cells to be clinically relevant, human chondrocytes are rarely employed in such studies. In this study, we evaluated the applicability of culture techniques established for juvenile bovine and adult canine chondrocytes to human chondrocytes obtained from fresh or expired osteochondral allografts. Human chondrocytes were expanded and encapsulated in 2% agarose scaffolds measuring ∅3-4mm×2.3mm, with cell seeding densities ranging from 15 to 90×10(6)cells/mL. Subsets of constructs were subjected to transient or sustained TGF-β treatment, or provided channels to enhance nutrient transport. Human cartilaginous constructs physically resembled native human cartilage, and reached compressive Young's moduli of up to ~250kPa (corresponding to the low end of ranges reported for native knee cartilage), dynamic moduli of ~950kPa (0.01Hz), and contained 5.7% wet weight (%/ww) of glycosaminoglycans (≥ native levels) and 1.5%/ww collagen. We found that the initial seeding density had pronounced effects on tissue outcomes, with high cell seeding densities significantly increasing nearly all measured properties. Transient TGF-β treatment was ineffective for adult human cells, and tissue construct properties plateaued or declined beyond 28 days of culture. Finally, nutrient channels improved construct mechanical properties, presumably due to enhanced rates of mass transport. These results demonstrate that our previously established culture system can be successfully translated to human chondrocytes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optimization of human corneal endothelial cell culture: density dependency of successful cultures in vitro.

PubMed

Peh, Gary S L; Toh, Kah-Peng; Ang, Heng-Pei; Seah, Xin-Yi; George, Benjamin L; Mehta, Jodhbir S

2013-05-03

Global shortage of donor corneas greatly restricts the numbers of corneal transplantations performed yearly. Limited ex vivo expansion of primary human corneal endothelial cells is possible, and a considerable clinical interest exists for development of tissue-engineered constructs using cultivated corneal endothelial cells. The objective of this study was to investigate the density-dependent growth of human corneal endothelial cells isolated from paired donor corneas and to elucidate an optimal seeding density for their extended expansion in vitro whilst maintaining their unique cellular morphology. Established primary human corneal endothelial cells were propagated to the second passage (P2) before they were utilized for this study. Confluent P2 cells were dissociated and seeded at four seeding densities: 2,500 cells per cm2 ('LOW'); 5,000 cells per cm2 ('MID'); 10,000 cells per cm2 ('HIGH'); and 20,000 cells per cm2 ('HIGH(×2)'), and subsequently analyzed for their propensity to proliferate. They were also subjected to morphometric analyses comparing cell sizes, coefficient of variance, as well as cell circularity when each culture became confluent. At the two lower densities, proliferation rates were higher than cells seeded at higher densities, though not statistically significant. However, corneal endothelial cells seeded at lower densities were significantly larger in size, heterogeneous in shape and less circular (fibroblastic-like), and remained hypertrophic after one month in culture. Comparatively, cells seeded at higher densities were significantly homogeneous, compact and circular at confluence. Potentially, at an optimal seeding density of 10,000 cells per cm2, it is possible to obtain between 10 million to 25 million cells at the third passage. More importantly, these expanded human corneal endothelial cells retained their unique cellular morphology. Our results demonstrated a density dependency in the culture of primary human corneal endothelial cells. Sub-optimal seeding density results in a decrease in cell saturation density, as well as a loss in their proliferative potential. As such, we propose a seeding density of not less than 10,000 cells per cm2 for regular passage of primary human corneal endothelial cells.

Culture of Macrophage Colony-stimulating Factor Differentiated Human Monocyte-derived Macrophages.

PubMed

Jin, Xueting; Kruth, Howard S

2016-06-30

A protocol is presented for cell culture of macrophage colony-stimulating factor (M-CSF) differentiated human monocyte-derived macrophages. For initiation of experiments, fresh or frozen monocytes are cultured in flasks for 1 week with M-CSF to induce their differentiation into macrophages. Then, the macrophages can be harvested and seeded into culture wells at required cell densities for carrying out experiments. The use of defined numbers of macrophages rather than defined numbers of monocytes to initiate macrophage cultures for experiments yields macrophage cultures in which the desired cell density can be more consistently attained. Use of cryopreserved monocytes reduces dependency on donor availability and produces more homogeneous macrophage cultures.

Enhanced ecological succession following phosphate mining. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Best, G.R.; Wallace, P.M.; Dunn, W.J.

This research addressed four components thought to be essential for enhancing establishment of native forested ecosystems on phosphate surface-mined lands. Those components were: multispecies mixture of seeds, mycorrhizal fungi symbionts, soil nutrients, and organic matter. Studies of plant community succession and mycorrhizal colonization revealed that within three years the majority of invading plants had levels of mycorrhizal infection higher than the level in mature ecosystems. Mycorrhizal inoculation greatly enhanced the growth of sweat gum (Liquidambor styraciflun), and a composite of mycorrhizal species from phosphate lands was more effective than Glomus macrocarpum, a common Florida nature mycorrhizal fungus. Soil seed banksmore » in reclaimed wetlands approached the density and diversity of seed banks in natural marshes in about five years, although the actual vegetation present was not always as diverse, dense, or well developed in the reclaimed marshes unless wetland soil had been applied. An effective method for mechanically planting several species of seeds plus mycorrhizal inoculum was the use of several row planters attached to a tractor mounted tool bar. During the initial growing season, mulch, topsoil and endomycorrhizal inoculum enhanced growth, density, and species richness of tree seedlings, while ectomycorrhizal inoculum had almost no effect, and gypsum application and phosphate-free fertilizer had negative effects.« less

Direct observation of electrothermal instability structures on intensely Ohmically heated aluminum with current flowing in a surface skin layer

NASA Astrophysics Data System (ADS)

Awe, Thomas

2017-10-01

Implosions on the Z Facility assemble high-energy-density plasmas for radiation effects and ICF experiments, but achievable stagnation pressures and temperatures are degraded by the Magneto-Rayleigh-Taylor (MRT) instability. While the beryllium liners (tubes) used in Magnetized Liner Inertial Fusion (MagLIF) experiments are astonishingly smooth (10 to 50 nm RMS roughness), they also contain distributed micron-scale resistive inclusions, and large MRT amplitudes are observed. Early in the implosion, an electrothermal instability (ETI) may provide a perturbation which greatly exceeds the initial surface roughness of the liner. Resistive inhomogeneities drive nonuniform current density and Joule heating, resulting in locally higher temperature, and thus still higher resistivity. Such unstable temperature and pressure growth produce density perturbations which seed MRT. For MagLIF liners, ETI seeding of MRT has been inferred by evaluating late-time MRT, but a direct observation of ETI is not made. ETI is directly observed on the surface of 1.0-mm-diameter solid Al rods pulsed to 1 MA in 100 ns via high resolution gated optical imaging (2 ns temporal and 3 micron spatial resolution). Aluminum 6061 alloy rods, with micron-scale resistive inclusions, consistently first demonstrate overheating from distinct, 10-micron-scale, sub-eV spots, which 5-10 ns later merge into azimuthally stretched elliptical spots and discrete strata (40-100 microns wide by 10 microns tall). Axial plasma filaments form shortly thereafter. Surface plasma can be suppressed for rods coated with dielectric, enabling extended study of the evolution of stratified ETI structures, and experimental inference of ETI growth rates. This fundamentally new and highly 3-dimensional dataset informs ETI physics, including when the ETI seed of MRT may be initiated.

Final Report for Emergency Stabilization and Rehabilitation Treatment Monitoring of the Keeney Pass, Cow Hollow, Double Mountain, and Farewell Bend Fires

USGS Publications Warehouse

Wirth, Troy A.; Pyke, David A.

2009-01-01

A strategy for monitoring post-fire seedings in the sagebrush steppe of the Intermountain West was developed and used to monitor four example fires in the Vale, Oregon District of the Bureau of Land Management (BLM). We began to develop a potential approach by (1) reviewing previous vegetation monitoring manuals produced by the Federal government to determine what techniques and approaches had been approved for use, and (2) monitoring a set of example fire rehabilitation projects from 2006 through 2008. We reviewed seven vegetation monitoring manuals approved for use by the Federal government. From these seven manuals, we derived a set of design elements appropriate for monitoring post-fire rehabilitation and stabilization projects. These design elements consisted of objectives, stratification, control plots, random sampling, data quality, and statistical analysis. Additionally, we chose three quantitative vegetation field procedures that were objective and repeatable to be used in conjunction with these six design elements. During the spring and summer of 2006 to 2008, U.S. Geological Survey personnel monitored vegetation in seven post-fire seeding treatments in four burned areas in the Vale district of the BLM in eastern Oregon. Treatments monitored included a native and non-native seeding in each of the Farewell Bend, Double Mountain, and Keeney Pass fires, and a native seeding at the Cow Hollow fire. All fires occurred in 2005. There generally was a low level of plant establishment for all seedings by 2008. The quantitative objective established by the BLM was to achieve 5 seeded grass plants/m2 by the end of 3 years as a result of the seeding. There was an estimated 3.97 and 6.28 plants/m2 in 2006 and 1.06 and 0.85 plants/m2 seeded perennial grasses in 2008 from the Keeney Pass non-native and native seeding, respectively. The Cow Hollow seeding resulted in the lowest establishment of perennial seeded grasses of the four project areas with 0.69 plants/m2 in 2006 and 0.09 plants/m2 in 2008. Density of seeded perennial grasses at the Double Mountain non-native and native seeding were 2.72 and 3.86 plants/m2 in 2006 and 0.90 and 1.74 plants/m2 in 2008, respectively. The Farewell Bend non-native seeding resulted in 5.62 plants/m2 in 2006 and 0.42 plants/m2 in 2008 while the native seeding had 2.22 seeded grass plants/m2 in 2006 and 0.44 plants/m2 by 2008. The primary reason for low level of establishment on most treatments except the Cow Hollow seeding was most likely the unfavorable timing and amount of precipitation in 2007 and 2008. Measurements of density within the first 3 years provide the best estimate of initial seeding success. Increases in cover due to the seedings were not detectable in the first 3 years following seeding in this monitoring effort. Changes in cover resulting from the treatments may be detectable in cases where the seedings were very successful in the first 3 years following seeding, but in areas with lower annual average precipitation, may not occur consistently. As a result, cover of seeded species may not be a good indication of seeding success in the early years after treatment. However, cover is useful for monitoring initial patterns of abundance of naturally recovering vegetation, exotic annual grasses and forbs, and bare ground. Cover measurements at these four sites revealed patterns common to most of the treatment areas in cover of litter, bare ground, and exotic annuals in response to drill seeding and weather patterns. There was a rapid increase in litter at all treatments after the fire. Additionally, there was less litter in treatment plots than in the control plots in 2006 probably due to the mechanical action of the seed drill. There also was a corresponding decrease in bare ground from 2006 to 2008. Initially, higher bare ground cover at treatment plots appears to be due to the mechanical action of the seed drill. Cover of annual grasses, primarily Bromus tectorum,

Hybrid Tissue Engineering Scaffolds by Combination of Three-Dimensional Printing and Cell Photoencapsulation.

PubMed

Markovic, Marica; Van Hoorick, Jasper; Hölzl, Katja; Tromayer, Maximilian; Gruber, Peter; Nürnberger, Sylvia; Dubruel, Peter; Van Vlierberghe, Sandra; Liska, Robert; Ovsianikov, Aleksandr

2015-05-01

Three-dimensional (3D) printing offers versatile possibilities for adapting the structural parameters of tissue engineering scaffolds. However, it is also essential to develop procedures allowing efficient cell seeding independent of scaffold geometry and pore size. The aim of this study was to establish a method for seeding the scaffolds using photopolymerizable cell-laden hydrogels. The latter facilitates convenient preparation, and handling of cell suspension, while distributing the hydrogel precursor throughout the pores, before it is cross-linked with light. In addition, encapsulation of living cells within hydrogels can produce constructs with high initial cell loading and intimate cell-matrix contact, similar to that of the natural extra-cellular matrix (ECM). Three dimensional scaffolds were produced from poly(lactic) acid (PLA) by means of fused deposition modeling. A solution of methacrylamide-modified gelatin (Gel-MOD) in cell culture medium containing photoinitiator Li-TPO-L was used as a hydrogel precursor. Being an enzymatically degradable derivative of natural collagen, gelatin-based matrices are biomimetic and potentially support the process of cell-induced remodeling. Preosteoblast cells MC3T3-E1 at a density of 10 × 10 6 cells per 1 mL were used for testing the seeding procedure and cell proliferation studies. Obtained results indicate that produced constructs support cell survival and proliferation over extended duration of our experiment. The established two-step approach for scaffold seeding with the cells is simple, rapid, and is shown to be highly reproducible. Furthermore, it enables precise control of the initial cell density, while yielding their uniform distribution throughout the scaffold. Such hybrid tissue engineering constructs merge the advantages of rigid 3D printed constructs with the soft hydrogel matrix, potentially mimicking the process of ECM remodeling.

Optimizing Hill Seeding Density for High-Yielding Hybrid Rice in a Single Rice Cropping System in South China

PubMed Central

Wang, Danying; Chen, Song; Wang, Zaiman; Ji, Chenglin; Xu, Chunmei; Zhang, Xiufu; Chauhan, Bhagirath Singh

2014-01-01

Mechanical hill direct seeding of hybrid rice could be the way to solve the problems of high seeding rates and uneven plant establishment now faced in direct seeded rice; however, it is not clear what the optimum hill seeding density should be for high-yielding hybrid rice in the single-season rice production system. Experiments were conducted in 2010 and 2011 to determine the effects of hill seeding density (25 cm×15 cm, 25 cm×17 cm, 25 cm×19 cm, 25 cm×21 cm, and 25 cm×23 cm; three to five seeds per hill) on plant growth and grain yield of a hybrid variety, Nei2you6, in two fields with different fertility (soil fertility 1 and 2). In addition, in 2012 and 2013, comparisons among mechanical hill seeding, broadcasting, and transplanting were conducted with three hybrid varieties to evaluate the optimum seeding density. With increases in seeding spacing from 25 cm×15 cm to 25 cm×23 cm, productive tillers per hill increased by 34.2% and 50.0% in soil fertility 1 and 2. Panicles per m2 declined with increases in seeding spacing in soil fertility 1. In soil fertility 2, no difference in panicles per m2 was found at spacing ranging from 25 cm×17 cm to 25 cm×23 cm, while decreases in the area of the top three leaves and aboveground dry weight per shoot at flowering were observed. Grain yield was the maximum at 25 cm×17 cm spacing in both soil fertility fields. Our results suggest that a seeding density of 25 cm×17 cm was suitable for high-yielding hybrid rice. These results were verified through on-farm demonstration experiments, in which mechanical hill-seeded rice at this density had equal or higher grain yield than transplanted rice. PMID:25290342

A model for the formation of the Local Group

NASA Technical Reports Server (NTRS)

Peebles, P. J. E.; Melott, A. L.; Holmes, M. R.; Jiang, L. R.

1989-01-01

Observational tests of a model for the formation of the Local Group are presented and analyzed in which the mass concentration grows by gravitational accretion of local-pressure matter onto two seed masses in an otherwise homogeneous initial mass distribution. The evolution of the mass distribution is studied in an analytic approximation and a numerical computation. The initial seed mass and separation are adjusted to produce the observed present separation and relative velocity of the Andromeda Nebula and the Galaxy. If H(0) is adjusted to about 80 km/s/Mpc with density parameter Omega = 1, then the model gives a good fit to the motions of the outer members of the Local Group. The same model gives particle orbits at radius of about 100 kpc that reasonably approximate the observed distribution of redshifts of the Galactic satellites.

Influence of initial seed distribution on the pattern formation of the phase field crystals

NASA Astrophysics Data System (ADS)

Starodumov, Ilya; Galenko, Peter; Kropotin, Nikolai; Alexandrov, Dmitri V.

2017-11-01

The process of crystal growth can be expressed as a transition of atomic structure to a finally stable state or to a metastable state. In the Phase Field Crystal Model (PFC-model) these states are described by regular distributions of the atomic density. Getting the system into any metastable condition may be caused by the peculiarities of the computational domain, initial and boundary conditions. However, an important factor in the formation of the crystal structure can be the initial disturbance. In the report we show how different types of initial disturbance can change the finally stable state of crystal structure in equilibrium.

Small-mammal seed predation limits the recruitment and abundance of two perennial grassland forbs.

PubMed

Bricker, Mary; Pearson, Dean; Maron, John

2010-01-01

Although post-dispersal seed predators are common and often reduce seed density, their influence on plant population abundance remains unclear. On the one hand, increasing evidence suggests that many plant populations are seed limited, implying that seed predators could reduce plant abundance. On the other hand,.it is generally uncertain whether the magnitude of seed limitation imposed by granivores is strong enough to overcome density-dependent processes that could compensate for seed loss at later stages. We examined the impact of seed predation by small mammals, primarily deer mice (Peromyscus maniculatus), on seedling recruitment and subsequent plant establishment of two perennial grassland forbs in western Montana, USA: Lupinus sericeus (Fabaceae) and Lithospermum ruderale (Boraginaceae). The experiment combined graded densities of seed addition for each species with a small-mammal exclusion treatment. Seedling recruitment and plant establishment were monitored in the experimental plots for up to three years. For both species, small-mammal exclusion increased the total number of seedlings that emerged, and these effects were still significant three years after seed addition, resulting in greater numbers of established plants inside exclosures than in control plots. We also found evidence of seed limitation, with increasing density of seeds added leading to increased numbers of seedlings. Results from seed addition and small-mammal exclusion experiments in later years also revealed significant impacts of small mammals on seedling emergence. These results suggest that granivores can have potentially important impacts in limiting forb abundance in grasslands communities.

Influence of richness and seeding density on invasion resistance in experimental tallgrass prairie restorations

USGS Publications Warehouse

Nemec, Kristine T.; Allen, Craig R.; Helzer, Christopher J.; Wedin, David A.

2013-01-01

In recent years, agricultural producers and non-governmental organizations and agencies have restored thousands of hectares of cropland to grassland in the Great Plains of the United States. However, little is known about the relationships between richness and seeding density in these restorations and resistance to invasive plant species. We assessed the effects of richness and seeding density on resistance to invasive and other unseeded plant species in experimental tallgrass prairie plots in central Nebraska. In 2006, twenty-four 55 m × 55 m plots were planted with six replicates in each of four treatments: high richness (97 species typically planted by The Nature Conservancy), at low and high seeding densities, and low richness (15 species representing a typical Conservation Reserve Program mix, CP25), at low and high seeding densities. There was a significant negative relationship between richness and basal cover of unseeded perennial forbs/legumes and unseeded perennial/annual grasses, abundance of bull thistle (Cirsium vulgare), and the number of inflorescences removed from smooth brome (Bromus inermis) transplants. Invasion resistance may have been higher in the high richness treatments because of the characteristics of the dominant species in these plots or because of greater interspecific competition for limiting resources among forbs/legumes with neighboring plants belonging to the same functional group. Seeding density was not important in affecting invasion resistance, except in the cover of unseeded grasses. Increasing seed mix richness may be more effective than increasing the seeding density for decreasing invasion by unseeded perennial species, bull thistle, and smooth brome.

93 Years of stand density and land-use legacy research at the Coulter Ranch Study Site

Treesearch

Andrew J. Sanchez Meador; Margaret M. Moore

2008-01-01

In 1913, the Fort Valley Experimental Forest initiated an unprecedented case-study experiment to determine the effects of harvesting methods on tree regeneration and growth on a ponderosa pine-Gambel oak forest at Coulter Ranch in northern Arizona. The harvesting methods examined were seed-tree, group selection, and light selection. In addition, the effects of...

Gravitational Wave Signals from the First Massive Black Hole Seeds

NASA Astrophysics Data System (ADS)

Hartwig, Tilman; Agarwal, Bhaskar; Regan, John A.

2018-05-01

Recent numerical simulations reveal that the isothermal collapse of pristine gas in atomic cooling haloes may result in stellar binaries of supermassive stars with M* ≳ 104M⊙. For the first time, we compute the in-situ merger rate for such massive black hole remnants by combining their abundance and multiplicity estimates. For black holes with initial masses in the range 104 - 6M⊙ merging at redshifts z ≳ 15 our optimistic model predicts that LISA should be able to detect 0.6 mergers per year. This rate of detection can be attributed, without confusion, to the in-situ mergers of seeds from the collapse of very massive stars. Equally, in the case where LISA observes no mergers from heavy seeds at z ≳ 15 we can constrain the combined number density, multiplicity, and coalesence times of these high-redshift systems. This letter proposes gravitational wave signatures as a means to constrain theoretical models and processes that govern the abundance of massive black hole seeds in the early Universe.

Timing of seed dispersal generates a bimodal seed bank depth distribution

USGS Publications Warehouse

Espinar, J.L.; Thompson, K.; Garcia, L.V.

2005-01-01

The density of soil seed banks is normally highest at the soil surface and declines monotonically with depth. Sometimes, for a variety of reasons, peak density occurs below the surface but, except in severely disturbed soils, it is generally true that deeper seeds are older. In seasonally dry habitats that develop deep soil cracks during the dry season, it is possible that some seeds fall down cracks and rapidly become deeply buried. We investigated this possibility for three dominant clonal perennials (Scirpus maritimus, S. litoralis, and Juncus subulatus) in the Don??ana salt marsh, a nontidal marsh with a Mediterranean climate located in southwest Spain. Two species, which shed most of their seed during the dry season and have seeds with low buoyancy, had bimodal viable seed depth distributions, with peak densities at the surface and at 16-20 cm. A third species, which shed most seeds after soil cracks had closed and had seeds with high buoyancy, had viable seeds only in surface soil. Bimodal seed bank depth distributions may be relatively common in seasonally dry habitats with fine-textured soils, but their ecological significance has not been investigated.

Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires.

PubMed

Hardiman, Nigel; Dietz, Kristina Charlotte; Bride, Ian; Passfield, Louis

2017-01-01

Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.

Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires

NASA Astrophysics Data System (ADS)

Hardiman, Nigel; Dietz, Kristina Charlotte; Bride, Ian; Passfield, Louis

2017-01-01

Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.

Numerical analyses of baseline JT-60SA design concepts with the COREDIV code

NASA Astrophysics Data System (ADS)

Zagórski, R.; Gałązka, K.; Ivanova-Stanik, I.; Stępniewski, W.; Garzotti, L.; Giruzzi, G.; Neu, R.; Romanelli, M.

2017-06-01

JT-60SA reference design scenarios at high (#3) and low (#2) density have been analyzed with the help of the self-consistent COREDIV code. Simulations results for a standard C wall and full W wall have been compared in terms of the influence of impurities, both intrinsic (C, W) and seeded (N, Ar, Ne, Kr), on the radiation losses and plasma parameters. For scenario #3 in a C environment, the regime of detachment on divertor plates can be achieved with N or Ne seeding, whereas for the low density and high power scenario (#2), the C and seeding impurity radiation does not effectively reduce power to the targets. In this case, only an increase of either average density or edge density together with Kr seeding might help to develop conditions with strong radiation losses and semi-detached conditions in the divertor. The calculations show that, in the case of a W divertor, the power load to the plate is mitigated by seeding and the central plasma dilution is smaller compared to the C divertor. For the high density case (#3) with Ne seeding, operation in full detachment mode is predicted. Ar seems to be an optimal choice for the low-density high-power scenario #2, showing a wide operating window, whereas Ne leads to high plasma dilution at high seeding levels albeit not achieving semi-detached conditions in the divertor.

[Characteristics of soil seed banks in logging gaps of forests at different succession stages in Changbai Mountains].

PubMed

Zhang, Zhi-Ting; Song, Xin-Zhang; Xiao, Wen-Fa; Gao, Bao-Jia; Guo, Zhong-Ling

2009-06-01

An investigation was made on the soil seed banks in the logging gaps of Populus davidiana--Betula platyphylla secondary forest, secondary broad-leaved forest, and broad-leaved Korean pine mixed forest at their different succession stages in Changbai Mountains. Among the test forests, secondary broad-leaved forest had the highest individual density (652 ind x m(-2)) in its soil seed bank. With the succession of forest community, the diversity and uniformity of soil seed bank increased, but the dominance decreased. The seed density of climax species such as Pinus koraiensis, Abies nephrolepis, and Acer mono increased, whereas that of Maackia amurensis and Fraxinus mandshurica decreased. Moreover, the similarity in species composition between soil seed bank and the seedlings within logging gaps became higher. The individual density and similarity between soil seed bank and the seedlings in non-logging gaps were similar to those in logging gaps. All of these indicated that soil seed bank provided rich seed resources for forest recovery and succession, and the influence of soil seed bank on seedlings regeneration increased with the succession.

Effect of Seed Density on Splash Cup Seed Dispersal

NASA Astrophysics Data System (ADS)

Wigger, Patrick; Pepper, Rachel

2017-11-01

Splash cup plants are plants that utilize a small, mm-sized cup filled with seeds as a method of seed dispersal. The cup uses kinetic energy of an incident raindrop in order to project the seeds away from the plant up to 1 meter. The dispersal distance is important to ensure the offspring are not clustered too tightly to the parent plant. It has previously been found that a cup angle of 40 degrees to the horizontal is optimal for maximum dispersal of water from cups with no seeds. In this study we examine if the 40 degree cup is optimal for cups containing seeds with varying densities. We released uniform water drops above 5.0 mm 3D printed models of splash cups, using 1.0 mm plastic and glass microspheres of varying densities to simulate seeds. We observed the dispersal characteristics of each bead type by measuring the final seed locations after each splash, and by recording high speed video to determine the angle and velocity of the seeds as they exited the cup.

Consumers limit the abundance and dynamics of a perennial shrub with a seed bank

USGS Publications Warehouse

Kauffman, M.J.; Maron, J.L.

2006-01-01

For nearly 30 years, ecologists have argued that predators of seeds and seedlings seldom have population-level effects on plants with persistent seed banks and density-dependent seedling survival. We parameterized stage-based population models that incorporated density dependence and seed dormancy with data from a 5.5-year experiment that quantified how granivorous mice and herbivorous voles influence bush lupine (Lupinus arboreus) demography. We asked how seed dormancy and density-dependent seedling survival mediate the impacts of these consumers in dune and grassland habitats. In dune habitat, mice reduced analytical ?? (the intrinsic rate of population growth) by 39%, the equilibrium number of above-ground plants by 90%, and the seed bank by 98%; voles had minimal effects. In adjacent grasslands, mice had minimal effects, but seedling herbivory by voles reduced analytical ?? by 15% and reduced both the equilibrium number of aboveground plants and dormant seeds by 63%. A bootstrap analysis demonstrated that these consumer effects were robust to parameter uncertainty. Our results demonstrate that the quantitative strengths of seed dormancy and density-dependent seedling survival-not their mere existence-critically mediate consumer effects. This study suggests that plant population dynamics and distribution may be more strongly influenced by consumers of seeds and seedlings than is currently recognized. ?? 2006 by The University of Chicago.

A model of the relationship between weedy rice seed-bank dynamics and rice-crop infestation and damage in Jiangsu Province, China.

PubMed

Zhang, Zheng; Dai, Weimin; Song, Xiaoling; Qiang, Sheng

2014-05-01

A heavy infestation of weedy rice leading to no harvested rice has never been predicted in China due to a lack of knowledge about the weedy rice seed bank. We studied the seed-bank dynamics of weedy rice for three consecutive years and analyzed the relationship between seed-bank density and population density in order to predict future weedy rice infestations of direct-seeded rice at six sites along the Yangtze River in Jiangsu Province, China. The seed-bank density of weedy rice in all six sites displayed an increasing trend with seasonal fluctuations. Weedy rice seeds found in the 0-10 cm soil layer contributed most to seedling emergence. An exponential curve expressed the relationship between cultivated rice yield loss and adult weedy rice density. Based on data collected during the weedy rice life-cycle, a semi-empirical mathematic model was developed that fits well with the experimental data in a way that could be used to predict seed-bank dynamics. By integrating the semi-empirical model and the exponential curve, weedy rice infestation levels and crop losses can be predicted based on the seed-bank dynamics so that a practical control can be adopted before rice planting. © 2013 Society of Chemical Industry.

Efficacy of Selected Insecticides Applied to Hybrid Rice Seed

PubMed Central

Adams, A.; Gore, J.; Musser, F.; Cook, D.; Walker, T.; Dobbins, C.

2016-01-01

Hybrid rice and insecticide seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel, have altered the landscape of rice production. The effect of reduced seeding rates on seed treatment efficacy in hybrid rice has not been studied. During 2011 and 2012, an experiment was conducted at seven locations to determine the relationship between low seeding rates used in hybrid rice and efficacy of selected insecticidal seed treatments as measured by rice water weevil densities and yield. Labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin were compared with higher rates of these products to determine if labeled rates provide an acceptable level of control of the rice water weevil. Study locations were divided into low, moderate, and high groups based on rice water weevil larval densities. All seed treatments and seed treatment rates reduced rice water weevil densities. However, there was no observed yield or economic benefit from the use of an insecticidal seed treatment in areas of low pressure. Differences in yield were observed among seed treatments and seed treatment rates in moderate and high pressure locations, and all seed treatments yielded better than the untreated plots, but these differences were not always economical. All seed treatments showed an economic advantage in areas of high weevil pressure, and there were no differences among seed treatment products or rates, suggesting that currently labeled seed treatment rates in hybrid rice are effective for rice water weevil management. PMID:26537671

93 years of stand density and land-use legacy research at the Coulter Ranch Study Site (P-53)

Treesearch

Andrew J. Sanchez Meador; Margaret M. Moore

2008-01-01

In 1913, the Fort Valley Experimental Forest initiated an unprecedented case-study experiment to determine the effects of harvesting methods on tree regeneration and growth on a ponderosa pine-Gambel oak forest at Coulter Ranch in northern Arizona. The harvesting methods examined were seed-tree, group selection, and light selection. In addition, the effects of...

Grazing disturbance increases transient but decreases persistent soil seed bank.

PubMed

Ma, Miaojun; Walck, Jeffrey L; Ma, Zhen; Wang, Lipei; Du, Guozhen

2018-04-30

Very few studies have examined whether the impacts of grazing disturbance on soil seed banks occur directly or indirectly through aboveground vegetation and soil properties. The potential role of the seed bank in alpine wetland restoration is also unknown. We used SEM (structural equation modeling) to explore the direct effect of grazing disturbance on the seed bank and the indirect effect through aboveground vegetation and soil properties. We also studied the role of the seed bank on the restoration potential in wetlands with various grazing intensities: low (fenced, winter grazed only), medium (seasonally grazed), and high (whole-year grazed). For the seed bank, species richness and density per plot showed no difference among grazing intensities for each depth (0-5, 5-10, 10-15 cm) and for the whole depth (0-15 cm) in spring and summer. There was no direct effect of grazing disturbance on seed bank richness and density both in spring and summer, and also no indirect effect on the seed bank through its direct effect on vegetation richness and abundance. Grazing disturbance indirectly increased spring seed bank density but decreased summer seed bank density through its direct effect (negative correlation) on soil moisture and total nitrogen and its indirect effect on vegetation abundance. Species composition of the vegetation changed with grazing regime, but that of the seed bank did not. An increased trend of similarity between the seed bank and aboveground vegetation with increased grazing disturbance was found in the shallow depth and in the whole depth only in spring. Although there was almost no change in seed bank size with grazing intensities, grazing disturbance increased the quantity of transient seeds but decreased persistent seeds. Persistent seeds stored in the soil could play a crucial role in vegetation regeneration and in restoration of degraded wetland ecosystems. The seed bank should be an integral part of alpine wetland restoration programs. © 2018 by the Ecological Society of America.

Tailoring the nanoscale morphology of HKUST-1 thin films via codeposition and seeded growth

PubMed Central

Brower, Landon J; Gentry, Lauren K; Napier, Amanda L

2017-01-01

Integration of surface-anchored metal-organic frameworks (surMOFs) within hierarchical architectures is necessary for potential sensing, electronic, optical, or separation applications. It is important to understand the fundamentals of film formation for these surMOFs in order to develop strategies for their incorporation with nanoscale control over lateral and vertical dimensions. This research identified processing parameters to control the film morphology for surMOFs of HKUST-1 fabricated by codeposition and seeded deposition. Time and temperature were investigated to observe film formation, to control film thickness, and to tune morphology. Film thickness was investigated by ellipsometry, while film structure and film roughness were characterized by atomic force microscopy. Films formed via codeposition resulted in nanocrystallites anchored to the gold substrate. A dynamic process at the interface was observed with a low density of large particulates (above 100 nm) initially forming on the substrate; and over time these particulates were slowly replaced by the prevalence of smaller crystallites (ca. 10 nm) covering the substrate at a high density. Elevated temperature was found to expedite the growth process to obtain the full range of surface morphologies with reasonable processing times. Seed crystals formed by the codeposition method were stable and nucleated growth throughout a subsequent layer-by-layer deposition process. These seed crystals templated the final film structure and tailor the features in lateral and vertical directions. Using codeposition and seeded growth, different surface morphologies with controllable nanoscale dimensions can be designed and fabricated for integration of MOF systems directly into device architectures and sensor platforms. PMID:29181287

Tailoring the nanoscale morphology of HKUST-1 thin films via codeposition and seeded growth.

PubMed

Brower, Landon J; Gentry, Lauren K; Napier, Amanda L; Anderson, Mary E

2017-01-01

Integration of surface-anchored metal-organic frameworks (surMOFs) within hierarchical architectures is necessary for potential sensing, electronic, optical, or separation applications. It is important to understand the fundamentals of film formation for these surMOFs in order to develop strategies for their incorporation with nanoscale control over lateral and vertical dimensions. This research identified processing parameters to control the film morphology for surMOFs of HKUST-1 fabricated by codeposition and seeded deposition. Time and temperature were investigated to observe film formation, to control film thickness, and to tune morphology. Film thickness was investigated by ellipsometry, while film structure and film roughness were characterized by atomic force microscopy. Films formed via codeposition resulted in nanocrystallites anchored to the gold substrate. A dynamic process at the interface was observed with a low density of large particulates (above 100 nm) initially forming on the substrate; and over time these particulates were slowly replaced by the prevalence of smaller crystallites (ca. 10 nm) covering the substrate at a high density. Elevated temperature was found to expedite the growth process to obtain the full range of surface morphologies with reasonable processing times. Seed crystals formed by the codeposition method were stable and nucleated growth throughout a subsequent layer-by-layer deposition process. These seed crystals templated the final film structure and tailor the features in lateral and vertical directions. Using codeposition and seeded growth, different surface morphologies with controllable nanoscale dimensions can be designed and fabricated for integration of MOF systems directly into device architectures and sensor platforms.

Distinguishing Raman from strongly coupled Brillouin amplification for short pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, Qing; Barth, Ido; Edwards, Matthew R.

2016-05-15

Plasma-based amplification by strongly coupled Brillouin scattering has recently been suggested for the compression of a short seed laser to ultrahigh intensities in sub-quarter-critical-density plasmas. However, by employing detailed spectral analysis of particle-in-cell simulations in the same parameter regime, we demonstrate that, in fact, Raman backscattering amplification is responsible for the growth and compression of the high-intensity, leading spike, where most of the energy compression occurs, while the ion mode only affects the low-intensity tail of the amplified pulse. The critical role of the initial seed shape is identified. A number of subtleties in the numerical simulations are also pointedmore » out.« less

Development of SiC Large Tapered Crystal Growth

NASA Technical Reports Server (NTRS)

Neudeck, Phil

2011-01-01

Research Focus Area: Power Electronics, Temperature Tolerant Devices. Demonstrate initial feasibility of totally new "Large Tapered Crystal" (LTC) process for growing vastly improved large-diameter wide-band gap wafers. Addresses Targets: The goal of this research is to experimentally investigate and demonstrate feasibility of the key unproven LTC growth processes in SiC. Laser-assisted growth of long SiC fiber seeds. Radial epitaxial growth enlargement of seeds into large SiC boules. Uniqueness and Impacts open a new technology path to large-diameter SiC and GaN wafers with 1000-fold defect density improvement at 2-4 fold lower cost. Leapfrog improvement in wide band gap power device capability and cost.

Statistics of primordial density perturbations from discrete seed masses

NASA Technical Reports Server (NTRS)

Scherrer, Robert J.; Bertschinger, Edmund

1991-01-01

The statistics of density perturbations for general distributions of seed masses with arbitrary matter accretion is examined. Formal expressions for the power spectrum, the N-point correlation functions, and the density distribution function are derived. These results are applied to the case of uncorrelated seed masses, and power spectra are derived for accretion of both hot and cold dark matter plus baryons. The reduced moments (cumulants) of the density distribution are computed and used to obtain a series expansion for the density distribution function. Analytic results are obtained for the density distribution function in the case of a distribution of seed masses with a spherical top-hat accretion pattern. More generally, the formalism makes it possible to give a complete characterization of the statistical properties of any random field generated from a discrete linear superposition of kernels. In particular, the results can be applied to density fields derived by smoothing a discrete set of points with a window function.

Responses of predatory invertebrates to seeding density and plant species richness in experimental tallgrass prairie restorations

USGS Publications Warehouse

Nemec, Kristine T.; Allen, Craig R.; Danielson, Stephen D.; Helzer, Christopher J.

2014-01-01

In recent decades, agricultural producers and non-governmental organizations have restored thousands of hectares of former cropland in the central United States with native grasses and forbs. However, the ability of these grassland restorations to attract predatory invertebrates has not been well documented, even though predators provide an important ecosystem service to agricultural producers by naturally regulating herbivores. This study assessed the effects of plant richness and seeding density on the richness and abundance of surface-dwelling (ants, ground beetles, and spiders) and aboveground (ladybird beetles) predatory invertebrates. In the spring of 2006, twenty-four 55 m × 55 m-plots were planted to six replicates in each of four treatments: high richness (97 species typically planted by The Nature Conservancy), at low and high seeding densities, and low richness (15 species representing a typical Natural Resources Conservation Service Conservation Reserve Program mix, CP25), at low and high seeding densities. Ants, ground beetles, and spiders were sampled using pitfall traps and ladybird beetles were sampled using sweep netting in 2007–2009. The abundance of ants, ground beetles, and spiders showed no response to seed mix richness or seeding density but there was a significant positive effect of richness on ladybird beetle abundance. Seeding density had a significant positive effect on ground beetle and spider species richness and Shannon–Weaver diversity. These results may be related to differences in the plant species composition and relative amount of grass basal cover among the treatments rather than richness.

A strong conditional mutualism limits and enhances seed dispersal and germination of a tropical palm

USGS Publications Warehouse

Klinger, R.; Rejmanek, M.

2010-01-01

Seed predation and seed dispersal can have strong effects on early life history stages of plants. These processes have often been studied as individual effects, but the degree to which their relative importance co-varies with seed predator abundance and how this influences seed germination rates is poorly understood. Therefore, we used a combination of observations and field experiments to determine the degree to which germination rates of the palm Astrocaryum mexicanum varied with abundance of a small mammal seed predator/disperser, Heteromysdesmarestianus, in a lowland tropical forest. Patterns of abundance of the two species were strongly related; density of H. desmarestianus was low in sites with low density of A. mexicanum and vice versa. Rates of predation and dispersal of A. mexicanum seeds depended on abundance of H. desmarestianus; sites with high densities of H. desmarestianus had the highest rates of seed predation and lowest rates of seed germination, but a greater total number of seeds were dispersed and there was greater density of seedlings, saplings, and adults of A. mexicanum in these sites. When abundance of H. desmarestianus was experimentally reduced, rates of seed predation decreased, but so did dispersal of A. mexicanum seeds. Critically, rates of germination of dispersed seeds were 5 times greater than undispersed seeds. The results suggest that the relationship between A. mexicanum and H. desmarestianus is a conditional mutualism that results in a strong local effect on the abundance of each species. However, the magnitude and direction of these effects are determined by the relative strength of opposing, but related, mechanisms. A. mexicanum nuts provide H. desmarestianus with a critical food resource, and while seed predation on A. mexicanum nuts by H. desmarestianus is very intense, A. mexicanum ultimately benefits because of the relatively high germination rates of its seeds that are dispersed by H. desmarestianus. ?? The Author(s) 2010.

Soil seed bank recovery occurs more rapidly than expected in semi-arid Mediterranean gypsum vegetation.

PubMed

Olano, J M; Caballero, I; Escudero, A

2012-01-01

Seed banks are critical in arid ecosystems and ensure the persistence of species. Despite the importance of seed banks, knowledge about their formation and the extent to which a seed bank can recover after severe perturbation remains scarce. If undisturbed, soil seed banks reflect a long vegetation history; therefore, we would expect that new soil seed banks and those of undisturbed soils require long periods to become similar with respect to both density and composition. In contrast, if soil seed banks are only a short- to mid-term reservoir in which long-term accumulation constitutes only a tiny fraction, they will recover rapidly from the vegetation. To shed light on this question, we evaluated seed bank formation in a semi-arid gypsum community. Soils from 300 plots were replaced with sterilized soil in an undisturbed semi-arid Mediterranean community. Seasonal changes in seed bank density and composition were monitored for 3 years by comparing paired sterilized and control soil samples at each plot. Differences in seed bank density between sterilized and control soil disappeared after 18 months. The composition of sterilized seed banks was correlated with that of the control plots from the first sampling date, and both were highly correlated with vegetation. Nearly 24 % of the seed bank density could be attributed to secondary dispersal. Most seeds died before emergence (66·41-71·33 %), whereas the rest either emerged (14·08-15·48 %) or persisted in the soil (14·59-18·11 %). Seed banks can recover very rapidly even under the limiting and stressful conditions of semi-arid environments. This recovery is based mainly on the seed rain at small scales together with secondary dispersal from intact seed banks in the vicinity. These results emphasize the relevance of processes occurring on short spatial scales in determining community structure.

The accumulation of genetic diversity within a canopy-stored seed bank.

PubMed

Ayre, David; O'Brien, Eleanor; Ottewell, Kym; Whelan, Rob

2010-07-01

Many plants regenerate after fire from a canopy-stored seed bank, in which seed are housed in fire resistant confructescences (cones) that remain on maternal plants. This strategy would be favoured if plants accumulate a sufficiently large and genetically diverse seed bank during interfire intervals. We use a 16-year demographic study and surveys of microsatellite variation to quantify and explain the rate of accumulation of genetic diversity within the canopy seed bank of the shrub Banksia spinulosa. Flowering and fruit set were highly variable. An initial sample in 1991 of 354 reproductively mature plants generated 426 cones over 16 years, of which only 55 cones from 40 maternal plants persisted until 2005. By genotyping seed from these 55 cones we demonstrated that genetic diversity accumulated rapidly within the seed bank. Resampling revealed that diversity was determined by the number, not the age, of cones. Cones were widely distributed among plants, outcrossing rates were high (mean t(m) = 1.00 +/- 0.04) and biparental inbreeding low. Adults displayed little evidence of isolation by distance and the genotypic diversity of seed cohorts was independent of the density of neighbouring potential sires. We therefore estimate that within at least 13 individual years the number of cones produced per year (14-63) would have contained 100% of the adult genetic diversity. We conclude that a highly outcrossed mating system and relatively widespread pollen dispersal ensure the rapid development of a genetically diverse and spatially and temporally homogeneous seed bank.

Waterbird communities and seed biomass in managed and reference-restored wetlands in the Mississippi Alluvial Valley

USGS Publications Warehouse

Tapp, Jessica L.; Weegman, Matthew M.; Webb, Elisabeth B.; Kaminski, Richard M.; Davis, J. Brian

2018-01-01

The Natural Resources Conservation Service (NRCS) commenced the Migratory Bird Habitat Initiative (MBHI) in summer 2010 after the April 2010 Deepwater Horizon oil spill in the Gulf of Mexico. The MBHI enrolled in the program 193,000 ha of private wet- and cropland inland from potential oil-impaired wetlands. We evaluated waterfowl and other waterbird use and potential seed/tuber food resources in NRCS Wetland Reserve Program easement wetlands managed via MBHI funding and associated reference wetlands in the Mississippi Alluvial Valley of Arkansas, Louisiana, Mississippi, and Missouri. In Louisiana and Mississippi, nearly three times more dabbling ducks and all ducks combined were observed on managed than reference wetlands. Shorebirds and waterbirds other than waterfowl were nearly twice as abundant on managed than referenced wetlands. In Arkansas and Missouri, managed wetlands had over twice more dabbling ducks and nearly twice as many duck species than reference wetlands. Wetlands managed via MBHI in Mississippi and Louisiana contained ≥1.3 times more seed and tuber biomass known to be consumed by waterfowl than reference wetlands. Seed and tuber resources did not differ between wetlands in Arkansas and Missouri. While other studies have documented greater waterbird densities on actively than nonmanaged wetlands, our results highlighted the potential for initiatives focused on managing conservation easements to increase waterbird use and energetic carrying capacity of restored wetlands for waterbirds.

Use of Irrigation to Extend the Seeding Window for Final Reclamation at Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

TRW Environmental Safety

2000-08-01

The U.S. Department of Energy has implemented a program to investigate the feasibility of various techniques for reclaiming lands disturbed during site characterization at Yucca Mountain. As part of this program, two studies were conducted in 1997 to assess the effects of combinations of seeding date (date that seeds are planted) and supplemental irrigation on densities of native plant species at Yucca Mountain. Study objectives were to (1) determine whether the traditional seeding window (October-December) could be extended through combinations of seeding date and irrigation date, (2) determine which combination of seeding date and irrigation was most successful, and (3)more » assess the effects of irrigation versus natural precipitation on seedling establishment. In the first study, a multi-species seed mix of 16 native species was sown into plots on four dates (12/96, 2/97, 3/97, and 4/97). Irrigation treatments were control (no irrigation) or addition of 80 mm of supplemental water applied over a one month period. Plant densities were sampled in August and again in October, 1997. In the second study, Larrea tridentata and Lycium andersonii, two species that are common at Yucca Mountain, but difficult to establish from seed, were sown together into plots in January and August, 1997. Half the plots were irrigated with approximately 250 mm of water between August 18 and September 11, while the remaining plots received no irrigation (control). Plant densities were sampled in October, 1997. The August census for the multi-species mix study showed irrigated plots that were sown in February, March and April had higher plant densities and more species than plots that were not irrigated. Irrigation had no effect on plant densities on plots that were seeded in December. Plots were used again in October following 18 mm of precipitation in September. Densities of three species, Ambrosia dumosa, Hymenoclea salsola, and L. tridentata, (warm-season species) were lower on irrigated plots sown in December, February, and March, and showed no response to irrigation on plots sown in April. Therefore, early spring irrigation did not facilitate establishment of warm-season species. These results suggest that these species are dependent upon precipitation while temperatures are warm in late summer or fall. However, control plots that were seeded in December had acceptable densities of these species. A more practical approach might be to avoid irrigation costs by seeding in December and waiting for fall precipitation. The remaining species (cool-season species) showed an opposite response to supplemental water with greater densities on irrigated plots sown in February, March, and April, and no response to irrigation on plots sown in December. While these results show that irrigation can extend the seeding window for cool-season species should it be necessary, it was also apparent that if seeds are sown by late December, irrigation is not necessary to achieve acceptable plant densities.« less

The Global Statistical Response of the Outer Radiation Belt During Geomagnetic Storms

NASA Astrophysics Data System (ADS)

Murphy, K. R.; Watt, C. E. J.; Mann, I. R.; Jonathan Rae, I.; Sibeck, D. G.; Boyd, A. J.; Forsyth, C. F.; Turner, D. L.; Claudepierre, S. G.; Baker, D. N.; Spence, H. E.; Reeves, G. D.; Blake, J. B.; Fennell, J.

2018-05-01

Using the total radiation belt electron content calculated from Van Allen Probe phase space density, the time-dependent and global response of the outer radiation belt during storms is statistically studied. Using phase space density reduces the impacts of adiabatic changes in the main phase, allowing a separation of adiabatic and nonadiabatic effects and revealing a clear modality and repeatable sequence of events in storm time radiation belt electron dynamics. This sequence exhibits an important first adiabatic invariant (μ)-dependent behavior in the seed (150 MeV/G), relativistic (1,000 MeV/G), and ultrarelativistic (4,000 MeV/G) populations. The outer radiation belt statistically shows an initial phase dominated by loss followed by a second phase of rapid acceleration, while the seed population shows little loss and immediate enhancement. The time sequence of the transition to the acceleration is also strongly μ dependent and occurs at low μ first, appearing to be repeatable from storm to storm.

Spatial variation in reproductive effort of a southern Australian seagrass.

PubMed

Smith, Timothy M; York, Paul H; Macreadie, Peter I; Keough, Michael J; Ross, D Jeff; Sherman, Craig D H

2016-09-01

In marine environments characterised by habitat-forming plants, the relative allocation of resources into vegetative growth and flowering is an important indicator of plant condition and hence ecosystem health. In addition, the production and abundance of seeds can give clues to local resilience. Flowering density, seed bank, biomass and epiphyte levels were recorded for the temperate seagrass Zostera nigricaulis in Port Phillip Bay, south east Australia at 14 sites chosen to represent several regions with different physicochemical conditions. Strong regional differences were found within the large bay. Spathe and seed density were very low in the north of the bay (3 sites), low in the centre of the bay (2 sites) intermediate in the Outer Geelong Arm (2 sites), high in Swan Bay (2 sites) and very high in the Inner Geelong Arm (3 sites). In the south (2 sites) seed density was low and spathe density was high. These regional patterns were largely consistent for the 5 sites sampled over the three year period. Timing of flowering was consistent across sites, occurring from August until December with peak production in October, except during the third year of monitoring when overall densities were lower and peaked in November. Seagrass biomass, epiphyte load, canopy height and stem density showed few consistent spatial and temporal patterns. Variation in spathe and seed density and morphology across Port Phillip Bay reflects varying environmental conditions and suggests that northern sites may be restricted in their ability to recover from disturbance through sexual reproduction. In contrast, sites in the west and south of the bay have greater potential to recover from disturbances due to a larger seed bank and these sites could act as source populations for sites where seed production is low. Copyright © 2016 Elsevier Ltd. All rights reserved.

The numerical and functional responses of a granivorous rodent and the fate of Neotropical tree seeds

USGS Publications Warehouse

Klinger, R.; Rejmanek, M.

2009-01-01

Despite their potential to provide mechanistic explanations of rates of seed dispersal and seed fate, the functional and numerical responses of seed predators have never been explicitly examined within this context. Therefore, we investigated the numerical response of a small-mammal seed predator, Heteromys desmarestianus, to disturbance-induced changes in food availability and evaluated the degree to which removal and fate of seeds of eight tree species in a lowland tropical forest in Belize were related to the functional response of H. desmarestianus to varying seed densities. Mark-recapture trapping was used to estimate abundance of H. desmarestianus in six 0.5-ha grids from July 2000 to September 2002. Fruit availability and seed fate were estimated in each grid, and two experiments nested within the grids were used to determine (1) the form of the functional response for nine levels of fruit density (2-32 fruits/m 2), (2) the removal rate and handling times, and (3) the total proportion of fruits removed. The total proportion of fruits removed was determined primarily by the numerical response of H. desmarestianus to fruit availability, while removal rates and the proportion of seeds eaten or cached were related primarily to the form of the functional response. However, the numerical and functional responses interacted; H. desmarestianus showed strong spatial and temporal numerical responses to total fruit availability, and their density relative to fruit availability resulted in variation in the form of the functional response. Types I, II, and III functional responses were observed, as were density-independent responses, and these responses varied both among and within fruit species. The highest proportions of fruits were eaten when the Type III functional response was detected, which was when fruit availability was high relative to H. desmarestianus population density. Numerous idiosyncratic influences on seed fate have been documented, but our results indicate that shifts in the numerical and functional responses of seed predators to seasonal and interannual variation in seed availability potentially provide a general mechanistic explanation for patterns of removal and fate for vertebrate-dispersed seeds. ?? 2009 by the Ecological Society of America.

Community-wide spatial and temporal discordances of seed-seedling shadows in a tropical rainforest.

PubMed

Rother, Débora Cristina; Pizo, Marco Aurélio; Siqueira, Tadeu; Rodrigues, Ricardo Ribeiro; Jordano, Pedro

2015-01-01

Several factors decrease plant survival throughout their lifecycles. Among them, seed dispersal limitation may play a major role by resulting in highly aggregated (contagious) seed and seedling distributions entailing increased mortality. The arrival of seeds, furthermore, may not match suitable environments for seed survival and, consequently, for seedling establishment. In this study, we investigated spatio-temporal patterns of seed and seedling distribution in contrasting microhabitats (bamboo and non-bamboo stands) from the Brazilian Atlantic Forest. Spatial distribution patterns, spatial concordance between seed rain and seedling recruitment between subsequent years in two fruiting seasons (2004-2005 and 2007-2009), and the relation between seeds and seedlings with environmental factors were examined within a spatially-explicit framework. Density and species richness of both seeds and seedlings were randomly distributed in non-bamboo stands, but showed significant clustering in bamboo stands. Seed and seedling distributions showed across-year inconsistency, suggesting a marked spatial decoupling of the seed and seedling stages. Generalized linear mixed effects models indicated that only seed density and seed species richness differed between stand types while accounting for variation in soil characteristics. Our analyses provide evidence of marked recruitment limitation as a result of the interplay between biotic and abiotic factors. Because bamboo stands promote heterogeneity in the forest, they are important components of the landscape. However, at high densities, bamboos may limit recruitment for the plant community by imposing marked discordances of seed arrival and early seedling recruitment.

Modifying mixing and instability growth through the adjustment of initial conditions in a high-energy-density counter-propagating shear experiment on OMEGA

DOE PAGES

Merritt, E. C.; Doss, F. W.; Loomis, E. N.; ...

2015-06-24

Counter-propagating shear experiments conducted at the OMEGA Laser Facility have been evaluating the effect of target initial conditions, specifically the characteristics of a tracer foil located at the shear boundary, on Kelvin-Helmholtz instability evolution and experiment transition toward nonlinearity and turbulence in the high-energy-density (HED) regime. Experiments are focused on both identifying and uncoupling the dependence of the model initial turbulent length scale in variable-density turbulence models of k-ϵ type on competing physical instability seed lengths as well as developing a path toward fully developed turbulent HED experiments. We present results from a series of experiments controllably and independently varyingmore » two initial types of scale lengths in the experiment: the thickness and surface roughness (surface perturbation scale spectrum) of a tracer layer at the shear interface. We show that decreasing the layer thickness and increasing the surface roughness both have the ability to increase the relative mixing in the system, and thus theoretically decrease the time required to begin transitioning to turbulence in the system. In addition, we also show that we can connect a change in observed mix width growth due to increased foil surface roughness to an analytically predicted change in model initial turbulent scale lengths.« less

Seed Regeneration Potential of Canopy Gaps at Early Formation Stage in Temperate Secondary Forests, Northeast China

PubMed Central

Yan, Qiao-Ling; Zhu, Jiao-Jun; Yu, Li-Zhong

2012-01-01

Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01), especially in medium and small gaps (<500 m2). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation. PMID:22745771

Modeling the size-density relationship in direct-seeded slash pine stands

Treesearch

Quang V. Cao; Thomas J. Dean; V. Clark Baldwin

2000-01-01

The relationship between quadratic mean diameter and tree density appeared curvilinear on a log–log scale, based on data from direct-seeded slash pine (Pinus elliotti var. elliotti Engelm.) stands. The self-thinning trajectory followed a straight line for high tree density levels and then turned away from this line as tree density...

Competition between harvester ants and rodents in the cold desert

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landeen, D.S.; Jorgensen, C.D.; Smith, H.D.

1979-09-30

Local distribution patterns of three rodent species (Perognathus parvus, Peromyscus maniculatus, Reithrodontomys megalotis) were studied in areas of high and low densities of harvester ants (Pogonomyrmex owyheei) in Raft River Valley, Idaho. Numbers of rodents were greatest in areas of high ant-density during May, but partially reduced in August; whereas, the trend was reversed in areas of low ant-density. Seed abundance was probably not the factor limiting changes in rodent populations, because seed densities of annual plants were always greater in areas of high ant-density. Differences in seasonal population distributions of rodents between areas of high and low ant-densities weremore » probably due to interactions of seed availability, rodent energetics, and predation.« less

Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest.

PubMed

Bagchi, Robert; Philipson, Christopher D; Slade, Eleanor M; Hector, Andy; Phillips, Sam; Villanueva, Jerome F; Lewis, Owen T; Lyal, Christopher H C; Nilus, Reuben; Madran, Adzley; Scholes, Julie D; Press, Malcolm C

2011-11-27

Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen-Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen-Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m(2)) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen-Connell mechanism at this site, it may influence the recruitment of particular species.

Gravity Wave Seeding of Equatorial Plasma Bubbles

NASA Technical Reports Server (NTRS)

Singh, Sardul; Johnson, F. S.; Power, R. A.

1997-01-01

Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

Using Phase Space Density Profiles to Investigate the Radiation Belt Seed Population

NASA Astrophysics Data System (ADS)

Boyd, A. J.; Spence, H.; Reeves, G. D.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Turner, D. L.

2013-12-01

It is believed that particles with energies of 100s of keV play a critical role in the acceleration of electrons within the radiation belt. Through wave particle interactions, these so called 'seed electrons' can be accelerated up to energies greater than 1 MeV. Using data from the MagEIS (Magnetic Electron Ion Spectrometer) Instrument onboard the Van Allen Probes we calculate phase space density within the radiation belts over a wide range of mu and K values. These phase space density profiles are combined with those from THEMIS, in order to see how the phase space density evolves over a large range of L*. In this presentation we examine how the seed electron population evolves in both time and L* during acceleration events. Comparing this to the evolution of the higher mu electron population allows us to determine what role the seed electrons played in the acceleration process. Finally, we compare several of these storms to examine the importance of the seed population to the acceleration process.

Comparative effects of using black seed (Nigella sativa), cumin seed (Cuminum cyminum), probiotic or prebiotic on growth performance, blood haematology and serum biochemistry of broiler chicks.

PubMed

Alimohamadi, K; Taherpour, K; Ghasemi, H A; Fatahnia, F

2014-06-01

A 42-day trial was conducted to compare the effects of the following seven experimental diets, which varied in black seed, cumin seed, probiotic or prebiotic concentrations, on the broiler chicks: control (no additives), diet BS1 (4 g/kg black seed), diet BS2 (8 g/kg black seed), diet CS1 (4 g/kg cumin seed), diet CS2 (8 g/kg cumin seed), diet Pro (1 g/kg probiotic Primalac(®)) and diet Pre (2 g/kg prebiotic Fermacto(®)). A total of 420 1-day-old male broiler chicks, initially weighing an average of 43 g, were distributed into 28 floor pens at a stocking density of 15 birds per pen. At 28 day of age, the body weight in the birds fed diets BS2, CS2 and Pro was significantly higher than in the control group, but final body weight was not affected. Additionally, the birds fed diets BS2, Pro and Pre exhibited better feed conversion ratio than control birds from 0 to 42 day of age. Diets BS2, CS2 and Pro also statistically increased the relative weight of thymus and bursa of Fabricius, whereas only diet Pro decreased the abdominal fat percentage compared with control diet. Regarding the haematological parameters, feeding diet BS2 yielded a significant increase in red blood cell count, haemoglobin concentration and haematocrit percentage compared with control diet. Serum total cholesterol and low-density lipoprotein cholesterol levels in the birds fed diets BS2, Pro and Pre were also significantly lower than in the birds fed the control diet. Without exception, no diets affected feed intake, internal organs weights, carcass characteristics, antibody titres against Newcastle and influenza viruses and leucocyte subsets. In general, current study showed promising results regarding the use of spice additives as growth and health promoters, especially at higher levels of their incorporation in the diets, which were comparable to the probiotic- or prebiotic-containing diets. Journal of Animal Physiology and Animal Nutrition © 2013 Blackwell Verlag GmbH.

Oxygen mapping: Probing a novel seeding strategy for bone tissue engineering.

PubMed

Westphal, Ines; Jedelhauser, Claudia; Liebsch, Gregor; Wilhelmi, Arnd; Aszodi, Attila; Schieker, Matthias

2017-04-01

Bone tissue engineering (BTE) utilizing biomaterial scaffolds and human mesenchymal stem cells (hMSCs) is a promising approach for the treatment of bone defects. The quality of engineered tissue is crucially affected by numerous parameters including cell density and the oxygen supply. In this study, a novel oxygen-imaging sensor was introduced to monitor the oxygen distribution in three dimensional (3D) scaffolds in order to analyze a new cell-seeding strategy. Immortalized hMSCs, pre-cultured in a monolayer for 30-40% or 70-80% confluence, were used to seed demineralized bone matrix (DBM) scaffolds. Real-time measurements of oxygen consumption in vitro were simultaneously performed by the novel planar sensor and a conventional needle-type sensor over 24 h. Recorded oxygen maps of the novel planar sensor revealed that scaffolds, seeded with hMSCs harvested at lower densities (30-40% confluence), exhibited rapid exponential oxygen consumption profile. In contrast, harvesting cells at higher densities (70-80% confluence) resulted in a very slow, almost linear, oxygen decrease due to gradual achieving the stationary growth phase. In conclusion, it could be shown that not only the seeding density on a scaffold, but also the cell density at the time point of harvest is of major importance for BTE. The new cell seeding strategy of harvested MSCs at low density during its log phase could be a useful strategy for an early in vivo implantation of cell-seeded scaffolds after a shorter in vitro culture period. Furthermore, the novel oxygen imaging sensor enables a continuous, two-dimensional, quick and convenient to handle oxygen mapping for the development and optimization of tissue engineered scaffolds. Biotechnol. Bioeng. 2017;114: 894-902. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

HFR1 Sequesters PIF1 to Govern the Transcriptional Network Underlying Light-Initiated Seed Germination in Arabidopsis[C][W][OPEN

PubMed Central

Shi, Hui; Zhong, Shangwei; Mo, Xiaorong; Liu, Na; Nezames, Cynthia D.; Deng, Xing Wang

2013-01-01

Seed germination is the first step for seed plants to initiate a new life cycle. Light plays a predominant role in promoting seed germination, where the initial phase is mediated by photoreceptor phytochrome B (phyB). Previous studies showed that PHYTOCHROME-INTERACTING FACTOR1 (PIF1) represses seed germination downstream of phyB. Here, we identify a positive regulator of phyB-dependent seed germination, LONG HYPOCOTYL IN FAR-RED1 (HFR1). HFR1 blocks PIF1 transcriptional activity by forming a heterodimer with PIF1 that prevents PIF1 from binding to DNA. Our whole-genomic analysis shows that HFR1 and PIF1 oppositely mediate the light-regulated transcriptome in imbibed seeds. Through the HFR1–PIF1 module, light regulates expression of numerous genes involved in cell wall loosening, cell division, and hormone pathways to initiate seed germination. The functionally antagonistic HFR1–PIF1 pair constructs a fail-safe mechanism for fine-tuning seed germination during low-level illumination, ensuring a rapid response to favorable environmental changes. This study identifies the HFR1–PIF1 pair as a central module directing the whole genomic transcriptional network to rapidly initiate light-induced seed germination. PMID:24179122

Dependency of subcellular reactions during PDT on the metabolic state of cell cultures probed by different microscopic techniques

NASA Astrophysics Data System (ADS)

Rueck, Angelika C.; Schneckenburger, Herbert; Strauss, Wolfgang S. L.; Gschwend, Michael H.; Beck, Gerd C.; Kunzi-Rapp, Karin; Steiner, Rudolf W.

1994-02-01

Various microscopic techniques were used to study the dependency of photodynamically induced subcellular reactions on the metabolic state of cell cultures. TPPS4 and AlS2-3Pc were incubated in RR 1022 epithelial cells with varying cell density. To attain almost isolated cells (low cell density) or confluent growing cells (high cell density) 25 cells/mm2 or 500 cells/mm2 were seeded, respectively. Low cell density irradiation with blue light led to a change in the initial cytoplasmatic fluorescence pattern. For both sensitizers, TPPS4 as well as AlS2-3, a fluorescence relocalization and fluorescence intensity increase could be detected, moreover in the case of TPPS4 a fluorescence formation in the nucleus and nucleoli were detected. In contrast, for confluent growing cells no redistribution was observed.

Effects of low-Z and high-Z impurities on divertor detachment and plasma confinement

DOE PAGES

Wang, H. Q.; Guo, Houyang Y.; Petrie, Thomas W.; ...

2017-03-18

The impurity-seeded detached divertor is essential for heat exhaust in ITER and other reactor-relevant devices. Dedicated experiments with injection of N 2, Ne and Ar have been performed in DIII-D to assess the impact of the different impurities on divertor detachment and confinement. Seeding with N 2, Ne and Ar all promote divertor detachment, greatly reducing heat flux near the strike point. The upstream plasma density at the onset of detachment decreases with increasing impurity-puffing flow rates. For all injected impurity species, the confinement and pedestal pressure are correlated with the impurity content and the ratio of separatrix loss powermore » to the L-H transition threshold power. As the divertor plasma approaches detachment, the high-Z impurity seeding tends to degrade the core confinement owing to the increased core radiation. In particular, Ar injection leads to an increase in core radiation, up to 50% of the injected power, and a reduction in pedestal temperature over 60%, thus significantly degrading the confinement, i.e., with H 98 reducing from 1.1 to below 0.7. As for Ne seeding, H 98 near 0.8 can be maintained during the detachment phase with the pedestal temperature being reduced by about 50%. In contrast, in the N 2 seeded plasmas, radiation is predominately confined in the boundary plasma, with up to 50% of heating power being radiated in the divertor region and less than 25% in the core at the onset of detachment. In the case of strong N 2 gas puffing, the confinement recovers during the detachment, from ~20% reduction at the onset of the detachment to greater than that before the seeding. The core and pedestal temperatures feature a reduction of 30% from the initial attached phase and remain nearly constant during the detachment phase. The improvement in confinement appears to arise from the increase in pedestal and core density despite the temperature reduction.« less

Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest

PubMed Central

Bagchi, Robert; Philipson, Christopher D.; Slade, Eleanor M.; Hector, Andy; Phillips, Sam; Villanueva, Jerome F.; Lewis, Owen T.; Lyal, Christopher H. C.; Nilus, Reuben; Madran, Adzley; Scholes, Julie D.; Press, Malcolm C.

2011-01-01

Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen–Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen–Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m2) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen–Connell mechanism at this site, it may influence the recruitment of particular species. PMID:22006965

Simulated warming shifts the flowering phenology and sexual reproduction of Cardamine hirsuta under different Planting densities

PubMed Central

Cao, YuSong; Xiao, Yian; Huang, Haiqun; Xu, Jiancheng; Hu, Wenhai; Wang, Ning

2016-01-01

Climate warming can shift the reproductive phenology of plant, and hence dramatically reduced the reproductive capacity both of density-dependent and -independent plant species. But it is still unclear how climate warming affects flowering phenology and reproductive allocation of plant under different planting densities. Here, we assessed the impact of simulated warming on flowering phenology and sexual reproduction in the ephemeral herb Cardamine hirsuta under four densities. We found that simulated warming delayed the onset of flowering averagely for 3.6 days but preceded the end of flowering for about 1 day, which indicated climate warming shortened the duration of the flowering. And the flowering amplitude in the peak flowering day also dramatically increased in the simulated warming treatment, which caused a mass-flowering pattern. Climate warming significantly increased the weights of the fruits, seeds and seed, but reduced fruit length and sexual reproductive allocation under all the four densities. The duration of flowering was shortened and the weights of the fruits, seeds and seed, and sexual reproductive allocation were reduced under The highest density. PMID:27296893

Conditions for Optimal Growth of Black Hole Seeds

NASA Astrophysics Data System (ADS)

Pacucci, Fabio; Natarajan, Priyamvada; Volonteri, Marta; Cappelluti, Nico; Urry, C. Megan

2017-12-01

Supermassive black holes weighing up to ˜109 M ⊙ are in place by z ˜ 7, when the age of the universe is ≲1 Gyr. This implies a time crunch for their growth, since such high masses cannot be easily reached in standard accretion scenarios. Here, we explore the physical conditions that would lead to optimal growth wherein stable super-Eddington accretion would be permitted. Our analysis suggests that the preponderance of optimal conditions depends on two key parameters: the black hole mass and the host galaxy central gas density. In the high-efficiency region of this parameter space, a continuous stream of gas can accrete onto the black hole from large to small spatial scales, assuming a global isothermal profile for the host galaxy. Using analytical initial mass functions for black hole seeds, we find an enhanced probability of high-efficiency growth for seeds with initial masses ≳104 M ⊙. Our picture suggests that a large population of high-z lower-mass black holes that formed in the low-efficiency region, with low duty cycles and accretion rates, might remain undetectable as quasars, since we predict their bolometric luminosities to be ≲1041 erg s-1. The presence of these sources might be revealed only via gravitational wave detections of their mergers.

The effects of seed size on hybrids formed between oilseed rape (Brassica napus) and wild brown mustard (B. juncea).

PubMed

Liu, Yong-Bo; Tang, Zhi-Xi; Darmency, Henri; Stewart, C Neal; Di, Kun; Wei, Wei; Ma, Ke-ping

2012-01-01

Seed size has significant implications in ecology, because of its effects on plant fitness. The hybrid seeds that result from crosses between crops and their wild relatives are often small, and the consequences of this have been poorly investigated. Here we report on plant performance of hybrid and its parental transgenic oilseed rape (Brassica napus) and wild B. juncea, all grown from seeds sorted into three seed-size categories. Three seed-size categories were sorted by seed diameter for transgenic B. napus, wild B. juncea and their transgenic and non-transgenic hybrids. The seeds were sown in a field at various plant densities. Globally, small-seeded plants had delayed flowering, lower biomass, fewer flowers and seeds, and a lower thousand-seed weight. The seed-size effect varied among plant types but was not affected by plant density. There was no negative effect of seed size in hybrids, but it was correlated with reduced growth for both parents. Our results imply that the risk of further gene flow would probably not be mitigated by the small size of transgenic hybrid seeds. No fitness cost was detected to be associated with the Bt-transgene in this study.

Role of Multicellular Aggregates in Biofilm Formation

PubMed Central

Kragh, Kasper N.; Hutchison, Jaime B.; Melaugh, Gavin; Rodesney, Chris; Roberts, Aled E. L.; Irie, Yasuhiko; Jensen, Peter Ø.; Diggle, Stephen P.; Allen, Rosalind J.

2016-01-01

ABSTRACT In traditional models of in vitro biofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process. This makes it likely that biofilms are often seeded by aggregates and single cells, yet how these aggregates impact biofilm initiation and development is not known. Here we use a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms. We find that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. Other advantages of seeding by aggregates, such as earlier switching to a biofilm-like phenotype and enhanced resilience toward antibiotics and immune response, may add to this ecological benefit. Our findings suggest that current models of biofilm formation should be reconsidered to incorporate the role of aggregates in biofilm initiation. PMID:27006463

Cell Seeding Densities in Autologous Chondrocyte Implantation Techniques for Cartilage Repair.

PubMed

Foldager, Casper Bindzus; Gomoll, Andreas H; Lind, Martin; Spector, Myron

2012-04-01

Cartilage repair techniques have been among the most intensively investigated treatments in orthopedics for the past decade, and several different treatment modalities are currently available. Despite the extensive research effort within this field, the generation of hyaline cartilage remains a considerable challenge. There are many parameters attendant to each of the cartilage repair techniques that can affect the amount and types of reparative tissue generated in the cartilage defect, and some of the most fundamental of these parameters have yet to be fully investigated. For procedures in which in vitro-cultured autologous chondrocytes are implanted under a periosteal or synthetic membrane cover, or seeded onto a porous membrane or scaffold, little is known about how the number of cells affects the clinical outcome. Few published clinical studies address the cell seeding density that was employed. The principal objective of this review is to provide an overview of the cell seeding densities used in cell-based treatments currently available in the clinic for cartilage repair. Select preclinical studies that have informed the use of specific cell seeding densities in the clinic are also discussed.

Waterfowl foraging in winter-flooded ricefields: Any agronomic benefits for farmers?

PubMed

Brogi, Anne; Pernollet, Claire A; Gauthier-Clerc, Michel; Guillemain, Matthieu

2015-12-01

Winter-flooding of ricefields provides foraging habitat to waterfowl, which in return may bring agronomic benefits to farmers. Our study experimentally tested the effect of mallards (Anas platyrhynchos) on the standing stalks and weed seed bank in the Camargue (France), both of which present major challenges for farmers. Three duck densities were tested: (D1) 5 ducks ha(-1) (historical nocturnal density), (D2) 23 ducks ha(-1) (present nocturnal density), and (D3) 300 ducks ha(-1) (Asian rice-duck farming density). The ducks reduced the stalks significantly: -27 % (D1), -52 % (D2), and -91 % (D3). Conversely, they decreased the number of seeds by only 3 % (D3) and the seed mass by about 21 % (D1 and D3), which was not significant. Besides they had no effect on seed species richness. This study clearly demonstrates that the winter-flooding effect on straw decomposition can be enhanced by waterfowl foraging, hence showing an agronomic benefit from ducks to farmers. However, there was no clear effect in terms of seed bank reduction.

Restoration of Mountain Big Sagebrush Steppe Following Prescribed Burning to Control Western Juniper

NASA Astrophysics Data System (ADS)

Davies, K. W.; Bates, J. D.; Madsen, M. D.; Nafus, A. M.

2014-05-01

Western juniper ( Juniperus occidentalis ssp. occidentalis Hook) encroachment into mountain big sagebrush ( Artemisia tridentata spp. vaseyana (Rydb.) Beetle) steppe has reduced livestock forage production, increased erosion risk, and degraded sagebrush-associated wildlife habitat. Western juniper has been successfully controlled with partial cutting followed by prescribed burning the next fall, but the herbaceous understory and sagebrush may be slow to recover. We evaluated the effectiveness of seeding perennial herbaceous vegetation and sagebrush at five sites where juniper was controlled by partially cutting and prescribed burning. Treatments tested at each site included an unseeded control, herbaceous seed mix (aerially seeded), and the herbaceous seed mix plus sagebrush seed. In the third year post-treatment, perennial grass cover and density were twice as high in plots receiving the herbaceous seed mix compared to the control plots. Sagebrush cover and density in the sagebrush seeded plots were between 74- and 290-fold and 62- and 155-fold greater than the other treatments. By the third year after treatment, sagebrush cover was as high as 12 % in the sagebrush seeded plots and between 0 % and 0.4 % where it was not seeded. These results indicate that aerial seeding perennial herbaceous vegetation can accelerate the recovery of perennial grasses which likely stabilize the site. Our results also suggest that seeding mountain big sagebrush after prescribed burning encroaching juniper can rapidly recover sagebrush cover and density. In areas where sagebrush habitat is limited, seeding sagebrush after juniper control may increase sagebrush habitat and decrease the risks to sagebrush-associated species.

Restoration of mountain big sagebrush steppe following prescribed burning to control western juniper.

PubMed

Davies, K W; Bates, J D; Madsen, M D; Nafus, A M

2014-05-01

Western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroachment into mountain big sagebrush (Artemisia tridentata spp. vaseyana (Rydb.) Beetle) steppe has reduced livestock forage production, increased erosion risk, and degraded sagebrush-associated wildlife habitat. Western juniper has been successfully controlled with partial cutting followed by prescribed burning the next fall, but the herbaceous understory and sagebrush may be slow to recover. We evaluated the effectiveness of seeding perennial herbaceous vegetation and sagebrush at five sites where juniper was controlled by partially cutting and prescribed burning. Treatments tested at each site included an unseeded control, herbaceous seed mix (aerially seeded), and the herbaceous seed mix plus sagebrush seed. In the third year post-treatment, perennial grass cover and density were twice as high in plots receiving the herbaceous seed mix compared to the control plots. Sagebrush cover and density in the sagebrush seeded plots were between 74- and 290-fold and 62- and 155-fold greater than the other treatments. By the third year after treatment, sagebrush cover was as high as 12 % in the sagebrush seeded plots and between 0 % and 0.4 % where it was not seeded. These results indicate that aerial seeding perennial herbaceous vegetation can accelerate the recovery of perennial grasses which likely stabilize the site. Our results also suggest that seeding mountain big sagebrush after prescribed burning encroaching juniper can rapidly recover sagebrush cover and density. In areas where sagebrush habitat is limited, seeding sagebrush after juniper control may increase sagebrush habitat and decrease the risks to sagebrush-associated species.

Comparison of secondary organic aerosol formation from toluene on initially wet and dry ammonium sulfate particles at moderate relative humidity

NASA Astrophysics Data System (ADS)

Liu, Tengyu; Huang, Dan Dan; Li, Zijun; Liu, Qianyun; Chan, ManNin; Chan, Chak K.

2018-04-01

The formation of secondary organic aerosol (SOA) has been widely studied in the presence of dry seed particles at low relative humidity (RH). At higher RH, initially dry seed particles can exist as wet particles due to water uptake by the seeds as well as the SOA. Here, we investigated the formation of SOA from the photooxidation of toluene using an oxidation flow reactor in the absence of NOx under a range of OH exposures on initially wet or dry ammonium sulfate (AS) seed particles at an RH of 68 %. The ratio of the SOA yield on wet AS seeds to that on dry AS seeds, the relative SOA yield, decreased from 1.31 ± 0.02 at an OH exposure of 4.66 × 1010 molecules cm-3 s to 1.01 ± 0.01 at an OH exposure of 5.28 × 1011 molecules cm-3 s. This decrease may be due to the early deliquescence of initially dry AS seeds after being coated by highly oxidized toluene-derived SOA. SOA formation lowered the deliquescence RH of AS and resulted in the uptake of water by both AS and SOA. Hence the initially dry AS seeds contained aerosol liquid water (ALW) soon after SOA formed, and the SOA yield and ALW approached those of the initially wet AS seeds as OH exposure and ALW increased, especially at high OH exposure. However, a higher oxidation state of the SOA on initially wet AS seeds than that on dry AS seeds was observed at all levels of OH exposure. The difference in mass fractions of m / z 29, 43 and 44 of SOA mass spectra, obtained using an aerosol mass spectrometer (AMS), indicated that SOA formed on initially wet seeds may be enriched in earlier-generation products containing carbonyl functional groups at low OH exposures and later-generation products containing acidic functional groups at high exposures. Our results suggest that inorganic dry seeds become at least partially deliquesced particles during SOA formation and hence that ALW is inevitably involved in the SOA formation at moderate RH. More laboratory experiments conducted with a wide variety of SOA precursors and inorganic seeds under different NOx and RH conditions are warranted.

Seed dispersal into wetlands: Techniques and results for a restored tidal freshwater marsh

USGS Publications Warehouse

Neff, K.P.; Baldwin, A.H.

2005-01-01

Although seed dispersal is assumed to be a major factor determining plant community development in restored wetlands, little research exists on density and species richness of seed available through dispersal in these systems. We measured composition and seed dispersal rates at a restored tidal freshwater marsh in Washington, DC, USA by collecting seed dispersing through water and wind. Seed dispersal by water was measured using two methods of seed collection: (1) stationary traps composed of coconut fiber mat along an elevation gradient bracketing the tidal range and (2) a floating surface trawl net attached to a boat. To estimate wind dispersal rates, we collected seed from stationary traps composed of coconut fiber mat positioned above marsh vegetation. We also collected a small number of samples of debris deposited along high tide lines (drift lines) and feces of Canada Goose to explore their seed content. We used the seedling emergence method to determine seed density in all samples, which involved placing the fiber mats or sample material on top of potting soil in a greenhouse misting room and enumerating emerging seedlings. Seedlings from a total of 125 plant species emerged during this study (including 82 in river trawls, 89 in stationary water traps, 21 in drift lines, 39 in wind traps, and 10 in goose feces). The most abundant taxa included Bidens frondosa, Boehmeria cylindrica, Cyperus spp., Eclipta prostrata, and Ludwigia palustris. Total seedling density was significantly greater for the stationary water traps (212 + 30.6 seeds/m2/month) than the equal-sized stationary wind traps (18 + 6.0 seeds/m(2)/month). Lower-bound estimates of total species richness based on the non-parametric Chao 2 asymptotic estimators were greater for seeds in water (106 + 1.4 for stationary water traps and 104 + 5.5 for trawl samples) than for wind (54 + 6.4). Our results indicate that water is the primary source of seeds dispersing to the site and that a species-rich pool of dispersing propagules is present, an interesting result given the urbanized nature of the surrounding landscape. However, species composition of dispersing seeds differed from vegetation of restored and natural tidal freshwater marshes, indicating that planting is necessary for certain species. At other restoration sites, information on densities of dispersing seeds can support decisions on which species to plant.

Waste rice seed in conventional and stripper-head harvested fields in California: Implications for wintering waterfowl

USGS Publications Warehouse

Fleskes, Joseph P.; Halstead, Brian J.; Casazza, Michael L.; Coates, Peter S.; Kohl, Jeffrey D.; Skalos, Daniel A.

2012-01-01

Waste rice seed is an important food for wintering waterfowl and current estimates of its availability are needed to determine the carrying capacity of rice fields and guide habitat conservation. We used a line-intercept method to estimate mass-density of rice seed remaining after harvest during 2010 in the Sacramento Valley (SACV) of California and compared results with estimates from previous studies in the SACV and Mississippi Alluvial Valley (MAV). Posterior mean (95% credible interval) estimates of total waste rice seed mass-density for the SACV in 2010 were 388 (336–449) kg/ha in conventionally harvested fields and 245 (198–307) kg/ha in stripper-head harvested fields; the 2010 mass-density is nearly identical to the mid-1980s estimate for conventionally harvested fields but 36% lower than the mid-1990s estimate for stripped fields. About 18% of SACV fields were stripper-head harvested in 2010 vs. 9–15% in the mid-1990s and 0% in the mid-1980s; but due to a 50% increase in planted rice area, total mass of waste rice seed in SACV remaining after harvest in 2010 was 43% greater than in the mid-1980s. However, total mass of seed-eating waterfowl also increased 82%, and the ratio of waste rice seed to seed-eating waterfowl mass was 21% smaller in 2010 than in the mid-1980s. Mass-densities of waste rice remaining after harvest in SACV fields are within the range reported for MAV fields. However, because there is a lag between harvest and waterfowl use in the MAV but not in the SACV, seed loss is greater in the MAV and estimated waste seed mass-density available to wintering waterfowl in SACV fields is about 5–30 times recent MAV estimates. Waste rice seed remains an abundant food source for waterfowl wintering in the SACV, but increased use of stripper-head harvesters would reduce this food. To provide accurate data on carrying capacities of rice fields necessary for conservation planning, trends in planted rice area, harvest method, and postharvest field treatment should be tracked and impacts of postharvest field treatment and other farming practices on waste rice seed availability should be investigated.

Fluid modeling of a high-voltage nanosecond pulsed xenon microdischarge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levko, Dmitry; Raja, Laxminarayan L.

2016-07-15

A computational modeling study of high-voltage nanosecond pulsed microdischarge in xenon gas at 10 atm is presented. The discharge is observed to develop as two streamers originating from the cathode and the anode, and propagating toward each other until they merge to form a single continuous discharge channel. The peak plasma density obtained in the simulations is ∼10{sup 24 }m{sup −3}, i.e., the ionization degree of plasma does not exceed 1%. The influence of the initial gas pre-ionization is established. It is seen that an increase in the seeded plasma density results in an increase in the streamer propagation velocity andmore » an increase in the plasma density obtained after the merging of two streamers.« less

Effectiveness of predator satiation in masting oaks is negatively affected by conspecific density.

PubMed

Bogdziewicz, Michał; Espelta, Josep M; Muñoz, Alberto; Aparicio, Jose M; Bonal, Raul

2018-04-01

Variation in seed availability shapes plant communities, and is strongly affected by seed predation. In some plant species, temporal variation in seed production is especially high and synchronized over large areas, which is called 'mast seeding'. One selective advantage of this phenomenon is predator satiation which posits that masting helps plants escape seed predation through starvation of predators in lean years, and satiation in mast years. However, even though seed predation can be predicted to have a strong spatial component and depend on plant densities, whether the effectiveness of predator satiation in masting plants changes according to the Janzen-Connell effect has been barely investigated. We studied, over an 8-year period, the seed production, the spatiotemporal patters of weevil seed predation, and the abundance of adult weevils in a holm oak (Quercus ilex) population that consists of trees interspersed at patches covering a continuum of conspecific density. Isolated oaks effectively satiate predators, but this is trumped by increasing conspecific plant density. Lack of predator satiation in trees growing in dense patches was caused by re-distribution of insects among plants that likely attenuated them against food shortage in lean years, and changed the type of weevil functional response from type II in isolated trees to type III in trees growing in dense patches. This study provides the first empirical evaluation of the notion that masting and predator satiation should be more important in populations that start to dominate their communities, and is consistent with the observation that masting is less frequent and less intense in diverse forests.

Wheat production in controlled environments

NASA Technical Reports Server (NTRS)

Salisbury, Frank B.; Bugbee, Bruce; Bubenheim, David

1987-01-01

Conditions are optimized for maximum yield and quality of wheat to be used in a controlled environment life support system (CELSS) in a Lunar or Martian base or a spacecraft. With yields of 23 to 57 g/sq m/d of edible biomass, a minimum size for a CELSS would be between 12 and 30 sq m per person, utilizing about 600 W/sq m of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon dioxide levels, humidity, and wind velocity are controlled in growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO3 and controlling the NO3/NH4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants sq m. Densities up to 2000 plants/sq m appear to increase seed yield. Biomass production increases almost linearily with increasing irradiance from 400 to 1700 micromol/sq m/s of photosynthetic photon flux, but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization.

Small-mammal seed predation limits the recruitment and abundance of two perennial grassland forbs

Treesearch

Mary Bricker; Dean Pearson; John Maron

2010-01-01

Although post-dispersal seed predators are common and often reduce seed density, their influence on plant population abundance remains unclear. On the one hand, increasing evidence suggests that many plant populations are seed limited, implying that seed predators could reduce plant abundance. On the other hand, it is generally uncertain whether the magnitude of seed...

Genetic diversity of dispersed seeds is highly variable among leks of the long-wattled umbrellabird

NASA Astrophysics Data System (ADS)

Ottewell, Kym; Browne, Luke; Cabrera, Domingo; Olivo, Jorge; Karubian, Jordan

2018-01-01

Frugivorous animals frequently generate clumped distributions of seeds away from source trees, but genetic consequences of this phenomenon remain poorly resolved. Seed dispersal of the palm Oenocarpus bataua by long-wattled umbrellabirds Cephalopterus penduliger generates high seed densities in leks (i.e., multi-male display sites), providing a suitable venue to investigate how dispersal by this frugivore may influence seed source diversity and genetic structure at local and landscape levels. We found moderate levels of maternal seed source diversity in primary seed rain across five leks in northwest Ecuador (unweighted mean alpha diversity α = 9.52, weighted mean αr = 3.52), with considerable variation among leks (αr range: 1.81-24.55). Qualitatively similar findings were obtained for allelic diversity and heterozygosity. Higher densities of O. bataua adults around leks were associated with higher values of αr and heterozygosity (non-significant trends) and allelic diversity (significant correlation). Seed source overlap between different leks was not common but did occur at low frequency, providing evidence for long-distance seed dispersal by umbrellabirds into leks. Our findings are consistent with the idea that seed pool diversity within leks may be shaped by the interaction between density of local trees, which can vary considerably between leks, and umbrellabird foraging ecology, particularly a lack of territorial defense of fruiting trees. Taken as a whole, this work adds to our growing appreciation of the ways resource distribution and associated frugivore foraging behaviors mechanistically shape seed dispersal outcomes and the distribution of plant genotypes across the landscape.

Electron cyclotron plasma startup in the GDT experiment

NASA Astrophysics Data System (ADS)

Yakovlev, D. V.; Shalashov, A. G.; Gospodchikov, E. D.; Solomakhin, A. L.; Savkin, V. Ya.; Bagryansky, P. A.

2017-01-01

We report on a new plasma startup scenario in the gas dynamic trap (GDT) magnetic mirror device. The primary 5 MW neutral beam injection (NBI) plasma heating system fires into a sufficiently dense plasma target (‘seed plasma’), which is commonly supplied by an arc plasma generator. In the reported experiments, a different approach to seed plasma generation is explored. One of the channels of the electron cyclotron resonance (ECR) heating system is used to ionize the neutral gas and build up the density of plasma to a level suitable for NBI capture. After a short transition of approximately 1 ms the discharge becomes essentially similar to a standard one initiated by the plasma gun. This paper presents the discharge scenario and experimental data on the seed plasma evolution during ECRH, along with the dependencies on incident microwave power, magnetic configuration and pressure of a neutral gas. The characteristics of the consequent high-power NBI discharge are studied and differences from the conventional scenario are discussed. A theoretical model describing the ECR breakdown and the seed plasma accumulation in a large-scale mirror trap is developed on the basis of the GDT experiment.

Effects of age and stand density of mother trees on early Pinus thunbergii seedling establishment in the coastal zone, China.

PubMed

Mao, Peili; Han, Guangxuan; Wang, Guangmei; Yu, Junbao; Shao, Hongbo

2014-01-01

Effects of age and stand density of mother tree on seed germination, seedling biomass allocation, and seedling growth of Pinus thunbergii were studied. The results showed that age of mother tree did not have significant influences on seed germination, but it was significant on seedling biomass allocation and growth. Seedlings from the minimum and maximum age of mother tree had higher leaf mass ratio and lower root mass ratio than from the middle age of mother tree. Moreover, they also had higher relative height growth rate and slenderness, which were related to their biomass allocation. Stand density of mother tree mainly demonstrated significant effects on seed germination and seedling growth. Seed from higher stand density of mother tree did not decrease germination rate, but had higher mean germination time, indicating that it delayed germination process. Seedlings of higher stand density of mother tree showed higher relative height growth rate and slenderness. These traits of offspring from higher stand density of mother tree were similar to its mother, indicating significant environmental maternal effects. So, mother tree identity of maternal age and environments had important effects on natural regeneration of the coastal P. thunbergii forest.

Effects of Age and Stand Density of Mother Trees on Early Pinus thunbergii Seedling Establishment in the Coastal Zone, China

PubMed Central

Mao, Peili; Han, Guangxuan; Wang, Guangmei; Yu, Junbao; Shao, Hongbo

2014-01-01

Effects of age and stand density of mother tree on seed germination, seedling biomass allocation, and seedling growth of Pinus thunbergii were studied. The results showed that age of mother tree did not have significant influences on seed germination, but it was significant on seedling biomass allocation and growth. Seedlings from the minimum and maximum age of mother tree had higher leaf mass ratio and lower root mass ratio than from the middle age of mother tree. Moreover, they also had higher relative height growth rate and slenderness, which were related to their biomass allocation. Stand density of mother tree mainly demonstrated significant effects on seed germination and seedling growth. Seed from higher stand density of mother tree did not decrease germination rate, but had higher mean germination time, indicating that it delayed germination process. Seedlings of higher stand density of mother tree showed higher relative height growth rate and slenderness. These traits of offspring from higher stand density of mother tree were similar to its mother, indicating significant environmental maternal effects. So, mother tree identity of maternal age and environments had important effects on natural regeneration of the coastal P. thunbergii forest. PMID:24955404

Tracing impacts of partner abundance in facultative pollination mutualisms: from individuals to populations.

PubMed

Geib, Jennifer C; Galen, Candace

2012-07-01

Partner abundance affects costs and benefits in obligate mutualisms, but its role in facultative partnerships is less clear. We address this gap in a pollination web consisting of two clovers (Trifolium) that differ in specialization on a bumble bee pollinator Bombus balteatus. We examine how pollination niche breadth affects plant responses to pollinator abundance, comparing early-flowering (specialized) and late-flowering (generalized) cohorts of T. parryi and early T. parryi to T. dasyphyllum, a pollination generalist. Co-pollinators disrupt the link between B. halteatus visitation and pollination rate for both clovers. Only for early-flowering T. parryi do visitation, pollination, and seed set increase with density of B. balteatus. Bumble bee density also alters timing of seed germination in T. parryi, with seeds from plants receiving augmented B. balteatus germinating sooner than seeds of open-pollinated counterparts. Benefits saturate at intermediate bumble bee densities. Despite strong effects of B. balteatus density on individual plant fitness components, population models suggest little impact of B. balteatus density on lamda in T. parryi or T. dasyphyllum. Findings show that functional redundancy in a pollinator guild mediates host-plant responses to partner density. Unexpected effects of pollinator density on life history schedule have implications for recruitment under pollinator decline.

Effects of planting density and genotype on loblolly pine stands growing in the mountains of southeastern Oklahoma

Treesearch

Rodney E. Will; Thomas C. Hennessey; Thomas B. Lynch; Robert Heinemann; Randal Holeman; Dennis Wilson; Keith Anderson; Gregory Campbell

2013-01-01

We determined the effects of planting density (4- by 4-, 6- by 6-, 8- by 8-, and 10- by 10-foot spacing) on stand-level height, diameter at breast height, stem volume, basal area, and periodic annual increment for two loblolly pine (Pinus taeda L.) seed sources. Seed sources for the 25-year-old stands were a North Carolina seed source (NCC 8-01) and...

Proceedings of the ARPA/AFML Review of Progress in Quantitative Nondestructive Evaluation

DTIC Science & Technology

1978-05-01

seeded with Fe, Si , SIC, low density SI3N4, C and pores in sizes ranging from 125 to 1000 ^m (0.005 to 0.040 Inches) as shown in the margins. Figure...are some blank areas where seeded defects are supposed to be, partic- ularly for the low density SI3N4 and the smallest size of SI and SIC, there 1s...shear wave Inspections of a seeded billet of NC-132, hot pressed silicon nitride. In this case the seeded defects are WC, Fe, BN, SIC, Si and C

Richtmyer-Meshkov evolution under steady shock conditions in the high-energy-density regime

DOE PAGES

Di Stefano, C. A.; Malamud, G.; Kuranz, C. C.; ...

2015-03-17

This work presents direct experimental evidence of long-predicted nonlinear aspects of the Richtmyer-Meshkov (RM) process, in which new modes first arise from the coupling of initially-present modes, and in which shorter-wavelength modes are eventually overtaken by longer-wavelength modes. This is accomplished using a technique we developed employing a long driving laser pulse to create a strong (Mach ~ 8) shock across a well-characterized material interface seeded by a two-mode sinusoidal perturbation. Furthermore, this technique further permits the shock to be sustained, without decay of the high-energy-density flow conditions, long enough for the system to evolve into the nonlinear phase.

Stability in and correlation between factors influencing genetic quality of seed lots in seed orchard of Pinus tabuliformis Carr. over a 12-year span.

PubMed

Li, Wei; Wang, Xiaoru; Li, Yue

2011-01-01

Coniferous seed orchards require a long period from initial seed harvest to stable seed production. Differential reproductive success and asynchrony are among the main factors for orchard crops year-to-year variation in terms of parental gametic contribution and ultimately the genetic gain. It is fundamental in both making predictions about the genetic composition of the seed crop and decisions about orchard roguing and improved seed orchard establishment. In this paper, a primary Chinese pine seed orchard with 49 clones is investigated for stability, variation and correlation analysis of factors which influence genetic quality of the seed lots from initial seed harvest to the stable seed production over a 12 years span. Results indicated that the reproductive synchrony index of pollen shedding has shown to be higher than that of the strobili receptivity, and both can be drastically influenced by the ambient climate factors. Reproductive synchrony index of the clones has certain relative stability and it could be used as an indication of the seed orchard status during maturity stage; clones in the studied orchard have shown extreme differences in terms of the gametic and genetic contribution to the seed crop at the orchard's early production phase specifically when they severe as either female or male parents. Those differences are closely related to clonal sex tendency at the time of orchard's initial reproduction. Clonal gamete contribution as male and female parent often has a negative correlation. Clone utilization as pollen, seed or both pollen and seed donors should consider the role it would play in the seed crop; due to numerous factors influencing on the mating system in seed orchards, clonal genetic contribution as male parent is uncertain, and it has major influence on the genetic composition in the seed orchard during the initial reproductive and seed production phase.

Cosmological explosions from cold dark matter perturbations

NASA Technical Reports Server (NTRS)

Scherrer, Robert J.

1992-01-01

The cosmological-explosion model is examined for a universe dominated by cold dark matter in which explosion seeds are produced from the growth of initial density perturbations of a given form. Fragmentation of the exploding shells is dominated by the dark-matter potential wells rather than the self-gravity of the shells, and particular conditions are required for the explosions to bootstrap up to very large scales. The final distribution of dark matter is strongly correlated with the baryons on small scales, but uncorrelated on large scales.

Interference between Redroot Pigweed (Amaranthus retroflexus L.) and Cotton (Gossypium hirsutum L.): Growth Analysis.

PubMed

Ma, Xiaoyan; Wu, Hanwen; Jiang, Weili; Ma, Yajie; Ma, Yan

2015-01-01

Redroot pigweed is one of the injurious agricultural weeds on a worldwide basis. Understanding of its interference impact in crop field will provide useful information for weed control programs. The effects of redroot pigweed on cotton at densities of 0, 0.125, 0.25, 0.5, 1, 2, 4, and 8 plants m(-1) of row were evaluated in field experiments conducted in 2013 and 2014 at Institute of Cotton Research, CAAS in China. Redroot pigweed remained taller and thicker than cotton and heavily shaded cotton throughout the growing season. Both cotton height and stem diameter reduced with increasing redroot pigweed density. Moreover, the interference of redroot pigweed resulted in a delay in cotton maturity especially at the densities of 1 to 8 weed plants m(-1) of row, and cotton boll weight and seed numbers per boll were reduced. The relationship between redroot pigweed density and seed cotton yield was described by the hyperbolic decay regression model, which estimated that a density of 0.20-0.33 weed plant m(-1) of row would result in a 50% seed cotton yield loss from the maximum yield. Redroot pigweed seed production per plant or per square meter was indicated by logarithmic response. At a density of 1 plant m(-1) of cotton row, redroot pigweed produced about 626,000 seeds m(-2). Intraspecific competition resulted in density-dependent effects on weed biomass per plant, a range of 430-2,250 g dry weight by harvest. Redroot pigweed biomass ha(-1) tended to increase with increasing weed density as indicated by a logarithmic response. Fiber quality was not significantly influenced by weed density when analyzed over two years; however, the fiber length uniformity and micronaire were adversely affected at density of 1 weed plant m(-1) of row in 2014. The adverse impact of redroot pigweed on cotton growth and development identified in this study has indicated the need of effective redroot pigweed management.

Interference between Redroot Pigweed (Amaranthus retroflexus L.) and Cotton (Gossypium hirsutum L.): Growth Analysis

PubMed Central

Ma, Xiaoyan; Wu, Hanwen; Jiang, Weili; Ma, Yajie; Ma, Yan

2015-01-01

Redroot pigweed is one of the injurious agricultural weeds on a worldwide basis. Understanding of its interference impact in crop field will provide useful information for weed control programs. The effects of redroot pigweed on cotton at densities of 0, 0.125, 0.25, 0.5, 1, 2, 4, and 8 plants m-1 of row were evaluated in field experiments conducted in 2013 and 2014 at Institute of Cotton Research, CAAS in China. Redroot pigweed remained taller and thicker than cotton and heavily shaded cotton throughout the growing season. Both cotton height and stem diameter reduced with increasing redroot pigweed density. Moreover, the interference of redroot pigweed resulted in a delay in cotton maturity especially at the densities of 1 to 8 weed plants m-1 of row, and cotton boll weight and seed numbers per boll were reduced. The relationship between redroot pigweed density and seed cotton yield was described by the hyperbolic decay regression model, which estimated that a density of 0.20–0.33 weed plant m-1 of row would result in a 50% seed cotton yield loss from the maximum yield. Redroot pigweed seed production per plant or per square meter was indicated by logarithmic response. At a density of 1 plant m-1 of cotton row, redroot pigweed produced about 626,000 seeds m-2. Intraspecific competition resulted in density-dependent effects on weed biomass per plant, a range of 430–2,250 g dry weight by harvest. Redroot pigweed biomass ha-1 tended to increase with increasing weed density as indicated by a logarithmic response. Fiber quality was not significantly influenced by weed density when analyzed over two years; however, the fiber length uniformity and micronaire were adversely affected at density of 1 weed plant m-1 of row in 2014. The adverse impact of redroot pigweed on cotton growth and development identified in this study has indicated the need of effective redroot pigweed management. PMID:26057386

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schuman, G.E.; Vicklund, L.E.; Belden, S.E.

In 1996, the Wyoming Department of Environmental Quality enacted regulations governing the reestablishment of woody shrubs on mined lands. The regulation required that an average density of one shrub m{sup -2} be reestablished on at least 20% of the disturbed land area and that the shrub composition must include dominant premine species. In Wyoming, and much of the Northern Great Plains, that meant that Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) had to be reestablished on mined lands. Artemisia tridentata Nutt. ssp. wyomingensis had proven difficult to reestablish on mined lands because of poor quality seed,more » seed dormancy and a poor understanding of the seedbed ecology of this species. Research in the last two decades has produced significant knowledge in the area of direct-seed establishment of Artemisia tridentata Nutt. ssp. wyomingensis on mined lands. Our research has shown that reducing grass seeding rates will reduce competition and result in larger sagebrush plants that are more likely to survive and provide greater structural diversity to the plant community. Economic analyses demonstrated that big sagebrush can be established at a cost of $0.01-0.05 per seedling using direct seeding methods compared to transplanting nursery grown seedlings, estimated to cost $0.72-$1.65 per seedling (depending on size) to grow and from $1.30-$2.40 to plant (flat land to 2:1 slopes). An adequate level of precipitation will be necessary to ensure successful establishment of this species no matter what method of propagation is selected and direct seeding gives greater opportunity for success because of the demonstrated longevity of the seed to germinate 3-5 years after the initial seeding.« less

Distribution of western juniper seeds across an ecotone and implications for seed dispersal processes

USDA-ARS?s Scientific Manuscript database

Western juniper forests have been the focus of extensive research and management due to range expansion and infilling that began over a century ago. Understanding juniper seed dispersal is vital to identifying processes behind increases in density and range. Dispersal of Juniperus seeds has generall...

The influence of white pine blister rust on seed dispersal in whitebark pine

Treesearch

Shawn T. McKinney; Diana F. Tomback

2007-01-01

We tested the hypotheses that white pine blister rust (Cronartium ribicola J.C. Fisch.) damage in whitebark pine (Pinus albicaulis Engelm.) stands leads to reduced (1) seed cone density, (2) predispersal seed survival, and (3) likelihood of Clark's Nutcracker (Nucifraga columbiana (Wilson, 1811)) seed...

Seed rain dynamics following disturbance exclusion in a secondary tropical dry forest in Morelos, Mexico.

PubMed

Ceccon, Eliane; Hernández, Patricia

2009-01-01

In most of the legally protected areas in Mexico local inhabitants use natural resources, such as fire wood or cattle grazing. These frequent but low-intensity disturbances have consequences at various levels of the tropical ecosystems and strongly impact forest structure and its regeneration capacity. Despite their importance, the effects of these perturbations in many aspects of tropical forest ecology and in the forest's capacity to recover after disturbance exclusion remain poorly understood. Understanding the impact of these processes on tropical forests is necessary for rehabilitating these forests and enhancing their productivity. In this study, we evaluate the impact of twelve years of exclusion (E) of cattle grazing and fire wood extraction in the composition and dynamics of seed rain, and compare this assessment to a similar analysis in an area where these perturbations continued (without exclusion, WE). We found a strong seasonality in seed rain (96% of seeds fell in the dry season) in both areas. There were no significant differences between E and WE sites in relation to overall seed density, species richness and diversity. However, the distribution along the year of seed species density was significantly different among the E and WE sites. The Jaccard's similarity index between E and WE sites was relatively low (0.57). Barochory was the most common dispersal mode observed among the 23 species in terms of seed species density (48%), followed by anemochory (39%) and zoochory (13%). In relation to seed density, anemochory was the most frequent dispersal mode (88%). Most species in the zone were categorized as small seeds (92%), and there were no significant differences in the distribution of seed size between E and WE. The spatial pattern of dispersal of the four species with the highest relative importance value index, in both areas, was aggregated. Twelve years of disturbance exclusion were not enough to fully restore the seed rain of the area; some differences were already perceptible after this lapse. On the other hand, zoochorous species were almost absent from both sites. The re-introduction of climax and animal-dispersed species may be, in addition to perturbation exclusion, a viable strategy to accelerate ecological restoration in this area.

Subsonic and Supersonic shear flows in laser driven high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Gillespie, R. S.; Grosskopf, M. J.; Kuranz, C. C.; Visco, A.; Ditmar, J. R.; Aglitskiy, Y.; Weaver, J. L.; Velikovich, A. L.; Hurricane, O. A.; Hansen, J. F.; Remington, B. A.; Robey, H. F.; Bono, M. J.; Plewa, T.

2009-05-01

Shear flows arise in many high-energy-density (HED) and astrophysical systems, yet few laboratory experiments have been carried out to study their evolution in these extreme environments. Fundamentally, shear flows can initiate mixing via the Kelvin-Helmholtz (KH) instability and may eventually drive a transition to turbulence. We present two dedicated shear flow experiments that created subsonic and supersonic shear layers in HED plasmas. In the subsonic case the Omega laser was used to drive a shock wave along a rippled plastic interface, which subsequently rolled-upped into large KH vortices. In the supersonic shear experiment the Nike laser was used to drive Al plasma across a low-density foam surface also seeded with a ripple. Unlike the subsonic case, detached shocks developed around the ripples in response to the supersonic Al flow.

Resource Allocation and Seed Size Selection in Perennial Plants under Pollen Limitation.

PubMed

Huang, Qiaoqiao; Burd, Martin; Fan, Zhiwei

2017-09-01

Pollen limitation may affect resource allocation patterns in plants, but its role in the selection of seed size is not known. Using an evolutionarily stable strategy model of resource allocation in perennial iteroparous plants, we show that under density-independent population growth, pollen limitation (i.e., a reduction in ovule fertilization rate) should increase the optimal seed size. At any level of pollen limitation (including none), the optimal seed size maximizes the ratio of juvenile survival rate to the resource investment needed to produce one seed (including both ovule production and seed provisioning); that is, the optimum maximizes the fitness effect per unit cost. Seed investment may affect allocation to postbreeding adult survival. In our model, pollen limitation increases individual seed size but decreases overall reproductive allocation, so that pollen limitation should also increase the optimal allocation to postbreeding adult survival. Under density-dependent population growth, the optimal seed size is inversely proportional to ovule fertilization rate. However, pollen limitation does not affect the optimal allocation to postbreeding adult survival and ovule production. These results highlight the importance of allocation trade-offs in the effect pollen limitation has on the ecology and evolution of seed size and postbreeding adult survival in perennial plants.

Dispersal of seeds from splash-cup plants

NASA Astrophysics Data System (ADS)

Pepper, Rachel

2017-11-01

Splash cup plants disperse their seeds with the help of raindrops. The seeds sit in a small (mm-scale) conical cup and are ejected upon drop impact. The seeds are ejected at velocities up to five times the impact speed of the raindrop, and are dispersed up to 1 m away from the parent plant, which is only a few cm high. Previous work investigating the mechanism of this remarkable dispersal predicted an optimum cup opening angle of around 40°, which matched reasonably well with experiments performed with 3D-printed splash cup models. Those experiments were done with off-center drop impacts on initially empty cups with no seeds. We discuss similar experiments for cups that are not initially empty, but rather contain seed mimics, water, or both seeds and water. For some of these realistic initial states results are strikingly different from empty cups. Connections to theory will also be discussed.

Metastatic papillary craniopharyngioma: case study and study of tumor angiogenesis.

PubMed Central

Elmaci, Lhan; Kurtkaya-Yapicier, Ozlem; Ekinci, Gazanfer; Sav, Aydin; Pamir, M. Necmettin; Vidal, Sergio; Kovacs, Kalman; Scheithauer, Bernd W.

2002-01-01

We report a case of suprasellar papillary craniopharyngioma metastatic to the temporoparietal region 2 years after its initial resection. The literature documents examples of craniopharyngioma recurrences along the surgical tract, as well as remote ipsi- and contralateral metastases via cerebrospinal fluid seeding. Ours is the second report of a craniopharyngioma of papillary type to exhibit metastatic behavior. The tumor spread opposite the side of craniotomy. Although a rare occurrence, it confirms the limited capacity of histologically benign craniopharyngiomas to undergo meningeal seeding, likely the result of surgical manipulation. Immunohistochemical demonstration of increased microvascular density and vascular endothelial growth factor expression, as well as a high vascular endothelial growth receptor (VEGFR2) signal by in situ hybridization, suggests that tumor vascularity facilitated angiogenesis and may have been involved in the establishment and growth of the metastatic deposit. PMID:11916504

Linear velocity fields in non-Gaussian models for large-scale structure

NASA Technical Reports Server (NTRS)

Scherrer, Robert J.

1992-01-01

Linear velocity fields in two types of physically motivated non-Gaussian models are examined for large-scale structure: seed models, in which the density field is a convolution of a density profile with a distribution of points, and local non-Gaussian fields, derived from a local nonlinear transformation on a Gaussian field. The distribution of a single component of the velocity is derived for seed models with randomly distributed seeds, and these results are applied to the seeded hot dark matter model and the global texture model with cold dark matter. An expression for the distribution of a single component of the velocity in arbitrary local non-Gaussian models is given, and these results are applied to such fields with chi-squared and lognormal distributions. It is shown that all seed models with randomly distributed seeds and all local non-Guassian models have single-component velocity distributions with positive kurtosis.

A validated non-linear Kelvin-Helmholtz benchmark for numerical hydrodynamics

NASA Astrophysics Data System (ADS)

Lecoanet, D.; McCourt, M.; Quataert, E.; Burns, K. J.; Vasil, G. M.; Oishi, J. S.; Brown, B. P.; Stone, J. M.; O'Leary, R. M.

2016-02-01

The non-linear evolution of the Kelvin-Helmholtz instability is a popular test for code verification. To date, most Kelvin-Helmholtz problems discussed in the literature are ill-posed: they do not converge to any single solution with increasing resolution. This precludes comparisons among different codes and severely limits the utility of the Kelvin-Helmholtz instability as a test problem. The lack of a reference solution has led various authors to assert the accuracy of their simulations based on ad hoc proxies, e.g. the existence of small-scale structures. This paper proposes well-posed two-dimensional Kelvin-Helmholtz problems with smooth initial conditions and explicit diffusion. We show that in many cases numerical errors/noise can seed spurious small-scale structure in Kelvin-Helmholtz problems. We demonstrate convergence to a reference solution using both ATHENA, a Godunov code, and DEDALUS, a pseudo-spectral code. Problems with constant initial density throughout the domain are relatively straightforward for both codes. However, problems with an initial density jump (which are the norm in astrophysical systems) exhibit rich behaviour and are more computationally challenging. In the latter case, ATHENA simulations are prone to an instability of the inner rolled-up vortex; this instability is seeded by grid-scale errors introduced by the algorithm, and disappears as resolution increases. Both ATHENA and DEDALUS exhibit late-time chaos. Inviscid simulations are riddled with extremely vigorous secondary instabilities which induce more mixing than simulations with explicit diffusion. Our results highlight the importance of running well-posed test problems with demonstrated convergence to a reference solution. To facilitate future comparisons, we include as supplementary material the resolved, converged solutions to the Kelvin-Helmholtz problems in this paper in machine-readable form.

Disturbance frequency and vertical distribution of seeds affect long-term population dynamics: a mechanistic seed bank model.

PubMed

Eager, Eric Alan; Haridas, Chirakkal V; Pilson, Diana; Rebarber, Richard; Tenhumberg, Brigitte

2013-08-01

Seed banks are critically important for disturbance specialist plants because seeds of these species germinate only in disturbed soil. Disturbance and seed depth affect the survival and germination probability of seeds in the seed bank, which in turn affect population dynamics. We develop a density-dependent stochastic integral projection model to evaluate the effect of stochastic soil disturbances on plant population dynamics with an emphasis on mimicking how disturbances vertically redistribute seeds within the seed bank. We perform a simulation analysis of the effect of the frequency and mean depth of disturbances on the population's quasi-extinction probability, as well as the long-term mean and variance of the total density of seeds in the seed bank. We show that increasing the frequency of disturbances increases the long-term viability of the population, but the relationship between the mean depth of disturbance and the long-term viability of the population are not necessarily monotonic for all parameter combinations. Specifically, an increase in the probability of disturbance increases the long-term viability of the total seed bank population. However, if the probability of disturbance is too low, a shallower mean depth of disturbance can increase long-term viability, a relationship that switches as the probability of disturbance increases. However, a shallow disturbance depth is beneficial only in scenarios with low survival in the seed bank.

Seed rain and seed bank of third- and fifth-order streams on the western slope of the Cascade Range.

Treesearch

Janice M. Harmon; Jerry F. Franklin

1991-01-01

We compared the composition and density of the on-site vegetation, seed bank, and seed rain of three geomorphic and successional surfaces along third- and fifth-order streams on the western slope of the central Cascade Range in Oregon.The on-site vegetation generally was dominated by tree species, the seed bank by herb species, and the seed rain by tree and...

Floral display size, conspecific density and florivory affect fruit set in natural populations of Phlox hirsuta, an endangered species

PubMed Central

Ruane, Lauren G.; Rotzin, Andrew T.; Congleton, Philip H.

2014-01-01

Background and Aims Natural variation in fruit and seed set may be explained by factors that affect the composition of pollen grains on stigmas. Self-incompatible species require compatible outcross pollen grains to produce seeds. The siring success of outcross pollen grains, however, can be hindered if self (or other incompatible) pollen grains co-occur on stigmas. This study identifies factors that determine fruit set in Phlox hirsuta, a self-sterile endangered species that is prone to self-pollination, and its associated fitness costs. Methods Multiple linear regressions were used to identify factors that explain variation in percentage fruit set within three of the five known populations of this endangered species. Florivorous beetle density, petal colour, floral display size, local conspecific density and pre-dispersal seed predation were quantified and their effects on the ability of flowers to produce fruits were assessed. Key Results In all three populations, percentage fruit set decreased as florivorous beetle density increased and as floral display size increased. The effect of floral display size on fruit set, however, often depended on the density of nearby conspecific plants. High local conspecific densities offset – even reversed – the negative effects of floral display size on percentage fruit set. Seed predation by mammals decreased fruit set in one population. Conclusions The results indicate that seed production in P. hirsuta can be maximized by selectively augmenting populations in areas containing isolated large plants, by reducing the population sizes of florivorous beetles and by excluding mammals that consume unripe fruits. PMID:24557879

The effects of seeding sterile triticale on a native plant community after wildfire in a pinyon pinemountain mahogany woodland

USGS Publications Warehouse

Waitman, B.A.; Draper, T.M.; Esque, T.C.

2009-01-01

Post-fire seeding with grasses is a common practice for emergency rehabilitation of burned woodlands. However, most post-seeding monitoring does not address consequences to native flora. In November 2004, the US Forest Service hand-seeded triticale (Triticosecale Wittm. ex A. Camus), a sterile wheatrye hybrid, on a small burned area in the Spring Mountains of southern Nevada, United States. A monitoring project using paired plots was designed to quantify the effects of seeding triticale on density and species richness of native annual and perennial plants, cover of perennial plants, and aboveground production of annual plants. We did not find any effects of triticale seeding on annual plant species or most responses of perennial plants. However, the density of woody perennial seedlings was significantly lower 2 years after triticale was added. Although we found a smaller impact from seeding with exotic grass than other studies, quantifiable costs to native vegetation were observed. We caution against the use of non-native grass for seeding in areas with naturally low perennial recruitment. ?? IAWF 2009.

Development of new SNP derived cleaved amplified polymorphic sequence marker set and its successful utilization in the genetic analysis of seed color variation in barley.

PubMed

Bungartz, Annemarie; Klaus, Marius; Mathew, Boby; Léon, Jens; Naz, Ali Ahmad

2016-03-01

The aim of the present study was to develop a new cost effective PCR based CAPS marker set using advantages of high-throughput SNP genotyping. Initially, SNP survey was made using 20 diverse barley genotypes via 9k iSelect array genotyping that resulted in 6334 polymorphic SNP markers. Principle component analysis using this marker data showed fine differentiation of barley diverse gene pool. Till this end, we developed 200 SNP derived CAPS markers distributed across the genome covering around 991cM with an average marker density of 5.09cM. Further, we genotyped 68 CAPS markers in an F2 population (Cheri×ICB181160) segregating for seed color variation in barley. Genetic mapping of seed color revealed putative linkage of single nuclear gene on chromosome 1H. These findings showed the proof of concept for the development and utility of a newer cost effective genomic tool kit to analyze broader genetic resources of barley worldwide. Copyright © 2016 Elsevier Inc. All rights reserved.

Influence of soil pathogens on early regeneration success of tropical trees varies between forest edge and interior.

PubMed

Krishnadas, Meghna; Comita, Liza S

2018-01-01

Soil fungi are key mediators of negative density-dependent mortality in seeds and seedlings, and the ability to withstand pathogens in the shaded understory of closed-canopy forests could reinforce light gradient partitioning by tree species. For four species of tropical rainforest trees-two shade-tolerant and two shade-intolerant-we conducted a field experiment to examine the interactive effects of fungal pathogens, light, and seed density on germination and early seedling establishment. In a fully factorial design, seeds were sown into 1 m 2 plots containing soil collected from underneath conspecific adult trees, with plots assigned to forest edge (high light) or shaded understory, high or low density, and fungicide or no fungicide application. We monitored total seed germination and final seedling survival over 15 weeks. Shade-intolerant species were strongly constrained by light; their seedlings survived only at the edge. Fungicide application significantly improved seedling emergence and/or survival for three of the four focal species. There were no significant interactions between fungicide and seed density, suggesting that pathogen spread with increased aggregation of seeds and seedlings did not contribute to pathogen-mediated mortality. Two species experienced significant edge-fungicide interactions, but fungicide effects in edge vs. interior forest varied with species and recruitment stage. Our results suggest that changes to plant-pathogen interactions could affect plant recruitment in human-impacted forests subject to fragmentation and edge-effects.

Evaluating 3D bone tissue engineered constructs with different seeding densities using the alamarBlue assay and the effect on in vivo bone formation.

PubMed

Wilson, C E; Dhert, W J A; Van Blitterswijk, C A; Verbout, A J; De Bruijn, J D

2002-12-01

Bone tissue engineering using patient derived cells seeded onto porous scaffolds has gained much attention in recent years. Evaluating the viability of these 3D constructs is an essential step in optimizing the process. The alamarBlue (aB) assay was evaluated for its potential to follow in vitro cell proliferation on architecturally standardized hydroxyapatite scaffolds. The impact of the aB assayed and seeding density on subsequent in vivo bone formation was investigated. Twelve scaffolds were seeded with various densities from 250 to 2.5x10(6) cells/scaffold and assay by aB at 5 time points during the 7-day culture period. Twelve additional scaffolds were seeded with 2.5x10(5) cells/scaffold. Two control and 2 aB treated scaffolds were subcutaneously implanted into each of 6 nude mice for 6 weeks. Four observers ranked bone formation using a pair wise comparison of histological sections form each mouse. The aB assay successfully followed cell proliferation, however, the diffusion kinetics of the 3D constructs must be considered. The influence of in vitro aB treatment on subsequent in vivo bone formation cannot be ruled out but was not shown to be significant in the current study. The aB assay appears to be quite promising for evaluating a maximum or end-point viability of 3D tissue engineered constructs. Finally, higher seeding densities resulted in more observed bone formation.

Neighborhoods have little effect on fungal attack or insect predation of developing seeds in a grassland biodiversity experiment.

PubMed

Beckman, Noelle G; Dybzinski, Ray; Tilman, G David

2014-02-01

Numerous observational studies have documented conspecific negative density-dependence that is consistent with the Janzen-Connell Hypothesis (JCH) of diversity maintenance. However, there have been few experimental tests of a central prediction of the JCH: that removing host-specific enemies should lead to greater increases in per capita recruitment in areas of higher host density or lower relative phylogenetic diversity. Using spatially randomized plots of high and low host biomass in a temperate grassland biodiversity experiment, we treated developing seedheads of six prairie perennials to factorial applications of fungicide and insecticide. We measured predispersal seed production, seed viability, and seedling biomass. Results were highly species-specific and idiosyncratic. Effects of insect seed predators and fungal pathogens on predispersal responses varied with neither conspecific biomass nor phylogenetic diversity, suggesting that-at least at the predispersal stage and for the insect and fungal seed predators we were able to exclude-the JCH is not sufficient to contribute to negative conspecific density-dependence for these dominant prairie species.

Challenges of establishing big sgebrush (Artemisia tridentata) in rangeland restoration: effects of herbicide, mowing, whole-community seeding, and sagebrush seed sources

USGS Publications Warehouse

Brabec, Martha M.; Germino, Matthew J.; Shinneman, Douglas J.; Pilliod, David S.; McIlroy, Susan K.; Arkle, Robert S.

2015-01-01

The loss of big sagebrush (Artemisia tridentata Nutt.) on sites disturbed by fire has motivated restoration seeding and planting efforts. However, the resulting sagebrush establishment is often lower than desired, especially in dry areas. Sagebrush establishment may be increased by addressing factors such as seed source and condition or management of the plant community. We assessed initial establishment of seeded sagebrush and four populations of small outplants (from different geographies, climates, and cytotypes) and small sagebrush outplants in an early seral community where mowing, herbicide, and seeding of other native plants had been experimentally applied. No emergence of seeded sagebrush was detected. Mowing the site before planting seedlings led to greater initial survival probabilities for sagebrush outplants, except where seeding also occurred, and these effects were related to corresponding changes in bare soil exposure. Initial survival probabilities were > 30% greater for the local population of big sagebrush relative to populations imported to the site from typical seed transfer distances of ~320–800 km. Overcoming the high first-year mortality of outplanted or seeded sagebrush is one of the most challenging aspects of postfire restoration and rehabilitation, and further evaluation of the impacts of herb treatments and sagebrush seed sources across different site types and years is needed.

Short-term effects of experimental fires on a Mojave Desert seed bank

USGS Publications Warehouse

Esque, Todd C.; Young, James A.; Tracy, C. Richard

2010-01-01

A Mojave Desert shrub community was experimentally burned to understand changes in seed bank of desert annual plant species in response to wildfire. Seed mortality ranged from 55 to 80%, and fire caused significant losses of native and alien annual seeds. Schismus arabicus, Schismus barbatus, Bromus madritensis, Bromus tectorum, Erodium cicutarium and Plantago spp. made up >95% of the seed bank. Bromus spp. and Plantago spp. had proportionately greater mortality of seeds than did Schismus spp. and E. cicutarium. Schismus spp. can be lodged into soil cracks thus avoiding lethal temperatures. E. cicutarium has a self-drilling mechanism that places the seeds at greater depth in the soil. Greater seed mortality occurred beneath shrub canopies than interspaces for most species (Plantago, spp., Bromus spp., and E. cicutarium), but microsite had little effect on Schismus spp. Fire reduced the perennial Ambrosia dumosa densities under canopies. Fire reduced the mean number of species found in samples by about one species per plot and no species was extirpated on experimental plots. The relative abundances of common species did not change dramatically as a result of fire or microsite, however; seed densities varied by treatment and affected interpretations of species compositions.

SU-E-J-233: Effect of Brachytherapy Seed Artifacts in T2 and Proton Density Maps in MR Images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashouf, S; University of Toronto, Dept of Radiation Oncology, Toronto, Ontario; Fatemi-Ardekani, A

Purpose: This study aims at investigating the influence of brachytherapy seeds on T2 and proton density (PD) maps generated from MR images. Proton density maps can be used to extract water content. Since dose absorbed in tissue surrounding low energy brachytherapy seeds are highly influenced by tissue composition, knowing the water content is a first step towards implementing a heterogeneity correction algorithm using MR images. Methods: An LDR brachytherapy (IsoAid Advantage Pd-103) seed was placed in the middle of an agar-based gel phantom and imaged using a 3T Philips MR scanner with a 168-channel head coil. A multiple echo sequencemore » with TE=20, 40, 60, 80, 100 (ms) with large repetition time (TR=6259ms) was used to extract T2 and PD maps. Results: Seed artifacts were considerably reduced on T2 maps compared to PD maps. The variation of PD around the mean was obtained as −97% to 125% (±1%) while for T2 it was recorded as −71% to 24% (±1%). Conclusion: PD maps which are required for heterogeneity corrections are susceptible to artifacts from seeds. Seed artifacts on T2 maps, however, are significantly reduced due to not being sensitive to B0 field variation.« less

Comparisons of human amniotic mesenchymal stem cell viability in FDA-approved collagen-based scaffolds: Implications for engineered diaphragmatic replacement.

PubMed

Shieh, Hester F; Graham, Christopher D; Brazzo, Joseph A; Zurakowski, David; Fauza, Dario O

2017-06-01

We sought to examine amniotic fluid mesenchymal stem cell (afMSC) viability within two FDA-approved collagen-based scaffolds, as a prerequisite to clinical translation of afMSC-based engineered diaphragmatic repair. Human afMSCs were seeded in a human-derived collagen hydrogel and in a bovine-derived collagen sheet at 3 matching densities. Cell viability was analyzed at 1, 3, and 5days using an ATP-based 3D bioluminescence assay. Statistical comparisons were by ANOVA (P<0.05). There was a highly significant 3-way interaction between scaffold type, seeding density, and time in 3D culture as determinants of cell viability, clearly favoring the human hydrogel (P<0.001). In both scaffolds, cell viability was highest at the highest seeding density of 150,000 cells/mL. Time in 3D culture impacted cell viability at the optimal seeding density in the human hydrogel, with the highest levels on days 1 (P<0.001) and 5 (P=0.05) with no significant effect in the bovine sheet (P=0.39-0.96). Among clinically-approved cell delivery vehicles, mesenchymal stem cell viability is significantly enhanced in a collagen hydrogel when compared with a collagen sheet. Cell viability can be further optimized by seeding density and time in 3D culture. These data further support the regulatory viability of clinical trials of engineered diaphragmatic repair. N/A (animal and laboratory study). Copyright © 2017 Elsevier Inc. All rights reserved.

Spatial heterogeneity in post-dispersal predation on Prunus and Uvularia seeds.

PubMed

Webb, Sara L; Willson, Mary F

1985-08-01

We investigated effects of seed density, distance from parent, and habitat (woods, open field) on post-dispersal predation risk (chiefly by rodents) for seeds of Prunus virginiana (Rosaceae). Additional study of the habitat effect (woods, open field, treefall gap) was made with seeds of Prunus avium (Rosaceae) and Uvularia grandiflora (Liliaceae). Density of Prunus seeds (range 2-40 seeds/group) did not affect predation risk for individual seeds. Distance from parent plants did influence predation risk, which was greatest directly beneath parents. This distance effect primarily comprised a sharp drop in risk within 2 m of parents, a distance too small to generate a "spacing rule" for conspecifics.We found that habitat strongly influenced predation intensity. Rates of removal of Prunus seeds were higher in woods than in open fields, except when overall predation intensity was very low and no pattern could be discerned. Prunus seed removal rates were higher in closed woods than in treefall gaps. Consequently, a Prunus seed will more likely escape predation if dispersed to an open site. In contrast, Uvularia seed removal rates were higher in open fields than in woods but did not differ between closed woods and tree-fall gaps.Predation intensity was spatially patchy between and within experimental arrays, but was consistent over time at some specific points in space, possibly reflecting home ranges of seed predators.

Efficiency of seed production in southern pine seed orchards

Treesearch

David L. Bramlett

1977-01-01

Seed production in southern pine seed orchards can be evaluated by estimating the efficiency of four separate stages of cone, seed, and seedling development. Calculated values are: cone efficiency (CE), the ratio of mature cones to the initial flower crop; seed efficiency (SE), the ratio of filled seeds per cone to the seed potential; extraction efficiency (EE), the...

Improving crystal size distribution by internal seeding combined cooling/antisolvent crystallization with a cooling/heating cycle

NASA Astrophysics Data System (ADS)

Lenka, Maheswata; Sarkar, Debasis

2018-03-01

This work investigates the effect of internal seeding and an initial cooling/heating cycle on the final crystal size distribution (CSD) during a combined cooling/antisolvent crystallization of L-asparagine monohydrate from it's aqueous solution using isopropyl-alcohol as antisolvent. Internal seeds were generated by one-pot addition of various amounts of antisolvent to the crystallizer. It was then followed by a cooling/heating cycle to dissolve the fines produced and thus obtain a suitable initial seed. A combined cooling/antisolvent crystallization was then followed by employing a linear cooling profile with simultaneous addition of antisolvent with a constant mass flow rate to promote the growth of the internally generated seeds. The amount of initial antisolvent influences the characteristics of the internal seeds generated and the effect of initial amount of antisolvent on the final CSD is investigated. It was found that the introduction of a single cooling/heating cycle significantly improves the reproducibility of final CSD as well as the mean size. Overall, the study indicates that the application of internal seeding with a single cooling/heating cycle for fines dissolution is an effective technique to tailor crystal size distribution.

Apical Dominance and Planting Density Effects on Weed Suppression by Sunn Hemp (Crotalaria juncea L.)

USDA-ARS?s Scientific Manuscript database

A field study was conducted in 2008 and 2009 in Citra, Florida to evaluate the effects of seeding rate and removal of apical dominance of sunn hemp (Crotalaria juncea L.) on weed suppression and seed production of sunn hemp. Three seeding rates of sunn hemp were used; a representative seed producti...

Translocation of the neonicotinoid seed treatment clothianidin in maize

PubMed Central

Krupke, Christian H.

2017-01-01

Neonicotinoid seed treatments, typically clothianidin or thiamethoxam, are routinely applied to >80% of maize (corn) seed grown in North America where they are marketed as a targeted pesticide delivery system. Despite this widespread use, the amount of compound translocated into plant tissue from the initial seed treatment to provide protection has not been reported. Our two year field study compared concentrations of clothianidin seed treatments in maize to that of maize without neonicotinoid seed treatments and found neonicotinoids present in root tissues up to 34 days post planting. Plant-bound clothianidin concentrations followed an exponential decay pattern with initially high values followed by a rapid decrease within the first ~20 days post planting. A maximum of 1.34% of the initial seed treatment was successfully recovered from plant tissues in both study years and a maximum of 0.26% was recovered from root tissue. Our findings show neonicotinoid seed treatments may provide protection from some early season secondary maize pests. However, the proportion of the neonicotinoid seed treatment clothianidin translocated into plant tissues throughout the growing season is low overall and this observation may provide a mechanism to explain reports of inconsistent efficacy of this pest management approach and increasing detections of environmental neonicotinoids. PMID:28282441

Ecosystem services from keystone species: diversionary seeding and seed-caching desert rodents can enhance Indian ricegrass seedling establishment

USGS Publications Warehouse

Longland, William; Ostoja, Steven M.

2013-01-01

Seeds of Indian ricegrass (Achnatherum hymenoides), a native bunchgrass common to sandy soils on arid western rangelands, are naturally dispersed by seed-caching rodent species, particularly Dipodomys spp. (kangaroo rats). These animals cache large quantities of seeds when mature seeds are available on or beneath plants and recover most of their caches for consumption during the remainder of the year. Unrecovered seeds in caches account for the vast majority of Indian ricegrass seedling recruitment. We applied three different densities of white millet (Panicum miliaceum) seeds as “diversionary foods” to plots at three Great Basin study sites in an attempt to reduce rodents' over-winter cache recovery so that more Indian ricegrass seeds would remain in soil seedbanks and potentially establish new seedlings. One year after diversionary seed application, a moderate level of Indian ricegrass seedling recruitment occurred at two of our study sites in western Nevada, although there was no recruitment at the third site in eastern California. At both Nevada sites, the number of Indian ricegrass seedlings sampled along transects was significantly greater on all plots treated with diversionary seeds than on non-seeded control plots. However, the density of diversionary seeds applied to plots had a marginally non-significant effect on seedling recruitment, and it was not correlated with recruitment patterns among plots. Results suggest that application of a diversionary seed type that is preferred by seed-caching rodents provides a promising passive restoration strategy for target plant species that are dispersed by these rodents.

Mesquite seed density in fecal samples of Raramuri Criollo vs. Angus x Hereford cows grazing Chihuahuan Desert Rangeland

USDA-ARS?s Scientific Manuscript database

This study was part of a larger project investigating breed-related differences in feeding habits of Raramuri Criollo (RC) versus Angus x Hereford (AH) cows. Seed densities in fecal samples collected in July and August 2015 were analyzed to compare presumed mesquite bean consumption of RC and AH cow...

Cutleafgroundcherry (physalis angulata) density, biomass and seed production in peanut (arachis hypogaea L.) following regrowth due to inadequate control

USDA-ARS?s Scientific Manuscript database

A field experiment was conducted to evaluate herbicide and application timing on cutleaf groundcherry density, biomass, seed production, and crop yield in a peanut system. Treatments included: 1) a non-treated control; 2) hand pruning; 3) diclosulam applied preemergence (PRE) alone at 0.027 kg ai h...

Life history traits influence the strength of distance- and density-dependence at different life stages of two Amazonian palms.

PubMed

Choo, Juanita; Carasco, Cecilia; Alvarez-Loayza, Patricia; Simpson, Beryl B; Economo, Evan P

2017-07-01

Natural enemies are known to be important in regulating plant populations and contributing to species coexistence (Janzen-Connell effects). The strength of Janzen-Connell effects (both distance- and density-effects) varies across species, but the life history traits that may mediate such a variation are not well understood. This study examined Janzen-Connell effects across the life stages (seed through adult stages) of two sympatric palm species with distinct phenologies and shade tolerances, two traits that may mediate the strength and timing of Janzen-Connell effects. Populations of two common palm species, Attalea phalerata and Astrocaryum murumuru , were studied in Manu National Park, Peru. Seed predation experiments were conducted to assess Janzen-Connell effects at the seed stage. In the post-seed stages, spatial point pattern analyses of the distributions of individuals and biomass were used to infer the strength of distance- and density-effects. Seed predation was both negative distance- and density-dependent consistent with the Janzen-Connell effects. However, only seedling recruitment for asynchronously fruiting Attalea phalerata was depressed near adults while recruitment remained high for synchronously fruiting Astrocaryum murumuru , consistent with weak distance-effects. Negative density-effects were strong in the early stages for shade-intolerant Attalea phalerata but weak or absent in shade-tolerant Astrocaryum murumuru. Distance- and density-effects varied among the life stages of the two palm species in a manner that corresponded to their contrasting phenology and shade tolerance. Generalizing such connections across many species would provide a route to understanding how trait-mediated Janzen-Connell effects scale up to whole communities of species. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Seasonal dynamics of the plant community and soil seed bank along a successional gradient in a subalpine meadow on the Tibetan Plateau.

PubMed

Ma, Miaojun; Zhou, Xianhui; Qi, Wei; Liu, Kun; Jia, Peng; Du, Guozhen

2013-01-01

Knowledge about how change the importance of soil seed bank and relationship between seed mass and abundance during vegetation succession is crucial for understanding vegetation dynamics. Many studies have been conducted, but their ecological mechanisms of community assembly are not fully understood. We examined the seasonal dynamics of the vegetation and soil seed bank as well as seed size distribution along a successional gradient. We also explored the potential role of the soil seed bank in plant community regeneration, the relationship between seed mass and species abundance, and the relative importance of deterministic and stochastic processes along a successional gradient. Species richness of seed bank increased (shallow layer and the total) and seed density decreased (each layer and the total) significantly with succession. Species richness and seed density differed significantly between different seasons and among soil depths. Seed mass showed a significant negative relationship with relative abundance in the earliest successional stage, but the relationships were not significant in later stages. Seed mass showed no relationship with relative abundance in the whole successional series in seed bank. Results were similar for both July 2005 and April 2006. The seed mass and abundance relationship was determined by a complex interaction between small and larger seeded species and environmental factors. Both stochastic processes and deterministic processes were important determinants of the structure of the earliest stage. The importance of seed bank decreased with succession. The restoration of abandoned farmed and grazed meadows to the species-rich subalpine meadow in Tibetan Plateau can be successfully achieved from the soil seed bank. However, at least 20 years are required to fully restore an abandoned agricultural meadow to a natural mature subalpine meadow.

Regeneration potential of Taxodium distichum swamps and climate change

USGS Publications Warehouse

Middleton, B.A.

2009-01-01

Seed bank densities respond to factors across local to landscape scales, and therefore, knowledge of these responses may be necessary in forecasting the effects of climate change on the regeneration of species. This study relates the seed bank densities of species of Taxodium distichum swamps to local water regime and regional climate factors at five latitudes across the Mississippi River Alluvial Valley from southern Illinois to Louisiana. In an outdoor nursery setting, the seed banks of twenty-five swamps were exposed to non-flooded (freely drained) or flooded treatments, and the number and species of seeds germinating were recorded from each swamp during one growing season. Based on ANOVA analysis, the majority of dominant species had a higher rate of germination in non-flooded versus flooded treatments. Similarly, an NMS comparison, which considered the local water regime and regional climate of the swamps, found that the species of seeds germinating, almost completely shifted under non-flooded versus flooded treatments. For example, in wetter northern swamps, seeds of Taxodium distichum germinated in non-flooded conditions, but did not germinate from the same seed banks in flooded conditions. In wetter southern swamps, seeds of Eleocharis cellulosa germinated in flooded conditions, but did not germinate in non-flooded conditions. The strong relationship of seed germination and density relationships with local water regime and regional climate variables suggests that the forecasting of climate change effects on swamps and other wetlands needs to consider a variety of interrelated variables to make adequate projections of the regeneration responses of species to climate change. Because regeneration is an important aspect of species maintenance and restoration, climate drying could influence the species distribution of these swamps in the future. ?? 2008 Springer Science+Business Media B.V.

Effects of long-term trampling on the above-ground forest vegetation and soil seed bank at the base of limestone cliffs.

PubMed

Rusterholz, Hans-Peter; Verhoustraeten, Christine; Baur, Bruno

2011-11-01

Exposed limestone cliffs in central Europe harbor a highly divers flora with many rare and endangered species. During the past few decades, there has been increasing recreational use of these cliffs, which has caused local environmental disturbances. Successful restoration strategies hinge on identifying critical limitations. We examined the composition of aboveground forest vegetation and density and species composition of seeds in the soil seed bank at the base of four limestone cliffs in mixed deciduous forests that are intensively disturbed by human trampling and at four undisturbed cliffs in the Jura Mountains in northwestern Switzerland. We found that long-term human trampling reduced total aboveground vegetation cover at the base of cliffs and caused a significant shift in the plant-species composition. Compared with undisturbed cliffs, total seed density was lower in disturbed cliffs. Human trampling also altered the species composition of seeds in the soil seed bank. Seeds of unintentionally introduced, stress-tolerant, and ruderal species dominated the soil seed bank at the base of disturbed cliffs. Our findings indicate that a restoration of degraded cliff bases from the existing soil seed bank would result in a substantial change of the original unique plant composition. Active seed transfer, or seed flux from adjacent undisturbed forest areas, is essential for restoration success.

New Insights into Different Reproductive Effort and Sexual Recruitment Contribution between Two Geographic Zostera marina L. Populations in Temperate China

PubMed Central

Xu, Shaochun; Wang, Pengmei; Zhou, Yi; Zhang, Xiaomei; Gu, Ruiting; Liu, Xujia; Liu, Bingjian; Song, Xiaoyue; Xu, Shuai; Yue, Shidong

2018-01-01

Seagrasses are important components of global coastal ecosystems, and the eelgrass Zostera marina L. is widely distributed along the Atlantic and Pacific coasts in the temperate northern hemisphere, but limited datum related to the contribution of sexual reproduction to population recruitment have been reported. This study aimed to understand eelgrass sexual reproduction and population recruitment in Swan Lake (SLL), and Huiquan Bay (HQB) was included for comparison. Random sampling, permanent quadrats or cores and laboratory seed germination-based experimental methods were employed. The flowering, seed production, seed banks, seed germination, seedling survival, and seedling growth of eelgrass were investigated from July 2014 to December 2015 to evaluate the contribution of sexual reproduction to population recruitment. Results indicated a dominant role of asexual reproduction in HQB, while sexual reproduction played a relatively important role in SLL. The highest flowering shoot density in SLL was 517.27 ± 504.29 shoots m−2 (June) and represented 53.34% of the total shoots at the center site. The potential seed output per reproductive shoot and per unit area in SLL were 103.67 ± 37.95 seeds shoot−1 and 53,623.66 ± 19,628.11 seeds m−2, respectively. The maximum seed bank density in SLL was 552.21 ± 204.94 seeds m−2 (October). Seed germination mainly occurred from the middle of March to the end of May, and the highest seedling density was 296.88 ± 274.27 seedlings m−2 in April. The recruitment from seedlings accounted for 41.36% of the Z. marina population recruitment at the center site, while the sexual recruitment contribution at the patch site (50.52%) was greater than that at the center site. Seeds in SLL were acclimated to spring germination, while in HQB, they were acclimated to autumn germination (early October–late November). Seed bank density in HQB was very low, with a value of 254.35 ± 613.34 seeds m−2 (early October). However, seeds in HQB were significantly larger and heavier than those in SLL (size: P = 0.004; weight: P < 0.001). The recruitment from seedlings accounted for as low as 2.53% of the Z. marina population recruitment in HQB. Our laboratory seed germination experiment, which was conducted in autumn, showed that the seed germination percent in HQB was significantly greater than in SLL at optimal germination temperatures (10 and 15°C; P < 0.001). A laboratory seed germination test at suitable temperature may be a potential novel approach to identify the ecological differences among different geographic populations. It is suggested that the Z. marina population recruitment may have different strategies and adapt to specific local conditions, such as in SLL and HQB, and the temperature regime may control morphological and phonological variations. PMID:29483922

New Insights into Different Reproductive Effort and Sexual Recruitment Contribution between Two Geographic Zostera marina L. Populations in Temperate China.

PubMed

Xu, Shaochun; Wang, Pengmei; Zhou, Yi; Zhang, Xiaomei; Gu, Ruiting; Liu, Xujia; Liu, Bingjian; Song, Xiaoyue; Xu, Shuai; Yue, Shidong

2018-01-01

Seagrasses are important components of global coastal ecosystems, and the eelgrass Zostera marina L. is widely distributed along the Atlantic and Pacific coasts in the temperate northern hemisphere, but limited datum related to the contribution of sexual reproduction to population recruitment have been reported. This study aimed to understand eelgrass sexual reproduction and population recruitment in Swan Lake (SLL), and Huiquan Bay (HQB) was included for comparison. Random sampling, permanent quadrats or cores and laboratory seed germination-based experimental methods were employed. The flowering, seed production, seed banks, seed germination, seedling survival, and seedling growth of eelgrass were investigated from July 2014 to December 2015 to evaluate the contribution of sexual reproduction to population recruitment. Results indicated a dominant role of asexual reproduction in HQB, while sexual reproduction played a relatively important role in SLL. The highest flowering shoot density in SLL was 517.27 ± 504.29 shoots m -2 (June) and represented 53.34% of the total shoots at the center site. The potential seed output per reproductive shoot and per unit area in SLL were 103.67 ± 37.95 seeds shoot -1 and 53,623.66 ± 19,628.11 seeds m -2 , respectively. The maximum seed bank density in SLL was 552.21 ± 204.94 seeds m -2 (October). Seed germination mainly occurred from the middle of March to the end of May, and the highest seedling density was 296.88 ± 274.27 seedlings m -2 in April. The recruitment from seedlings accounted for 41.36% of the Z. marina population recruitment at the center site, while the sexual recruitment contribution at the patch site (50.52%) was greater than that at the center site. Seeds in SLL were acclimated to spring germination, while in HQB, they were acclimated to autumn germination (early October-late November). Seed bank density in HQB was very low, with a value of 254.35 ± 613.34 seeds m -2 (early October). However, seeds in HQB were significantly larger and heavier than those in SLL (size: P = 0.004; weight: P < 0.001). The recruitment from seedlings accounted for as low as 2.53% of the Z. marina population recruitment in HQB. Our laboratory seed germination experiment, which was conducted in autumn, showed that the seed germination percent in HQB was significantly greater than in SLL at optimal germination temperatures (10 and 15°C; P < 0.001). A laboratory seed germination test at suitable temperature may be a potential novel approach to identify the ecological differences among different geographic populations. It is suggested that the Z. marina population recruitment may have different strategies and adapt to specific local conditions, such as in SLL and HQB, and the temperature regime may control morphological and phonological variations.

Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Alnoor, Hatim; Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie; Iandolo, Donata; Willander, Magnus; Nur, Omer

2016-04-01

Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (˜575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.

Composition of soil seed banks in southern California coastal sage scrub and adjacent exotic grassland

Treesearch

Robert D. Cox; Edith B. Allen

2008-01-01

Soil seed banks are important to many plant communities and are recognized as an important component of management plans. Understanding seed bank composition and density is especially important when communities have been invaded by exotic species and must be managed to promote desirable species. We examined germinable soil seed banks in southern California coastal sage...

Effects of exotic grasses on soil seed banks in Southeastern Arizona grasslands

USGS Publications Warehouse

McLaughlin, S.P.; Bowers, Janice E.

2007-01-01

At the Appleton-Whittell Research Ranch, an ungrazed grassland preserve in southeastern Arizona, soil seed banks were sampled in June, August, and October 2002 and June 2003. Wildfire had previously burned 90% of the research ranch in May 2002. Seed density and species richness in burned native grassland (2 plots) were compared to those in burned exotic grassland (2 plots). Averaged over 4 sample dates, seed densities were as follows: burned native grassland, 591 ?? 243.1 seeds??m-2 and 784 ?? 334.9 seeds??m-2; burned exotic grassland, 501 ?? 198.9 seeds??m-2 and 196 ?? 123.8 seeds??m-2. Species richness in the seed bank, also averaged over 4 sample dates, was as follows: burned native grassland, 16.3 ?? 1.7 species??m -2 and 19.5 ?? 1.0 species??m-2; burned exotic grassland, 12.0 ?? 3.4 species??m-2 and 11.06 ?? 2.5 species??m-2. The seed bank of burned exotic grassland contained significantly fewer seeds and species than that of burned native grassland. In addition, the seed bank in burned exotic grassland comprised mainly exotic grasses, whereas annual and perennial herbs, most of them native, dominated the seed bank of burned native grassland. Of the 50 species detected in soil samples, only 20 had a persistent seed bank, and only 1 of these was a native perennial bunchgrass. The preponderance of transient species means that eradication of exotic grasses must be followed by reseeding of native grasses and herbs, perhaps repeatedly, if native grassland is to replace exotic grassland.

Do key dimensions of seed and seedling functional trait variation capture variation in recruitment probability?

PubMed

Larson, Julie E; Sheley, Roger L; Hardegree, Stuart P; Doescher, Paul S; James, Jeremy J

2016-05-01

Seedling recruitment is a critical driver of population dynamics and community assembly, yet we know little about functional traits that define different recruitment strategies. For the first time, we examined whether trait relatedness across germination and seedling stages allows the identification of general recruitment strategies which share core functional attributes and also correspond to recruitment outcomes in applied settings. We measured six seed and eight seedling traits (lab- and field-collected, respectively) for 47 varieties of dryland grasses and used principal component analysis (PCA) and cluster analysis to identify major dimensions of trait variation and to isolate trait-based recruitment groups, respectively. PCA highlighted some links between seed and seedling traits, suggesting that relative growth rate and root elongation rate are simultaneously but independently associated with seed mass and initial root mass (first axis), and with leaf dry matter content, specific leaf area, coleoptile tissue density and germination rate (second axis). Third and fourth axes captured separate tradeoffs between hydrothermal time and base water potential for germination, and between specific root length and root mass ratio, respectively. Cluster analysis separated six recruitment types along dimensions of germination and growth rates, but classifications did not correspond to patterns of germination, emergence or recruitment in the field under either of two watering treatments. Thus, while we have begun to identify major threads of functional variation across seed and seedling stages, our understanding of how this variation influences demographic processes-particularly germination and emergence-remains a key gap in functional ecology.

Continued results of the seeds in space experiment

NASA Technical Reports Server (NTRS)

Alston, Jim A.

1993-01-01

Two million seeds of 120 different varieties representing 106 species, 97 genera, and 55 plant families were flown aboard the Long Duration Exposure Facility (LDEF). The seed were housed on the Space Exposed Experiment Developed for Students (SEEDS) tray in the sealed canister number 6 and in two small vented canisters. The tray was in the F-2 position. The seed were germinated and the germination rates and the development of the resulting plants were compared to the performance of the control seed that stayed in Park Seed's seed storage facility. The initial results were presented in a paper at the First LDEF Post-Retrieval Symposium. There was a better survival rate of the seed in the sealed canister in space than in the storage facility at Park Seed. At least some of the seed in each of the vented canisters survived the exposure to vacuum for almost six years. The number of observed apparent mutations was very low. In the initial testing, the small seeded crops were not grown to maturity to check for mutations and obtain second generation seed. These small seeded crops have now been grown for evaluation and second generation seed collected.

Shock front distortion and Richtmyer-Meshkov-type growth caused by a small preshock nonuniformity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velikovich, A. L.; Wouchuk, J. G.; Huete Ruiz de Lira, C.

The response of a shock front to small preshock nonuniformities of density, pressure, and velocity is studied theoretically and numerically. These preshock nonuniformities emulate imperfections of a laser target, due either to its manufacturing, like joints or feeding tubes, or to preshock perturbation seeding/growth, as well as density fluctuations in foam targets, ''thermal layers'' near heated surfaces, etc. Similarly to the shock-wave interaction with a small nonuniformity localized at a material interface, which triggers a classical Richtmyer-Meshkov (RM) instability, interaction of a shock wave with periodic or localized preshock perturbations distributed in the volume distorts the shape of the shockmore » front and can cause a RM-type instability growth. Explicit asymptotic formulas describing distortion of the shock front and the rate of RM-type growth are presented. These formulas are favorably compared both to the exact solutions of the corresponding initial-boundary-value problem and to numerical simulations. It is demonstrated that a small density modulation localized sufficiently close to a flat target surface produces the same perturbation growth as an 'equivalent' ripple on the surface of a uniform target, characterized by the same initial areal mass modulation amplitude.« less

Control of edge localized modes by pedestal deposited impurity in the HL-2A tokamak

NASA Astrophysics Data System (ADS)

Zhang, Y. P.; Mazon, D.; Zou, X. L.; Zhong, W. L.; Gao, J. M.; Zhang, K.; Sun, P.; Dong, C. F.; Cui, Z. Y.; Liu, Yi; Shi, Z. B.; Yu, D. L.; Cheng, J.; Jiang, M.; Xu, J. Q.; Isobe, M.; Xiao, G. L.; Chen, W.; Song, S. D.; Bai, X. Y.; Zhang, P. F.; Yuan, G. L.; Ji, X. Q.; Li, Y. G.; Zhou, Y.; Delpech, L.; Ekedahl, A.; Giruzzi, G.; Hoang, T.; Peysson, Y.; Song, X. M.; Song, X. Y.; Li, X.; Ding, X. T.; Dong, J. Q.; Yang, Q. W.; Xu, M.; Duan, X. R.; Liu, Y.; the HL-2A Team

2018-04-01

Effect of the pedestal deposited impurity on the edge-localized mode (ELM) behaviour has been observed and intensively investigated in the HL-2A tokamak. Impurities have been externally seeded by a newly developed laser blow-off (LBO) system. Both mitigation and suppression of ELMs have been realized by LBO-seeded impurity. Measurements have shown that the LBO-seeded impurity particles are mainly deposited in the pedestal region. During the ELM mitigation phase, the pedestal density fluctuation is significantly increased, indicating that the ELM mitigation may be achieved by the enhancement of the pedestal transport. The transition from ELM mitigation to ELM suppression was triggered when the number of the LBO-seeded impurity exceeds a threshold value. During the ELM suppression phase, a harmonic coherent mode (HCM) is excited by the LBO-seeded impurity, and the pedestal density fluctuation is significantly decreased, the electron density is continuously increased, implying that HCM may reduce the pedestal turbulence, suppress ELMs, increase the pedestal pressure, thus extending the Peeling-Ballooning instability limit. It has been found that the occurance of the ELM mitigation and ELM suppression closely depends on the LBO laser spot diameter.

Factors Limiting Post-logging Seedling Regeneration by Big-leaf Mahogany (Swietenia macrophylla) in Southeastern Amazonia, Brazil, and Implications for Sustainable Management

Treesearch

James Grogan; Jurandir Galvao

2006-01-01

Post-logging seedling regeneration density by big-leaf mahogany (Swietenia macrophylla), a nonpioneer light-demanding timber species, is generally reported to be low to nonexistent. To investigate factors limiting seedling density following logging within the study region, we quantified seed production rates, germinability, dispersal patterns, and seed fates on the...

Integrating Soil Silicon Amendment into Management Programs for Insect Pests of Drill-Seeded Rice

PubMed Central

Way, Michael O.; Pearson, Rebecca A.; Stout, Michael J.

2017-01-01

Silicon soil amendment has been shown to enhance plant defenses against insect pests. Rice is a silicon-accumulating graminaceous plant. In the southern United States, the rice water weevil and stem borers are important pests of rice. Current management tactics for these pests rely heavily on the use of insecticides. This study evaluated the effects of silicon amendment when combined with current management tactics for these rice insect pests in the field. Field experiments were conducted from 2013 to 2015. Rice was drill-planted in plots subjected to factorial combinations of variety (conventional and hybrid), chlorantraniliprole seed treatment (treated and untreated), and silicon amendment (treated and untreated). Silicon amendment reduced densities of weevil larvae on a single sampling date in 2014, but did not affect densities of whiteheads caused by stem borers. In contrast, insecticidal seed treatment strongly reduced densities of both weevil larvae and whiteheads. Higher densities of weevil larvae were also observed in the hybrid variety in 2014, while higher incidences of whiteheads were observed in the conventional variety in 2014 and 2015. Silicon amendment improved rice yields, as did chlorantraniliprole seed treatment and use of the hybrid variety. PMID:28805707

Integrating Soil Silicon Amendment into Management Programs for Insect Pests of Drill-Seeded Rice.

PubMed

Villegas, James M; Way, Michael O; Pearson, Rebecca A; Stout, Michael J

2017-08-13

Silicon soil amendment has been shown to enhance plant defenses against insect pests. Rice is a silicon-accumulating graminaceous plant. In the southern United States, the rice water weevil and stem borers are important pests of rice. Current management tactics for these pests rely heavily on the use of insecticides. This study evaluated the effects of silicon amendment when combined with current management tactics for these rice insect pests in the field. Field experiments were conducted from 2013 to 2015. Rice was drill-planted in plots subjected to factorial combinations of variety (conventional and hybrid), chlorantraniliprole seed treatment (treated and untreated), and silicon amendment (treated and untreated). Silicon amendment reduced densities of weevil larvae on a single sampling date in 2014, but did not affect densities of whiteheads caused by stem borers. In contrast, insecticidal seed treatment strongly reduced densities of both weevil larvae and whiteheads. Higher densities of weevil larvae were also observed in the hybrid variety in 2014, while higher incidences of whiteheads were observed in the conventional variety in 2014 and 2015. Silicon amendment improved rice yields, as did chlorantraniliprole seed treatment and use of the hybrid variety.

Feedback controlled, reactor relevant, high-density, high-confinement scenarios at ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Lang, P. T.; Blanken, T. C.; Dunne, M.; McDermott, R. M.; Wolfrum, E.; Bobkov, V.; Felici, F.; Fischer, R.; Janky, F.; Kallenbach, A.; Kardaun, O.; Kudlacek, O.; Mertens, V.; Mlynek, A.; Ploeckl, B.; Stober, J. K.; Treutterer, W.; Zohm, H.; ASDEX Upgrade Team

2018-03-01

One main programme topic at the ASDEX Upgrade all-metal-wall tokamak is development of a high-density regime with central densities at reactor grade level while retaining high-confinement properties. This required development of appropriate control techniques capable of coping with the pellet tool, a powerful means of fuelling but one which presented challenges to the control system for handling of related perturbations. Real-time density profile control was demonstrated, raising the core density well above the Greenwald density while retaining the edge density in order to avoid confinement losses. Recently, a new model-based approach was implemented that allows direct control of the central density. Investigations focussed first on the N-seeding scenario owing to its proven potential to yield confinement enhancements. Combining pellets and N seeding was found to improve the divertor buffering further and enhance the operational range accessible. For core densities up to about the Greenwald density, a clear improvement with respect to the non-seeding reference was achieved; however, at higher densities this benefit is reduced. This behaviour is attributed to recurrence of an outward shift of the edge density profile, resulting in a reduced peeling-ballooning stability. This is similar to the shift seen during strong gas puffing, which is required to prevent impurity influx in ASDEX Upgrade. First tests indicate that highly-shaped plasma configurations like the ITER base-line scenario, respond very well to pellet injection, showing efficient fuelling with no measurable impact on the edge density profile.

Quinoa Seed Quality Response to Sodium Chloride and Sodium Sulfate Salinity

PubMed Central

Wu, Geyang; Peterson, Adam J.; Morris, Craig F.; Murphy, Kevin M.

2016-01-01

Quinoa (Chenopodium quinoa Willd.) is an Andean crop with an edible seed that both contains high protein content and provides high quality protein with a balanced amino acid profile in embryonic tissues. Quinoa is a halophyte adapted to harsh environments with highly saline soil. In this study, four quinoa varieties were grown under six salinity treatments and two levels of fertilization, and then evaluated for quinoa seed quality characteristics, including protein content, seed hardness, and seed density. Concentrations of 8, 16, and 32 dS m-1 of NaCl and Na2SO4, were applied to the soil medium across low (1 g N, 0.29 g P, 0.29 g K per pot) and high (3 g N, 0.85 g P, 0.86 g K per pot) fertilizer treatments. Seed protein content differed across soil salinity treatments, varieties, and fertilization levels. Protein content of quinoa grown under salinized soil ranged from 13.0 to 16.7%, comparable to that from non-saline conditions. NaCl and Na2SO4 exhibited different impacts on protein content. Whereas the different concentrations of NaCl did not show differential effects on protein content, the seed from 32 dS m-1 Na2SO4 contained the highest protein content. Seed hardness differed among varieties, and was moderately influenced by salinity level (P = 0.09). Seed density was affected significantly by variety and Na2SO4 concentration, but was unaffected by NaCl concentration. The samples from 8 dS m-1 Na2SO4 soil had lower density (0.66 g/cm3) than those from 16 dS m-1 and 32 dS m-1 Na2SO4, 0.74 and 0.72g/cm3, respectively. This paper identifies changes in critical seed quality traits of quinoa as influenced by soil salinity and fertility, and offers insights into variety response and choice across different abiotic stresses in the field environment. PMID:27375648

Seed weight - seedling size correlation in coastal Douglas-fir: genetic and environmental components.

Treesearch

Frank C. Sorensen; Robert K. Campbell

1992-01-01

The effect of seed weight on nursery seedling height was analyzed in two experiments. In expt. 1, 16 seeds per family from 111 families were individually weighed and sown in autumn. In expt. 2, a second group of 16 seeds were individually weighed and stratified and sown in spring. Four-tree noncontiguous family plots were randomly assigned to two densities in two...

Combining ability analysis for within-boll yield components in upland cotton (Gossypium hirsutum L.).

PubMed

Imran, M; Shakeel, A; Azhar, F M; Farooq, J; Saleem, M F; Saeed, A; Nazeer, W; Riaz, M; Naeem, M; Javaid, A

2012-08-24

Cotton is an important cash crop worldwide, accounting for a large percentage of world agricultural exports; however, yield per acre is still poor in many countries, including Pakistan. Diallel mating system was used to identify parents for improving within-boll yield and fiber quality parameters. Combining ability analysis was employed to obtain suitable parents for this purpose. The parental genotypes CP-15/2, NIAB Krishma, CIM-482, MS-39, and S-12 were crossed in complete diallel mating under green house conditions during 2009. The F₀ seed of 20 hybrids and five parents were planted in the field in randomized complete block design with three replications during 2010. There were highly significant differences among all F₁ hybrids and their parents. Specific combining ability (SCA) variance was greater than general combining ability (GCA) variance for bolls per plant (9.987), seeds per boll (0.635), seed density (5.672), lint per seed (4.174), boll size (3.69), seed cotton yield (0.315), and lint percentage (0.470), showing predominance of non-additive genes; while seed volume (3.84) was controlled by additive gene action based on maximum GCA variance. Cultivar MS-39 was found to be the best general combiner for seed volume (0.102), seeds per boll (0.448), and lint per seed (0.038) and its utilization produced valuable hybrids, including MS-39 x NIAB Krishma and MS-39 x S-12. The parental line CIM-482 had high GCA effects for boll size (0.33) and seeds per boll (0.90). It also showed good SCA with S-12 and NIAB Krishma for bolls per plant, with CP- 15/2 for boll size, and with MS-39 for seeds per boll. The hybrids, namely, CP-15/2 x NIAB Krishma, NIAB Krishma x S-12, NIAB Krishma x CIM-482, MS-39 x NIAB Krishma, MS-39 x CP-15/2, and S-12 x MS-39 showed promising results. Correlation analysis revealed that seed cotton yield showed significant positive correlation with bolls per plant, boll size and seeds per boll while it showed negative correlation with lint percentage and lint per seed. Seed volume showed significant negative correlation with seed density. Seeds per boll were positively correlated with boll size and negatively correlated with bolls per plant lint percentage and lint per seed. Similarly, lint per seed exhibited positive correlation with lint percentage and boll size showed significantly negative correlation with bolls per plant. Presence of non-additive genetic effects in traits like bolls per plant, seeds per boll, lint per seed, seed cotton yield, and lint percentage is indicative of later generation selection or heterosis breeding may be adopted. For boll size, seed volume and seed density early generation selection may be followed because of the presence of additive gene action. The parental material used in this study and cross combinations obtained from these parents may be exploited in future breeding endeavors.

Reduced availability of large seeds constrains Atlantic forest regeneration

NASA Astrophysics Data System (ADS)

Costa, Janaina B. P.; Melo, Felipe P. L.; Santos, Bráulio A.; Tabarelli, Marcelo

2012-02-01

Secondary forests are expanding in defaunated fragmented tropical landscapes, but their resilience potential remains poorly understood. In this study we used a chronosequence of advancing (19-62-yr old) Atlantic forest regeneration following slash-and-burn agriculture to infer successional shifts in seed rain in terms of seed density, species richness, taxonomic and functional composition, and local spatial distribution. After monitoring seed rain during 12 months in 60 1-m2 seed traps, we recorded over 400,000 seeds belonging to 180 morphospecies. From early to late-successional stage, seed rain decreased in density, increased in per capita species richness, gradually changed in species composition, and became less aggregated spatially. Regardless the age of forest stand, vertebrate-dispersed seeds accounted for 67-75% of all species recorded. Large-seeded species typical of old-growth forests, on the other hand, accounted for only 5-8% of the species recorded in the seed rain, a proportion around five times smaller than that reported for the old-growth forests of the same study site (31%). Our results suggest that the secondary forests considered, which are embedded in one of the largest (3500 ha) and best preserved remnant of the severely fragmented Atlantic forest of Northeast Brazil, may fail attaining older successional stages due to the reduced availability of large-seeded late-successional species. This regeneration constraint may be even stronger in smaller, more isolated forest remnants of the region, potentially reducing their ability to provide ecosystem services.

Potential for seed-mediated gene flow in agroecosystems from transgenic safflower (Carthamus tinctorius L.) intended for plant molecular farming.

PubMed

McPherson, Marc A; Yang, Rong-Cai; Good, Allen G; Nielson, Ryan L; Hall, Linda M

2009-04-01

Safflower has been transformed for field scale molecular farming of high-value proteins including several pharmaceuticals. Viable safflower seed remaining in the soil seed bank after harvest could facilitate seed and pollen-mediated gene flow. Seeds may germinate in subsequent years and volunteer plants may flower and potentially outcross with commodity safflower and/or produce seed. Seeds from volunteers could become admixed with conventional crops at harvest, and/or replenish the seed bank. Seed in following crops could be transported locally and internationally and facilitate gene flow in locations where regulatory thresholds and public acceptance differ from Canada. Seed-mediated gene flow was examined in three studies. Safflower seed loss and viability following harvest of commercial fields of a non-transgenic cultivar were determined. We assessed seed longevity of transgenic and non-transgenic safflower, on the soil surface and buried at two depths. Finally, we surveyed commercial safflower fields at different sites and measured density and growth stage of safflower volunteers, in other crops the following year and documented volunteer survival and viable seed production. Total seed loss at harvest in commercial fields, ranged from 231 to 1,069 seeds m(-2) and the number of viable seeds ranged from 81 to 518 seeds m(-2). Safflower has a relatively short longevity in the seed bank and no viable seeds were found after 2 years. Based on the seed burial studies it is predicted that winter conditions would reduce safflower seed viability on the soil surface by >50%, leaving between 40 and 260 viable seeds m(-2). The density of safflower volunteers emerging in the early spring of the following year ranged from 3 to 11 seedlings m(-2). Safflower volunteers did not survive in fields under chemical fallow, but in some cereal fields small numbers of volunteers did survive and generate viable seed. Results will be used to make recommendations for best management practices to reduce seed-mediated gene flow from commercial production of plant molecular farming with safflower.

Can salvage logging affect seed dispersal by birds into burned forests?

NASA Astrophysics Data System (ADS)

Rost, J.; Pons, P.; Bas, J. M.

2009-09-01

The recovery of vegetation in Mediterranean ecosystems after wildfire is mostly a result of direct regeneration, since the same species existing before the fire regenerate on-site by seeding or resprouting. However, the possibility of plant colonization by dispersal of seeds from unburned areas remains poorly studied. We addressed the role of the frugivorous, bird-dependent seed dispersal (seed rain) of fleshy-fruited plants in a burned and managed forest in the second winter after a fire, before on-site fruit production had begun. We also assessed the effect on seed rain of different microhabitats resulting from salvage logging (erosion barriers, standing snags, open areas), as well as the microhabitats of unlogged patches and an unburned control forest, taking account of the importance of perches as seed rain sites. We found considerable seed rain by birds in the burned area. Seeds, mostly from Olive trees Olea europaea and Evergreen pistaches Pistacia lentiscus, belonged to plants fruiting only in surrounding unburned areas. Seed rain was heterogeneous, and depended on microhabitat, with the highest seed density in the unburned control forest but closely followed by the wood piles of erosion barriers. In contrast, very low densities were found under perches of standing snags. Furthermore, frugivorous bird richness seemed to be higher in the erosion barriers than elsewhere. Our results highlight the importance of this specific post-fire management in bird-dependent seed rain and also may suggest a consequent heterogeneous distribution of fleshy-fruited plants in burned and managed areas. However, there needs to be more study of the establishment success of dispersed seeds before an accurate assessment can be made of the role of bird-mediated seed dispersal in post-fire regeneration.

Ord's kangaroo rats living in floodplain habitats: Factors contributing to habitat attraction

USGS Publications Warehouse

Miller, M.S.; Wilson, K.R.; Andersen, D.C.

2003-01-01

High densities of an aridland granivore, Ord's kangaroo rat (Dipodomys ordii), have been documented in floodplain habitats along the Yampa River in northwestern Colorado. Despite a high probability of inundation and attendant high mortality during the spring flood period, the habitat is consistently recolonized. To understand factors that potentially make riparian habitats attractive to D. ordii, we compared density and spatial pattern of seeds, density of a competitor (western harvester ant, Pogonomyrmex occidentalis), and digging energetics within floodplain habitats and between floodplain and adjacent upland habitats. Seed density within the floodplain was greatest in the topographically high (rarely flooded) floodplain and lowest immediately after a spring flood in the topographically low (frequently flooded) floodplain. Seed densities in adjacent upland habitat that never floods were higher than the lowest floodplain habitat. In the low floodplain prior to flooding, seeds had a clumped spatial pattern, which D. ordii is adept at exploiting; after spring flooding, a more random pattern resulted. Populations of the western harvester ant were low in the floodplain relative to the upland. Digging by D. ordii was energetically less expensive in floodplain areas than in upland areas. Despite the potential for mortality due to annual spring flooding, the combination of less competition from harvester ants and lower energetic costs of digging might promote the use of floodplain habitat by D. ordii.

Initial Results of the Spread F Experiment (SpreadFEx): Overview and Evidence of Possible Gravity Wave Excitation of Equatorial Plasma Bubbles

NASA Astrophysics Data System (ADS)

Fritts, D. C.

2007-05-01

The Spread F Experiment (SpreadFEx) was performed in Brazil by Brazilian and U.S. researchers during two ~20- day periods extending from September to November 2005. We employed extensive ground-based and space- based observations of gravity waves, plasma structures, electron densities, and mean atmospheric and ionospheric conditions using airglow, digisonde, VHF and meteor radar, balloon, GPS and satellite instrumentation at multiple sites in Brazil and with GUVI aboard the TIMED satellite. These measurements focused on deep convection, gravity waves, and plasma bubble structures. This comprehensive data set has provided the first promising indications of the specific roles of gravity waves arising from deep convection and other sources in contributing to the seeding of equatorial spread F and plasma bubbles extending to high altitudes. This talk will summarize the campaign results related to possible neutral atmosphere seeding of spread F and plasma bubbles during these observations. Specifically, our measurements have revealed significant neutral density (and related wind and temperature) perturbations extending from ~80 km well into the thermosphere and ionosphere. Many of these appear to arise from deep convection over the Amazon basin. Others occurring at larger scales under magnetically-disturbed conditions may have auroral or other higher-latitude sources. Both appear to lead, on occasion, to sufficiently large perturbations of the bottomside F layer to trigger plasma bubbles extending to much higher altitudes thereafter. Upon completion of our analyses, we believe that these observations will yield the first persuasive evidence of the role of neutral atmosphere gravity waves in the seeding of equatorial plasma bubbles.

Cone Characteristics and Seed Quality 10 Years After An Uneven-Aged Regeneration Cut In Shortleaf Pine Stands

Treesearch

Kenneth J. Grayson; Robert F. Wittwer; Michael G. Shelton

2002-01-01

Cone characteristics and seed quality for 16 released (stand density 14 square meters per hectare) and 16 unreleased (stand density 28 square meters per hectare) shortleaf pine (Pinus echinata Mill.) trees were described by d.b.h. class (28, 33, 38, 43 centimeters) and crown position (upper south, upper north, lower south, and lower north). The 38-...

Cytotoxicity of zinc oxide (ZnO) nanoparticles is influenced by cell density and culture format.

PubMed

Heng, Boon Chin; Zhao, Xinxin; Xiong, Sijing; Ng, Kee Woei; Boey, Freddy Yin-Chiang; Loo, Joachim Say-Chye

2011-06-01

A parameter that has often been overlooked in cytotoxicity assays is the density and confluency of mammalian cell monolayers utilized for toxicology screening. Hence, this study investigated how different cell seeding densities influenced their response to cytotoxic challenge with ZnO nanoparticles. Utilizing the same volume (1 ml per well) and concentration range (5-40 μg/ml) of ZnO nanoparticles, contradictory results were observed with higher-density cell monolayers (BEAS-2B cells) obtained either by increasing the number of seeded cells per well (50,000 vs. 200,000 cells per well of 12-well plate) or by seeding the same numbers of cells (50,000) within a smaller surface area (12-well vs. 48-well plate, 4.8 vs. 1.2 cm(2), respectively). Further experiments demonstrated that the data may be skewed by inconsistency in the mass/number of nanoparticles per unit area of culture surface, as well as by inconsistent nanoparticle to cell ratio. To keep these parameters constant, the same number of cells (50,000 per well) were seeded on 12-well plates, but with the cells being seeded at the edge of the well for the experimental group (by tilting the plate) to form a dense confluent monolayer, as opposed to a sparse monolayer for the control group seeded in the conventional manner. Utilizing such an experimental set-up for the comparative evaluation of four different cell lines (BEAS-2B, L-929, CRL-2922 and C2C12), it was observed that the high cell density monolayer was consistently more resistant to the cytotoxic effects of ZnO nanoparticles compared to the sparse monolayer for all four different cell types, with the greatest differences being observed above a ZnO concentration of 10 μg/ml. Hence, the results of this study demonstrate the need for the standardization of cell culture protocols utilized for toxicology screening of nanoparticles, with respect to cell density and mass/number of nanoparticles per unit area of culture surface.

Estimates of Optimal Operating Conditions for Hydrogen-Oxygen Cesium-Seeded Magnetohydrodynamic Power Generator

NASA Technical Reports Server (NTRS)

Smith, J. M.; Nichols, L. D.

1977-01-01

The value of percent seed, oxygen to fuel ratio, combustion pressure, Mach number, and magnetic field strength which maximize either the electrical conductivity or power density at the entrance of an MHD power generator was obtained. The working fluid is the combustion product of H2 and O2 seeded with CsOH. The ideal theoretical segmented Faraday generator along with an empirical form found from correlating the data of many experimenters working with generators of different sizes, electrode configurations, and working fluids, are investigated. The conductivity and power densities optimize at a seed fraction of 3.5 mole percent and an oxygen to hydrogen weight ratio of 7.5. The optimum values of combustion pressure and Mach number depend on the operating magnetic field strength.

Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alnoor, Hatim, E-mail: hatim.alnoor@liu.se; Iandolo, Donata; Willander, Magnus

Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealedmore » by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (∼575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.« less

Lack of recruitment in Lavandula stoechas subsp. pedunculata: a case of safe-site limitation

NASA Astrophysics Data System (ADS)

Sánchez, Ana M.; Peco, Begoña

2007-01-01

Lavandula stoechas subsp. pedunculata regeneration depends exclusively on the establishment of new individuals. Seed availability and seedling emergence and survival are therefore critical life stages and processes for species regeneration. In this study, seedling emergence and survival was monitored for two years in the scrub, both in clearings and adjacent to adult plants, and the surrounding perennial grassland, at 1, 3 and 5 m from the scrub. Soil seed bank spatial distribution was also studied for one year in the same two habitats, using the same sampling design. Soil seed availability in the scrub is high regardless of the distance from the adult individuals. On the contrary, the adjacent grassland shows a drastic fall in seed density, and almost no seedlings were observed there. In the scrub, seedling density was negatively related to distance from the three nearest adult plants in the clearings, and positively related to adult plant size beneath the adult Lavandula plants. There was also a negative relationship between seedling density and the percentage of bare soil. Only one seedling survived the first drought period, with no detection of effects of either position with respect to adult individuals or seedling density. We hypothesized that the study populations suffer a lack of appropriate safe sites within the scrubland while in the adjacent perennial grassland, observed low seed availability was added to safe-site limitation. That results in a lack of successful seedling establishments and a poor expansion potential of Lavandula scrublands, whose edges remain static in the short and medium term. As found in other Mediterranean scrubland, recruitment may only occur in years with particularly favourable weather, under disturbance regimes that increase seedling survival probability or when external dispersal agents increased seed availability in adequate places for Lavandula establishment.

The Springfield Weed and Seed Initiative: A Process Description and Evaluation.

ERIC Educational Resources Information Center

Hanna, Donald G.

A process description and preliminary evaluation are provided for the Weed and Seed initiative in Springfield (Illinois). This initiative involved local, state, and federal resources in projects that included (1) facility improvement, (2) drug prevention, (3) youth education and child care, (4) jobs and vocational training, (5) resident…

A radiobiology-based inverse treatment planning method for optimisation of permanent l-125 prostate implants in focal brachytherapy.

PubMed

Haworth, Annette; Mears, Christopher; Betts, John M; Reynolds, Hayley M; Tack, Guido; Leo, Kevin; Williams, Scott; Ebert, Martin A

2016-01-07

Treatment plans for ten patients, initially treated with a conventional approach to low dose-rate brachytherapy (LDR, 145 Gy to entire prostate), were compared with plans for the same patients created with an inverse-optimisation planning process utilising a biologically-based objective. The 'biological optimisation' considered a non-uniform distribution of tumour cell density through the prostate based on known and expected locations of the tumour. Using dose planning-objectives derived from our previous biological-model validation study, the volume of the urethra receiving 125% of the conventional prescription (145 Gy) was reduced from a median value of 64% to less than 8% whilst maintaining high values of TCP. On average, the number of planned seeds was reduced from 85 to less than 75. The robustness of plans to random seed displacements needs to be carefully considered when using contemporary seed placement techniques. We conclude that an inverse planning approach to LDR treatments, based on a biological objective, has the potential to maintain high rates of tumour control whilst minimising dose to healthy tissue. In future, the radiobiological model will be informed using multi-parametric MRI to provide a personalised medicine approach.

A radiobiology-based inverse treatment planning method for optimisation of permanent l-125 prostate implants in focal brachytherapy

NASA Astrophysics Data System (ADS)

Haworth, Annette; Mears, Christopher; Betts, John M.; Reynolds, Hayley M.; Tack, Guido; Leo, Kevin; Williams, Scott; Ebert, Martin A.

2016-01-01

Treatment plans for ten patients, initially treated with a conventional approach to low dose-rate brachytherapy (LDR, 145 Gy to entire prostate), were compared with plans for the same patients created with an inverse-optimisation planning process utilising a biologically-based objective. The ‘biological optimisation’ considered a non-uniform distribution of tumour cell density through the prostate based on known and expected locations of the tumour. Using dose planning-objectives derived from our previous biological-model validation study, the volume of the urethra receiving 125% of the conventional prescription (145 Gy) was reduced from a median value of 64% to less than 8% whilst maintaining high values of TCP. On average, the number of planned seeds was reduced from 85 to less than 75. The robustness of plans to random seed displacements needs to be carefully considered when using contemporary seed placement techniques. We conclude that an inverse planning approach to LDR treatments, based on a biological objective, has the potential to maintain high rates of tumour control whilst minimising dose to healthy tissue. In future, the radiobiological model will be informed using multi-parametric MRI to provide a personalised medicine approach.

The Seeding and Cultivation of a Tropical Species of Filamentous Ulva for Algal Biomass Production

PubMed Central

Carl, Christina; de Nys, Rocky; Paul, Nicholas A.

2014-01-01

Filamentous species of Ulva are ideal for cultivation because they are robust with high growth rates and maintained across a broad range of environments. Temperate species of filamentous Ulva are commercially cultivated on nets which can be artificially ‘seeded’ under controlled conditions allowing for a high level of control over seeding density and consequently biomass production. This study quantified for the first time the seeding and culture cycle of a tropical species of filamentous Ulva (Ulva sp. 3) and identified seeding density and nursery period as key factors affecting growth and biomass yield. A seeding density of 621,000 swarmers m-1 rope in combination with a nursery period of five days resulted in the highest growth rate and correspondingly the highest biomass yield. A nursery period of five days was optimal with up to six times the biomass yield compared to ropes under either shorter or longer nursery periods. These combined parameters of seeding density and nursery period resulted in a specific growth rate of more than 65% day−1 between 7 and 10 days of outdoor cultivation post-nursery. This was followed by a decrease in growth through to 25 days. This study also demonstrated that the timing of harvest is critical as the maximum biomass yield of 23.0±8.8 g dry weight m−1 (228.7±115.4 g fresh weight m−1) was achieved after 13 days of outdoor cultivation whereas biomass degraded to 15.5±7.3 g dry weight m−1 (120.2±71.8 g fresh weight m−1) over a longer outdoor cultivation period of 25 days. Artificially seeded ropes of Ulva with high biomass yields over short culture cycles may therefore be an alternative to unattached cultivation in integrated pond-based aquaculture systems. PMID:24897115

Quaking aspen reproduce from seed after wildfire in the mountains of southeastern Arizona

Treesearch

Ronald D. Quinn; Lin Wu

2001-01-01

Quaking aspen regenerated from seed after a stand replacement wildfire in the Chiricahua Mountains of southeastern Arizona. The wildfire had created gaps in the canopy so that aspen were able to establish from seed. Seedlings were found at a mean density of 0.17 m-2, 30 m or more from the nearest potential seed trees. Six clumps of aspen seedlings contained 18-186...

Regenerative potential and functional composition of soil seed banks in remnant evergreen broad-leaved forests under urbanization in South China

Treesearch

J. Wang; L. Huang; H. Ren; Z. Sun; Q. Guo

2015-01-01

Soil seed banks can act as an important source in forest regeneration, and the information on the seed bank composition is vital for determining the resilience of plant communities under severe environments such as urban settings. In this study, we examined the seed bank density and functional composition, and their relationships with aboveground vegetation in three...

Shelterwood regeneration of true fir: conclusion after 8 years

Treesearch

Robert J. Laacke; Jeanne H. Tomascheski

1986-01-01

Shelterwood cuttings on Swain Mountain Experimental Forest were measured to determine performance six to eight years after the shelterwood cutting and before shelterwood removal. Use of appropriate selecting criteria minimized windthrow of seed trees. Regeneration remained red fir, even where the major seed source was white fir. Density of seed trees may affect...

Seed size- and density-related hidden treatments in common biodiversity experiments

Treesearch

Qinfeng Guo

2011-01-01

With a few exceptions, most well-known field biodiversity experiments on ecosystem functioning have been conducted in plant communities (especially grasslands) in which different numbers of species are planted as treatments. In these experiments, investigators have either kept the total seed weight or seed number constant across treatment plots. However, although in...

Identification of nutrient and physical seed trait QTLs in the model legume, Lotus japonicus

USDA-ARS?s Scientific Manuscript database

Legume seeds have the potential to provide a significant portion of essential micronutrients to the human diet. To identify the genetic basis for seed nutrient density, quantitative trait locus (QTL) analysis was conducted with the Gifu B-129 x Miyakojima MG-20 recombinant inbred population from th...

Nonlinear Brillouin amplification of finite-duration seeds in the strong coupling regime

NASA Astrophysics Data System (ADS)

Lehmann, G.; Spatschek, K. H.

2013-07-01

Parametric plasma processes received renewed interest in the context of generating ultra-intense and ultra-short laser pulses up to the exawatt-zetawatt regime. Both Raman as well as Brillouin amplifications of seed pulses were proposed. Here, we investigate Brillouin processes in the one-dimensional (1D) backscattering geometry with the help of numerical simulations. For optimal seed amplification, Brillouin scattering is considered in the so called strong coupling (sc) regime. Special emphasis lies on the dependence of the amplification process on the finite duration of the initial seed pulses. First, the standard plane-wave instability predictions are generalized to pulse models, and the changes of initial seed pulse forms due to parametric instabilities are investigated. Three-wave-interaction results are compared to predictions by a new (kinetic) Vlasov code. The calculations are then extended to the nonlinear region with pump depletion. Generation of different seed layers is interpreted by self-similar solutions of the three-wave interaction model. Similar to Raman amplification, shadowing of the rear layers by the leading layers of the seed occurs. The shadowing is more pronounced for initially broad seed pulses. The effect is quantified for Brillouin amplification. Kinetic Vlasov simulations agree with the three-wave interaction predictions and thereby affirm the universal validity of self-similar layer formation during Brillouin seed amplification in the strong coupling regime.

Survival and death of seeds during liquid nitrogen storage: a case study on seeds with short lifespans.

PubMed

Ballesteros, D; Pence, V C

The low temperature of liquid nitrogen is assumed to stop ageing and preserve viability indefinitely, however there are few validating data sets. The use of seeds to test these assumptions is important because other cryopreserved systems lack quantitative measures of viability to allow comparisons among timed points. To evaluate survival of a collection of seeds with short lifespans stored 12-20 years in liquid nitrogen. Seeds from 11 species (26 accessions) were removed from cryostorage and evaluated for germination and normal growth. Germination of Plantago cordata and Betula spp. seeds did not decrease significantly during cryostorage. However, Populus deltoides and most Salix spp. accessions showed a significant decrease in germination, with further loss observed when P. deltoides seedlings were followed to the young plant stage. Seeds of initial low quality showed greater deterioration during cryostorage. Cryostorage maintained viability of Salix and Populus seeds longer than other temperatures. However, ageing was not completely stopped and seed longevity was shorter than that predicted for many other species. A high initial seed quality is important in order to obtain the maximum benefit of cryostorage.

Phenology, seed dispersal and difficulties in natural recruitment of the canopy tree Pachira quinata (Malvaceae).

PubMed

Castellanos, Maria Clara; Stevenson, Pablo R

2011-06-01

Life history and recruitment information of tropical trees in natural populations is scarce even for important commercial species. This study focused on a widely exploited Neotropical canopy species, Pachira quinata (Malvaceae), at the southernmost, wettest limit of its natural distribution, in the Colombian Amazonia. We studied phenological patterns, seed production and natural densities; assessed the importance of seed dispersal and density-dependent effects on recruitment, using field experiments. At this seasonal forest P. quinata was overrepresented by large adult trees and had very low recruitment caused by the combination of low fruit production, high seed predation and very high seedling mortality under continuous canopies mostly due to damping off pathogens. There was no evidence of negative distance or density effects on recruitment, but a clear requirement of canopy gaps for seedling survival and growth, where pathogen incidence was drastically reduced. In spite of the strong dependence on light for survival of seedlings, seeds germinated readily in the dark. At the study site, the population of P. quinata appeared to be declining, likely because recruitment depended on the rare combination of large gap formation with the presence of reproductive trees nearby. The recruitment biology of this species makes it very vulnerable to any type of logging in natural populations.

Iterative Reconstruction of Volumetric Particle Distribution for 3D Velocimetry

NASA Astrophysics Data System (ADS)

Wieneke, Bernhard; Neal, Douglas

2011-11-01

A number of different volumetric flow measurement techniques exist for following the motion of illuminated particles. For experiments that have lower seeding densities, 3D-PTV uses recorded images from typically 3-4 cameras and then tracks the individual particles in space and time. This technique is effective in flows that have lower seeding densities. For flows that have a higher seeding density, tomographic PIV uses a tomographic reconstruction algorithm (e.g. MART) to reconstruct voxel intensities of the recorded volume followed by the cross-correlation of subvolumes to provide the instantaneous 3D vector fields on a regular grid. A new hybrid algorithm is presented which iteratively reconstructs the 3D-particle distribution directly using particles with certain imaging properties instead of voxels as base functions. It is shown with synthetic data that this method is capable of reconstructing densely seeded flows up to 0.05 particles per pixel (ppp) with the same or higher accuracy than 3D-PTV and tomographic PIV. Finally, this new method is validated using experimental data on a turbulent jet.

Foraging decisions in wild versus domestic Mus musculus: What does life in the lab select for?

PubMed

Troxell-Smith, Sandra M; Tutka, Michal J; Albergo, Jessica M; Balu, Deebika; Brown, Joel S; Leonard, John P

2016-01-01

What does domestication select for in terms of foraging and anti-predator behaviors? We applied principles of patch use and foraging theory to test foraging strategies and fear responses of three strains of Mus musculus: wild-caught, control laboratory, and genetically modified strains. Foraging choices were quantified using giving-up densities (GUDs) under three foraging scenarios: (1) patches varying in microhabitat (covered versus open), and initial resource density (low versus high); (2) daily variation in auditory cues (aerial predators and control calls); (3) patches with varying seed aggregations. Overall, both domestic strains harvested significantly more food than wild mice. Each strain revealed a significant preference for foraging under cover compared to the open, and predator calls had no detectable effects on foraging. Both domestic strains biased their harvest toward high quality patches; wild mice did not. In terms of exploiting favorable and avoiding unfavorable distributions of seeds within patches, the lab strain performed best, the wild strain worst, and the mutant strain in between. Our study provides support for hypothesis that domestic animals have more energy-efficient foraging strategies than their wild counterparts, but retain residual fear responses. Furthermore, patch-use studies can reveal the aptitudes and priorities of both domestic and wild animals. Copyright © 2015 Elsevier B.V. All rights reserved.

Seed dispersal of the Australian cycad Macrozamia miquelii (Zamiaceae): are cycads megafauna-dispersed "grove forming" plants?

PubMed

Hall, John A; Walter, Gimme H

2013-06-01

Plants that invest in large, heavy seeds and colorful, fleshy fruits or analogous structures seem adapted for dispersal by large vertebrates. Some such plants, like Australian cycads in the genus Macrozamia, do not disperse well, which could be explained by seed-dispersal relationships with megafauna that are rare or extinct in contemporary ecosystems. Such plants provide an opportunity to investigate the ecological consequences of low seed-dispersal distances. • We investigated seed dispersal of Macrozamia miquelii in Central Queensland by tracking the fate of marked seeds, identifying the dispersal fauna and quantifying population demography and spatial structure. • We found that 70-100% of marked seeds remained within 1 m of maternal females (cycads are dioecious). Of the 812 seeds recovered (from 840 originally marked) only 24 dispersed >1 m from maternal females, the greatest observed dispersal being 5 m. We found an average of 2.2 seedlings and 0.7 juveniles within 1.5 m of mature females, which suggests that most seeds that remain in the vicinity of maternal females perish. Within-stand densities ranged between 1000 and 5000 plants/ha. The brushtail possum Trichosurus vulpecula was the only animal observed to move the seeds. • Macrozamia are adapted for dispersal by megafauna that are rare or absent in contemporary ecosystems. We argue that Macrozamia are "grove forming" plants that derive ecological benefit from existing as high-density, spatially discrete populations, the function of megafaunal dispersal adaptations being the infrequent dispersal of seeds en masse to establish new such groves in the landscape.

[Carbon density distribution characteristics and influencing factors in aerially seeded Pinus massoniana plantations].

PubMed

Pan, Ping; Han, Tian Yi; OuYang, Xun Zhi; Liu, Yuan Qiu; Zang, Hao; Ning, Jin Kui; Yang, Yang

2017-12-01

The distribution characteristics of carbon density under aerially seeded Pinus massoniana plantations in Ganzhou City of Jiangxi Province were studied. Total 15 factors, including site, stand, understory vegetation, litter and so on were selected to establish a relationship model between stand carbon density and influencing factors, and the main influencing factors were also screened. The results showed that the average carbon density was 98.29 t·hm -2 at stand level with soil layer (49.58 t·hm -2 ) > tree layer (45.25 t·hm -2 ) > understory vegetation layer (2.23 t·hm -2 ) > litter layer (1.23 t·hm -2 ). Significantly positive correlations were found among the tree, litter and soil layers, but not among the other layers. The main factors were tree density, avera-ge diameter at breast height (DBH), soil thickness, slope position, stand age and canopy density to affect carbon density in aerially seeded P. massoniana plantations. The partial correlation coefficients of the six main factors ranged from 0.331 to 0.434 with significance by t test. The multiple correlation coefficient of quantitative model I reached 0.796 with significance by F test (F=9.28). For stand density, the best tree density and canopy density were 1500-2100 plants·hm -2 and 0.4-0.7, respectively. The moderate density was helpful to improve ecosystem carbon sequestration. The carbon density increased with increasing stand age, DBH and soil thickness, and was higher in lower than middle and upper slope positions.

Effect of Seeding Particles on the Shock Structure of a Supersonic Jet

NASA Astrophysics Data System (ADS)

Porta, David; Echeverría, Carlos; Stern, Catalina

2012-11-01

The original goal of our work was to measure. With PIV, the velocity field of a supersonic flow produced by the discharge of air through a 4mm cylindrical nozzle. The results were superposed to a shadowgraph and combined with previous density measurements made with a Rayleigh scattering technique. The idea was to see if there were any changes in the flow field, close to the high density areas near the shocks. Shadowgraphs were made with and without seeding particles, (spheres of titanium dioxide). Surprisingly, it was observed that the flow structure with particles was shifted in the direction opposite to the flow with respect to the flow structure obtained without seeds. This result might contradict the belief that the seeding particles do not affect the flow and that the speed of the seeds correspond to the local speed of the flow. We acknowledge support from DGAPA UNAM through project IN117712 and from Facultad de Ciencias UNAM.

Changes in Spatial Patterns of Caragana stenophylla along a Climatic Drought Gradient on the Inner Mongolian Plateau

PubMed Central

Xie, Li-Na; Guo, Hong-Yu; Gabler, Christopher A.; Li, Qing-Fang; Ma, Cheng-Cang

2015-01-01

Few studies have investigated the influence of water availability on plant population spatial patterns. We studied changes in the spatial patterns of Caragana stenophylla along a climatic drought gradient within the Inner Mongolian Plateau, China. We examined spatial patterns, seed density, “nurse effects” of shrubs on seedlings, transpiration rates and water use efficiency (WUE) of C. stenophylla across semi-arid, arid, and intensively arid zones. Our results showed that patches of C. stenophylla populations shifted from a random to a clumped spatial pattern towards drier environments. Seed density and seedling survival rate of C. stenophylla decreased from the semi-arid zone to the intensively arid zone. Across the three zones, there were more C. stenophylla seeds and seedlings underneath shrub canopies than outside shrub canopies; and in the intensively arid zone, there were almost no seeds or seedlings outside shrub canopies. Transpiration rates of outer-canopy leaves and WUE of both outer-canopy and inner-canopy leaves increased from the semi-arid zone to the intensively arid zone. In the intensively arid zone, transpiration rates and WUE of inner-canopy leaves were significantly lower and higher, respectively, than those of outer-canopy leaves. We conclude that, as drought stress increased, seed density decreased, seed proportions inside shrubs increased, and “nurse effects” of shrubs on seedlings became more important. These factors, combined with water-saving characteristics associated with clumped spatial patterns, are likely driving the changes in C. stenophylla spatial patterns. PMID:25785848

The seed ecology of Iliamna logisepala (Torr.) Wiggins, an east Cascade endemic.

Treesearch

Richy J. Harrod; Charles B. Halpern

2005-01-01

We examined the seed ecology of Iliamna longisepala as an aid to developing a conservation strategy for this rare endemic forb of northcentral Washington. We conducted field, greenhouse, and laboratory studies to quantify: (1) densities of buried viable seed among sites with different histories of burning, (2) post-fire spatial distributions of...

Dynamics of dense direct-seeded stands of southern pines

Treesearch

J.C.G. Goelz

2006-01-01

Direct seeding of southern pines is an effective method of artificial regeneration, producing extremely dense stands when survival exceeds expectations. Long-term studies of dense direct-seeded stands provide ideal data for exploring development of stands as they approach the limit of maximum stand density. I present data from seven studies with ages of stands ranging...

Saving seeds: Optimally planning our Ex Situ conservation collections to ensure species' evolutionary potential

Treesearch

Sean M. Hoban

2017-01-01

In the face of ongoing environmental change, conservation and natural resource agencies are initiating or expanding ex situ seed collections from natural plant populations. Seed collections have many uses, including in provenance trials, breeding programs, seed orchards, gene banks for long-term conservation (live plants or seeds), restoration, reforestation, and...

Simultaneous density-field visualization and PIV of the Richtmyer-Meshkov instability

NASA Astrophysics Data System (ADS)

Prestridge, Katherine; Rightley, Paul; Benjamin, Robert; Kurnit, Norman; Boxx, Isaac; Vorobieff, Peter

1999-11-01

We describe a highly-detailed experimental characterization of the Richtmyer-Meshkov instability. A vertical curtain of heavy gas (SF_6) flows into the test section of an air-filled, horizontal shock tube, and the instability evolves after the passage of a Mach 1.2 shock past the curtain. The evolution of the curtain is visualized by seeding the SF6 with small (d ≈ 0.5 μm) glycol/water droplets using a modified theatrical fog generator. Because the event lasts only 1 ms and the initial conditions vary from test to test, rapid and high-resolution (both spatial and temporal) data acquisition is required in order to characterize the initial and dynamic conditions for each experimental event. A customized, frequency-doubled, burst mode Nd:YAG laser and a commercial single-pulse laser are used for the implementation of simultaneous density-field imaging and PIV diagnostics. We have provided data about flow scaling and mixing through image analysis, and PIV data gives us further quantitative physical insight into the evolution of the Richtmyer-Meshkov instability.

Globular cluster seeding by primordial black hole population

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgov, A.; Postnov, K., E-mail: dolgov@fe.infn.it, E-mail: kpostnov@gmail.com

Primordial black holes (PBHs) that form in the early Universe in the modified Affleck-Dine (AD) mechanism of baryogenesis should have intrinsic log-normal mass distribution of PBHs. We show that the parameters of this distribution adjusted to provide the required spatial density of massive seeds (≥ 10{sup 4} M {sub ⊙}) for early galaxy formation and not violating the dark matter density constraints, predict the existence of the population of intermediate-mass PBHs with a number density of 0∼ 100 Mpc{sup −3}. We argue that the population of intermediate-mass AD PBHs can also seed the formation of globular clusters in galaxies. Inmore » this scenario, each globular cluster should host an intermediate-mass black hole with a mass of a few thousand solar masses, and should not obligatorily be immersed in a massive dark matter halo.« less

Post-midnight equatorial irregularity distributions and vertical drift velocity variations during solstices

NASA Astrophysics Data System (ADS)

Su, S.-Y.; Liu, C. H.; Chao, C.-K.

2018-04-01

Longitudinal distributions of post-midnight equatorial ionospheric irregularity occurrences observed by ROCSAT-1 (1st satellite of the Republic of China) during moderate to high solar activity years in two solstices are studied with respect to the vertical drift velocity and density variations. The post-midnight irregularity distributions are found to be similar to the well-documented pre-midnight ones, but are different from some published distributions taken during solar minimum years. Even though the post-midnight ionosphere is sinking in general, longitudes of frequent positive vertical drift and high density seems to coincide with the longitudes of high irregularity occurrences. Large scatters found in the vertical drift velocity and density around the dip equator in different ROCSAT-1 orbits indicate the existence of large and frequent variations in the vertical drift velocity and density that seem to be able to provide sufficient perturbations for the Rayleigh-Taylor (RT) instability to cause the irregularity occurrences. The need of seeding agents such as gravity waves from atmospheric convective clouds to initiate the Rayleigh-Taylor instability may not be necessary.

The SEED Initiative

ERIC Educational Resources Information Center

Teich, Carolyn R.

2011-01-01

Committed to fulfilling the promise of the green economy, the American Association of Community Colleges (AACC) launched the Sustainability Education and Economic Development (SEED) initiative (www.theseedcenter.org) in October 2010. The project advances sustainability and clean energy workforce development practices at community colleges by…

Effectiveness of post-fire seeding at the Fitzner-Eberhardt Arid Land Ecology Reserve, Washington

USGS Publications Warehouse

Wirth, Troy A.; Pyke, David A.

2011-01-01

In August 2007, the Milepost 17 and Wautoma fires burned a combined total of 77,349 acres (31,302 hectares) of the Fitzner-Eberhardt Arid Land Ecology Reserve (ALE), part of the Hanford Reach National Monument administered by the U.S. Fish and Wildlife Service (USFWS) Mid-Columbia National Wildlife Refuge. In 2009, the USFWS implemented a series of seeding and herbicide treatments to mitigate potential negative consequences of these fires, including mortality of native vegetation, invasion of Bromus tectorum (cheatgrass), and soil erosion. Treatments included combinations of seeding (drill and aerial), herbicides, and one of six different mixtures of species. Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) also was planted by hand in a small area in the southern end of the fire perimeter. Due to differences in plant communities prior to the fire and the multiple treatments applied, treatments were grouped into five treatment associations including mid-elevation aerial seedings, low-elevation aerial seedings, low-elevation drill seedings, high-elevation drill seeding, and no seeding treatments. Data collected at the mid-elevation aerial seedings indicate that the seeding did not appear to increase the density of seedlings compared to the non-seeded area in 2010. At the low-elevation aerial seedings, there were significantly more seedlings at seeded areas as compared to non-seeded areas. Low densities of existing perennial plants probably fostered a low-competition environment enabling seeds to germinate and emerge in 2010 during adequate moisture. Low-elevation drill seedings resulted in significant emergence of seeded grasses in 2009 and 2010 and forbs in 2010. This was likely due to adequate precipitation and that the drill seeding assured soil-to-seed contact. At the high-elevation drill seeding, which was implemented in 2009, there were a high number of seedlings in 2010. Transplanting of A. tridentata following the fires resulted in variable survival rates that warrant further testing; however, transplants located closer to washes tended to have the highest survival rates. Overall, the low-elevation aerial and drill seedings, and the high-elevation drill seedings resulted in significant numbers of seedlings. Further research is needed on methods that provide land managers with critical information about whether or not to seed post-fire areas including status of pre-fire vegetation and estimates of plant mortality due to fire.

Hand-mouth transfer and potential for exposure to E. coli and F+ coliphage in beach sand, Chicago, Illinois

USGS Publications Warehouse

Whitman, R.L.; Przybyla-Kelly, K.; Shively, D.A.; Nevers, M.B.; Byappanahalli, M.N.

2009-01-01

Beach sand contains fecal indicator bacteria, often in densities greatly exceeding the adjacent swimming waters. We examined the transferability of Escherichia coli and F+ coliphage (MS2) from beach sand to hands in order to estimate the potential subsequent health risk. Sand with high initial E. coli concentrations was collected from a Chicago beach. Individuals manipulated the sand for 60 seconds, and rinse water was analysed for E. coli and coliphage. E. coli densities transferred were correlated with density in sand rather than surface area of an individual's hand, and the amount of coliphage transferred from seeded sand was different among individuals. In sequential rinsing, percentage reduction was 92% for E. coli and 98% for coliphage. Using dose-response estimates developed for swimming water, it was determined that the number of individuals per thousand that would develop gastrointestinal symptoms would be 11 if all E. coli on the fingertip were ingested or 33 if all E. coli on the hand were ingested. These results suggest that beach sand may be an important medium for microbial exposure; bacteria transfer is related to initial concentration in the sand; and rinsing may be effective in limiting oral exposure to sand-borne microbes of human concern.

Effect of tillage system on yield and weed populations of soybean ( Glycin Max L.).

PubMed

Hosseini, Seyed Z; Firouzi, Saeed; Aminpanah, Hashem; Sadeghnejhad, Hamid R

2016-03-01

Field experiment was conducted at Agricultural and Natural Resources Research Center of Golestan Province, Iran, to determine the effects of tillage system and weed management regime on yield and weed populations in soybean ( Glycin max L.). The experimental design was a split plot where the whole plot portion was a randomized complete block with three replicates. Main plots were tillage system: 1- No-till row crop seeding, 2- No-till seed drilling, 3- Tillage with disc harrow and drill planting, 4- Tillage with chisel packer and drill planting. The subplots were weed management regimes: 1-Weed control with herbicide application, 2- Hand weeding, 3- Herbicide application plus hand weeding, and 4- Non-weeding. Results indicated that the main effects of tillage system and weed management regime were significant for seed yield, pod number per plant, seed number per pod, weed density and biomass, while their interaction were significant only for weed density, weed biomass, and seed number per pod. The highest grain yields (3838 kg ha-1) were recorded for No-till row crop seeding. The highest seed yield (3877 kg ha-1) also was recorded for weed control with herbicide and hand weeding treatment, followed by hand weeding (3379 kg ha-1).

Tree seed rain and seed removal, but not the seed bank, impede forest recovery in bracken (Pteridium aquilinum (L.) Kuhn)-dominated clearings in the African highlands.

PubMed

Ssali, Fredrick; Moe, Stein R; Sheil, Douglas

2018-04-01

Considerable areas dominated by bracken Pteridium aquilinum (L.) Kuhn occur worldwide and are associated with arrested forest recovery. How forest recovery is impeded in these areas remains poorly understood, especially in the African highlands. The component processes that can lead to recruitment limitation-including low seed arrival, availability and persistence-are important determinants of plant communities and offer a potential explanation for bracken persistence. We investigated key processes that can contribute to recruitment limitation in bracken-dominated clearings in the Bwindi Impenetrable National Park, Uganda. We examined if differences in seed rain (dispersal limitation), soil seed bank, or seed removal (seed viability and persistence) can, individually or in combination, explain the differences in tree regeneration found between bracken-dominated areas and the neighboring forest. These processes were assessed along ten 50-m transects crossing the forest-bracken boundary. When compared to the neighboring forest, bracken clearings had fewer seedlings (bracken 11,557 ± 5482 vs. forest 34,515 ± 6066 seedlings/ha), lower seed rain (949 ± 582 vs. 1605 ± 335 tree seeds m -2  year -1 ), comparable but sparse soil seed bank (304 ± 236 vs. 264 ± 99 viable tree seeds/m 2 ), higher seed removal (70.1% ± 2.4% vs. 40.6% ± 2.4% over a 3-day interval), and markedly higher rodent densities (25.7 ± 5.4 vs. 5.0 ± 1.6 rodents per 100 trapping sessions). Camera traps revealed that rodents were the dominant animals visiting the seeds in our seed removal study. Synthesis : Recruitment limitation contributes to both the slow recovery of forest in bracken-dominated areas, and to the composition of the tree species that occur. Low seed arrival and low persistence of unburied seeds can both explain the reduced density of seedlings found in bracken versus neighboring forest. Seed removal, likely due to rodents, in particular appears sufficient to constrain forest recovery and impacts some species more severely than others.

Influence of Berry Heterogeneity on Phenolics and Antioxidant Activity of Grapes and Wines: A Primary Study of the New Winegrape Cultivar Meili (Vitis vinifera L.).

PubMed

Liu, Xu; Li, Jinlu; Tian, Yuping; Liao, Mingan; Zhang, Zhenwen

2016-01-01

Wine grapes are usually harvested in vineyards when they ripen. However, not all of the berries in a vineyard ripen homogeneously because of different microclimates around the clusters and berries. In this study, the influence of berry heterogeneity on the phenolic content and antioxidant capacity of grapes and wines under a continental monsoon climate was evaluated for a new wine grape cultivar Meili (Vitis vinifera L.). The total phenolic, flavonoid, flavanol, and monomeric anthocyanin contents in the skin and wine significantly increased with grape density; however, there was no significant difference in the seeds between the two lower densities. The highest values of DPPH free radical-scavenging activity, cupric-reducing antioxidant capacity, and hydroxyl radical-scavenging activity in the skin, seed and wine were detected for the densest berries. The sum of individual phenolic compounds in skin, seed and wine increased with berry density, though no significant difference for skin was observed between the two higher density classes. Hence, the chemical components of Meili grapes and wines were positively associated with the berry density at harvest under the continental monsoon climate.

Influence of Berry Heterogeneity on Phenolics and Antioxidant Activity of Grapes and Wines: A Primary Study of the New Winegrape Cultivar Meili (Vitis vinifera L.)

PubMed Central

Liu, Xu; Li, Jinlu; Tian, Yuping; Liao, Mingan; Zhang, Zhenwen

2016-01-01

Wine grapes are usually harvested in vineyards when they ripen. However, not all of the berries in a vineyard ripen homogeneously because of different microclimates around the clusters and berries. In this study, the influence of berry heterogeneity on the phenolic content and antioxidant capacity of grapes and wines under a continental monsoon climate was evaluated for a new wine grape cultivar Meili (Vitis vinifera L.). The total phenolic, flavonoid, flavanol, and monomeric anthocyanin contents in the skin and wine significantly increased with grape density; however, there was no significant difference in the seeds between the two lower densities. The highest values of DPPH free radical-scavenging activity, cupric-reducing antioxidant capacity, and hydroxyl radical-scavenging activity in the skin, seed and wine were detected for the densest berries. The sum of individual phenolic compounds in skin, seed and wine increased with berry density, though no significant difference for skin was observed between the two higher density classes. Hence, the chemical components of Meili grapes and wines were positively associated with the berry density at harvest under the continental monsoon climate. PMID:26974974

Resilience of Invaded Riparian Landscapes: The Potential Role of Soil-Stored Seed Banks

NASA Astrophysics Data System (ADS)

Tererai, Farai; Gaertner, Mirijam; Jacobs, Shayne M.; Richardson, David M.

2015-01-01

We investigated the potential role of soil-stored seed banks in driving vegetation recovery under varying intensities of invasion by the alien tree Eucalyptus camaldulensis along the Berg River in South Africa's Western Cape Province. We asked: How do richness, diversity, and composition of soil-stored seed banks vary with invasion intensity? What is the difference between the seed banks and above-ground vegetation with respect to species richness, diversity, composition, and structure? To what extent do soil-stored seed banks provide reliable sources for restoring native plant communities? Through a seedling-emergence approach, we compared seedling density, richness, and diversity in plots under varying Eucalyptus cover. Seed bank characteristics were also compared with those of the above-ground vegetation. Except in terms of diversity and density, the richness and composition of native species varied significantly among invasion conditions. Despite the paucity of native tree and shrub species in the seed bank, it was more diverse than extant vegetation. Some species occurred exclusively either in the seed bank or in the above-ground vegetation. Although this ecosystem has been degraded by several agents, including Eucalyptus invasion, soil-stored seed banks still offer modest potential for driving regeneration of native plant communities, but secondary invasions need to be managed carefully. Remnant populations of native plants in the above-ground vegetation remaining after E. camaldulensis clearing provide a more promising propagule source for rapid regeneration. Further work is needed to elucidate possible effects of invasion on successional pathways following E. camaldulensis removal and the effects of hydrochory on seed bank dynamics.

Heavy Metal Uptake by Novel Miscanthus Seed-Based Hybrids Cultivated in Heavy Metal Contaminated Soil

NASA Astrophysics Data System (ADS)

Krzyżak, Jacek; Pogrzeba, Marta; Rusinowski, Szymon; Clifton-Brown, John; McCalmont, Jon Paul; Kiesel, Andreas; Mangold, Anja; Mos, Michal

2017-09-01

When heavy metal contaminated soils are excluded from food production, biomass crops offer an alternative commercial opportunity. Perennial crops have potential for phytoremediation. Whilst the conditions at heavy metal contaminated sites are challenging, successful phytoremediation would bring significant economic and social benefits. Seed-based Miscanthus hybrids were tested alongside the commercial clone Miscanthus × giganteus on arable land, contaminated with Pb, Cd and Zn near Katowice. Before the randomized experimental plots were established (25m2 plots with plant density 2/m2) `time-zero' soil samples were taken to determine initial levels of total (aqua regia) and bioavailable (CaCl2 extraction) concentration of Pb, Cd and Zn. After the growing season plant material was sampled during autumn (October, green harvest) and winter (March, brown harvest) to determine differences in heavy metal uptake. Results after the first growing season are presented, including the plot establishment success, biomass yield and heavy metal uptake.

Conventional and two step sintering of PZT-PCN ceramics

NASA Astrophysics Data System (ADS)

Keshavarzi, Mostafa; Rahmani, Hooman; Nemati, Ali; Hashemi, Mahdieh

2018-02-01

In this study, PZT-PCN ceramic was made via sol-gel seeding method and effects of conventional sintering (CS) as well as two-step sintering (TSS) were investigated on microstructure, phase formation, density, dielectric and piezoelectric properties. First, high quality powder was achieved by seeding method in which the mixture of Co3O4 and Nb2O5 powder was added to the prepared PZT sol to form PZT-PCN gel. After drying and calcination, pyrochlore free PZT-PCN powder was synthesized. Second, CS and TSS were applied to achieve dense ceramic. The optimum temperature used for 2 h of conventional sintering was obtained at 1150 °C; finally, undesired ZrO2 phase formed in CS procedure was removed successfully with TSS procedure and dielectric and piezoelectric properties were improved compared to the CS procedure. The best electrical properties obtained for the sample sintered by TSS in the initial temperature of T 1 = 1200 °C and secondary temperature of T 2 = 1000 °C for 12 h.

[Effect of thinning intensities on fruiting regularities of Quercus liaotungensis forests in Huang-long and Qiaoshan mountains.

PubMed

Huang, Cai Zhi; Zhang, Wen Hui; Li, Gang; Yu, Shi Chuan; You, Jian Jian

2016-11-18

In order to clarify the impact of thinning intensities on fruiting regularity of Quercus liaotungensis forests, we took the Q. liaotungensis half-mature forests in Huanglong and Qiaoshan mountains on south of the Loess Plateau as the object of study, which were under close-to-natural management of different thinning intensities (CK, 10%, 20% and 30%). An analysis was made on stand density and percent of seed trees, seed number of sample tree and unit area, seed spatial distributions, seed characteristics of the Q. liaotungensis forests after 5 years of thinning. The results showed that, percent of seed trees, seed number per sample tree and percent of developed seeds of Q. liaotungensis forests increased with the increasing intensity, and showed a pattern of 30%>20%>10%>CK. Seed number per area reached the maximum number under 20% thinning, and showed a pattern of 20%>30%>CK>10%. From the seed spatial distribution in the canopy, the upper accounted for 73.6%, while the lower had 26.4%. The sunny side of canopy layer set relatively the most fruits of 65.8%, shady side only had 34.2%. Under thinning, further improving was geater under lower canopy than under upper canopy and so was on shady side than on sunny side. The seed long diameter, seed short diameter and 1000-seed mass of Q. liaotungensis forests increased with the increasing intensity, which reached the maximum under 30% thinning. 10% thinning did not significantly impact Q. liaotungensis fruiting, the thinning intensity of 20% was most conducive to the seed quantity and quality improvement of Q. liaotungensis, while the thinning intensity of 30% did not improve the fruiting, and lowered the total number of seeds. It was proposed that 20% thinning should be chosen (canopy density of 0.7) to effectively improve fruiting and quality of Q. liaotungensis.

Effectiveness of primate seed dispersers for an "oversized" fruit, Garcinia benthamii.

PubMed

McConkey, Kim R; Brockelman, Warren Y; Saralamba, Chanpen; Nathalang, Anuttara

2015-10-01

The largest fruits found in tropical forests may depend on complementary seed dispersal strategies. These fruits are dispersed most effectively by megafauna, but populations can persist where megafauna are absent or erratic visitors. Smaller animals often consume these large fruits, but their capacity to disperse these seeds effectively has rarely been assessed. We evaluated the contributions of gibbons (Hylobates lar) and other frugivores in the seed dispersal of the megafaunal fruit Garcinia benthamii, using the SDE (seed dispersal effectiveness) landscape. Gibbons preferentially consumed G. benthamii fruits and were the main seed disperser that we observed. However, gibbons became satiated when availability was high, with 57% of fruits falling to the ground unhandled. Recruitment of seedlings from gibbon-dispersed seeds was also very low. Elephants consumed G. benthamii fruit, but occurred at low density and were rare visitors to the trees. We suggest that gibbons might complement the seed dispersal role of elephants for G. benthamii, allowing limited recruitment in areas (such as the study site) where elephants occur at low density. Fruit availability varied between years; when availability was low, gibbons reliably consumed most of the crop and dispersed some seeds that established seedlings, albeit at low numbers (2.5 seedlings per crop). When fruit availability was high, the fruit supply overwhelmed the gibbons and other arboreal frugivores, ensuring a large abundance of fruit available to terrestrial seed dispersers. Although gibbons effectively dispersed more seeds at these times (20.7 seedlings per crop), there was the potential for elephants to move many more seeds. Complementary seed dispersal strategies may be important for megafaunal fruit, because they ensure that very large fruits are able to benefit from megafaunal dispersal but also persist where this dispersal becomes erratic. However, our data suggest that smaller seed dispersers might not be capable of replacing large dispersers, leading to potential changes in landscape-scale dispersal patterns where megafauna are absent.

Mortality among Seed Trees in Longleaf Pine Shelterwood Stands

Treesearch

William D. Boyer

1970-01-01

Mortality of longieaf pine (Pinus palustris Mill.) seed trees was recorded in 27 regeneration areas ranging from North Carolina to Louisiana. Annual mortality averaged 0.7 percent before, and 1.9 percent after a seed cut reduced stand density to about 30 square feet of basal area per acre. On a per-acre basis, however, annual losses averaged 0....

Seed-deposition and recruitment patterns of Clusia species in a disturbed tropical montane forest in Bolivia

NASA Astrophysics Data System (ADS)

Saavedra, Francisco; Hensen, Isabell; Apaza Quevedo, Amira; Neuschulz, Eike Lena; Schleuning, Matthias

2017-11-01

Spatial patterns of seed dispersal and recruitment of fleshy-fruited plants in tropical forests are supposed to be driven by the activity of animal seed dispersers, but the spatial patterns of seed dispersal, seedlings and saplings have rarely been analyzed simultaneously. We studied seed deposition and recruitment patterns of three Clusia species in a tropical montane forest of the Bolivian Andes and tested whether these patterns changed between habitat types (forest edge vs. forest interior), distance to the fruiting tree and consecutive recruitment stages of the seedlings. We recorded the number of seeds deposited in seed traps to assess the local seed-deposition pattern and the abundance and distribution of seedlings and saplings to evaluate the spatial pattern of recruitment. More seeds were removed and deposited at the forest edge than in the interior. The number of deposited seeds decreased with distance from the fruiting tree and was spatially clustered in both habitat types. The density of 1-yr-old seedlings and saplings was higher at forest edges, whereas the density of 2-yr-old seedlings was similar in both habitat types. While seedlings were almost randomly distributed, seeds and saplings were spatially clustered in both habitat types. Our findings demonstrate systematic changes in spatial patterns of recruits across the plant regeneration cycle and suggest that the differential effects of biotic and abiotic factors determine plant recruitment at the edges and in the interior of tropical montane forests. These differences in the spatial distribution of individuals across recruitment stages may have strong effects on plant community dynamics and influence plant species coexistence in disturbed tropical forests.

A generalized population dynamics model for reproductive interference with absolute density dependence.

PubMed

Kyogoku, Daisuke; Sota, Teiji

2017-05-17

Interspecific mating interactions, or reproductive interference, can affect population dynamics, species distribution and abundance. Previous population dynamics models have assumed that the impact of frequency-dependent reproductive interference depends on the relative abundances of species. However, this assumption could be an oversimplification inappropriate for making quantitative predictions. Therefore, a more general model to forecast population dynamics in the presence of reproductive interference is required. Here we developed a population dynamics model to describe the absolute density dependence of reproductive interference, which appears likely when encounter rate between individuals is important. Our model (i) can produce diverse shapes of isoclines depending on parameter values and (ii) predicts weaker reproductive interference when absolute density is low. These novel characteristics can create conditions where coexistence is stable and independent from the initial conditions. We assessed the utility of our model in an empirical study using an experimental pair of seed beetle species, Callosobruchus maculatus and Callosobruchus chinensis. Reproductive interference became stronger with increasing total beetle density even when the frequencies of the two species were kept constant. Our model described the effects of absolute density and showed a better fit to the empirical data than the existing model overall.

Genetic dissection of seed oil and protein content and identification of networks associated with oil content in Brassica napus.

PubMed

Chao, Hongbo; Wang, Hao; Wang, Xiaodong; Guo, Liangxing; Gu, Jianwei; Zhao, Weiguo; Li, Baojun; Chen, Dengyan; Raboanatahiry, Nadia; Li, Maoteng

2017-04-10

High-density linkage maps can improve the precision of QTL localization. A high-density SNP-based linkage map containing 3207 markers covering 3072.7 cM of the Brassica napus genome was constructed in the KenC-8 × N53-2 (KNDH) population. A total of 67 and 38 QTLs for seed oil and protein content were identified with an average confidence interval of 5.26 and 4.38 cM, which could explain up to 22.24% and 27.48% of the phenotypic variation, respectively. Thirty-eight associated genomic regions from BSA overlapped with and/or narrowed the SOC-QTLs, further confirming the QTL mapping results based on the high-density linkage map. Potential candidates related to acyl-lipid and seed storage underlying SOC and SPC, respectively, were identified and analyzed, among which six were checked and showed expression differences between the two parents during different embryonic developmental periods. A large primary carbohydrate pathway based on potential candidates underlying SOC- and SPC-QTLs, and interaction networks based on potential candidates underlying SOC-QTLs, was constructed to dissect the complex mechanism based on metabolic and gene regulatory features, respectively. Accurate QTL mapping and potential candidates identified based on high-density linkage map and BSA analyses provide new insights into the complex genetic mechanism of oil and protein accumulation in the seeds of rapeseed.

Chemical, morphological and functional properties of Brazilian jackfruit (Artocarpus heterophyllus L.) seeds starch.

PubMed

Madruga, Marta Suely; de Albuquerque, Fabíola Samara Medeiros; Silva, Izis Rafaela Alves; do Amaral, Deborah Silva; Magnani, Marciane; Queiroga Neto, Vicente

2014-01-15

Starches used in food industry are extracted from roots, tubers and cereals. Seeds of jackfruit are abundant and contain high amounts of starch. They are discarded during the fruit processing or consumption and can be an alternative source of starch. The starch was extract from the jackfruit seeds and characterised to chemical, morphological and functional properties. Soft and hard jackfruit seeds showed starch content of 92.8% and 94.5%, respectively. Starch granules showed round and bell shape and some irregular cuts on their surface with type-A crystallinity pattern, similar to cereals starches. The swelling power and solubility of jackfruit starch increased with increasing temperature, showing opaque pastes. The soft seeds starch showed initial and final gelatinisation temperature of 36°C and 56°C, respectively; while hard seeds starch presented initial gelatinisation at 40°C and final at 61°C. These results suggest that the Brazilian jackfruit seeds starches could be used in food products. Copyright © 2013 Elsevier Ltd. All rights reserved.

Physiology and biochemistry of recalcitrant Guarea guidonia (L.) Sleumer seeds

Treesearch

Kristina F. Connor; F.T. Bonner

1998-01-01

Investigations of recalcitrant, or desiccation-sensitive, seeds have as yet failed to identify the causes of this phenomenon. Experiments with Guarea guidonia (L.) Sleumer (American muskwood) were initiated to determine the effects of desiccation on the physiology and biochemistry of the seeds of this tropical tree species. Seeds were air-dried at...

Genes expressed by the biological control bacterium Pseudomonas protegens Pf-5 on seed surfaces

USDA-ARS?s Scientific Manuscript database

Propagules of many fungal and oomycete plant pathogens can remain dormant in the soil for months or years but germinate quickly in response to seed exudates, producing germ tubes or mycelia that infect seeds. Consequently, the spermosphere is often the initial point of interaction between seed-infec...

Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands

PubMed Central

Campos, Valeria E.; Miguel, Florencia; Cona, Mónica I.

2016-01-01

The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR) and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR). The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: “seed predators”, “scatter-hoarders”, and “opportunistic frugivores”. Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure) at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus) and a scatter-hoarder (Microcavia asutralis). In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum), who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe) and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase habitat heterogeneity, allowing for the activity of medium-sized mammals who, behaving as opportunistic frugivores, did the most significant seed removal. PMID:27655222

Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands.

PubMed

Campos, Claudia M; Campos, Valeria E; Miguel, Florencia; Cona, Mónica I

The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR) and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR). The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: "seed predators", "scatter-hoarders", and "opportunistic frugivores". Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure) at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus) and a scatter-hoarder (Microcavia asutralis). In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum), who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe) and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase habitat heterogeneity, allowing for the activity of medium-sized mammals who, behaving as opportunistic frugivores, did the most significant seed removal.

Freeing Crop Genetics through the Open Source Seed Initiative

PubMed Central

Luby, Claire H.; Goldman, Irwin L.

2016-01-01

For millennia, seeds have been freely available to use for farming and plant breeding without restriction. Within the past century, however, intellectual property rights (IPRs) have threatened this tradition. In response, a movement has emerged to counter the trend toward increasing consolidation of control and ownership of plant germplasm. One effort, the Open Source Seed Initiative (OSSI, www.osseeds.org), aims to ensure access to crop genetic resources by embracing an open source mechanism that fosters exchange and innovation among farmers, plant breeders, and seed companies. Plant breeders across many sectors have taken the OSSI Pledge to create a protected commons of plant germplasm for future generations. PMID:27093567

Freeing Crop Genetics through the Open Source Seed Initiative.

PubMed

Luby, Claire H; Goldman, Irwin L

2016-04-01

For millennia, seeds have been freely available to use for farming and plant breeding without restriction. Within the past century, however, intellectual property rights (IPRs) have threatened this tradition. In response, a movement has emerged to counter the trend toward increasing consolidation of control and ownership of plant germplasm. One effort, the Open Source Seed Initiative (OSSI, www.osseeds.org), aims to ensure access to crop genetic resources by embracing an open source mechanism that fosters exchange and innovation among farmers, plant breeders, and seed companies. Plant breeders across many sectors have taken the OSSI Pledge to create a protected commons of plant germplasm for future generations.

A Fiberless Seed Mutation in Cotton Is Associated with Lack of Fiber Cell Initiation in Ovule Epidermis and Alterations in Sucrose Synthase Expression and Carbon Partitioning in Developing Seeds1

PubMed Central

Ruan, Yong-Ling; Chourey, Prem S.

1998-01-01

Fiber cell initiation in the epidermal cells of cotton (Gossypium hirsutum L.) ovules represents a unique example of trichome development in higher plants. Little is known about the molecular and metabolic mechanisms controlling this process. Here we report a comparative analysis of a fiberless seed (fls) mutant (lacking fibers) and a normal (FLS) mutant to better understand the initial cytological events in fiber development and to analyze the metabolic changes that are associated with the loss of a major sink for sucrose during cellulose biosynthesis in the mutant seeds. On the day of anthesis (0 DAA), the mutant ovular epidermal cells lacked the typical bud-like projections that are seen in FLS ovules and are required for commitment to the fiber development pathway. Cell-specific gene expression analyses at 0 DAA showed that sucrose synthase (SuSy) RNA and protein were undetectable in fls ovules but were in abundant, steady-state levels in initiating fiber cells of the FLS ovules. Tissue-level analyses of developing seeds 15 to 35 DAA revealed an altered temporal pattern of SuSy expression in the mutant relative to the normal genotype. Whether the altered programming of SuSy expression is the cause or the result of the mutation is unknown. The developing seeds of the fls mutant have also shown several correlated changes that represent altered carbon partitioning in seed coats and cotyledons as compared with the FLS genotype. PMID:9765525

A fiberless seed mutation in cotton is associated with lack of fiber cell initiation in ovule epidermis and alterations in sucrose synthase expression and carbon partitioning in developing seeds

PubMed

Ruan; Chourey

1998-10-01

Fiber cell initiation in the epidermal cells of cotton (Gossypium hirsutum L.) ovules represents a unique example of trichome development in higher plants. Little is known about the molecular and metabolic mechanisms controlling this process. Here we report a comparative analysis of a fiberless seed (fls) mutant (lacking fibers) and a normal (FLS) mutant to better understand the initial cytological events in fiber development and to analyze the metabolic changes that are associated with the loss of a major sink for sucrose during cellulose biosynthesis in the mutant seeds. On the day of anthesis (0 DAA), the mutant ovular epidermal cells lacked the typical bud-like projections that are seen in FLS ovules and are required for commitment to the fiber development pathway. Cell-specific gene expression analyses at 0 DAA showed that sucrose synthase (SuSy) RNA and protein were undetectable in fls ovules but were in abundant, steady-state levels in initiating fiber cells of the FLS ovules. Tissue-level analyses of developing seeds 15 to 35 DAA revealed an altered temporal pattern of SuSy expression in the mutant relative to the normal genotype. Whether the altered programming of SuSy expression is the cause or the result of the mutation is unknown. The developing seeds of the fls mutant have also shown several correlated changes that represent altered carbon partitioning in seed coats and cotyledons as compared with the FLS genotype.

Density measurement in air with saturable absorbing seed gas

NASA Technical Reports Server (NTRS)

Baganoff, D.

1982-01-01

Approaches which have the potential to make density measurements in a compressible flow, where one or more laser beams are used as probes, were investigated. Saturation in sulfur hexafluoride iodine and a crossed beam technique where one beam acts as a saturating beam and the other is at low intensity and acts as a probe beam are considered. It is shown that a balance between an increase in fluorescence intensity with increasing pressure from line broadening and the normal decrease in intensity with increasing pressure from quenching can be used to develop a linear relation between fluorescence intensity and number density and lead to a new density measurement scheme. The method is used to obtain a density image of the cross section of an iodine seeded underexpanded supersonic jet of nitrogen, by illuminating the cross section by a sheet of laser light.

Density of Jatropha curcas Seed Oil and its Methyl Esters: Measurement and Estimations

NASA Astrophysics Data System (ADS)

Veny, Harumi; Baroutian, Saeid; Aroua, Mohamed Kheireddine; Hasan, Masitah; Raman, Abdul Aziz; Sulaiman, Nik Meriam Nik

2009-04-01

Density data as a function of temperature have been measured for Jatropha curcas seed oil, as well as biodiesel jatropha methyl esters at temperatures from above their melting points to 90 ° C. The data obtained were used to validate the method proposed by Spencer and Danner using a modified Rackett equation. The experimental and estimated density values using the modified Rackett equation gave almost identical values with average absolute percent deviations less than 0.03% for the jatropha oil and 0.04% for the jatropha methyl esters. The Janarthanan empirical equation was also employed to predict jatropha biodiesel densities. This equation performed equally well with average absolute percent deviations within 0.05%. Two simple linear equations for densities of jatropha oil and its methyl esters are also proposed in this study.

Three-dimensional imaging of the ultracold plasma formed in a supersonic molecular beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulz-Weiling, Markus; Grant, Edward

Double-resonant excitation of nitric oxide in a seeded supersonic molecular beam forms a state-selected Rydberg gas that evolves to form an ultracold plasma. This plasma travels with the propagation of the molecular beam in z over a variable distance as great as 600 mm to strike an imaging detector, which records the charge distribution in the dimensions, x and y. The ω{sub 1} + ω{sub 2} laser crossed molecular beam excitation geometry convolutes the axial Gaussian distribution of NO in the molecular beam with the Gaussian intensity distribution of the perpendicularly aligned laser beam to create an ellipsoidal volume of Rydbergmore » gas. Detected images describe the evolution of this initial density as a function of selected Rydberg gas initial principal quantum number, n{sub 0}, ω{sub 1} laser pulse energy (linearly related to Rydberg gas density, ρ{sub 0}) and flight time. Low-density Rydberg gases of lower principal quantum number produce uniformly expanding, ellipsoidal charge-density distributions. Increase either of n{sub 0} or ρ{sub 0} breaks the ellipsoidal symmetry of plasma expansion. The volume bifurcates to form repelling plasma volumes. The velocity of separation depends on n{sub 0} and ρ{sub 0} in a way that scales uniformly with ρ{sub e}, the density of electrons formed in the core of the Rydberg gas by prompt Penning ionization. Conditions under which this electron gas drives expansion in the long axis dimension of the ellipsoid favours the formation of counter-propagating shock waves.« less

Quantitative 3D shape description of dust particles from treated seeds by means of X-ray micro-CT.

PubMed

Devarrewaere, Wouter; Foqué, Dieter; Heimbach, Udo; Cantre, Dennis; Nicolai, Bart; Nuyttens, David; Verboven, Pieter

2015-06-16

Crop seeds are often treated with pesticides before planting. Pesticide-laden dust particles can be abraded from the seed coating during planting and expelled into the environment, damaging nontarget organisms. Drift of these dust particles depends on their size, shape and density. In this work, we used X-ray micro-CT to examine the size, shape (sphericity) and porosity of dust particles from treated seeds of various crops. The dust properties quantified in this work were very variable in different crops. This variability may be a result of seed morphology, seed batch, treatment composition, treatment technology, seed cleaning or an interaction of these factors. The intraparticle porosity of seed treatment dust particles varied from 0.02 to 0.51 according to the crop and generally increased with particle size. Calculated settling velocities demonstrated that accounting for particle shape and porosity is important in drift studies. For example, the settling velocity of dust particles with an equivalent diameter of 200 μm may vary between 0.1 and 1.2 m s(-1), depending on their shape and density. Our analysis shows that in a wind velocity of 5 m s(-1), such particles ejected at 1 m height may travel between 4 and 50 m from the source before settling. Although micro-CT is a valuable tool to characterize dust particles, the current image processing methodology limits the number of particles that can be analyzed.

Repeated drought alters resistance of seed bank regeneration in baldcypress swamps of North America

USGS Publications Warehouse

Lei, Ting; Middleton, Beth A.

2018-01-01

Recurring drying and wetting events are likely to increase in frequency and intensity in predicted future droughts in the central USA and alter the regeneration potential of species. We explored the resistance of seed banks to successive droughts in 53 sites across the nine locations in baldcypress swamps in the southeastern USA. Along the Mississippi River Alluvial Valley and northern Gulf of Mexico, we investigated the capacity of seed banks to retain viable seeds after successive periods of drying and wetting in a greenhouse study. Mean differences in species richness and seed density were compared to examine the interactions of successive droughts, geographical location and water regime. The results showed that both species richness and total density of germinating seedlings decreased over repeated drought trials. These responses were more pronounced in geographical areas with higher annual mean temperature. In seed banks across the southeastern swamp region, most species were exhausted after Trial 2 or 3, except for semiaquatic species in Illinois and Tennessee, and aquatic species in Texas. Distinct geographical trends in seed bank resistance to drought demonstrate that climate-induced drying of baldcypress swamps could influence the regeneration of species differently across their ranges. Despite the health of adult individuals, lack of regeneration may push ecosystems into a relict status. Seed bank depletion by germination without replenishment may be a major conservation threat in a future with recurring droughts far less severe than megadrought. Nevertheless, the protection of moist refugia might aid conservation.

Green tea seed oil reduces weight gain in C57BL/6J mice and influences adipocyte differentiation by suppressing peroxisome proliferator-activated receptor-gamma.

PubMed

Kim, Na-Hyung; Choi, Sun-Kyung; Kim, Su-Jin; Moon, Phil-Dong; Lim, Hun-Sun; Choi, In-Young; Na, Ho-Jeong; An, Hyo-Jin; Myung, Noh-Yil; Jeong, Hyun-Ja; Um, Jae-Young; Hong, Seung-Heon; Kim, Hyung-Min

2008-11-01

Given that tea contains a number of chemical constituents possessing medicinal and pharmacological properties, green tea seed is also believed to contain many biologically active compounds such as saponin, flavonoids, vitamins, and oil materials. However, little is known about the physiologic functions of green tea seed oil. The aim of this study is to investigate the anti-obesity effects of green tea seed oil in C57BL/6J mice and in preadipocyte 3T3L-1 cell lines. In vivo, three groups of mice were fed with a standard diet, a high-fat diet containing 30% shortening, or 30% of green tea seed oil based on a standard diet for 85 days. The levels of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride, glucose, and alanine aminotransferase in blood were analyzed at the end of the study. The mice given green tea seed oil gained less weight compared to mice given the shortening diet (p < 0.01). The plasma level of total cholesterol was decreased by a significant level of 32.4% in mice given the green tea seed oil compared to the mice given the shortening diet (p < 0.01). In addition, 3T3-L1 cells were treated for 2 days to evaluate effects of green tea seed oil on adipocyte differentiation. Green tea seed oil inhibited expression of peroxisome proliferator-activated receptor-gamma(2) and CCAAT/enhancer binding protein-alpha in adipocytes and adipose tissue from the experimental animals. These results indicate that the anti-obesity effects of green tea seed oil might be, in part, through suppression of transcription factors related to adipocyte differentiation.

Relativistic Eulerian Vlasov simulations of the amplification of seed pulses by Brillouin backscattering in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shoucri, M., E-mail: Shoucri.Magdi@ireq.ca; Matte, J.-P.; Vidal, F.

We apply an Eulerian Vlasov code to study the amplification by Brillouin scattering of a short seed laser pulse by a long pump laser pulse in an underdense plasma. The stimulated Brillouin backscattering interaction is the coupling of the pump and seed electromagnetic waves propagating in opposite directions, and the ion plasma wave. The code solves the one-dimensional relativistic Vlasov-Maxwell set of equations. Large amplitude ion waves are generated. In the simulations we present, the density plateau of the plasma is n{sub e}=0.3 n{sub c} (n{sub c} is the critical density), which excludes spurious stimulated Raman scattering amplification (which can occurmore » only if n{sub e}« less

Combinatoric analysis of heterogeneous stochastic self-assembly.

PubMed

D'Orsogna, Maria R; Zhao, Bingyu; Berenji, Bijan; Chou, Tom

2013-09-28

We analyze a fully stochastic model of heterogeneous nucleation and self-assembly in a closed system with a fixed total particle number M, and a fixed number of seeds Ns. Each seed can bind a maximum of N particles. A discrete master equation for the probability distribution of the cluster sizes is derived and the corresponding cluster concentrations are found using kinetic Monte-Carlo simulations in terms of the density of seeds, the total mass, and the maximum cluster size. In the limit of slow detachment, we also find new analytic expressions and recursion relations for the cluster densities at intermediate times and at equilibrium. Our analytic and numerical findings are compared with those obtained from classical mass-action equations and the discrepancies between the two approaches analyzed.

Positive density-dependent reproduction regulated by local kinship and size in an understorey tropical tree

PubMed Central

Castilla, Antonio R.; Pope, Nathaniel; Jha, Shalene

2016-01-01

Background and Aims Global pollinator declines and continued habitat fragmentation highlight the critical need to understand reproduction and gene flow across plant populations. Plant size, conspecific density and local kinship (i.e. neighbourhood genetic relatedness) have been proposed as important mechanisms influencing the reproductive success of flowering plants, but have rarely been simultaneously investigated. Methods We conducted this study on a continuous population of the understorey tree Miconia affinis in the Forest Dynamics Plot on Barro Colorado Island in central Panama. We used spatial, reproductive and population genetic data to investigate the effects of tree size, conspecific neighbourhood density and local kinship on maternal and paternal reproductive success. We used a Bayesian framework to simultaneously model the effects of our explanatory variables on the mean and variance of maternal viable seed set and siring success. Key Results Our results reveal that large trees had lower proportions of viable seeds in their fruits but sired more seeds. We documented differential effects of neighbourhood density and local kinship on both maternal and paternal reproductive components. Trees in more dense neighbourhoods produced on average more viable seeds, although this positive density effect was influenced by variance-inflation with increasing local kinship. Neighbourhood density did not have significant effects on siring success. Conclusions This study is one of the first to reveal an interaction among tree size, conspecific density and local kinship as critical factors differentially influencing maternal and paternal reproductive success. We show that both maternal and paternal reproductive success should be evaluated to determine the population-level and individual traits most essential for plant reproduction. In addition to conserving large trees, we suggest the inclusion of small trees and the conservation of dense patches with low kinship as potential strategies for strengthening the reproductive status of tropical trees. PMID:26602288

Positive density-dependent reproduction regulated by local kinship and size in an understorey tropical tree.

PubMed

Castilla, Antonio R; Pope, Nathaniel; Jha, Shalene

2016-02-01

Global pollinator declines and continued habitat fragmentation highlight the critical need to understand reproduction and gene flow across plant populations. Plant size, conspecific density and local kinship (i.e. neighbourhood genetic relatedness) have been proposed as important mechanisms influencing the reproductive success of flowering plants, but have rarely been simultaneously investigated. We conducted this study on a continuous population of the understorey tree Miconia affinis in the Forest Dynamics Plot on Barro Colorado Island in central Panama. We used spatial, reproductive and population genetic data to investigate the effects of tree size, conspecific neighbourhood density and local kinship on maternal and paternal reproductive success. We used a Bayesian framework to simultaneously model the effects of our explanatory variables on the mean and variance of maternal viable seed set and siring success. Our results reveal that large trees had lower proportions of viable seeds in their fruits but sired more seeds. We documented differential effects of neighbourhood density and local kinship on both maternal and paternal reproductive components. Trees in more dense neighbourhoods produced on average more viable seeds, although this positive density effect was influenced by variance-inflation with increasing local kinship. Neighbourhood density did not have significant effects on siring success. This study is one of the first to reveal an interaction among tree size, conspecific density and local kinship as critical factors differentially influencing maternal and paternal reproductive success. We show that both maternal and paternal reproductive success should be evaluated to determine the population-level and individual traits most essential for plant reproduction. In addition to conserving large trees, we suggest the inclusion of small trees and the conservation of dense patches with low kinship as potential strategies for strengthening the reproductive status of tropical trees. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Investigation of crystallization kinetics of sodium bicarbonate in a continuous stirred tank crystallizer

NASA Astrophysics Data System (ADS)

Zhu, Yi; Haut, Benoît; Halloin, Veronique; Delplancke-Ogletree, Marie-Paule

2005-08-01

In our previous work [J. Crystal Growth 263 (2004) 459], a supersaturation determination method using a high-precision densimeter was designed and developed for monitoring sodium bicarbonate supersaturation in the sodium carbonate-bicarbonate system, a two-component solution in equilibrium. In the present paper, we apply this method to the study of sodium bicarbonate continuous crystallization. It gives us access to the sodium bicarbonate supersaturation evolution. The sodium bicarbonate supersaturation evolution and their crystallization kinetics obtained in a continuous stirred tank crystallizer are investigated under different operational conditions, such as residence time, initial supersaturation and seeding. The induction time determined by density measurements is discussed. Mathematical modeling is used to interpret the supersaturation evolution. It is shown that measuring the density gives satisfying performances for studying the crystallization of a two-component solution in equilibrium, such as the sodium carbonate-bicarbonate system.

Seasonal Variation in the Fate of Seeds under Contrasting Logging Regimes

PubMed Central

Fleury, Marina; Rodrigues, Ricardo R.; do Couto, Hilton T. Z.; Galetti, Mauro

2014-01-01

Seed predators and dispersers may drive the speed and structure of forest regeneration in natural ecosystems. Rodents and ants prey upon and disperse seeds, yet empirical studies on the magnitude of these effects are lacking. Here, we examined the role of ants and rodents on seed predation in 4 plant species in a successional gradient on a tropical rainforest island. We found that (1) seeds are mostly consumed rather than dispersed; (2) rates of seed predation vary by habitat, season, and species; (3) seed size, shape, and hardness do not affect the probability of being depredated. Rodents were responsible for 70% of seed predation and were negligible (0.14%) seed dispersers, whereas ants were responsible for only 2% of seed predation and for no dispersal. We detected seasonal and habitat effects on seed loss, with higher seed predation occurring during the wet season and in old-growth forests. In the absence of predators regulating seed-consumer populations, the densities of these resilient animals explode to the detriment of natural regeneration and may reduce diversity and carrying capacity for consumers and eventually lead to ecological meltdown. PMID:24614500

Seasonal variation in the fate of seeds under contrasting logging regimes.

PubMed

Fleury, Marina; Rodrigues, Ricardo R; do Couto, Hilton T Z; Galetti, Mauro

2014-01-01

Seed predators and dispersers may drive the speed and structure of forest regeneration in natural ecosystems. Rodents and ants prey upon and disperse seeds, yet empirical studies on the magnitude of these effects are lacking. Here, we examined the role of ants and rodents on seed predation in 4 plant species in a successional gradient on a tropical rainforest island. We found that (1) seeds are mostly consumed rather than dispersed; (2) rates of seed predation vary by habitat, season, and species; (3) seed size, shape, and hardness do not affect the probability of being depredated. Rodents were responsible for 70% of seed predation and were negligible (0.14%) seed dispersers, whereas ants were responsible for only 2% of seed predation and for no dispersal. We detected seasonal and habitat effects on seed loss, with higher seed predation occurring during the wet season and in old-growth forests. In the absence of predators regulating seed-consumer populations, the densities of these resilient animals explode to the detriment of natural regeneration and may reduce diversity and carrying capacity for consumers and eventually lead to ecological meltdown.

Nanocomposite Porous Microcarriers Based on Strontium-Substituted HA- g-Poly(γ-benzyl-l-glutamate) for Bone Tissue Engineering.

PubMed

Yan, Shifeng; Xia, Pengfei; Xu, Shenghua; Zhang, Kunxi; Li, Guifei; Cui, Lei; Yin, Jingbo

2018-05-04

Porous microcarriers have aroused increasing attention recently, which can create a protected environment for sufficient cell seeding density, facilitate oxygen and nutrient transfer, and well support the cell attachment and growth. In this study, porous microcarriers fabricated from the strontium-substituted hydroxyapatite- graft-poly(γ-benzyl-l-glutamate) (Sr10-HA- g-PBLG) hybrid nanocomposite were developed. The surface grating of PBLG, the micromorphology and element distribution, mechanical strength, in vitro degradation, and Sr 2+ ion release of the obtained Sr10-HA- g-PBLG porous microcarriers were investigated, respectively. The grafting ratio and the molecular weight of the grafted PBLG of Sr10-HA- g-PBLG could be effectively controlled by varying the initial ratio of BLG-NCA to Sr10-HA-NH 2 . The microcarriers exhibited a highly porous and interconnected microstructure with the porosity of about 90% and overall density of 1.03-1.06 g/cm 3 . Also, the degradation rate of Sr10-HA-PBLG microcarriers could be effectively controlled and long-term Sr 2+ release was obtained. The Sr10-HA-PBLG microcarriers allowed cells adhesion, infiltration, and proliferation and promoted the osteogenic differentiation of rabbit adipose-derived stem cells (ADSCs). Successful healing of femoral bone defect was proved by injection of the ADSCs-seeded Sr10-HA-PBLG microcarriers in a rabbit model.

Polyculture Engineering technology of larasati red tilapia (Oreochromis niloticus) and white shrimp (Litopenaeus vannamei) based for protease enzyme

NASA Astrophysics Data System (ADS)

Samidjan, I.; Rachmawati, D.

2018-04-01

The objective is polyculture technology of red tilapia larasati fish and white shrimp with different combinations density. The material is saline red tilapia larasati 3.29 ± 0.018 g and white shrimp with initial weight 1.39 ± 0.025 g. Seeds are density of red tilapia larasati larvae 5 and 10 larvae / m2 fish. And white shrimp 5 larvae / m2 and 10 larvae / m2. An artificial feed used enzyme dose of 2.25 g / kg. The experimental using complete randomized design 4 treatments and 3 replications that is given seeds 5 larvae / m2 larvae red tilapia larasati and given 5 larvae / m2 white shrimp (A), 5 larvae / m2 red tilapia) and 10 m2 / m2 of white shrimp (B), 10 m2 larvae and 5 m2 white shrimp (C), 10 m2 larvae and 10 m2 white shrimp (D)). The data were growth of absolute weight, survival rate, FCR, and water quality data (temperature, salinity, pH, O2, NO2, NH3). Data were analyzed of variance (F test). The results showed significantly effect (P <0.01) on the growth. The highest absolute growth in D treatment were red tilapia larasati (185.75 ± 0.50g) and white shrimp (25.25 ± 0.95 g).

Three-dimensional graphene sheets with NiO nanobelt outgrowths for enhanced capacity and long term high rate cycling Li-ion battery anode material

NASA Astrophysics Data System (ADS)

Shi, Waipeng; Zhang, Yingmeng; Key, Julian; Shen, Pei Kang

2018-03-01

An efficient synthesis method to grow well attached NiO nanobelts from 3D graphene sheets (3DGS) is reported herein. Ni-ion exchanged resin provides the initial Ni reactant portion, which serves both as a catalyst to form 3DGS and then as a seeding agent to grow the NiO nanobelts. The macroporous structure of 3DGS provides NiO containment to achieve a high cycling stability of up to 445 mAh g-1 after 360 cycles (and >112% capacity retention after 515 cycles) at a high current density of 2 A g-1. With a 26.8 wt.% content of NiO on 3DGS, increases in specific and volumetric capacity were 41.6 and 75.7% respectively over that of 3DGS at matching current densities. Therefore, the seeded growth of NiO nanobelts from 3DGS significantly boosts volumetric capacity, while 3DGS enables high rate long term cycling of the NiO. The high rate cycling stability of NiO on 3DGS can be attributed to (i) good attachment and contact to the large surface of 3DGS, (ii) high electron conductivity and rapid Li-ion transfer (via the interconnected, highly conductive graphitized walls of 3DGS) and (iii) buffering void space in 3DGS to contain volume expansion of NiO during charge/discharge.

Artemisia tridenata seed bank densities following wildfires

USDA-ARS?s Scientific Manuscript database

Big sagebrush (Artemisia spp.) is a critical shrub to such sagebrush obligate species as sage grouse, (Centocercus urophasianus), mule deer (Odocoileus hemionus), and pygmy rabbit (Brachylagus idahoensis). Big sagebrush do not sprout after wildfires and big sagebrush seed is generally short-lived a...

Big sagebrush seed bank densities following wildfires

USDA-ARS?s Scientific Manuscript database

Big sagebrush (Artemisia spp.) is a critical shrub to many wildlife species including sage grouse (Centrocercus urophasianus), mule deer (Odocoileus hemionus), and pygmy rabbit (Brachylagus idahoensis). Big sagebrush is killed by wildfires and big sagebrush seed is generally short-lived and do not s...

Measuring bitterbrush seed production on plants with variable crown density...complete counts per plant suggested

Treesearch

Donald W. Seegrist; Donald L. Neal; Richard L. Hubbard

1966-01-01

A sampling study was made of the number of bitterbrush seeds per trap from plots in northeastern California. The count per trap had a large variation for each plant. This variation was not reduced to an acceptable low level by grouping the seed traps according to their position relative to the plant crown. In the absence of additional information, it is recommended...

Effects of sib-mating and wind pollination on nursery seedling size, growth components, and phenology of Douglas-fir seed-orchard progenies.

Treesearch

Frank C. Sorensen

1997-01-01

Polymix outcross (X), full-sib (FS), and wind-pollination (WP) families were produced on 25 seed trees and 10 half-sib families on 10 of the same trees in a Pseudotsuga menziesii (Mirb.) Franco var. menziesii seedling seed orchard. Seedlings were raised at two sowing densities for 2 years in the nursery, and inbreeding depression in seedling size...

Accelerated craniofacial bone regeneration through dense collagen gel scaffolds seeded with dental pulp stem cells

NASA Astrophysics Data System (ADS)

Chamieh, Frédéric; Collignon, Anne-Margaux; Coyac, Benjamin R.; Lesieur, Julie; Ribes, Sandy; Sadoine, Jérémy; Llorens, Annie; Nicoletti, Antonino; Letourneur, Didier; Colombier, Marie-Laure; Nazhat, Showan N.; Bouchard, Philippe; Chaussain, Catherine; Rochefort, Gael Y.

2016-12-01

Therapies using mesenchymal stem cell (MSC) seeded scaffolds may be applicable to various fields of regenerative medicine, including craniomaxillofacial surgery. Plastic compression of collagen scaffolds seeded with MSC has been shown to enhance the osteogenic differentiation of MSC as it increases the collagen fibrillary density. The aim of the present study was to evaluate the osteogenic effects of dense collagen gel scaffolds seeded with mesenchymal dental pulp stem cells (DPSC) on bone regeneration in a rat critical-size calvarial defect model. Two symmetrical full-thickness defects were created (5 mm diameter) and filled with either a rat DPSC-containing dense collagen gel scaffold (n = 15), or an acellular scaffold (n = 15). Animals were imaged in vivo by microcomputer tomography (Micro-CT) once a week during 5 weeks, whereas some animals were sacrificed each week for histology and histomorphometry analysis. Bone mineral density and bone micro-architectural parameters were significantly increased when DPSC-seeded scaffolds were used. Histological and histomorphometrical data also revealed significant increases in fibrous connective and mineralized tissue volume when DPSC-seeded scaffolds were used, associated with expression of type I collagen, osteoblast-associated alkaline phosphatase and osteoclastic-related tartrate-resistant acid phosphatase. Results demonstrate the potential of DPSC-loaded-dense collagen gel scaffolds to benefit of bone healing process.

Complex patchy colloids shaped from deformable seed particles through capillary interactions.

PubMed

Meester, V; Kraft, D J

2018-02-14

We investigate the mechanisms underlying the reconfiguration of random aggregates of spheres through capillary interactions, the so-called "colloidal recycling" method, to fabricate a wide variety of patchy particles. We explore the influence of capillary forces on clusters of deformable seed particles by systematically varying the crosslink density of the spherical seeds. Spheres with a poorly crosslinked polymer network strongly deform due to capillary forces and merge into large spheres. With increasing crosslink density and therefore rigidity, the shape of the spheres is increasingly preserved during reconfiguration, yielding patchy particles of well-defined shape for up to five spheres. In particular, we find that the aspect ratio between the length and width of dumbbells, L/W, increases with the crosslink density (cd) as L/W = B - A·exp(-cd/C). For clusters consisting of more than five spheres, the particle deformability furthermore determines the patch arrangement of the resulting particles. The reconfiguration pathway of clusters of six densely or poorly crosslinked seeds leads to octahedral and polytetrahedral shaped patchy particles, respectively. For seven particles several geometries were obtained with a preference for pentagonal dipyramids by the rigid spheres, while the soft spheres do rarely arrive in these structures. Even larger clusters of over 15 particles form non-uniform often aspherical shapes. We discuss that the reconfiguration pathway is largely influenced by confinement and geometric constraints. The key factor which dominates during reconfiguration depends on the deformability of the spherical seed particles.

Limited by the host: Host age hampers establishment of holoparasite Cuscuta epithymum

NASA Astrophysics Data System (ADS)

Meulebrouck, Klaar; Verheyen, Kris; Brys, Rein; Hermy, Martin

2009-07-01

A good understanding of the relationship between plant establishment and the ecosystem of which they are part of is needed to conserve rare plant species. Introduction experiments offer a direct test of recruitment limitation, but generally only the seed germination and seedling phases are monitored. Thus the relative importance of different establishment stages in the process of recruitment is not considered. This is particularly true for parasitic plants where empirical data are generally missing. During two consecutive growing seasons we examined the effect of heathland management applications, degree of heathland succession (pioneer, building and mature phase) and seed-density on the recruitment and establishment of the endangered holoparasite Cuscuta epithymum. In general, recruitment after two growing seasons was low with 4.79% of the sown seeds that successfully emerged to the seedling stage and a final establishment of 89 flowering adults (i.e. <1.5% of the sown seeds). Although a higher seed-density resulted in a higher number of seedlings, seed-density did not significantly affected relative germination percentages. The management type and subsequent heath succession had no significant effect on seedling emergence; whereas, seedling attachment to the host, establishment and growth to full-grown size were hampered in older heath vegetation (i.e. high, dense, and mature canopy). Establishment was most successful in turf-cut pioneer heathland, characterised by a relatively open and low vegetation of young Calluna vulgaris. The age of C. vulgaris, C. epithymum's main host, proved to be the most limiting factor. These results emphasise the importance of site quality (i.e. successional phase of its host) on recruitment success of C. epithymum, which is directly affected by the management applied to the vegetation. Lack of any heathland management will thus seriously restrict establishment of the endangered parasite.

Pollination of a native plant changes with distance and density of invasive plants in a simulated biological invasion.

PubMed

Bruckman, Daniela; Campbell, Diane R

2016-08-01

Effects of an exotic plant on pollination may change as the invasive increases in density. Quantity of pollinator visits to a native may increase, decrease, or change nonlinearly, while visit quality is likely to decrease with greater interspecific pollen movement. How visit quantity and quality contribute to the effect on reproductive success at each invasion stage has not been measured. We simulated four stages of invasion by Brassica nigra by manipulating the neighborhood of potted plants of the native Phacelia parryi in a field experiment. Stages were far from the invasion, near the invasion, intermixed with the invasive at low density, and intermixed at high density. We measured pollinator visitation, conspecific and invasive pollen deposition, and seed set for P. parryi at each stage. Native individuals near invasive plants and within areas of low invasive density showed greatest seed production, as expected from concurrent changes in conspecific and invasive pollen deposition. Those plants experienced facilitation of visits and received more conspecific pollen relative to plants farther from invasives. Native individuals within high invasive density also received frequent visits by many pollinators (although not honeybees), but the larger receipt of invasive pollen predicted interference with pollen tubes that matched patterns in seed set. Pollinator visitation was highest when exotic plants were nearby. Detrimental effects of heterospecific pollen deposition were highest at high exotic density. Our study quantified how reproduction benefits from near proximity to a showy invasive, but is still vulnerable when the invasive reaches high density. © 2016 Botanical Society of America.

Analysis of Peanut Seed Oil by NIR

USDA-ARS?s Scientific Manuscript database

Near infrared reflectance spectra (NIRS) were collected from Arachis hypogaea seed samples and used in predictive models to rapidly identify varieties with high oleic acid. The method was developed for shelled peanut seeds with intact testa. Spectra were evaluated initially by principal component an...

Dynamic compressive loading enhances cartilage matrix synthesis and distribution and suppresses hypertrophy in hMSC-laden hyaluronic acid hydrogels.

PubMed

Bian, Liming; Zhai, David Y; Zhang, Emily C; Mauck, Robert L; Burdick, Jason A

2012-04-01

Mesenchymal stem cells (MSCs) are being recognized as a viable cell source for cartilage repair, and there is growing evidence that mechanical signals play a critical role in the regulation of stem cell chondrogenesis and in cartilage development. In this study we investigated the effect of dynamic compressive loading on chondrogenesis, the production and distribution of cartilage specific matrix, and the hypertrophic differentiation of human MSCs encapsulated in hyaluronic acid (HA) hydrogels during long term culture. After 70 days of culture, dynamic compressive loading increased the mechanical properties, as well as the glycosaminoglycan (GAG) and collagen contents of HA hydrogel constructs in a seeding density dependent manner. The impact of loading on HA hydrogel construct properties was delayed when applied to lower density (20 million MSCs/ml) compared to higher seeding density (60 million MSCs/ml) constructs. Furthermore, loading promoted a more uniform spatial distribution of cartilage matrix in HA hydrogels with both seeding densities, leading to significantly improved mechanical properties as compared to free swelling constructs. Using a previously developed in vitro hypertrophy model, dynamic compressive loading was also shown to significantly reduce the expression of hypertrophic markers by human MSCs and to suppress the degree of calcification in MSC-seeded HA hydrogels. Findings from this study highlight the importance of mechanical loading in stem cell based therapy for cartilage repair in improving neocartilage properties and in potentially maintaining the cartilage phenotype.

Genetic dissection of seed oil and protein content and identification of networks associated with oil content in Brassica napus

PubMed Central

Chao, Hongbo; Wang, Hao; Wang, Xiaodong; Guo, Liangxing; Gu, Jianwei; Zhao, Weiguo; Li, Baojun; Chen, Dengyan; Raboanatahiry, Nadia; Li, Maoteng

2017-01-01

High-density linkage maps can improve the precision of QTL localization. A high-density SNP-based linkage map containing 3207 markers covering 3072.7 cM of the Brassica napus genome was constructed in the KenC-8 × N53-2 (KNDH) population. A total of 67 and 38 QTLs for seed oil and protein content were identified with an average confidence interval of 5.26 and 4.38 cM, which could explain up to 22.24% and 27.48% of the phenotypic variation, respectively. Thirty-eight associated genomic regions from BSA overlapped with and/or narrowed the SOC-QTLs, further confirming the QTL mapping results based on the high-density linkage map. Potential candidates related to acyl-lipid and seed storage underlying SOC and SPC, respectively, were identified and analyzed, among which six were checked and showed expression differences between the two parents during different embryonic developmental periods. A large primary carbohydrate pathway based on potential candidates underlying SOC- and SPC-QTLs, and interaction networks based on potential candidates underlying SOC-QTLs, was constructed to dissect the complex mechanism based on metabolic and gene regulatory features, respectively. Accurate QTL mapping and potential candidates identified based on high-density linkage map and BSA analyses provide new insights into the complex genetic mechanism of oil and protein accumulation in the seeds of rapeseed. PMID:28393910

Characterization biometric and morphophysiological of Peach rootstock seeds using images of their seedling vigor.

PubMed

Souza, Aline Das Graças; Smiderle, Oscar Jose; Bianchi, Valmor Joao

2018-04-26

This study aimed to evaluate the efficiency of using the computerized imaging seed analysis system (SAS) in the biometric and morphophysiological characterization of seeds and the initial growth of seedlings from peach rootstocks. The experimental design was completely randomized with five replicates of 20 seeds. The variables analyzed were degree of seed humidity, length and width of seeds measured by SAS technology and manual measurements, mean germination time, germination percentage, radicle length and width, taproot length, length of the aerial part and taproot/aerial part ratio. The highest seed length, germination percentage (100%) and lower germination time (11.3), were obtained with the cv. Capdeboscq while, 'Tsukuba 1', 2' and 3' had intermediate seedlings length, varying from 1.55 to 1.65 cm with mean germination times between 14.5 and 18.0 days and average germination percentage of 96%. The computerized analysis of images is fast and efficient for biometric evaluations such as seed width and length, as well as initial growth of peach tree seedlings. The cvs Capdeboscq, Flordaguard and Tsukuba 2 presented greater radicle width, length and a mean taproot/aerial part ratio equal to 2, as well as higher number of adventitious roots, which indicated a strong positive correlation between radicle length, taproot length and initial seedling growth. The continuity of the research will certainly allow the development of reliable procedures for other species, besides allowing the identification of wider alternatives for the use of this system for the expansion of knowledge in the areas of physiology and evaluation of the physiological potential of seeds. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

SOME ENGINEERING PROPERTIES OF SHELLED AND KERNEL TEA (Camellia sinensis) SEEDS.

PubMed

Altuntas, Ebubekir; Yildiz, Merve

2017-01-01

Camellia sinensis is the source of tea leaves and it is an economic crop now grown around the World. Tea seed oil has been used for cooking in China and other Asian countries for more than a thousand years. Tea is the most widely consumed beverages after water in the world. It is mainly produced in Asia, central Africa, and exported throughout the World. Some engineering properties (size dimensions, sphericity, volume, bulk and true densities, friction coefficient, colour characteristics and mechanical behaviour as rupture force of shelled and kernel tea ( Camellia sinensis ) seeds were determined in this study. This research was carried out for shelled and kernel tea seeds. The shelled tea seeds used in this study were obtained from East-Black Sea Tea Cooperative Institution in Rize city of Turkey. Shelled and kernel tea seeds were characterized as large and small sizes. The average geometric mean diameter and seed mass of the shelled tea seeds were 15.8 mm, 10.7 mm (large size); 1.47 g, 0.49 g (small size); while the average geometric mean diameter and seed mass of the kernel tea seeds were 11.8 mm, 8 mm for large size; 0.97 g, 0.31 g for small size, respectively. The sphericity, surface area and volume values were found to be higher in a larger size than small size for the shelled and kernel tea samples. The shelled tea seed's colour intensity (Chroma) were found between 59.31 and 64.22 for large size, while the kernel tea seed's chroma values were found between 56.04 68.34 for large size, respectively. The rupture force values of kernel tea seeds were higher than shelled tea seeds for the large size along X axis; whereas, the rupture force values of along X axis were higher than Y axis for large size of shelled tea seeds. The static coefficients of friction of shelled and kernel tea seeds for the large and small sizes higher values for rubber than the other friction surfaces. Some engineering properties, such as geometric mean diameter, sphericity, volume, bulk and true densities, the coefficient of friction, L*, a*, b* colour characteristics and rupture force of shelled and kernel tea ( Camellia sinensis ) seeds will serve to design the equipment used in postharvest treatments.

Large-scale microwave anisotropy from gravitating seeds

NASA Technical Reports Server (NTRS)

Veeraraghavan, Shoba; Stebbins, Albert

1992-01-01

Topological defects could have seeded primordial inhomogeneities in cosmological matter. We examine the horizon-scale matter and geometry perturbations generated by such seeds in an expanding homogeneous and isotropic universe. Evolving particle horizons generally lead to perturbations around motionless seeds, even when there are compensating initial underdensities in the matter. We describe the pattern of the resulting large angular scale microwave anisotropy.

Germination and field survival of white-topped pitcher plant seeds

Treesearch

Kristina Connor; Hilliard Gibbs

2012-01-01

A study was initiated to determine longevity of white-topped pitcher plant (Sarracenia leucophylla, Raf.) seeds in the field and in cold storage. Thirty seed pods were harvested in August 2009 from plants located in Alabama 38 miles from the Gulf Coast. Of the 10,000+ seeds extracted from the pods, some were buried outside in screen-wire bags and...

Role of fire in regeneration from seed: Chapter 14

USGS Publications Warehouse

Keeley, Jon E.; Fotheringham, C.J.; Fenner, M.

2000-01-01

The effects of fire on seed germination and plant regeneration are discussed. Among the topics considered are the triggering of opening of serotinous fruits or cones by fire, the breaking of dormancy in seeds in the soil seed bank, the effects of smoke on germination, and the role of fire in initiating seedling recruitment by opening gaps in closed vegetation.

A Funding Initiative for Community-Based Participatory Research: Lessons from the Harvard Catalyst Seed Grants

PubMed Central

Tendulkar, Shalini A.; Chu, Jocelyn; Opp, Jennifer; Geller, Alan; DiGirolamo, Ann; Gandelman, Ediss; Grullon, Milagro; Patil, Pratima; King, Stacey; Hacker, Karen

2013-01-01

Background The National Institutes of Health–funded Clinical and Translational Science Awards (CTSA) have increasingly focused on community-engaged research and funded investigators for community-based participatory research (CBPR). However, because CBPR is a collaborative process focused on community-identified research topics, the Harvard CTSA and its Community Advisory Board (CERAB) funded community partners through a CBPR initiative. Objectives We describe lessons learned from this seed grants initiative designed to stimulate community–academic CBPR partnerships. Methods The CBPR program of the Harvard CTSA and the CERAB developed this initiative and each round incorporated participant and advisory feedback toward program improvement. Lessons Learned Although this initiative facilitated relevant and innovative research, challenges included variable community research readiness, insufficient project time, and difficulties identifying investigators for new partnerships. Conclusion Seed grants can foster innovative CBPR projects. Similar initiatives should consider preliminary assessments of community research readiness as well as strategies for meaningful academic researcher engagement. PMID:21441667

Seed bank and established vegetation in the last remnants of the Mexican Central Plateau wetlands: the Lerma marshes.

PubMed

Zepeda, Carmen; Lot, Antonio; Nemiga, Xanat Antonio; Manjarrez, Javier

2014-06-01

Seed banks play a central role in vegetation dynamics of many wetlands. Therefore, knowledge of seed reservoirs in the soils of aquatic communities should provide useful tools for conservation and restoration efforts. This study was conducted in the Lerma marshes, one of the last remnants of the vast wetlands that were once in the Mexican Central Plateau. The main objective was to determine the composition and abundance of seed bank and its relationship with established vegetation of the three Lerma marshes. In each marsh, we systematically selected 18 to 40 sampling sites. In each site, the composition of vascular plant vegetation was evaluated in two 10m lines perpendicular to the shore. Every 0.5m, we determined the coverage of species by measuring the intercepted length for each plant or group of plants. At each sampling site where we had evaluated the established vegetation, we collected a sample of the top 10cm of sediment; the soil cores were divided into an upper layer (0-5cm) and a lower layer (5-10cm). These samples were used to evaluate the seed bank by the seedling emergence method. All samples were placed in a greenhouse at 20-25 degrees C and remained flooded for 15 weeks. Forty-nine species were recorded in the vegetation. Chiconahuapan had the richest and most diverse flora and the greatest number of perennial species. A life-forms analysis showed that perennial herbs, especially rooted-emergent hydrophytes, dominated in the three wetlands. Sixty-one species were identified in the total seed bank; Chimaliapan had the most diverse total seed bank, whereas the mean seedling density was higher in Chignahuapan. Only two species of the total seed bank of each marsh had a density greater than 10% of the total, and more than half were uncommon. The upper layer of sediment (0-5cm) contained two times more seeds/m2 and species per sample than the lower layer (5-10cm), and there was a significant decrease of seed density with depth. The detrended correspondence analysis produced a clear separation between the composition of the seed banks and established vegetation. In general, in each marsh there was less species diversity in the established vegetation than in the seed bank. Dominance by a few species in the seed bank, the presence of opportunistic species, and the low representation of established species in the seed bank suggest wetland degradation and a low probability of regenerating the natural communities from the seed bank. To ensure the permanence of these marshes, their biodiversity, and therefore the environmental services they provide, up to date planning is a must, and efforts to control and monitor hydrology, water quality, and the influence of human activities are suggested.

Investigation of the operating conditions to morphology evolution of β-L-glutamic acid during seeded cooling crystallization

NASA Astrophysics Data System (ADS)

Zhang, Fangkun; Liu, Tao; Huo, Yan; Guan, Runduo; Wang, Xue Z.

2017-07-01

In this paper the effects of operating conditions including cooling rate, initial supersaturation, and seeding temperature were investigated on the morphology evolution of β-L-glutamic acid (β-LGA) during seeded cooling crystallization. Based on the results of in-situ image acquisition of the crystal morphology evolution during the crystallization process, it was found that the crystal products tend to be plate-like or short rod-like under a slow cooling rate, low initial supersaturation, and low seeding temperature. In the opposite, the operating conditions of a faster cooling rate, higher initial supersaturation, and higher seeding temperature tend to produce long rod-like or needle-like crystals, and meanwhile, the length and width of crystal products will be increased together with a wider crystal size distribution (CSD). The aspect ratio of crystals, defined by the crystal length over width measured from in-situ or sample images, was taken as a shape index to analyze the crystal morphologies. Based on comparative analysis of the experimental results, guidelines on these operating conditions were given for obtaining the desired crystal shapes, along with the strategies for obtaining a narrower CSD for better product quality. Experimental verifications were performed to illustrate the proposed guidelines on the operating conditions for seeded cooling crystallization of LGA solution.

Plasma treatment switches the regime of wetting and floating of pepper seeds.

PubMed

Shapira, Yekaterina; Multanen, Victor; Whyman, Gene; Bormashenko, Yelena; Chaniel, Gilad; Barkay, Zahava; Bormashenko, Edward

2017-09-01

Cold radiofrequency plasma treatment modified wetting and floating regimes of pepper seeds. The wetting regime of plasma-treated seeds was switched from the Wenzel-like partial wetting to the complete wetting. No hydrophobic recovery following the plasma treatment was registered. Environmental scanning electron microscopy of the fine structure of the (three-phase) triple line observed with virgin and plasma-treated seeds is reported. Plasma treatment promoted rapid sinking of pepper seeds placed on the water/air interface. Plasma treatment did not influence the surface topography of pepper seeds, while charged them electrically. Electrostatic repulsion of floating plasma-treated seeds was observed. The surface charge density was estimated from the data extracted from floating of charged seeds and independently with the electrostatic pendulum as σ≈1-2μC/m 2 . Copyright © 2017 Elsevier B.V. All rights reserved.

On the relative contributions of wind vs. animals to seed dispersal of four Sierra Nevada pines.

PubMed

Vander Wall, Stephen B

2008-07-01

Selective pressures that influence the form of seed dispersal syndromes are poorly understood. Morphology of plant propagules is often used to infer the means of dispersal, but morphology can be misleading. Several species of pines, for example, have winged seeds adapted for wind dispersal but owe much of their establishment to scatter-hoarding animals. Here the relative importance of wind vs. animal dispersal is assessed for four species of pines of the eastern Sierra Nevada that have winged seeds but differed in seed size: lodgepole pine (Pinus contorta murrayana, 8 mg); ponderosa pine (Pinus ponderosa ponderosa, 56 mg); Jeffrey pine (Pinus jeffreyi, 160 mg); and sugar pine (Pinus lambertiana, 231 mg). Pre-dispersal seed mortality eliminated much of the ponderosa pine seed crop (66%), but had much less effect on Jeffrey pine (32% of seeds destroyed), lodgepole pine (29%), and sugar pine (7%). When cones opened most filled seeds were dispersed by wind. Animals removed > 99% of wind-dispersed Jeffrey and sugar pine seeds from the ground within 60 days, but animals gathered only 93% of lodgepole pine seeds and 38% of ponderosa pine seeds during the same period. Animals gathered and scatter hoarded radioactively labeled ponderosa, Jeffrey, and sugar pine seeds, making a total of 2103 caches over three years of study. Only three lodgepole pine caches were found. Caches typically contained 1-4 seeds buried 5-20 mm deep, depths suitable for seedling emergence. Although Jeffrey and sugar pine seeds are initially wind dispersed, nearly all seedlings arise from animal caches. Lodgepole pine is almost exclusively wind dispersed, with animals acting as seed predators. Animals treated ponderosa pine in an intermediate fashion. Two-phased dispersal of large, winged pine seeds appears adaptive; initial wind dispersal helps to minimize pre-dispersal seed mortality whereas scatter hoarding by animals places seeds in sites with a higher probability of seedling establishment.

Spectral Characteristics of VLF Sferics Associated With RHESSI TGFs

NASA Astrophysics Data System (ADS)

Mezentsev, Andrew; Lehtinen, Nikolai; Østgaard, Nikolai; Pérez-Invernón, F. J.; Cummer, Steven A.

2018-01-01

We compared the modeled energy spectral density of very low frequency (VLF) radio emissions from terrestrial gamma ray flashes (TGFs) with the energy spectral density of VLF radio sferics recorded by Duke VLF receiver simultaneously with those TGFs. In total, six events with world wide lightning location network (WWLLN) defined locations were analyzed to exhibit a good fit between the modeled and observed energy spectral densities. In VLF range the energy spectral density of the TGF source current moment is found to be dominated by the contribution of secondary low-energy electrons and independent of the relativistic electrons which play their role in low-frequency (LF) range. Additional spectral modulation by the multiplicity of TGF peaks was found and demonstrated a good fit for two TGFs whose VLF sferics consist of two overlapping pulses each. The number of seeding pulses in TGF defines the spectral shape in VLF range, which allows to retrieve this number from VLF sferics, assuming they were radiated by TGFs. For two events it was found that the number of seeding pulses is small, of the order of 10. For the rest of the events the lower boundary of the number of seeding pulses was found to be between 10 to 103.

Seed germination of cirsium arvense and Lepidium latifolium: Implications for management of montane wetlands

USGS Publications Warehouse

Laubhan, M.K.; Shaffer, T.L.

2006-01-01

Cirsium arvense and Lepidium latifolium are species that can aggressively invade wetland margins and potentially reduce biodiversity and alter ecosystem function. Although expansion of these species primarily occurs via rhizomatous growth, seeds are thought to be important in initial establishment. We conducted this study to investigate differences in seed germination of C. arvense and L. latifolium in montane wetlands of Colorado and Wyoming, USA. We used germination chambers to simulate environmental conditions (photoperiod, day/night temperature) during three periods of the growing season at each site and evaluated seed germination in relation to three soil moisture levels and two soil depths. A combination of shallow (<1 cm) seed burial and wet conditions resulted in the greatest germination probability of C. arvense (x = 63.0%), 95% CI = 41.2-80.5%), whereas deep (2-3 cm) seed burial and saturated moisture conditions resulted in almost no germination (x?? = 0.3%, 95% CI = 0.1-1.3%). The maximum germination probability of 44.0% (CI = 28.1-61.4%) for L. latifolium also occurred in the shallow burial and wet treatment; however, only effects of seed burial were significant (P < 0.05). The estimated mean germination probability of deeply buried seeds was <1.0% (CI = 0.3-1.4%) compared to 32% (CI = 19.7-47.9%) for shallowly buried seeds. Our results suggest that each species has the ability to germinate at similar rates throughout the growing season and across a large portion of the moisture gradient. This suggests that management actions, including water-level manipulations, at any time during the growing season may stimulate germination. Although burial of seed to depths of 2-3 cm reduced the germination potential of both species, the use of mechanical implements may be problematic in established stands because new plants of both species easily sprout from root buds. Further, disturbance resulting from such actions diminishes the density and vigor of other plants already present, which may ultimately decrease the competitive resistance of the disturbed environment to invasion by outside species. Detection of new invasions is a critical component of any integrated weed management program. Our results indicate that the incidence of C. arvense and L. latifolium germination is most likely in areas with seeds that are within 1 cm of the soil surface and soil moisture is 75-100% of field capacity for extended periods. ?? 2006, The Society of Wetland Scientists.

Modulation of chondrogenic differentiation of human mesenchymal stem cells in jellyfish collagen scaffolds by cell density and culture medium.

PubMed

Pustlauk, W; Paul, B; Brueggemeier, S; Gelinsky, M; Bernhardt, A

2017-06-01

Studies on tissue-engineering approaches for the regeneration of traumatized cartilage focus increasingly on multipotent human mesenchymal stem cells (hMSCs) as an alternative to autologous chondrocytes. The present study applied porous scaffolds made of collagen from the jellyfish Rhopilema esculentum for the in vitro chondrogenic differentiation of hMSCs. Culture conditions in those scaffolds differ from conditions in high-density pellet cultures, making a re-examination of these data necessary. We systematically investigated the influence of seeding density, basic culture media [Dulbecco's modified Eagle's medium (DMEM), α-minimum essential medium (α-MEM)] with varying glucose content and supplementation with fetal calf serum (FCS) or bovine serum albumin (BSA) on the chondrogenic differentiation of hMSCs. Gene expression analyses of selected markers for chondrogenic differentiation and hypertrophic development were conducted. Furthermore, the production of cartilage extracellular matrix (ECM) was analysed by quantification of sulphated glycosaminoglycan and collagen type II contents. The strongest upregulation of chondrogenic markers, along with the highest ECM deposition was observed in scaffolds seeded with 2.4 × 10 6 cells/cm 3 after cultivation in high-glucose DMEM and 0.125% BSA. Lower seeding densities compared to high-density pellet cultures were sufficient to induce in vitro chondrogenic differentiation of hMSCs in collagen scaffolds, which reduces the amount of cells required for the seeding of scaffolds and thus the monolayer expansion period. Furthermore, examination of the impact of FCS and α-MEM on chondrogenic MSC differentiation is an important prerequisite for the development of an osteochondral medium for simultaneous osteogenic and chondrogenic differentiation in biphasic scaffolds for osteochondral tissue regeneration. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Impacts of Insect Herbivores on Plant Populations.

PubMed

Myers, Judith H; Sarfraz, Rana M

2017-01-31

Apparent feeding damage by insects on plants is often slight. Thus, the influences of insect herbivores on plant populations are likely minor. The role of insects on host-plant populations can be elucidated via several methods: stage-structured life tables of plant populations manipulated by herbivore exclusion and seed-addition experiments, tests of the enemy release hypothesis, studies of the effects of accidentally and intentionally introduced insect herbivores, and observations of the impacts of insect species that show outbreak population dynamics. These approaches demonstrate that some, but not all, insect herbivores influence plant population densities. At times, insect-feeding damage kills plants, but more often, it reduces plant size, growth, and seed production. Plant populations for which seed germination is site limited will not respond at the population level to reduced seed production. Insect herbivores can influence rare plant species and need to be considered in conservation programs. Alterations due to climate change in the distributions of insect herbivores indicate the possibility of new influences on host plants. Long-term studies are required to show if density-related insect behavior stabilizes plant populations or if environmental variation drives most temporal fluctuations in plant densities. Finally, insects can influence plant populations and communities through changing the diversity of nonhost species, modifying nutrient fluxes, and rejuvenating over mature forests.

A global analysis of bidirectional interactions in alpine plant communities shows facilitators experiencing strong reciprocal fitness costs.

PubMed

Schöb, Christian; Michalet, Richard; Cavieres, Lohengrin A; Pugnaire, Francisco I; Brooker, Rob W; Butterfield, Bradley J; Cook, Bradley J; Kikvidze, Zaal; Lortie, Christopher J; Xiao, Sa; Al Hayek, Patrick; Anthelme, Fabien; Cranston, Brittany H; García, Mary-Carolina; Le Bagousse-Pinguet, Yoann; Reid, Anya M; le Roux, Peter C; Lingua, Emanuele; Nyakatya, Mawethu J; Touzard, Blaise; Zhao, Liang; Callaway, Ragan M

2014-04-01

Facilitative interactions are defined as positive effects of one species on another, but bidirectional feedbacks may be positive, neutral, or negative. Understanding the bidirectional nature of these interactions is a fundamental prerequisite for the assessment of the potential evolutionary consequences of facilitation. In a global study combining observational and experimental approaches, we quantified the impact of the cover and richness of species associated with alpine cushion plants on reproductive traits of the benefactor cushions. We found a decline in cushion seed production with increasing cover of cushion-associated species, indicating that being a benefactor came at an overall cost. The effect of cushion-associated species was negative for flower density and seed set of cushions, but not for fruit set and seed quality. Richness of cushion-associated species had positive effects on seed density and modulated the effects of their abundance on flower density and fruit set, indicating that the costs and benefits of harboring associated species depend on the composition of the plant assemblage. Our study demonstrates 'parasitic' interactions among plants over a wide range of species and environments in alpine systems, and we consider their implications for the possible selective effects of interactions between benefactor and beneficiary species. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

An Arabidopsis thaliana embryo arrest mutant exhibiting germination potential

USDA-ARS?s Scientific Manuscript database

The ability to initiate radicle elongation, or germination potential, occurs in developing embryos before the completion of seed maturation. Green embryos after walking-stick stage in developing Arabidopsis thaliana seeds germinate when excised from seeds and incubated in MS media containing 1 % suc...

Impact of Thiamethoxam Seed Treatment on Growth and Yield of Rice, Oryza sativa.

PubMed

Lanka, S K; Senthil-Nathan, S; Blouin, D J; Stout, M J

2017-04-01

Neonicotinoid seed treatments are widely used in agriculture. In rice, Oryza sativa L., in the southern United States, neonicotinoid seed treatments are used to manage early-season populations of the rice water weevil, Lissorhoptrus oryzophilus Kuschel. In addition to their effects on pests, neonicotinoid seed treatments may benefit crop plants directly by increasing plant growth or altering plant responses to stresses. As part of an effort to assess the overall benefits of thiamethoxam seed treatment in rice, rice emergence, growth, and yield were evaluated. In a growth chamber, rice emergence from the soil was 1-2 d more rapid from treated than untreated seeds. These laboratory results were supported by field experiments that revealed higher stand counts from thiamethoxam-treated plots than from untreated plots. Yields from thiamethoxam treatments were no higher than those from untreated plots under conditions in which weevil larvae were absent, a result inconsistent with the hypothesis that thiamethoxam imparts direct yield benefits. In a series of field experiments conducted to compare the relationship between weevil larval densities and rice yields in plots treated with several rates of thiamethoxam or chlorantraniliprole (another widely used seed treatment insecticide), the relationship between weevil density and yield did not differ markedly among both seed treatments. Overall yields from both seed treatments did not differ significantly, despite more effective control in chlorantraniliprole-treated plots. These results provide strong support for effect of thiamethoxam on early-season growth of rice, but only weak support for its direct effect on rice yields. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Prevalence and strength of density-dependent tree recruitment

Treesearch

Kai Zhu; Christopher W. Woodall; Joao V.D. Monteiro; James S. Clark

2015-01-01

Density dependence could maintain diversity in forests, but studies continue to disagree on its role. Part of the disagreement results from the fact that different studies have evaluated different responses (survival, recruitment, or growth) of different stages (seeds, seedlings, or adults) to different inputs (density of seedlings, density or distance to adults). Most...

The focusing effect in backward Raman amplification in plasma

NASA Astrophysics Data System (ADS)

Li, Zhaoli; Peng, Hao; Zuo, Yanlei; Su, Jingxin; Yang, Suhui

2018-04-01

In this paper, the focusing effect on backward Raman amplification in plasma is investigated. A fluid model, used to simulate the backward Raman amplification and including the relativistic, ponderomotive, and thermal self-focusing and the mutual-focusing effect simultaneously, is proposed and investigated. The focusing effect is shown to severely distort the profile of the seed when the seed intensity was as high as 10 17 W/cm2. Reducing the plasma density can relax the focusing effect, but at the cost of decreasing the amplification efficiency. Changing the profile of the seed has a limited effect on mitigating the focusing effect. A Gaussian profile of the pump and a defocusing shape of the plasma density seem to be an effective way to mitigate the focusing effect without decreasing the amplification efficiency.

Seed bank characteristics of the Nymphoides peltata population in Lake Taihu

NASA Astrophysics Data System (ADS)

Huang, Wei; Chen, Qiuwen; Chen, Kaining

2015-08-01

The Nymphoides peltata (N. peltata) population has shown rapid expansion in Lake Taihu, China, in recent years. The core question is whether N. peltata seeds have contributed to the expansion. To address this, we randomly selected three N. peltata stands to investigate the seed bank characteristics of N. peltata in Lake Taihu. Results showed that N. peltata had high seed production, with a maximum seed yield of 1763 seeds per m2. Density of intact and fragmented seeds decreased rapidly with sediment depth. Few intact or fragmented seeds were distributed at depths greater than 4 cm in the sediment. Spatial distribution of the seed bank indicated that most seeds sank to the sediment within the N. peltata stands, and few seeds took advantage of their floating ability. Seeds recovered from the sediment during April to June had a low germination rate, and no seeds germinated during October to April. Cold exposure treatment increased the germination rate remarkably. No seedlings were found in the field from January 2012 to December 2012, indicating that few seeds were successfully established in the surveyed area. The results suggested that sexual reproduction had little direct contribution to the N. peltata expansion in this large shallow lake.

Seed-bank structure and plant-recruitment conditions regulate the dynamics of a grassland-shrubland Chihuahuan ecotone.

PubMed

Moreno-de Las Heras, Mariano; Turnbull, Laura; Wainwright, John

2016-09-01

Large areas of desert grasslands in the southwestern United States have shifted to sparse shrublands dominated by drought-tolerant woody species over the last 150 yr, accompanied by accelerated soil erosion. An important step toward the understanding of patterns in species dominance and vegetation change at desert grassland-shrubland transitions is the study of environmental limitations imposed by the shrub-encroachment phenomenon on plant establishment. Here, we analyze the structure of soil seed banks, environmental limitations for seed germination (i.e., soil-water availability and temperature), and simulated seedling emergence and early establishment of dominant species (black grama, Bouteloua eriopoda, and creosotebush, Larrea tridentata) across a Chihuahuan grassland-shrubland ecotone (Sevilleta National Wildlife Refuge, New Mexico, USA). Average viable seed density in soils across the ecotone is generally low (200-400 seeds/m 2 ), although is largely concentrated in densely vegetated areas (with peaks up to 800-1,200 seeds/m 2 in vegetated patches). Species composition in the seed bank is strongly affected by shrub encroachment, with seed densities of grass species sharply decreasing in shrub-dominated sites. Environmental conditions for seed germination and seedling emergence are synchronized with the summer monsoon. Soil-moisture conditions for seedling establishment of B. eriopoda take place with a recurrence interval ranging between 5 and 8 yr for grassland and shrubland sites, respectively, and are favored by strong monsoonal precipitation. Limited L. tridentata seed dispersal and a narrow range of rainfall conditions for early seedling establishment (50-100 mm for five to six consecutive weeks) constrain shrub-recruitment pulses to localized and episodic decadal events (9-25 yr recurrence intervals) generally associated with late-summer rainfall. Re-establishment of B. eriopoda in areas now dominated by L. tridentata is strongly limited by the lack of seeds and decreased plant-available soil moisture for seedling establishment. © 2016 by the Ecological Society of America.

Effects of methanol-to-oil ratio, catalyst amount and reaction time on the FAME yield by in situ transesterification of rubber seeds (Hevea brasiliensis)

NASA Astrophysics Data System (ADS)

Abdulkadir, Bashir Abubakar; Uemura, Yoshimitsu; Ramli, Anita; Osman, Noridah B.; Kusakabe, Katsuki; Kai, Takami

2014-10-01

In this research, biodiesel is produced by in situ transesterification (direct transesterification) method from the rubber seeds using KOH as a catalyst. The influence of methanol to seeds mass ratio, duration of reaction, and catalyst loading was investigated. The result shows that, the best ratio of seeds to methanol is 1:6 (10 g seeds with 60 g methanol), 120 minutes reaction time and catalyst loading of 3.0 g. The maximum FAME yield obtain was 70 %. This findings support FAME production from the seeds of rubber tree using direct transesterifcation method from the seeds of rubber tree as an alternative to diesel fuel. Also, significant properties of biodiesel such as cloud point, density, pour point, specific gravity, and viscosity were investigated.

Tissue engineering of ligaments: a comparison of bone marrow stromal cells, anterior cruciate ligament, and skin fibroblasts as cell source.

PubMed

Van Eijk, F; Saris, D B F; Riesle, J; Willems, W J; Van Blitterswijk, C A; Verbout, A J; Dhert, W J A

2004-01-01

Anterior cruciate ligament (ACL) reconstruction surgery still has important problems to overcome, such as "donor site morbidity" and the limited choice of grafts in revision surgery. Tissue engineering of ligaments may provide a solution for these problems. Little is known about the optimal cell source for tissue engineering of ligaments. The aim of this study is to determine the optimal cell source for tissue engineering of the anterior cruciate ligament. Bone marrow stromal cells (BMSCs), ACL, and skin fibroblasts were seeded onto a resorbable suture material [poly(L-lactide/glycolide) multifilaments] at five different seeding densities, and cultured for up to 12 days. All cell types tested attached to the suture material, proliferated, and synthesized extracellular matrix rich in collagen type I. On day 12 the scaffolds seeded with BMSCs showed the highest DNA content (p < 0.01) and the highest collagen production (p < 0.05 for the two highest seeding densities). Scaffolds seeded with ACL fibroblasts showed the lowest DNA content and collagen production. Accordingly, BMSCs appear to be the most suitable cells for further study and development of tissue-engineered ligament.

Myrmecochory and short-term seed fate in Rhamnus alaternus: Ant species and seed characteristics

NASA Astrophysics Data System (ADS)

Bas, J. M.; Oliveras, J.; Gómez, C.

2009-05-01

Benefits conferred on plants in ant-mediated seed dispersal mutualisms (myrmecochory) depend on the fate of transported seeds. We studied the effects of elaiosome presence, seed size and seed treatment (with and without passage through a bird's digestive tract) on short-term seed fate in Rhamnus alaternus. In our study, we define short-term seed, or initial, seed fate, as the location where ants release the seeds after ant contact with it. The elaiosomes had the most influence on short-term fate, i.e. whether or not seeds were transported to the nest. The workers usually transported big seeds more often than small ones, but small ants did not transport large seeds. Effect of seed size on transport depended on the ant species and on the treatment of the seed (manual extraction simulating a direct fall from the parent plant vs. bird deposition corresponding to preliminary primary dispersal). Probability of removal of elaiosome-bearing seeds to the nest by Aphaenogaster senilis increased with increasing seed weight.

Biological Networks Underlying Soybean Seed Oil Composition and Content

USDA-ARS?s Scientific Manuscript database

Soybean is the most important oil crop in the United States. Production of soybean seed oil requires coordinated expression of many biological components and pathways, which is further regulated by seed development and phyto-hormones. A new research project is initiated in my laboratory to delineat...

Does seeding after wildfires in rangelands reduce erosion or invasive species?

USGS Publications Warehouse

Pyke, David A.; Wirth, Troy A.; Beyers, Jan L.

2013-01-01

Mitigation of ecological damage caused by rangeland wildfires has historically been an issue restricted to the western United States. It has focused on conservation of ecosystem function through reducing soil erosion and spread of invasive plants. Effectiveness of mitigation treatments has been debated recently. We reviewed recent literature to conduct a meta-analysis of seeding after wildfires to determine if seedings may (1) protect ecosystems against soil erosion and (2) reduce invasion or abundance of undesirable nonnative plant species. Effectiveness of postfire seedings was examined in 8 erosion and 19 invasive species cases. Seeding has little effect on erosion during the first year after fire and is highly dependent upon initial establishment and coverage of species in successive years. Among all seeding cases, 28% reduced, 67% were neutral, and 5% increased invasive species abundance. Older seedings were more likely to show reductions in invasives than younger seedings. Seedings with high plant establishment were more likely to reduce invasives than those with low establishment. Studies are needed that examine (1) frequency of adequate establishment of postfire seedings and causal factors of success or failure, (2) long-term impacts of seeding along a range of initial establishment and concomitant plant coverage over time as it relates to erosion and abundance of invasive plant species, and (3) auxiliary treatments designed to increase likelihood of germination and establishment given the inevitable variability of environmental conditions. These studies would aid land managers in deciding when postfire treatments are required and their likely level of success.

Influence of Afforestation on the Species Diversity of the Soil Seed Bank and Understory Vegetation in the Hill-Gullied Loess Plateau, China.

PubMed

Wang, Ning; Jiao, Juying; Jia, Yanfeng; Wang, Dongli

2017-10-24

The Chinese Loess Plateau region has long been suffering from serious soil erosion. Thus, large-scale afforestation has continued during the past decades in order to control soil erosion. Afforestation can dramatically alter nutrient cycles, affect soil-carbon storage, and change hydrology. However, it is unknown how afforestation influences species diversity of the soil seed bank and understory vegetation compared with spontaneous restoration of abandoned land. Forest land with trees planted 30 years ago, abandoned slope land restored spontaneously for 30 years, and the corresponding slopes with remnant natural vegetation were selected as sampling sites. The species richness both in the soil seed bank and vegetation was significantly higher on the afforested slope compared to the spontaneously restored abandoned land. The species similarity between the afforested slope and the remnant slope land was high both in the soil seed bank and standing vegetation compared to the abandoned land. The soil seed bank density varied from 1778 ± 187 to 3896 ± 221 seeds/m², and more than half of it was constituted by annual and biennial species, with no significant difference among sampling habitats. However, the afforested slope had higher seed density of grass and shrub/subshrubs compared to the abandoned slope. The present study indicates that in the study region, characterized by serious soil erosion, afforestation can better facilitate vegetation succession compared to spontaneously restoration of abandoned slope land.

Influence of Afforestation on the Species Diversity of the Soil Seed Bank and Understory Vegetation in the Hill-Gullied Loess Plateau, China

PubMed Central

Wang, Ning; Jiao, Juying; Jia, Yanfeng; Wang, Dongli

2017-01-01

The Chinese Loess Plateau region has long been suffering from serious soil erosion. Thus, large-scale afforestation has continued during the past decades in order to control soil erosion. Afforestation can dramatically alter nutrient cycles, affect soil-carbon storage, and change hydrology. However, it is unknown how afforestation influences species diversity of the soil seed bank and understory vegetation compared with spontaneous restoration of abandoned land. Forest land with trees planted 30 years ago, abandoned slope land restored spontaneously for 30 years, and the corresponding slopes with remnant natural vegetation were selected as sampling sites. The species richness both in the soil seed bank and vegetation was significantly higher on the afforested slope compared to the spontaneously restored abandoned land. The species similarity between the afforested slope and the remnant slope land was high both in the soil seed bank and standing vegetation compared to the abandoned land. The soil seed bank density varied from 1778 ± 187 to 3896 ± 221 seeds/m2, and more than half of it was constituted by annual and biennial species, with no significant difference among sampling habitats. However, the afforested slope had higher seed density of grass and shrub/subshrubs compared to the abandoned slope. The present study indicates that in the study region, characterized by serious soil erosion, afforestation can better facilitate vegetation succession compared to spontaneously restoration of abandoned slope land. PMID:29064405

Using In Situ Symbiotic Seed Germination to Restore Over-collected Medicinal Orchids in Southwest China.

PubMed

Shao, Shi-Cheng; Burgess, Kevin S; Cruse-Sanders, Jennifer M; Liu, Qiang; Fan, Xu-Li; Huang, Hui; Gao, Jiang-Yun

2017-01-01

Due to increasing demand for medicinal and horticultural uses, the Orchidaceae is in urgent need of innovative and novel propagation techniques that address both market demand and conservation. Traditionally, restoration techniques have been centered on ex situ asymbiotic or symbiotic seed germination techniques that are not cost-effective, have limited genetic potential and often result in low survival rates in the field. Here, we propose a novel in situ advanced restoration-friendly program for the endangered epiphytic orchid species Dendrobium devonianum , in which a series of in situ symbiotic seed germination trials base on conspecific fungal isolates were conducted at two sites in Yunnan Province, China. We found that percentage germination varied among treatments and locations; control treatments (no inoculum) did not germinate at both sites. We found that the optimal treatment, having the highest in situ seed germination rate (0.94-1.44%) with no significant variation among sites, supported a warm, moist and fixed site that allowed for light penetration. When accounting for seed density, percentage germination was highest (2.78-2.35%) at low densities and did not vary among locations for the treatment that supported optimal conditions. Similarly for the same treatment, seed germination ranged from 0.24 to 5.87% among seasons but also did vary among sites. This study reports on the cultivation and restoration of an endangered epiphytic orchid species by in situ symbiotic seed germination and is likely to have broad application to the horticulture and conservation of the Orchidaceae.

Optimization of cell seeding in a 2D bio-scaffold system using computational models.

PubMed

Ho, Nicholas; Chua, Matthew; Chui, Chee-Kong

2017-05-01

The cell expansion process is a crucial part of generating cells on a large-scale level in a bioreactor system. Hence, it is important to set operating conditions (e.g. initial cell seeding distribution, culture medium flow rate) to an optimal level. Often, the initial cell seeding distribution factor is neglected and/or overlooked in the design of a bioreactor using conventional seeding distribution methods. This paper proposes a novel seeding distribution method that aims to maximize cell growth and minimize production time/cost. The proposed method utilizes two computational models; the first model represents cell growth patterns whereas the second model determines optimal initial cell seeding positions for adherent cell expansions. Cell growth simulation from the first model demonstrates that the model can be a representation of various cell types with known probabilities. The second model involves a combination of combinatorial optimization, Monte Carlo and concepts of the first model, and is used to design a multi-layer 2D bio-scaffold system that increases cell production efficiency in bioreactor applications. Simulation results have shown that the recommended input configurations obtained from the proposed optimization method are the most optimal configurations. The results have also illustrated the effectiveness of the proposed optimization method. The potential of the proposed seeding distribution method as a useful tool to optimize the cell expansion process in modern bioreactor system applications is highlighted. Copyright © 2017 Elsevier Ltd. All rights reserved.

Twenty Years of Prescribed Burning Influence the Development of Direct-Seeded Longleaf Pine on a Wet Pine Site in Louisiana

Treesearch

James D. Haywood; Harold E. Grelen

2000-01-01

Prescribed burning treatments were applied over a 20 yr period in a commonly randomized field study to determine the effects of various fire regimes on vegetation in a direct seeded standof longleaf pine (Pinus palustris Mill.). Seeding was done in November 1968. The study area was broadcast-burned about 16 months after seeding. The initial...

Germinant size of jack pine in relation to seed size and geographic origin

Treesearch

C.W. Yeatman

1966-01-01

The initial size of conifer seedlings is closely related to seed size (Hadders 1963), and seed size is a maternal characteristic that is highly subject to environmental modification (Mergen et al. 1964; Righter 1945). The effect of seed weight must be accounted for in critical studies of seedlings which attempt to attribute differences in growth to specific genetic or...

Dry fermentation of agricultural residues

NASA Astrophysics Data System (ADS)

Jewell, W. J.; Chandler, J. A.; Dellorto, S.; Fanfoni, K. J.; Fast, S.; Jackson, D.; Kabrick, R. M.

1981-09-01

A dry fermentation process is discussed which converts agricultural residues to methane, using the residues in their as produced state. The process appears to simplify and enhance the possibilities for using crop residues as an energy source. The major process variables investigated include temperature, the amount and type of inoculum, buffer requirements, compaction, and pretreatment to control the initial available organic components that create pH problems. A pilot-scale reactor operation on corn stover at a temperature of 550 C, with 25 percent initial total solids, a seed-to-feed ratio of 2.5 percent, and a buffer-to-feed ratio of 8 percent achieved 33 percent total volatile solids destruction in 60 days. Volumetric biogas yields from this unit were greater than 1 vol/vol day for 12 days, and greater than 0.5 vol/vol day for 32 days, at a substrate density of 169 kg/m (3).

All-trans-retinoic acid and 13-cis-retinoic acid: pharmacokinetics and biological activity in different cell culture models of human keratinocytes.

PubMed

Schroeder, M; Zouboulis, C C

2007-02-01

Despite its known biological effect on epithelial cells, 13- CIS-retinoic acid shows low binding affinity to either cellular retinoic acid-binding proteins or nuclear retinoid receptors compared to its isomer all- TRANS-retinoic acid. We have postulated a prodrug-drug relation with 13- CIS-retinoic acid which isomerizes to all- TRANS-retinoic acid. On the other hand, the biological effects of these two compounds can differ in the widely used cell culture models of HaCaT and normal primary keratinocytes. In this study, we seeded HaCaT and normal keratinocytes at high densities leading to early confluence in order to imitate high keratinocyte proliferation, such as in acne and psoriasis, while to model decreased keratinocyte proliferation, as in aged and steroid-damaged skin, cells were seeded at a low density. High performance liquid chromatography was administered to examine retinoid uptake and metabolism in monolayer HaCaT and normal keratinocyte cultures and the 4-methylumbelliferyl heptanoate assay to estimate cell growth at different cell densities. Major qualitative and quantitative differences were detected in the two cell types regarding intracellular 13- CIS-retinoic acid isomerization to all- TRANS-retinoic acid. On the other hand, the two retinoic acid isomers showed similar effects on cell growth of both cell types tested with increasing proliferation at low cell densities, but being rather inactive at high ones in normal keratinocytes and exhibiting an antiproliferative effect in HaCaT keratinocytes. The missing effect of retinoids on cell proliferation in high seeding densities of normal keratinocytes may indicate that the normalizing activity of retinoids on hyperkeratotic diseases, such as acne or psoriasis, is likely to be carried out by modulation of cell differentiation than cell growth. On the other hand, induced keratinocyte proliferation in low seeding densities may provide an explanation for the acanthosis induced by topical retinoids in aged and steroid-damaged skin.

X-ray lines as a density diagnostic in DT plasmas near 100x solid density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bailey, D.S.

1977-10-19

The use of electron impact broadened resonance lines to diagnose near-term high density diagnostics is discussed. In particular, the question of how to choose seed and pusher materials to have discernible broadening effects while maintaining line visibility is discussed.

Monitoring viability of seeds in gene banks: developing software tools to increase efficiency

USDA-ARS?s Scientific Manuscript database

Monitoring the decline of seed viability is essential for effective long term seed storage in ex situ collections. Recent FAO Genebank Standards recommend monitoring intervals at one-third the time predicted for viability to fall to 85% of initial viability. This poster outlines the development of ...

Improving sustainable seed yield in Wyoming big sagebrush

Treesearch

Jeremiah C. Armstrong

2007-01-01

As part of the Great Basin Restoration Initiative, the effects of browsing, competition removal, pruning, fertilization and seed collection methods on increasing seed production in Wyoming big sagebrush (Artemisia tridentata Nutt. spp wyomingensis Beetle & Young) were studied. Study sites were located in Idaho, Nevada, and Utah. A split-plot...

Evaluating cotton seed gland initiation by microscopy

USDA-ARS?s Scientific Manuscript database

Gossypol is a terpenoid aldehyde found in cotton (Gossypium hirsutum L.) glands and helps protect the seed from pests and pathogens. However, gossypol is toxic to many animals, so the seed is used mainly in cattle feed, as ruminants are tolerant to the effects of gossypol. In order to develop strat...

Stages and Spatial Scales of Recruitment Limitation in Southern Appalachain Forests

Treesearch

James S. Clark; Eric Macklin; Leslie Wood

1998-01-01

Recruitment limitation of tree population dynamics is poorly understood, because fecundity and dispersal are difficult to characterize in closed stands. We present an approach that estimates seed production and dispersal under closed canopies and four limitations on recruitment: tree density and location, fecundity, seed dispersal, and establishment. Consistent...

Seed rain, soil seed bank, seed loss and regeneration of Castanopsis fargesii (Fagaceae) in a subtropical evergreen broad-leaved forest

USGS Publications Warehouse

Du, X.; Guo, Q.; Gao, X.; Ma, K.

2007-01-01

Understanding the seed rain and seed loss dynamics in the natural condition has important significance for revealing the natural regeneration mechanisms. We conducted a 3-year field observation on seed rain, seed loss and natural regeneration of Castanopsis fargesii Franch., a dominant tree species in evergreen broad-leaved forests in Dujiangyan, southwestern China. The results showed that: (1) there were marked differences in (mature) seed production between mast (733,700 seeds in 2001) and regular (51,200 and 195,600 seeds in 2002 and 2003, respectively) years for C. fargesii. (2) Most seeds were dispersed in leaf litter, humus and 0-2 cm depth soil in seed bank. (3) Frequency distributions of both DBH and height indicated that C. fargesii had a relatively stable population. (4) Seed rain, seed ground density, seed loss, and leaf fall were highly dynamic and certain quantity of seeds were preserved on the ground for a prolonged time due to predator satiation in both the mast and regular years so that the continuous presence of seed bank and seedling recruitments in situ became possible. Both longer time observations and manipulative experiments should be carried out to better understand the roles of seed dispersal and regeneration process in the ecosystem performance. ?? 2006 Elsevier B.V. All rights reserved.

Edge Mechanisms for Power Excursion Control in Burning Plasmas

NASA Astrophysics Data System (ADS)

Hill, M. D.; Stacey, W. M.

2017-10-01

ITER must have active and preferably also passive control mechanisms that will limit inadvertent plasma power excursions which could trigger runaway fusion heating. We are identifying and investigating the potential of ion-orbit loss, impurity seeding, and various divertor ``choking'' phenomena to control or limit sudden increases in plasma density or temperature by reducing energy confinement, increasing radiation loss, etc., with the idea that such mechanisms could be tested on DIII-D and other existing tokamaks. We are assembling an edge-divertor code (GTEDGE-2) with a neutral transport model and a burn dynamics code, for this purpose. One potential control mechanism is the enhanced ion orbit loss from the thermalized ion distribution that would result from heating of the thermalized plasma ion distribution. Another possibility is impurity seeding with ions whose emissivity would increase sharply if the edge temperature increased. Enhanced radiative losses should also reduce the thermal energy flux across the separatrix, perhaps dropping the plasma into the poorer L-mode confinement regime. We will present some initial calculations to quantify these ideas. Work supported by US DOE under DE-FC02-04ER54698.

Defect reduction in seeded aluminum nitride crystal growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.

2017-04-18

Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Defect reduction in seeded aluminum nitride crystal growth

DOEpatents

Bondokov, Robert T.; Morgan, Kenneth E.; Schowalter, Leo J.; Slack, Glen A.

2017-06-06

Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density .ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Defect reduction in seeded aluminum nitride crystal growth

DOEpatents

Bondokov, Robert T.; Schowalter, Leo J.; Morgan, Kenneth; Slack, Glen A; Rao, Shailaja P.; Gibb, Shawn Robert

2017-09-26

Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

New Embedded Denotes Fuzzy C-Mean Application for Breast Cancer Density Segmentation in Digital Mammograms

NASA Astrophysics Data System (ADS)

Othman, Khairulnizam; Ahmad, Afandi

2016-11-01

In this research we explore the application of normalize denoted new techniques in advance fast c-mean in to the problem of finding the segment of different breast tissue regions in mammograms. The goal of the segmentation algorithm is to see if new denotes fuzzy c- mean algorithm could separate different densities for the different breast patterns. The new density segmentation is applied with multi-selection of seeds label to provide the hard constraint, whereas the seeds labels are selected based on user defined. New denotes fuzzy c- mean have been explored on images of various imaging modalities but not on huge format digital mammograms just yet. Therefore, this project is mainly focused on using normalize denoted new techniques employed in fuzzy c-mean to perform segmentation to increase visibility of different breast densities in mammography images. Segmentation of the mammogram into different mammographic densities is useful for risk assessment and quantitative evaluation of density changes. Our proposed methodology for the segmentation of mammograms on the basis of their region into different densities based categories has been tested on MIAS database and Trueta Database.

Accelerated craniofacial bone regeneration through dense collagen gel scaffolds seeded with dental pulp stem cells

PubMed Central

Chamieh, Frédéric; Collignon, Anne-Margaux; Coyac, Benjamin R.; Lesieur, Julie; Ribes, Sandy; Sadoine, Jérémy; Llorens, Annie; Nicoletti, Antonino; Letourneur, Didier; Colombier, Marie-Laure; Nazhat, Showan N.; Bouchard, Philippe; Chaussain, Catherine; Rochefort, Gael Y.

2016-01-01

Therapies using mesenchymal stem cell (MSC) seeded scaffolds may be applicable to various fields of regenerative medicine, including craniomaxillofacial surgery. Plastic compression of collagen scaffolds seeded with MSC has been shown to enhance the osteogenic differentiation of MSC as it increases the collagen fibrillary density. The aim of the present study was to evaluate the osteogenic effects of dense collagen gel scaffolds seeded with mesenchymal dental pulp stem cells (DPSC) on bone regeneration in a rat critical-size calvarial defect model. Two symmetrical full-thickness defects were created (5 mm diameter) and filled with either a rat DPSC-containing dense collagen gel scaffold (n = 15), or an acellular scaffold (n = 15). Animals were imaged in vivo by microcomputer tomography (Micro-CT) once a week during 5 weeks, whereas some animals were sacrificed each week for histology and histomorphometry analysis. Bone mineral density and bone micro-architectural parameters were significantly increased when DPSC-seeded scaffolds were used. Histological and histomorphometrical data also revealed significant increases in fibrous connective and mineralized tissue volume when DPSC-seeded scaffolds were used, associated with expression of type I collagen, osteoblast-associated alkaline phosphatase and osteoclastic-related tartrate-resistant acid phosphatase. Results demonstrate the potential of DPSC-loaded-dense collagen gel scaffolds to benefit of bone healing process. PMID:27934940

Lallemantia reylenne seeds as superdisintegrant: Formulation and evaluation of nimesulide orodispersible tablets

PubMed Central

Malik, Karan; Arora, Gurpreet; Singh, Inderbir; Arora, Sandeep

2011-01-01

Aim: Orodispersible tablets also known as fast dissolving tablets disintegrate instantaneously within the mouth and thus can be consumed without water. The present study was aimed to formulate orodispersible tablets of nimesulide by using Lallemantia reylenne seeds as natural superdisintegrant. Materials and Methods: Powdered lallemantia seeds were characterized for powder flow properties (bulk density, tapped density, carr's consolidation index, hausner ratio, angle of repose), swelling index, viscosity, pH, and loss on drying. The prepared tablets were evaluated for different tablet parametric tests, wetting time, water absorption ratio, effective pore radius, porosity, packing fraction, in vitro and in vivo disintegration time, in vitro dissolution and stability studies. Results and Discussion: Increase in Lallementia reylenne concentration had an appreciable effect on tablet hardness and friability which clearly indicated binding potential of the seeds. Water absorption ratio increased with increase in Lallemantia reylenne concentration from batch A1 to A4. Water uptake coupled natural polymer swelling could be the most probable mechanism for concentration dependent reduction in disintegration time by the Lallemantia reylenne seeds. Porosity of the formulated tablets was found to increase from batch A1-A4. The in vitro disintegration results were in line with in vivo disintegration results. Conclusion: It could be concluded that Lallemantia reylenne seeds could be used as natural superdisintegrant in the formulation of orodispersible tablets. PMID:23071942

Seeding the initial population with feasible solutions in metaheuristic optimization of steel trusses

NASA Astrophysics Data System (ADS)

Kazemzadeh Azad, Saeid

2018-01-01

In spite of considerable research work on the development of efficient algorithms for discrete sizing optimization of steel truss structures, only a few studies have addressed non-algorithmic issues affecting the general performance of algorithms. For instance, an important question is whether starting the design optimization from a feasible solution is fruitful or not. This study is an attempt to investigate the effect of seeding the initial population with feasible solutions on the general performance of metaheuristic techniques. To this end, the sensitivity of recently proposed metaheuristic algorithms to the feasibility of initial candidate designs is evaluated through practical discrete sizing of real-size steel truss structures. The numerical experiments indicate that seeding the initial population with feasible solutions can improve the computational efficiency of metaheuristic structural optimization algorithms, especially in the early stages of the optimization. This paves the way for efficient metaheuristic optimization of large-scale structural systems.

Size-guided multi-seed heuristic method for geometry optimization of clusters: Application to benzene clusters.

PubMed

Takeuchi, Hiroshi

2018-05-08

Since searching for the global minimum on the potential energy surface of a cluster is very difficult, many geometry optimization methods have been proposed, in which initial geometries are randomly generated and subsequently improved with different algorithms. In this study, a size-guided multi-seed heuristic method is developed and applied to benzene clusters. It produces initial configurations of the cluster with n molecules from the lowest-energy configurations of the cluster with n - 1 molecules (seeds). The initial geometries are further optimized with the geometrical perturbations previously used for molecular clusters. These steps are repeated until the size n satisfies a predefined one. The method locates putative global minima of benzene clusters with up to 65 molecules. The performance of the method is discussed using the computational cost, rates to locate the global minima, and energies of initial geometries. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Statistical properties of the radiation belt seed population

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, A. J.; Spence, H. E.; Huang, C. -L.

Here, we present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular, we investigate the relationship between the tens and hundreds of keV seed electrons and >1 MeV core radiation belt electron population. Using a cross-correlation analysis, we find that the seed and core populations are well correlated with a coefficient of ≈0.73 with a time lag of 10–15 h. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of themore » acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of hundreds of keV electrons is only one of several conditions required for MeV electron radiation belt acceleration.« less

Statistical properties of the radiation belt seed population

DOE PAGES

Boyd, A. J.; Spence, H. E.; Huang, C. -L.; ...

2016-07-25

Here, we present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular, we investigate the relationship between the tens and hundreds of keV seed electrons and >1 MeV core radiation belt electron population. Using a cross-correlation analysis, we find that the seed and core populations are well correlated with a coefficient of ≈0.73 with a time lag of 10–15 h. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of themore » acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of hundreds of keV electrons is only one of several conditions required for MeV electron radiation belt acceleration.« less

Formation of qualified BaHfO3 doped Y0.5Gd0.5Ba2Cu3O7-δ film on CeO2 buffered IBAD-MgO tape by self-seeding pulsed laser deposition

NASA Astrophysics Data System (ADS)

Liu, Linfei; Wang, Wei; Yao, Yanjie; Wu, Xiang; Lu, Saidan; Li, Yijie

2018-05-01

Improvement in the in-filed transport properties of REBa2Cu3O7-δ (RE = rare earth elements, REBCO) coated conductor is needed to meet the performance requirements for various practical applications, which can be accomplished by introducing artificial pinning centers (APCs), such as second phase dopant. However, with increasing dopant level the critical current density Jc at 77 K in zero applied magnetic field decreases. In this paper, in order to improve Jc we propose a seed layer technique. 5 mol% BaHfO3 (BHO) doped Y0.5Gd0.5Ba2Cu3O7-δ (YGBCO) epilayer with an inserted seed layer was grown on CeO2 buffered ion beam assisted deposition MgO (IBAD-MgO) tape by pulsed laser deposition. The effect of the conditions employed to prepare the seed layer, including tape moving speed and chemical composition, on the quality of 5 mol% BHO doped YGBCO epilayer was systematically investigated by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) observations. It was found that all the samples with seed layer have higher Jc (77 K, self-field) than the 5 mol% BHO doped YGBCO film without seed layer. The seed layer could inhibit deterioration of the Jc at 77 K and self-filed. Especially, the self-seed layer (5 mol% BHO doped YGBCO seed layer) was more effective in improving the crystal quality, surface morphology and superconducting performance. At 4.2 K, the 5 mol% BHO doped YGBCO film with 4 nm thick self-seed layer had a very high flux pinning force density Fp of 860 GN/m3 for B//c under a 9 T field, and more importantly, the peak of the Fp curve was not observed.

The role of seed bank in the dynamics of understorey in an oak forest in Hungary.

PubMed

Koncz, G; Papp, Mária; Török, P; Kotroczó, Zs; Krakomperger, Zs; Matus, G; Tóthmérész, B

2010-01-01

We studied the potential role of seed bank in the dynamics of the understorey in a turkey oak-sessile oak forest (Querceteum petraeae-cerris) in Hungary. We used long-term records of the herb layer (1973-2006) and the seed bank composition of 2006 to assess the role of seed bank in the regeneration of herb layer. The total cover of herb layer decreased from 22% (1973) to 6% (1988), and remained low (<10%) till 2006; coinciding with the increasing cover of secondary canopy dominated by Acer campestre. We found a low density seed bank (ca. 1300 seeds/m2). Altogether 33 species were germinated from the soil samples. A few generalist weed species composed the majority of seed bank. It was possible to assign a seed bank type for 19 species; 14 species out of 19 was long-term persistent. We found that the characteristic perennial forest herbs and grasses had only sparse seed bank. The Jaccard similarity between vegetation and seed bank was low (<30%). Our results suggest that the continuous establishment of forest herbs are not based on local persistent seed bank; it should be based on vegetative spreading and/or seed rain.

Flow Visualization of Density in a Cryogenic Wind Tunnel Using Planar Rayleigh and Raman Scattering

NASA Technical Reports Server (NTRS)

Herring, Gregory C.; Shirinzadeh, Behrooz

2002-01-01

Using a pulsed Nd:YAG laser (532 nm) and a gated, intensified charge-coupled device, planar Rayleigh and Raman scattering techniques have been used to visualize the unseeded Mach 0.2 flow density in a 0.3-meter transonic cryogenic wind tunnel. Detection limits are determined for density measurements by using both unseeded Rayleigh and Raman (N2 vibrational) methods. Seeding with CO2 improved the Rayleigh flow visualization at temperatures below 150 K. The seeded Rayleigh version was used to demonstrate the observation of transient flow features in a separated boundary layer region, which was excited with an oscillatory jet. Finally, a significant degradation of the laser light sheet, in this cryogenic facility, is discussed.

Influence of key processing parameters and seeding density effects of microencapsulated chondrocytes fabricated using electrohydrodynamic spraying.

PubMed

Gansau, Jennifer; Kelly, Lara; Buckley, Conor

2018-06-11

Cell delivery and leakage during injection remains a challenge for cell-based intervertebral disc regeneration strategies. Cellular microencapsulation may offer a promising approach to overcome these limitations by providing a protective niche during intradiscal injection. Electrohydrodynamic spraying (EHDS) is a versatile one-step approach for microencapsulation of cells using a high voltage electric field. The primary objective of this work was to characterise key processing parameters such as applied voltage (0, 5, 10 or 15kV), emitter needle gauge (21, 26 or 30G), alginate concentration (1, 2 or 3%) and flow rate (50, 100, 250 or 500 µl/min) to regulate the morphology of alginate microcapsules and subsequent cell viability when altering these parameters. The effect of initial cell seeding density (5, 10 and 20x10⁶ cells/ml) on subsequent matrix accumulation of microencapsulated articular chondrocytes was also evaluated. Results showed that increasing alginate concentration and thus viscosity increased overall microcapsule size but also affected the geometry towards ellipsoidal-shaped gels. Altering the electric field strength and needle diameter regulated microcapsule size towards a smaller diameter with increasing voltage and smaller needle diameter. Needle size did not appear to affect cell viability when operating with lower alginate concentrations (1% and 2%), although higher concentrations (3%) and thus higher viscosity hydrogels resulted in diminished viability with decreasing needle diameter. Increasing cell density resulted in decreased cell viability and a concomitant decrease in DNA content, perhaps due to competing nutrient demands as a result of more closely packed cells. However, higher cell densities resulted in increased levels of extracellular matrix accumulated. Overall, this work highlights the potential of EHDS as a controllable and versatile approach to fabricate microcapsules for injectable delivery which can be used in a variety of applications such as drug development or cell therapies. . © 2018 IOP Publishing Ltd.

Getting the biggest birch for the bang: restoring and expanding upland birchwoods in the Scottish Highlands by managing red deer

PubMed Central

Tanentzap, Andrew J; Zou, James; Coomes, David A

2013-01-01

High deer populations threaten the conservation value of woodlands and grasslands, but predicting the success of deer culling, in terms of allowing vegetation to recover, is difficult. Numerical simulation modeling is one approach to gain insight into the outcomes of management scenarios. We develop a spatially explicit model to predict the responses of Betula spp. to red deer (Cervus elaphus) and land management in the Scottish Highlands. Our model integrates a Bayesian stochastic stage-based matrix model within the framework of a widely used individual-based forest simulation model, using data collected along spatial and temporal gradients in deer browsing. By initializing our model with the historical spatial locations of trees, we find that densities of juvenile trees (<3 m tall) predicted after 9–13 years closely match counts observed in the field. This is among the first tests of the accuracy of a dynamical simulation model for predicting the responses of tree regeneration to herbivores. We then test the relative importance of deer browsing, ground cover vegetation, and seed availability in facilitating landscape-level birch regeneration using simulations in which we varied these three variables. We find that deer primarily control transitions of birch to taller (>3 m) height tiers over 30 years, but regeneration also requires suitable ground cover for seedling establishment. Densities of adult seed sources did not influence regeneration, nor did an active management scenario where we altered the spatial configuration of adults by creating “woodland islets”. Our results show that managers interested in maximizing tree regeneration cannot simply reduce deer densities but must also improve ground cover for seedling establishment, and the model we develop now enables managers to quantify explicitly how much both these factors need to be altered. More broadly, our findings emphasize the need for land managers to consider the impacts of large herbivores rather than their densities. PMID:23919137

The effect of rodent seed predation on four species of California annual grasses.

PubMed

Borchert, M I; Jain, S K

1978-01-01

The effect of seed predation by Microtus californicus and Mus musculus on plant numbers of four species of California annual grasses was investigated for one year period on a grassland near Davis, California. In winter, mice utilized dead star thistle plants for cover when grasses in open areas were short, but moved into open areas when grass grew tall in spring.Using exclosures and plots sown with known quantities of seed, it was estimated that a mouse population (approximate density 120/acre) consumed 75% of Avena fatua seed, 44% of Hordeum leporinum seed, and 37% of Bromus diandrus seed. Mice showed a strong preference for Avena seed.Plant numbers of Avena and Hordeum were reduced by 62% and 30%, respectively. Hordeum, Lolium, and to a lesser extent, Bromus responded to a competitive release from Avena by increases in plant size and reproductive output. In addition, seed predation markedly increased seed to adult plant survivorship of Avena, Hordeum, and Bromus.Vertebrate seed predation is discussed as a potentially important factor in the yearly patterns of plant population regulation in California annual grasslands.

Ant Abundance along a Productivity Gradient: Addressing Two Conflicting Hypotheses

PubMed Central

Segev, Udi; Kigel, Jaime; Lubin, Yael; Tielbörger, Katja

2015-01-01

The number of individuals within a population or community and their body size can be associated with changes in resource supply. While these relationships may provide a key to better understand the role of abiotic vs. biotic constraints in animal communities, little is known about the way size and abundance of organisms change along resource gradients. Here, we studied this interplay in ants, addressing two hypotheses with opposite predictions regarding variation in population densities along resource gradients- the ‘productivity hypothesis’ and the ‘productivity-based thinning hypothesis’. The hypotheses were tested in two functional groups of ground-dwelling ants that are directly primary consumers feeding on seeds: specialized seed-eaters and generalist species. We examined variations in colony density and foraging activity (a size measurement of the forager caste) in six ant assemblages along a steep productivity gradient in a semi-arid region, where precipitation and plant biomass vary 6-fold over a distance of 250km. An increase in the density or foraging activity of ant colonies along productivity gradients is also likely to affect competitive interactions among colonies, and consequently clinal changes in competition intensity were also examined. Ant foraging activity increased with productivity for both functional groups. However, colony density revealed opposing patterns: it increased with productivity for the specialized seed-eaters, but decreased for the generalist species. Competition intensity, evaluated by spatial partitioning of species at food baits and distribution of colonies, was uncorrelated with productivity in the specialized seed-eaters, but decreased with increasing productivity in the generalists. Our results provide support for two contrasting hypotheses regarding the effect of resource availability on the abundance of colonial organisms- the ‘productivity hypothesis’ for specialized seed-eaters and the ‘productivity-based thinning hypothesis’ for generalist species. These results also stress the importance of considering the role of functional groups in studies of community structure. PMID:26176853

[Initial growth processes in seeds in magnetic fields, strengthened or weakened in relation to the geomagnetic field].

PubMed

Es'kov, E K; Rodionov, Iu A

2010-01-01

The effects of modifications of magnetic fields, simulating anomalies of natural magnetism of the Earth, were studied in the seeds of peas and winter wheat. It has been shown that strengthening or weakening of the geomagnetic field inhibits water absorption and initial growth processes. The influence of magnetic fields on the orientation of rootlets and development of plantlets is determined. The connection between the magnetic susceptibility of seeds and content of heavy metals in them is established, which obviously concerns the magnetic susceptibility and magnetotropism in plants.

Seed dispersal by wind, birds, and bats between Philippine montane rainforest and successional vegetation.

PubMed

Ingle, Nina M R

2003-01-01

In the moist Neotropics, vertebrate frugivores have a much greater role in the dispersal of forest and successional woody plants than wind, and bats rather than birds play the dominant role in dispersing early successional species. I investigated whether these patterns also occurred in a Philippine montane rainforest and adjacent successional vegetation. I also asked whether seed mass was related to probability of dispersal between habitats. A greater number of woody species and stems in the forest produced vertebrate-dispersed seeds than wind-dispersed seeds. Although input of forest seeds into the successional area was dominated by vertebrate-dispersed seeds in terms of species richness, wind-dispersed seeds landed in densities 15 times higher. Frugivorous birds dispersed more forest seeds and species into the successional area than bats, and more successional seeds and species into the forest. As expected, seed input declined with distance from source habitat. Low input of forest seeds into the successional area at the farthest distance sampled, 40 m from forest edge, particularly for vertebrate-dispersed seeds, suggests very limited dispersal out of forest even into a habitat in which woody successional vegetation provides perches and fruit resources. For species of vertebrate-dispersed successional seeds, probability of dispersal into forest declined significantly with seed mass.

Seed dispersal limitations shift over time in tropical forest restoration.

PubMed

Reid, J Leighton; Holl, Karen D; Zahawi, Rakan A

2015-06-01

Past studies have shown that tropical forest regeneration on degraded farmlands is initially limited by lack of seed dispersal, but few studies have tracked changes in abundance and composition of seed rain past the first few years after land abandonment. We measured seed rain for 12 months in 10 6-9-year-old restoration sites and five mature, reference forests in southern Costa Rica in order to learn (1) if seed rain limitation persists past the first few years of regeneration; (2) how restoration treatments influence seed community structure and composition; and (3) whether seed rain limitation is contingent on landscape context. Each restoration site contained three 0.25-ha treatment plots: (1) a naturally regenerating control, (2) tree islands, and (3) a mixed-species tree plantation. Sites spanned a deforestation gradient with 9-89% forest area within 500 m around the treatment plots. Contrary to previous studies, we found that tree seeds were abundant and ubiquitous across all treatment plots (585.1 ± 142.0 seeds · m(-2) · yr(-1) [mean ± SE]), indicating that lack of seed rain ceased to limit forest regeneration within the first decade of recovery. Pioneer trees and shrubs comprised the vast majority of seeds, but compositional differences between restoration sites and reference forests were driven by rarer, large-seeded species. Large, animal-dispersed tree seeds were more abundant in tree islands (4.6 ± 2.9 seeds · m(-2) · yr(-1)) and plantations (5.8 ± 3.0 seeds · m(-2) · yr(-1)) than control plots (0.2 ± 0.1 seeds · m(-2) · yr(-1)), contributing to greater tree species richness in actively restored plots. Planted tree species accounted for < 1% of seeds. We found little evidence for landscape forest cover effects on seed rain, consistent with previous studies. We conclude that seed rain limitation shifted from an initial, complete lack of tree seeds to a specific limitation on large-seeded, mature forest species over the first decade. Although total seed abundance was equal among restoration treatments, tree plantations and tree islands continued to diversify seed rain communities compared to naturally regenerating controls. Compositional differences between regenerating plots and mature forests suggest that large-seeded tree species are appropriate candidates for enrichment planting.

From seed production to seedling establishment: Important steps in an invasive process

NASA Astrophysics Data System (ADS)

Ferreras, Ana Elisa; Galetto, Leonardo

2010-03-01

It is widely accepted that exotic invasive species are one of the most important ecological and economic problems. Reproductive and establishment traits are considered key features of a population expansion process, but few works have studied many of these simultaneously. This work examines how large the differences are in reproductive and establishment traits between two Fabaceae, the exotic invasive, Gleditsia triacanthos and the native, Acacia aroma. Gleditsia is a serious leguminous woody invader in various parts of the world and Acacia is a common native tree of Argentina. Both species have similar dispersal mechanisms and their reproductive phenology overlaps. We chose 17 plants of each species in a continuous forest of the Chaco Serrano Forest of Córdoba, Argentina. In each plant we measured fruit production, fruit removal (exclusion experiments), seed predation (pre- and post-dispersal), seed germination, seed bank (on each focal tree, three sampling periods during the year), and density of seedlings (around focal individuals and randomly in the study site). Gleditsia presented some traits that could favour the invasion process, such as a higher number of seeds per plant, percentage of scarified seed germination and density of seedlings around the focal individuals, than Acacia. On the other hand, Gleditsia presented a higher percentage of seed predation. The seed bank was persistent in both species and no differences were observed in fruit removal. This work highlights the importance of simultaneously studying reproductive and establishment variables involved in the spreading of an exotic invasive species. It also gives important insight into the variables to be considered when planning management strategies. The results are discussed from the perspective of some remarkable hypotheses on invasive species and may contribute to rethinking some aspects of the theory on invasive species.

Seeds in space experiment results

NASA Technical Reports Server (NTRS)

Alston, Jim A.

1991-01-01

Two million seeds of 120 different varieties representing 106 species, 97 genera, and 55 plant families were flown aboard the Long Duration Exposure Facility (LDEF). The seeds were housed on the space exposed experiment developed for students (SEEDS) tray in sealed canister number six and in two small vented canisters. The tray was in the F-2 position. The seeds were germinated and the germination rates and development of the resulting plants compared to the control seed that stayed in Park Seed's seed storage facility. The initial results are presented. There was a better survival rate in the sealed canister in space than in the storage facility at Park Seed. At least some of the seeds in each of the vented canisters survived the exposure to vacuum for almost six years. The number of observed apparent mutations was very low.

Method and system of filtering and recommending documents

DOEpatents

Patton, Robert M.; Potok, Thomas E.

2016-02-09

Disclosed is a method and system for discovering documents using a computer and providing a small set of the most relevant documents to the attention of a human observer. Using the method, the computer obtains a seed document from the user and generates a seed document vector using term frequency-inverse corpus frequency weighting. A keyword index for a plurality of source documents can be compared with the weighted terms of the seed document vector. The comparison is then filtered to reduce the number of documents, which define an initial subset of the source documents. Initial subset vectors are generated and compared to the seed document vector to obtain a similarity value for each comparison. Based on the similarity value, the method then recommends one or more of the source documents.

Evaluation of Seeds of Science/Roots of Reading Project: "Shoreline Science" and "Terrarium Investigations." CSE Technical Report 676

ERIC Educational Resources Information Center

Wang, Jia; Baker, Eva L.

2006-01-01

This project was initiated in order to evaluate two literacy and science integrated instruction units, "Shoreline Science" and "Terrarium Investigations," designed by the Lawrence Hall of Science "Seeds of Science/Roots of Reading" Project ("Seeds/Roots"). We examined how the integrated units affect student…

Seed enhancement/upgrading techniques: Read the seed

Treesearch

Kim R. Creasy

2002-01-01

To the nursery industry in Canada, seed enhancing and upgrading techniques have ever increasingly become and are now an integral part of their operations prior to greenhouse sowing. The terms "enhancing" and "upgrading" can be used interchangeably, but they essentially mean the same thing. It's the idea of improving the quality of initial...

Improvement of a Harvester Based, Multispectral, Seed Cotton Fiber Quality Sensor

USDA-ARS?s Scientific Manuscript database

A multispectral sensor for in-situ seed cotton fiber quality measurement was developed and tested at Texas A&M University. Results of initial testing of the sensor using machine harvested seed cotton have shown promise. Improvements have been made to the system and the measurement method to meet t...

Transformation of Morinda citrifolia via simple mature seed imbibition method.

PubMed

Lee, J J; Ahmad, S; Roslan, H A

2013-12-15

Morinda citrifolia, is a valuable medicinal plant with a wide range of therapeutic properties and extensive transformation study on this plant has yet been known. Present study was conducted to establish a simple and reliable transformation protocol for M. citrifolia utilising Agrobacterium tumefaciens via direct seed exposure. In this study, the seeds were processed by tips clipping and dried and subsequently incubated in inoculation medium. Four different parameters during the incubation such as incubation period, bacterial density, temperature and binary vectors harbouring beta-glucuronidase (GUS) gene (pBI121 and pGSA1131), were tested to examine its effect on transformation efficiency. The leaves from the treated and germinated seedlings were analysed via Polymerase Chain Reaction (PCR), histochemical assay of the GUS gene and reverse transcription-PCR (RT-PCR). Results of the study showed that Agrobacterium strain LBA4404 with optical density of 1.0 and 2 h incubation period were optimum for M. citrifolia transformation. It was found that various co-cultivation temperatures tested and type of vector used did not affect the transformation efficiency. The highest transformation efficiency for M. citrifolia direct seed transformation harbouring pBI121 and pGSA1131 was determined to be 96.8% with 2 h co-cultivation treatment and 80.4% when using bacterial density of 1.0, respectively. The transformation method can be applied for future characterization study of M. citrifolia.

Spectral Characteristics of VLF Sferics Associated With RHESSI TGFs.

PubMed

Mezentsev, Andrew; Lehtinen, Nikolai; Østgaard, Nikolai; Pérez-Invernón, F J; Cummer, Steven A

2018-01-16

We compared the modeled energy spectral density of very low frequency (VLF) radio emissions from terrestrial gamma ray flashes (TGFs) with the energy spectral density of VLF radio sferics recorded by Duke VLF receiver simultaneously with those TGFs. In total, six events with world wide lightning location network (WWLLN) defined locations were analyzed to exhibit a good fit between the modeled and observed energy spectral densities. In VLF range the energy spectral density of the TGF source current moment is found to be dominated by the contribution of secondary low-energy electrons and independent of the relativistic electrons which play their role in low-frequency (LF) range. Additional spectral modulation by the multiplicity of TGF peaks was found and demonstrated a good fit for two TGFs whose VLF sferics consist of two overlapping pulses each. The number of seeding pulses in TGF defines the spectral shape in VLF range, which allows to retrieve this number from VLF sferics, assuming they were radiated by TGFs. For two events it was found that the number of seeding pulses is small, of the order of 10. For the rest of the events the lower boundary of the number of seeding pulses was found to be between 10 to 10 3 .

High Residue Winter Cover Crops Deplete Winter Annual Weed Seed Across a Landscape in a Long-Term Tillage Study

USDA-ARS?s Scientific Manuscript database

High residue conservation agriculture systems have the potential to maximize environmental benefits achieved when practicing reduced tillage. A greenhouse study was conducted in 2006 through 2008 to determine the effects of cover crop residue on weed seed density within the soil seedbank under varyi...

Nutrient homeostasis, C:N:S ratios, protein, and oil content in Cuphea seed

USDA-ARS?s Scientific Manuscript database

Macro- and micro-nutrient densities, carbon:nitrogen (C:N), nitrogen:sulphur (N:S), protein, and oil contents and interrelationships were assessed during a 3-year study in seeds of the indeterminate Cuphea germplasm line PSR23 selected from an inter-specific cross between two species of the Lythrace...

The Assessment of Parameters Affecting the Quality of Cord Blood by the Appliance of the Annexin V Staining Method and Correlation with CFU Assays

PubMed Central

Radke, Teja Falk; Barbosa, David; Duggleby, Richard Charles; Saccardi, Riccardo; Querol, Sergio; Kögler, Gesine

2013-01-01

The assessment of nonviable haematopoietic cells by Annexin V staining method in flow cytometry has recently been published by Duggleby et al. Resulting in a better correlation with the observed colony formation in methylcellulose assays than the standard ISHAGE protocol, it presents a promising method to predict cord blood potency. Herein, we applied this method for examining the parameters during processing which potentially could affect cord blood viability. We could verify that the current standards regarding time and temperature are sufficient, since no significant difference was observed within 48 hours or in storage at 4°C up to 26°C. However, the addition of DMSO for cryopreservation alone leads to an inevitable increase in nonviable haematopoietic stem cells from initially 14.8% ± 4.3% to at least 30.6% ± 5.5%. Furthermore, CFU-assays with varied seeding density were performed in order to evaluate the applicability as a quantitative method. The results revealed that only in a narrow range reproducible clonogenic efficiency (ClonE) could be assessed, giving at least a semiquantitative estimation. We conclude that both Annexin V staining method and CFU-assays with defined seeding density are reliable means leading to a better prediction of the final potency. Especially Annexin V, due to its fast readout, is a practical tool for examining and optimising specific steps in processing, while CFU-assays add a functional confirmation. PMID:23533443

Purslane (Portulaca oleracea) Seed Consumption And Aerobic Training Improves Biomarkers Associated with Atherosclerosis in Women with Type 2 Diabetes (T2D).

PubMed

Dehghan, Firouzeh; Soori, Rahman; Gholami, Khadijeh; Abolmaesoomi, Mitra; Yusof, Ashril; Muniandy, Sekaran; Heidarzadeh, Sara; Farzanegi, Parvin; Ali Azarbayjani, Mohammad

2016-12-05

The aim of this study was to investigate the responses of atherosclerosis plaque biomarkers to purslane seed consumption and aerobic training in women with T2D. 196 women with T2D were assigned into; (1) placebo (PL), (2) aerobic training+placebo (AT + PL), 3) purslane seeds (PS), aerobic training+purslane seeds (AT + PS). The training program and purslane seeds consumption (2.5 g lunch and 5 g dinner) were carried out for 16 weeks. The components of purslane seed were identified and quantified by GC-MS. Blood samples were withdrawn via venipuncture to examine blood glucose, low-density lipoprotein (LDL), high-density lipoprotein (HDL), cholesterol, triglycerides (TG), creatinine, urea, uric acid, NF-κB, GLP1, GLP1R, TIMP-1, MMP2, MMP9, CRP, CST3, and CTSS expressions. Blood glucose, LDL, cholesterol, TG, creatinine, urea, and uric acid levels in the (P), (AT), and (AT + PS) groups were significantly decreased compared to the pre-experimental levels or the placebo group, while HDL, significantly increased. Furthermore, the protein and mRNA levels of NF-κB, TIMP-1, MMP2 &9, CRP, CST3, and CTSS in the (P), (AT), (AT + PS) significantly decreased compared to pre-experimental or the placebo group, while level of GLP1 and GLP1-R increased drastically. Findings suggest that purslane seed consumption alongside exercising could improve atherosclerosis plaque biomarkers through synergistically mechanisms in T2D.

Temporal dynamics of iris yellow spot virus and its vector, Thrips tabaci (Thysanoptera: Thripidae), in seeded and transplanted onion fields.

PubMed

Hsu, Cynthia L; Hoepting, Christine A; Fuchs, Marc; Shelton, Anthony M; Nault, Brian A

2010-04-01

Onion thrips, Thrips tabaci (Lindeman) (Thysanoptera: Thripidae), can reduce onion bulb yield and transmit iris yellow spot virus (IYSV) (Bunyaviridae: Tospovirus), which can cause additional yield losses. In New York, onions are planted using seeds and imported transplants. IYSV is not seed transmitted, but infected transplants have been found in other U.S. states. Transplants are also larger than seeded onions early in the season, and thrips, some of which may be viruliferous, may preferentially colonize larger plants. Limited information is available on the temporal dynamics of IYSV and its vector in onion fields. In 2007 and 2008, T. tabaci and IYSV levels were monitored in six seeded and six transplanted fields. We found significantly more thrips in transplanted fields early in the season, but by the end of the season seeded fields had higher levels of IYSV. The percentage of sample sites with IYSV-infected plants remained low (<12%) until August, when infection levels increased dramatically in some fields. The densities of adult and larval thrips in August and September were better predictors of final IYSV levels than early season thrips densities. For 2007 and 2008, the time onions were harvested may have been more important in determining IYSV levels than whether the onions were seeded or transplanted. Viruliferous thrips emigrating from harvested onion fields into nonharvested ones may be increasing the primary spread of IYSV in late-harvested onions. Managing T. tabaci populations before harvest, and manipulating the spatial arrangement of fields based on harvest date could mitigate the spread of IYSV.

Using In Situ Symbiotic Seed Germination to Restore Over-collected Medicinal Orchids in Southwest China

PubMed Central

Shao, Shi-Cheng; Burgess, Kevin S.; Cruse-Sanders, Jennifer M.; Liu, Qiang; Fan, Xu-Li; Huang, Hui; Gao, Jiang-Yun

2017-01-01

Due to increasing demand for medicinal and horticultural uses, the Orchidaceae is in urgent need of innovative and novel propagation techniques that address both market demand and conservation. Traditionally, restoration techniques have been centered on ex situ asymbiotic or symbiotic seed germination techniques that are not cost-effective, have limited genetic potential and often result in low survival rates in the field. Here, we propose a novel in situ advanced restoration-friendly program for the endangered epiphytic orchid species Dendrobium devonianum, in which a series of in situ symbiotic seed germination trials base on conspecific fungal isolates were conducted at two sites in Yunnan Province, China. We found that percentage germination varied among treatments and locations; control treatments (no inoculum) did not germinate at both sites. We found that the optimal treatment, having the highest in situ seed germination rate (0.94-1.44%) with no significant variation among sites, supported a warm, moist and fixed site that allowed for light penetration. When accounting for seed density, percentage germination was highest (2.78-2.35%) at low densities and did not vary among locations for the treatment that supported optimal conditions. Similarly for the same treatment, seed germination ranged from 0.24 to 5.87% among seasons but also did vary among sites. This study reports on the cultivation and restoration of an endangered epiphytic orchid species by in situ symbiotic seed germination and is likely to have broad application to the horticulture and conservation of the Orchidaceae. PMID:28638388

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria.

PubMed

Bittencourt-Oliveira, M C; Hereman, T C; Macedo-Silva, I; Cordeiro-Araújo, M K; Sasaki, F F C; Dias, C T S

2015-05-01

We evaluated the effect of crude extracts of the microcystin-producing (MC+) cyanobacteria Microcystis aeruginosa on seed germination and initial development of lettuce and arugula, at concentrations between 0.5 μg.L(-1) and 100 μg.L(-1) of MC-LR equivalent, and compared it to crude extracts of the same species without the toxin (MC-). Crude extracts of the cyanobacteria with MC (+) and without MC (-) caused different effects on seed germination and initial development of the salad green seedlings, lettuce being more sensitive to both extracts when compared to arugula. Crude extracts of M. aeruginosa (MC+) caused more evident effects on seed germination and initial development of both species of salad greens than MC-. Concentrations of 75 μg.L(-1) and 100 μg.L(-1) of MC-LR equivalent induced a greater occurrence of abnormal seedlings in lettuce, due to necrosis of the radicle and shortening of this organ in normal seedlings, as well as the reduction in total chlorophyll content and increase in the activity of the antioxidant enzyme peroxidase (POD). The MC- extract caused no harmful effects to seed germination and initial development of seedlings of arugula. However, in lettuce, it caused elevation of POD enzyme activity, decrease in seed germination at concentrations of 75 μg.L(-1) (MC-75) and 100 μg.L(-1) (MC-100), and shortening of the radicle length, suggesting that other compounds present in the cyanobacteria extracts contributed to this result. Crude extracts of M. aeruginosa (MC-) may contain other compounds, besides the cyanotoxins, capable of causing inhibitory or stimulatory effects on seed germination and initial development of salad green seedlings. Arugula was more sensitive to the crude extracts of M. aeruginosa (MC+) and (MC-) and to other possible compounds produced by the cyanobacteria.

Anti-atherogenic properties of Deglet Noor Date seeds (Phoenix dactylifera) Methanol extract on Diet-Induced Hypercholesterolemic Rats

NASA Astrophysics Data System (ADS)

Saryono, S.; Eliyan, J.; Herdiati, D.; Khikmatullah, AA; Silvana, CP; Adi, HP

2017-02-01

This is the first study to investigate the completely anti-atherogenic effect of Deglet Noor Date seeds methanol extract administration on diet-induced hypercholesterolemic rats. About 24 male Wistar rats were divided into 6 groups. The normal control (NC) group, Hypercholesterolemic Control (HC) group was given high cholesterol diet, and Simvastatin Control (SC) group was given 0.18 mg/200g simvastatin after high cholesterol diet induction. The treatment groups of T0.25, T0.5 and T1 were given supplementation of 0.25, 0.5 and 1 g/kg of dates seed extract after high cholesterol diet induction, respectively for 21 days. Blood was collected from orbitals plexus vein for plasma lipid profile analysis. The levels of Total Cholesterol (TC), Low-Density Lipoprotein (LDL) and Atherogenic Index (AI) values were significantly decreased (p<0.05) on diet-induced hypercholesterolemic rats after supplemented with date seeds extract (T0.25, T0.5 and T1) but not in Triglycerides (TG). Along with that, High Density Lipoprotein (HDL) level was significantly increased (p<0.05). However, the T1 group was the best anti-atherogenic activity in compared to other groups. Results showed that plasma lipid profile was significant to get better after supplemented with date seeds extract.

Cosmic string loops as the seeds of super-massive black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bramberger, Sebastian F.; Brandenberger, Robert H.; Jreidini, Paul

2015-06-01

Recent discoveries of super-massive black holes at high redshifts indicate a possible tension with the standard ΛCDM paradigm of early universe cosmology which has difficulties in explaining the origin of the required nonlinear compact seeds which trigger the formation of these super-massive black holes. Here we show that cosmic string loops which result from a scaling solution of strings formed during a phase transition in the very early universe lead to an additional source of compact seeds. The number density of string-induced seeds dominates at high redshifts and can help trigger the formation of the observed super-massive black holes.

Reproductive strategy of the intertidal seagrass Zostera japonica under different levels of disturbance and tidal inundation

NASA Astrophysics Data System (ADS)

Suonan, Zhaxi; Kim, Seung Hyeon; Qin, Le-Zheng; Lee, Kun-Seop

2017-10-01

Zostera japonica populations along the coastline of the northwestern Pacific Ocean are declining, mainly due to anthropogenic and natural disturbances. Although reproductive strategy is an important factor in achieving population persistence, changes in the reproductive strategy of Z. japonica under anthropogenic disturbances and tidal stresses are largely unknown. Thus, the duration and frequency of flowering, reproductive effort, potential seed production, and seed density in sediments were measured at three study stations (undisturbed upper, undisturbed lower, and disturbed stations), which were classified based on the levels of inundation stress and clamming activity, in monospecific meadows of Z. japonica on the southern coast of Korea. The flowering duration was approximately six months in the disturbed station, with disturbance due to clam harvesting, whereas the duration was about five months in the undisturbed lower station, and only three months in the undisturbed upper station. The maximum flowering frequency was 25.5% in the disturbed station, which was approximately 4- and 2-fold higher than in the undisturbed upper (6.1%) and lower (12.3%) stations, respectively. A similar trend in reproductive effort was also found among the three study stations. Potential seed production was 7850, 6220, and 1560 seeds m-2 in the disturbed, undisturbed lower, and undisturbed upper stations, respectively. The annual maximum seed density in sediments was also higher in the disturbed and undisturbed lower stations than in the undisturbed upper station, but the densities were relatively low (ranging from 71 to 254 seeds m-2) at all three study stations. It was found that the allocation to sexual reproduction was highest in the disturbed station, followed by the undisturbed lower station, and lowest in the undisturbed upper station, suggesting that sexual reproduction in Z. japonica tends to be enhanced under disturbed and inundated environmental conditions for population persistence.

Fitness of Crop-Wild Hybrid Sunflower under Competitive Conditions: Implications for Crop-to-Wild Introgression

PubMed Central

Mercer, Kristin L.; Emry, D. Jason; Snow, Allison A.; Kost, Matthew A.; Pace, Brian A.; Alexander, Helen M.

2014-01-01

Understanding the likelihood and extent of introgression of novel alleles in hybrid zones requires comparison of lifetime fitness of parents and hybrid progeny. However, fitness differences among cross types can vary depending on biotic conditions, thereby influencing introgression patterns. Based on past work, we predicted that increased competition would enhance introgression between cultivated and wild sunflower (Helianthus annuus) by reducing fitness advantages of wild plants. To test this prediction, we established a factorial field experiment in Kansas, USA where we monitored the fitness of four cross types (Wild, F1, F2, and BCw hybrids) under different levels of interspecific and intraspecific competition. Intraspecific manipulations consisted both of density of competitors and of frequency of crop-wild hybrids. We recorded emergence of overwintered seeds, survival to reproduction, and numbers of seeds produced per reproductive plant. We also calculated two compound fitness measures: seeds produced per emerged seedling and seeds produced per planted seed. Cross type and intraspecific competition affected emergence and survival to reproduction, respectively. Further, cross type interacted with competitive treatments to influence all other fitness traits. More intense competition treatments, especially related to density of intraspecific competitors, repeatedly reduced the fitness advantage of wild plants when considering seeds produced per reproductive plant and per emerged seedling, and F2 plants often became indistinguishable from the wilds. Wild fitness remained superior when seedling emergence was also considered as part of fitness, but the fitness of F2 hybrids relative to wild plants more than quadrupled with the addition of interspecific competitors and high densities of intraspecific competitors. Meanwhile, contrary to prediction, lower hybrid frequency reduced wild fitness advantage. These results emphasize the importance of taking a full life cycle perspective. Additionally, due to effects of exogenous selection, a given hybrid generation may be especially well-suited to hastening introgression under particular environmental conditions. PMID:25295859

Fitness of crop-wild hybrid sunflower under competitive conditions: implications for crop-to-wild introgression.

PubMed

Mercer, Kristin L; Emry, D Jason; Snow, Allison A; Kost, Matthew A; Pace, Brian A; Alexander, Helen M

2014-01-01

Understanding the likelihood and extent of introgression of novel alleles in hybrid zones requires comparison of lifetime fitness of parents and hybrid progeny. However, fitness differences among cross types can vary depending on biotic conditions, thereby influencing introgression patterns. Based on past work, we predicted that increased competition would enhance introgression between cultivated and wild sunflower (Helianthus annuus) by reducing fitness advantages of wild plants. To test this prediction, we established a factorial field experiment in Kansas, USA where we monitored the fitness of four cross types (Wild, F1, F2, and BCw hybrids) under different levels of interspecific and intraspecific competition. Intraspecific manipulations consisted both of density of competitors and of frequency of crop-wild hybrids. We recorded emergence of overwintered seeds, survival to reproduction, and numbers of seeds produced per reproductive plant. We also calculated two compound fitness measures: seeds produced per emerged seedling and seeds produced per planted seed. Cross type and intraspecific competition affected emergence and survival to reproduction, respectively. Further, cross type interacted with competitive treatments to influence all other fitness traits. More intense competition treatments, especially related to density of intraspecific competitors, repeatedly reduced the fitness advantage of wild plants when considering seeds produced per reproductive plant and per emerged seedling, and F2 plants often became indistinguishable from the wilds. Wild fitness remained superior when seedling emergence was also considered as part of fitness, but the fitness of F2 hybrids relative to wild plants more than quadrupled with the addition of interspecific competitors and high densities of intraspecific competitors. Meanwhile, contrary to prediction, lower hybrid frequency reduced wild fitness advantage. These results emphasize the importance of taking a full life cycle perspective. Additionally, due to effects of exogenous selection, a given hybrid generation may be especially well-suited to hastening introgression under particular environmental conditions.

Choices and consequences of oviposition by a pollinating seed predator, Hadena ectypa (Noctuidae), on its host plant, Silene stellata (Caryophyllaceae).

PubMed

Kula, Abigail A R; Dudash, Michele R; Fenster, Charles B

2013-06-01

Pollinating seed predators are models for the study of mutualisms. These insects have dual effects on host-plant fitness, through pollination as adults and flower and fruit predation as larvae. A rarely examined question is whether pollinating seed-predator oviposition choices are influenced by plant floral and size traits and the potential consequences of oviposition for host-plant reproduction. • We quantified oviposition by a pollinating seed predator, Hadena ectypa, on its host, Silene stellata, to determine if oviposition was associated with specific plant traits and whether oviposition was significantly correlated with fruit initiation or flower and fruit predation over three years. We also quantified whether stigmatic pollen loads of flowers visited by Hadena that both fed on nectar and oviposited were greater than when Hadena only fed on nectar. • Hadena had significant preference for plants having flowers with long corolla tubes in all three years. Moth oviposition was correlated with other traits only in some years. Oviposition did not increase stigmatic pollen loads. We observed significant positive relationships between both oviposition and fruit initiation and oviposition and flower/fruit predation. • Hadena ectypa oviposition choices were based consistently on floral tube length differences among individuals, and the consequences of oviposition include both fruit initiation (due to pollination while feeding on nectar prior to oviposition) and larval flower/fruit predation. The positive association between oviposition and fruit initiation may explain the long-term maintenance of facultative pollinating seed-predator interactions.

Wheat production in controlled environments.

PubMed

Salisbury, F B; Bugbee, B; Bubenheim, D

1987-01-01

Our goal is to optimize conditions for maximum yield and quality of wheat to be used in a controlled-environment, life-support system (CELSS) in a Lunar or Martian base or perhaps in a space craft. With yields of 23 to 57 g m-2 d-1 of edible biomass, a minimum size for a CELSS would be between 12 and 30 m2 per person, utilizing about 600 W m-2 of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon-dioxide levels, humidity, and wind velocity are controlled in state-of-the-art growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO3 and controlling the NO3/NH4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants per meter2. Densities up to 2000 plants m-2 appear to increase seed yield. Biomass production increases almost linearly with increasing irradiance from 400 to 1700 micromoles m-2 s-1 of photosynthetic photon flux (PPF), but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization. High temperatures (25 to 27 degrees C) and long days shorten the life cycle and promote rapid growth, but cooler temperatures (20 degrees C) and shorter days greatly increase seed number per head and thus yield (g m-2). The life cycle is lengthened in these conditions but yield per day (g m-2 d-1) is still increased. We have evaluated about 600 cultivars from around the world and have developed several breeding lines for our controlled conditions. Some of our ultra-dwarf lines (30 to 50 cm tall) look especially promising with high yields and high harvest indices (percent edible biomass).

Wheat production in controlled environments

NASA Astrophysics Data System (ADS)

Salisbury, Frank B.; Bugbee, Bruce; Bubenheim, David

Our goal is to optimize conditions for maximum yield and quality of wheat to be used in a controlled-environment, life-support system (CELSS) in a Lunar or Martian base or perhaps in a space craft. With yields of 23 to 57 g m-2 d-1 of edible biomass, a minimum size for a CELSS would be between 12 and 30 m2 per person, utilizing about 600 W m-2 of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon-dioxide levels, humidity, and wind velocity are controlled in state-of-the-art growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO3 and controlling the NO3/NH4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants per meter2. Densities up to 2000 plants m-2 appear to increase seed yield. Biomass production increases almost linearily with increasing irradiance from 400 to 1700 μmol m-2 s-1 of photosynthetic photon flux (PPF), but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization. High temperatures (25 to 27°C) and long days shorten the life cycle and promote rapid growth, but cooler temperatures (20°C) and shorter days greatly increase seed number per head and thus yield (g m-2). The life cycle is lengthened in these conditions but yield per day (g m-2 d-1) is still increased. We have evaluated about 600 cultivars from around the world and have developed several breeding lines for our controlled conditions. Some of our ultra-dwarf lines (30 to 50 cm tall) look especially promising with high yields and high harvest indices (percent edible biomass).

Pollen density on the stigma affects endogenous gibberellin metabolism, seed and fruit set, and fruit quality in Pyrus pyrifolia.

PubMed

Zhang, Caixi; Tateishi, Naoya; Tanabe, Kenji

2010-10-01

To clarify the relationship between pollen density and gametophytic competition in Pyrus pyrifolia, gametophytic performance, gibberellin metabolism, fruit set, and fruit quality were investigated by modifying P. pyrifolia pollen grain number and density with Lycopodium spores. Higher levels of pollen density improved seed viability, fruit set, and fruit quality. Treatments with the highest pollen density showed a significantly increased fruit growth rate and larger fruit at harvest. High pollen density increased germination rate and gave a faster pollen tube growth, both in vivo and in vitro. Endogenous gibberellin (GA) concentrations increased in pollen tubes soon after germination and the concentration of two growth-active GAs, GA(3), and GA(4), was positively correlated to final fruit size, cell numbers in the mesocarp, and pollen tube growth rate. These two GAs appear to be biosynthesized de novo in pollen tube and are the main pollen-derived bioactive GAs found after pollen germination. GA(1) levels in the pollen tube appear to be related to a pollen-style interaction that occurred after the pollen grains landed on the stigma.

Seed/catalyst-free vertical growth of high-density electrodeposited zinc oxide nanostructures on a single-layer graphene

NASA Astrophysics Data System (ADS)

Aziz, Nur Suhaili Abd; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2014-02-01

We report the seed/catalyst-free vertical growth of high-density electrodeposited ZnO nanostructures on a single-layer graphene. The absence of hexamethylenetetramine (HMTA) and heat has resulted in the formation of nanoflake-like ZnO structure. The results show that HMTA and heat are needed to promote the formation of hexagonal ZnO nanostructures. The applied current density plays important role in inducing the growth of ZnO on graphene as well as in controlling the shape, size, and density of ZnO nanostructures. High density of vertically aligned ZnO nanorods comparable to other methods was obtained. The quality of the ZnO nanostructures also depended strongly on the applied current density. The growth mechanism was proposed. According to the growth timing chart, the growth seems to involve two stages which are the formation of ZnO nucleation and the enhancement of the vertical growth of nanorods. ZnO/graphene hybrid structure provides several potential applications in electronics and optoelectronics such as photovoltaic devices, sensing devices, optical devices, and photodetectors.

Mapping of AFLP markers linked to seed coat colour loci in Brassica juncea (L.) Czern.

PubMed

Sabharwal, V; Negi, M S; Banga, S S; Lakshmikumaran, M

2004-06-01

Association mapping of the seed-coat colour with amplified fragment length polymorphism (AFLP) markers was carried out in 39 Brassica juncea lines. The lines had genetically diverse parentages and varied for seed-coat colour and other morphological characters. Eleven AFLP primer combinations were used to screen the 39 B. juncea lines, and a total of 335 polymorphic bands were detected. The bands were analysed for association with seed-coat colour using multiple regression analysis. This analysis revealed 15 markers associated with seed-coat colour, obtained with eight AFLP primer combinations. The marker E-ACA/M-CTG(350 )explained 69% of the variation in seed-coat colour. This marker along with markers E-AAC/M-CTC(235 )and E-AAC/M-CTA(250) explained 89% of the total variation. The 15 associated markers were validated for linkage with the seed-coat colour loci using a recombinant inbred line (RIL) mapping population. Bands were amplified with the eight AFLP primer combinations in 54 RIL progenies. Of the 15 associated markers, 11 mapped on two linkage groups. Eight markers were placed on linkage group 1 at a marker density of 6.0 cM, while the remaining three were mapped on linkage group 2 at a marker density of 3.6 cM. Marker E-ACA/M-CTG(350 )co-segregated with Gene1 controlling seed-coat colour; it was specific for yellow seed-coat colour and mapped to linkage group 1. Marker E-AAC/M-CTC(235) (AFLP8), which had been studied previously, was present on linkage group 2; it was specific for brown seed-coat colour. Since AFLP markers are not adapted for large-scale applications in plant breeding, it is important to convert these to sequence-characterised amplified region (SCAR) markers. Marker E-AAC/M-CTC(235) (AFLP8) had been previously converted into a SCAR. Work is in progress to convert the second of the linked markers, E-ACA/M-CTG(350), to a SCAR. The two linked AFLP markers converted to SCARs will be useful for developing yellow-seeded B. juncea lines by means of marker-assisted selection.

Continued results of the seeds in space experiment

NASA Technical Reports Server (NTRS)

Alston, Jim A.

1992-01-01

Two million seeds of 120 different varieties representing 106 species, 97 genera, and 55 plant families were flown aboard the Long Duration Exposure Facility (LDEF). The seeds were housed on the Space Exposed Experiment Developed for Students (SEEDS) tray in the sealed canister number 6 and in two small vented canisters. The seeds were germinated and the germination rates and development of the resulting plants compared to the control seed that stayed in the storage facility. There was a better survival rate in the sealed canister in space than in the storage facility. At least some of the seed in the vented canisters survived the exposure to vacuum for almost six years. The number of observed mutations was very low. In the initial testing, the small seeded crops were not grown to maturity to check for mutation and obtain a second generation seed. These small seeded crops are now being grown for evaluation.

String stabilized ribbon growth a method for seeding same

DOEpatents

Sachs, Emanuel M.

1987-08-25

This invention is a method of initiating or seeding the growth of a crystalline or polycrystalline ribbon by the String Stabilized Ribbon Growth Method. The method for seeding the crystal growth comprises contacting a melt surface with a seed and two strings used in edge stabilization. The wetted strings attach to the wetted seed as a result of the freezing of the liquid melt. Upon drawing the seed, which is attached to the strings, away from the melt surface a melt liquid meniscus, a seed junction, and a growth interface forms. Further pulling of the attached seed causes a crystal ribbon to grow at the growth interface. The boundaries of the growing ribbon are: at the top the seed junction, at the bottom the freezing boundary of the melt liquid meniscus, and at the edges frozen-in strings.

Comparison of waste pumpkin material and its potential use in extruded snack foods.

PubMed

Norfezah, M N; Hardacre, A; Brennan, C S

2011-08-01

Material was produced from Crown pumpkin (Cucurbita maxima) processed from fractions of the fruit which are regarded as waste stream products (peel, flesh and seed). The flour from the three different fractions (peel, flesh and seed) of Crown pumpkin flour was incorporated into an extruded snack product formulation at levels 10%, 30% and 50% (w/w with corn grit) and processed in a twin-screw extruder to make 10 expanded snack products. Proximate analysis was carried out to determine the nutritional value of the raw pumpkin and pumpkin flour. A physical analysis of the product was used to determine its color, the expansion ratio, bulk density and texture. Inclusion of waste stream material (peel and seed) at 10%, yielded extruded products with similar expansion and density characteristics to the control sample; however, an inclusion of greater than 10% yielded significant challenges to product quality (hardness of the product).

Three-dimensional organization of dermal fibroblasts by macromass culture.

PubMed

Deshpande, Manisha

2008-01-01

The three-dimensional organization of cells by high-cell-seeding-density culture, termed 'macromass culture', is described. By macromass culture, dermal fibroblasts can be made to organize themselves into a unified three-dimensional form without the aid of a scaffold, and macroscopic constructs, named macromasses, can be made wholly from cells. The sole factor causing three-dimensional organization is culture of cells at high cell seeding density per unit area. No scaffold or extraneous matrix is used for the generation of macromasses; they are of completely cellular origin. No other agents or external influences such as tissue-inducing chemicals, tissue-inducing growth factors, substratum with special properties, rotational culture, centrifugation etc. are employed for macromass formation, and all seeded cells become part of the cohesive construct. These three-dimensional constructs have the potential for use as in vitro tissue analogues, and a possible application for in vitro cytotoxicity testing is demonstrated.

Performance by heifers grazing sod-seeded cool-season annuals seeded on different dates using two tillage intensities

USDA-ARS?s Scientific Manuscript database

A total of 120 Gelbvieh x Angus crossbred heifers (552'2.5 lb initial BW) grazed pastures of common bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with wheat (Triticum aestivum L.) and annual ryegrass (Lolium multiflorum Lam.) for a 3-year study to compare the effect of seeding dates and till...

Particle size affects Brassica seed meal-induced pathogen suppression of Rhizoctonia solani AG-5

USDA-ARS?s Scientific Manuscript database

R. solani AG-5 is a component of the pathogen complex that incites apple replant disease, and is suppressed via multiple mechanisms in response to B. juncea seed meal (SM) amendment. Allyl isothiocyanate (AITC) functions in suppression of this pathogen during the initial 24 h period post-seed meal a...

Volatile emission in dry seeds as a way to probe chemical reactions during initial asymptomatic deterioration

USDA-ARS?s Scientific Manuscript database

The nature and kinetics of reactions in dry seeds determines how long they survive. We used gas chromatography to assay volatile organic compounds (VOC) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry and humid (15, 33 and 75% RH...

Non-serotinous woody plants behave as aerial seed bank species when a late-summer wildfire coincides with a mast year.

PubMed

Pounden, Edith; Greene, David F; Michaletz, Sean T

2014-10-01

Trees which lack obvious fire-adaptive traits such as serotinous seed-bearing structures or vegetative resprouting are assumed to be at a dramatic disadvantage in recolonization via sexual recruitment after fire, because seed dispersal is invariably quite constrained. We propose an alternative strategy in masting tree species with woody cones or cone-like structures: that the large clusters of woody tissue in a mast year will sufficiently impede heat transfer that a small fraction of seeds can survive the flaming front passage; in a mast year, this small fraction would be a very large absolute number.In Kootenay National Park in British Columbia, we examined regeneration by Engelmann spruce (Picea engelmannii), a non-serotinous conifer, after two fires, both of which coincided with mast years. Coupling models of seed survivorship within cones and seed maturation schedule to a spatially realistic recruitment model, we show that (1) the spatial pattern of seedlings on a 630 m transect from the forest edge into the burn was best explained if there was in situ seed dissemination by burnt trees; (2) in areas several hundred meters from any living trees, recruitment density was well correlated with local prefire cone density; and (3) spruce was responding exactly like its serotinous codominant, lodgepole pine (Pinus contorta).We conclude that non-serotinous species can indeed behave like aerial seed bank species in mast years if the fire takes place late in the seed maturation period. Using the example of the circumpolar boreal forest, while the joint probability of a mast year and a late-season fire will make this type of event rare (we estimate P = 0.1), nonetheless, it would permit a species lacking obvious fire-adapted traits to occasionally establish a widespread and abundant cohort on a large part of the landscape.

The Importance of Tree Size and Fecundity for Wind Dispersal of Big-Leaf Mahogany

PubMed Central

Norghauer, Julian M.; Nock, Charles A.; Grogan, James

2011-01-01

Seed dispersal by wind is a critical yet poorly understood process in tropical forest trees. How tree size and fecundity affect this process at the population level remains largely unknown because of insufficient replication across adults. We measured seed dispersal by the endangered neotropical timber species big-leaf mahogany (Swietenia macrophylla King, Meliaceae) in the Brazilian Amazon at 25 relatively isolated trees using multiple 1-m wide belt transects extended 100 m downwind. Tree diameter and fecundity correlated positively with increased seed shadow extent; but in combination large, high fecundity trees contributed disproportionately to longer-distance dispersal events (>60 m). Among three empirical models fitted to seed density vs. distance in one dimension, the Student-t (2Dt) generally fit best (compared to the negative exponential and inverse power). When seedfall downwind was modelled in two dimensions using a normalised sample, it peaked furthest downwind (c. 25 m) for large, high-fecundity trees; with the inverse Gaussian and Weibull functions providing comparable fits that were slightly better than the lognormal. Although most seeds fell within 30 m of parent trees, relatively few juveniles were found within this distance, resulting in juvenile-to-seed ratios peaking at c. 35–45 m. Using the 2Dt model fits to predict seed densities downwind, coupled with known fecundity data for 2000–2009, we evaluated potential Swietenia regeneration near adults (≤30 m dispersal) and beyond 30 m. Mean seed arrival into canopy gaps >30 m downwind was more than 3× greater for large, high fecundity trees than small, high-fecundity trees. Tree seed production did not necessarily scale up proportionately with diameter, and was not consistent across years, and this resulting intraspecific variation can have important consequences for local patterns of dispersal in forests. Our results have important implications for management and conservation of big-leaf mahogany populations, and may apply to other threatened wind-dispersed Meliaceae trees. PMID:21408184

Effective seeding strategy in evolutionary prisoner's dilemma games on online social networks

NASA Astrophysics Data System (ADS)

Xu, Bo; Shi, Huibin; Wang, Jianwei; Huang, Yun

2015-04-01

This paper explores effective seeding strategies in prisoner's dilemma game (PDG) on online social networks, i.e. the optimal strategy to obtain global cooperation with minimum cost. Three distinct seeding strategies are compared by performing computer simulations on real online social network datasets. Our finding suggests that degree centrality seeding outperforms other strategies regardless of the initial payoff setting or network size. Celebrities of online social networks play key roles in preserving cooperation.

Bone formation by three-dimensional stromal osteoblast culture in biodegradable polymer scaffolds

NASA Technical Reports Server (NTRS)

Ishaug, S. L.; Crane, G. M.; Miller, M. J.; Yasko, A. W.; Yaszemski, M. J.; Mikos, A. G.; McIntire, L. V. (Principal Investigator)

1997-01-01

Bone formation was investigated in vitro by culturing stromal osteoblasts in three-dimensional (3-D), biodegradable poly(DL-lactic-co-glycolic acid) foams. Three polymer foam pore sizes, ranging from 150-300, 300-500, and 500-710 microns, and two different cell seeding densities, 6.83 x 10(5) cells/cm2 and 22.1 x 10(5) cells/cm2, were examined over a 56-day culture period. The polymer foams supported the proliferation of seeded osteoblasts as well as their differentiated function, as demonstrated by high alkaline phosphatase activity and deposition of a mineralized matrix by the cells. Cell number, alkaline phosphatase activity, and mineral deposition increased significantly over time for all the polymer foams. Osteoblast foam constructs created by seeding 6.83 x 10(5) cells/cm2 on foams with 300-500 microns pores resulted in a cell density of 4.63 x 10(5) cells/cm2 after 1 day in culture; they had alkaline phosphatase activities of 4.28 x 10(-7) and 2.91 x 10(-6) mumol/cell/min on Days 7 and 28, respectively; and they had a cell density that increased to 18.7 x 10(5) cells/cm2 by Day 56. For the same constructs, the mineralized matrix reached a maximum penetration depth of 240 microns from the top surface of the foam and a value of 0.083 mm for mineralized tissue volume per unit of cross sectional area. Seeding density was an important parameter for the constructs, but pore size over the range tested did not affect cell proliferation or function. This study suggests the feasibility of using poly(alpha-hydroxy ester) foams as scaffolding materials for the transplantation of autogenous osteoblasts to regenerate bone tissue.

Effect of Electron Seeding on Experimentally Measured Multipactor Discharge Threshold

NASA Astrophysics Data System (ADS)

Noland, Jonathan; Graves, Timothy; Lemon, Colby; Looper, Mark; Farkas, Alex

2012-10-01

Multipactor is a vacuum phenomenon in which electrons, moving in resonance with an externally applied electric field, impact material surfaces. If the number of secondary electrons created per primary electron impact averages more than unity, the resonant interaction can lead to an electron avalanche. Multipactor is a generally undesirable phenomenon, as it can cause local heating, absorb power, or cause detuning of RF circuits. In order to increase the probability of multipactor initiation, test facilities often employ various seeding sources such as radioactive sources (Cesium 137, Strontium 90), electron guns, or photon sources. Even with these sources, the voltage for multipactor initiation is not certain as parameters such as material type, RF pulse length, and device wall thickness can all affect seed electron flux and energy in critical gap regions, and hence the measured voltage threshold. This study investigates the effects of seed electron source type (e.g., photons versus beta particles), material type, gap size, and RF pulse length variation on multipactor threshold. In addition to the experimental work, GEANT4 simulations will be used to estimate the production rate of low energy electrons (< 5 keV) by high energy electrons and photons. A comparison of the experimental fluxes to the typical energetic photon and particle fluxes experienced by spacecraft in various orbits will also be made. Initial results indicate that for a simple, parallel plate device made of aluminum, there is no threshold variation (with seed electrons versus with no seed electrons) under continuous-wave RF exposure.

Mag-seeding of rat bone marrow stromal cells into porous hydroxyapatite scaffolds for bone tissue engineering.

PubMed

Shimizu, Kazunori; Ito, Akira; Honda, Hiroyuki

2007-09-01

Bone tissue engineering has been investigated as an alternative strategy for autograft transplantation. In the process of tissue engineering, cell seeding into three-dimensional (3-D) scaffolds is the first step for constructing 3-D tissues. We have proposed a methodology of cell seeding into 3-D porous scaffolds using magnetic force and magnetite nanoparticles, which we term Mag-seeding. In this study, we applied this Mag-seeding technique to bone tissue engineering using bone marrow stromal cells (BMSCs) and 3-D hydroxyapatite (HA) scaffolds. BMSCs were magnetically labeled with our original magnetite cationic liposomes (MCLs) having a positive surface charge to improve adsorption to cell surface. Magnetically labeled BMSCs were seeded onto a scaffold, and a 1-T magnet was placed under the scaffold. By using Mag-seeding, the cells were successfully seeded into the internal space of scaffolds with a high cell density. The cell seeding efficiency into HA scaffolds by Mag-seeding was approximately threefold larger than that by static-seeding (conventional method, without a magnet). After a 14-d cultivation period using the osteogenic induction medium by Mag-seeding, the level of two representative osteogenic markers (alkaline phosphatase and osteocalcin) were significantly higher than those by static-seeding. These results indicated that Mag-seeding of BMSCs into HA scaffolds is an effective approach to bone tissue engineering.

Factors influencing the natural regeneration of the pioneering shrub Calligonum mongolicum in sand dune stabilization plantations in arid deserts of northwest China.

PubMed

Fan, Baoli; McHugh, Allen David; Guo, Shujiang; Ma, Quanlin; Zhang, Jianhui; Zhang, Xiaojuan; Zhang, Weixing; Du, Juan; Yu, Qiushi; Zhao, Changming

2018-03-01

Calligonum mongolicum is a successful pioneer shrub to combat desertification, which is widely used for vegetation restoration in the desert regions of northwest China. In order to reveal the limitations to natural regeneration of C. mongolicum by asexual and sexual reproduction, following the process of sand dune stabilization, we assessed clonal shoots, seedling emergence, soil seed bank density, and soil physical characteristics in mobile and stabilized sand dunes. Controlled field and pot experiments were also conducted to assess germination and seedling emergence in different dune soil types and seed burial depths. The population density of mature C. mongolicum was significantly different after sand dune stabilization. Juvenile density of C. mongolicm was much lower in stabilized sand dunes than mobile sand dune. There was no significant difference in soil seed bank density at three soil depths between mobile and stabilized sand dunes, while the emergence of seedlings in stabilized dunes was much lower than emergence in mobile dunes. There was no clonal propagation found in stabilized dunes, and very few C. mongolicum seedlings were established on stabilized sand dunes. Soil clay and silt content, air-filled porosity, and soil surface compaction were significantly changed from mobile sand dune to stabilized dunes. Seedling emergence of C. mongolicm was highly dependent on soil physical condition. These results indicated that changes in soil physical condition limited clonal propagation and seedling emergence of C. mongolicum in stabilized sand dunes. Seed bank density was not a limiting factor; however, poor seedling establishment limited C. mongolicum's further natural regeneration in stabilized sand dunes. Therefore, clonal propagation may be the most important mode for population expansion in mobile sand dunes. As a pioneer species C. mongolicum is well adapted to propagate in mobile sand dune conditions, it appears unlikely to survive naturally in stabilized sand dune plantations.

Production of prodigiosin and chitinases by tropical Serratia marcescens strains with potential to control plant pathogens.

PubMed

Gutiérrez-Román, Martha Ingrid; Holguín-Meléndez, Francisco; Bello-Mendoza, Ricardo; Guillén-Navarro, Karina; Dunn, Michael F; Huerta-Palacios, Graciela

2012-01-01

The potential of three Serratia marcescens strains (CFFSUR-B2, CFFSUR-B3 and CFFSUR-B4) isolated from tropical regions in Mexico to inhibit the mycelial growth and conidial germination of Colletotrichum gloeosporioides, causal agent of fruit anthracnose, was evaluated. The ability of these strains to produce prodigiosin and chitinases when cultivated in oil seed-based media (peanut, sesame, soybean and castor bean) and in Luria-Bertani medium was determined. All of the strains exhibited similar fungal antagonistic activities and inhibited myceliar growth by more than 40% while inhibiting conidial germination by 81-89% (P = 0.01). The highest level of prodigiosin (40 μg/ml) was produced in the peanut-based medium while growth in soybean-based medium allowed the highest production of chitinases (56 units/ml), independent of the strain used. Strain CFFSUR-B2 grown in peanut medium was used to evaluate the effect of inoculum density and initial pH on metabolite production. The amount of prodigiosin produced increased with greater inoculum densities, with an initial density of 1 × 10(12) resulting in the highest production (60 μg/ml). Prodigiosin production was not affected by pH. The strains studied have the advantage of being adapted to tropical climates and are able to produce chitinases in the absence of chitin induction in vitro. These characteristics suggest their potential as biocontrol agents for fungal pathogens in tropical regions of the world.

Effects of Drift-Shell Splitting by Chorus Waves on Radiation Belt Electrons

NASA Astrophysics Data System (ADS)

Chan, A. A.; Zheng, L.; O'Brien, T. P., III; Tu, W.; Cunningham, G.; Elkington, S. R.; Albert, J.

2015-12-01

Drift shell splitting in the radiation belts breaks all three adiabatic invariants of charged particle motion via pitch angle scattering, and produces new diffusion terms that fully populate the diffusion tensor in the Fokker-Planck equation. Based on the stochastic differential equation method, the Radbelt Electron Model (REM) simulation code allows us to solve such a fully three-dimensional Fokker-Planck equation, and to elucidate the sources and transport mechanisms behind the phase space density variations. REM has been used to perform simulations with an empirical initial phase space density followed by a seed electron injection, with a Tsyganenko 1989 magnetic field model, and with chorus wave and ULF wave diffusion models. Our simulation results show that adding drift shell splitting changes the phase space location of the source to smaller L shells, which typically reduces local electron energization (compared to neglecting drift-shell splitting effects). Simulation results with and without drift-shell splitting effects are compared with Van Allen Probe measurements.

Effects of seed predators of different body size on seed mortality in Bornean logged forest.

PubMed

Hautier, Yann; Saner, Philippe; Philipson, Christopher; Bagchi, Robert; Ong, Robert C; Hector, Andy

2010-07-19

The Janzen-Connell hypothesis proposes that seed and seedling enemies play a major role in maintaining high levels of tree diversity in tropical forests. However, human disturbance may alter guilds of seed predators including their body size distribution. These changes have the potential to affect seedling survival in logged forest and may alter forest composition and diversity. We manipulated seed density in plots beneath con- and heterospecific adult trees within a logged forest and excluded vertebrate predators of different body sizes using cages. We show that small and large-bodied predators differed in their effect on con- and heterospecific seedling mortality. In combination small and large-bodied predators dramatically decreased both con- and heterospecific seedling survival. In contrast, when larger-bodied predators were excluded small-bodied predators reduced conspecific seed survival leaving seeds coming from the distant tree of a different species. Our results suggest that seed survival is affected differently by vertebrate predators according to their body size. Therefore, changes in the body size structure of the seed predator community in logged forests may change patterns of seed mortality and potentially affect recruitment and community composition.

Effects of Seed Predators of Different Body Size on Seed Mortality in Bornean Logged Forest

PubMed Central

Hautier, Yann; Saner, Philippe; Philipson, Christopher; Bagchi, Robert; Ong, Robert C.; Hector, Andy

2010-01-01

Background The Janzen-Connell hypothesis proposes that seed and seedling enemies play a major role in maintaining high levels of tree diversity in tropical forests. However, human disturbance may alter guilds of seed predators including their body size distribution. These changes have the potential to affect seedling survival in logged forest and may alter forest composition and diversity. Methodology/Principal Findings We manipulated seed density in plots beneath con- and heterospecific adult trees within a logged forest and excluded vertebrate predators of different body sizes using cages. We show that small and large-bodied predators differed in their effect on con- and heterospecific seedling mortality. In combination small and large-bodied predators dramatically decreased both con- and heterospecific seedling survival. In contrast, when larger-bodied predators were excluded small-bodied predators reduced conspecific seed survival leaving seeds coming from the distant tree of a different species. Conclusions/Significance Our results suggest that seed survival is affected differently by vertebrate predators according to their body size. Therefore, changes in the body size structure of the seed predator community in logged forests may change patterns of seed mortality and potentially affect recruitment and community composition. PMID:20657841

[Effect of decimeter polarized electromagnetic radiation on germinating capacity of seeds].

PubMed

Polevik, N D

2013-01-01

The effect of a polarization structure of electromagnetic radiation on the germinating capacity of seeds of such weeds as Green foxtail (Setaria viridis) and Green amaranth (Amaranthus retroflexus) has been studied. Seeds have been exposed to impulse electromagnetic radiation in a frequency of 896 MHz with linear, elliptical right-handed and elliptical left-handed polarizations at different power flux density levels. It is determined that the effect of the right-handed polarized electromagnetic radiation increases and the influence of the left-handed polarized one reduces the germinating capacity of seeds compared to the effect of the linearly polarized electromagnetic radiation. It is shown that the seeds have an amplitude polarization selectivity as evinced by the major effect of the right-handed polarized radiation on seeds. An electrodynamic model as the right-handed elliptically polarized antenna with the given quantity of the ellipticity of polarization is suggested to use in description of this selectivity.

Vertical growth of ZnO nanorods on ZnO seeded FTO substrate for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.

2018-04-01

Zinc oxide (ZnO) nanorods (NRs) were electrochemically grown on fluorine doped tin oxide (FTO) and ZnO seeded FTO substrates. X-ray diffraction (XRD) patterns, Raman spectra and photoluminescence (PL) spectra reveal that the hexagonal wurtzite structured ZnO grown on a seeded FTO substrate has a high crystallinity, crystal quality and less atomic defects. Felid emission scanning electron microscope (FE-SEM) images display a high growth density of NRs grown on seeded FTO substrate compared to NRs grown on FTO substrate. The efficiency of the DSSCs based on NRs grown on FTO and seeded FTO substrates is 0.85 and 1.52 %, respectively. UV-Vis absorption spectra and electrochemical impedance spectra depict that the NRs grown on seeded FTO photoanode have higher dye absorption and charge recombination resistance than that of the NRs grown on FTO substrate.

Forcasting Shortleaf Pine Seed Crops in the Ouachita Mountains

Treesearch

Michael G. Shelton; Robert F. Wittwer

2004-01-01

We field tested a cone-rating system to forecast seed crops from 1993 to 1996 in 28 shortleaf pine (Pinus echinata Mill.) stands, which represented a wide range of stand conditions. Sample trees were visually assigned to one of three cone-density classes based on cone spacing, occurrence of cones in clusters, and distribution of cones within the...

Cotyledon density measurements on valencia peanuts grown in the Southwest United States as a tool for developing food products

USDA-ARS?s Scientific Manuscript database

Valencia peanuts (Arachis hypogaea L. ssp. fastigiata) are able to complete seed development in an environment where extreme temperature variation and water deficit are common and growing season is short. Valencia seed can command a premium in food products as consumers like special properties like...

Characterization and optimization of cell seeding in scaffolds by factorial design: quality by design approach for skeletal tissue engineering.

PubMed

Chen, Yantian; Bloemen, Veerle; Impens, Saartje; Moesen, Maarten; Luyten, Frank P; Schrooten, Jan

2011-12-01

Cell seeding into scaffolds plays a crucial role in the development of efficient bone tissue engineering constructs. Hence, it becomes imperative to identify the key factors that quantitatively predict reproducible and efficient seeding protocols. In this study, the optimization of a cell seeding process was investigated using design of experiments (DOE) statistical methods. Five seeding factors (cell type, scaffold type, seeding volume, seeding density, and seeding time) were selected and investigated by means of two response parameters, critically related to the cell seeding process: cell seeding efficiency (CSE) and cell-specific viability (CSV). In addition, cell spatial distribution (CSD) was analyzed by Live/Dead staining assays. Analysis identified a number of statistically significant main factor effects and interactions. Among the five seeding factors, only seeding volume and seeding time significantly affected CSE and CSV. Also, cell and scaffold type were involved in the interactions with other seeding factors. Within the investigated ranges, optimal conditions in terms of CSV and CSD were obtained when seeding cells in a regular scaffold with an excess of medium. The results of this case study contribute to a better understanding and definition of optimal process parameters for cell seeding. A DOE strategy can identify and optimize critical process variables to reduce the variability and assists in determining which variables should be carefully controlled during good manufacturing practice production to enable a clinically relevant implant.

Measuring short distance dispersal of Alliaria petiolata and determining potential long distance dispersal mechanisms

PubMed Central

Anderson, Roger C.

2018-01-01

Introduction Alliaria petiolata, an herbaceous plant, has invaded woodlands in North America. Its ecology has been thoroughly studied, but an overlooked aspect of its biology is seed dispersal distances and mechanisms. We measured seed dispersal distances in the field and tested if epizoochory is a potential mechanism for long-distance seed dispersal. Methods Dispersal distances were measured by placing seed traps in a sector design around three seed point sources, which consisted of 15 second-year plants transplanted within a 0.25 m radius circle. Traps were placed at intervals ranging from 0.25–3.25 m from the point source. Traps remained in the field until a majority of seeds were dispersed. Eight probability density functions were fitted to seed trap counts via maximum likelihood. Epizoochory was tested as a potential seed dispersal mechanism for A. petiolata through a combination of field and laboratory experiments. To test if small mammals transport A. petiolata seeds in their fur, experimental blocks were placed around dense A. petiolata patches. Each block contained a mammal inclusion treatment (MIT) and control. The MIT consisted of a wood-frame (31 × 61× 31 cm) covered in wire mesh, except for the two 31 × 31 cm ends, placed over a germination tray filled with potting soil. A pan filled with bait was placed in the center of the tray. The control frame (11 × 31 × 61 cm) was placed over a germination tray and completely covered in wire mesh to exclude animal activity. Treatments were in the field for peak seed dispersal. In March, trays were moved to a greenhouse and A. petiolata seedlings were counted and then compared between treatments. To determine if A. petiolata seeds attach to raccoon (Procyon lotor) and white-tailed deer (Odocoileus virginianus) fur, wet and dry seeds were dropped onto wet and dry fur. Furs were rotated 180 degrees and the seeds that remained attached were counted. To measure seed retention, seeds were dropped on furs and rotated as before, then the furs were agitated for one hour. The seeds retained in the fur were counted. Results For the seed dispersal experiment, the 2Dt function provided the best fit and was the most biologically meaningful. It predicted that seed density rapidly declined with distance from the point source. Mean dispersal distance was 0.52 m and 95% of seeds dispersed within 1.14 m. The epizoochory field experiment showed increased mammal activity and A. petiolata seedlings in germination trays of the MIT compared to control. Laboratory studies showed 3–26% of seeds were attached and retained by raccoon and deer fur. Retention significantly increased if either seed or fur were wet (57–98%). Discussion Without animal seed vectors, most seeds fall within a short distance of the seed source; however, long distance dispersal may be accomplished by epizoochory. Our data are consistent with A. petiolata’s widespread distribution and development of dense clusters of the species in invaded areas. PMID:29576955

Implications of nonrandom seed abscission and global stilling for migration of wind-dispersed plant species.

PubMed

Thompson, Sally E; Katul, Gabriel G

2013-06-01

Migration of plant populations is a potential survival response to climate change that depends critically on seed dispersal. Biological and physical factors determine dispersal and migration of wind-dispersed species. Recent field and wind tunnel studies demonstrate biological adaptations that bias seed release toward conditions of higher wind velocity, promoting longer dispersal distances and faster migration. However, another suite of international studies also recently highlighted a global decrease in near-surface wind speeds, or 'global stilling'. This study assessed the implications of both factors on potential plant population migration rates, using a mechanistic modeling framework. Nonrandom abscission was investigated using models of three seed release mechanisms: (i) a simple drag model; (ii) a seed deflection model; and (iii) a 'wear and tear' model. The models generated a single functional relationship between the frequency of seed release and statistics of the near-surface wind environment, independent of the abscission mechanism. An Inertial-Particle, Coupled Eulerian-Lagrangian Closure model (IP-CELC) was used to investigate abscission effects on seed dispersal kernels and plant population migration rates under contemporary and potential future wind conditions (based on reported global stilling trends). The results confirm that nonrandom seed abscission increased dispersal distances, particularly for light seeds. The increases were mitigated by two physical feedbacks: (i) although nonrandom abscission increased the initial acceleration of seeds from rest, the sensitivity of the seed dispersal to this initial condition declined as the wind speed increased; and (ii) while nonrandom abscission increased the mean dispersal length, it reduced the kurtosis of seasonal dispersal kernels, and thus the chance of long-distance dispersal. Wind stilling greatly reduced the modeled migration rates under biased seed release conditions. Thus, species that require high wind velocities for seed abscission could experience threshold-like reductions in dispersal and migration potential if near-surface wind speeds continue to decline. © 2013 Blackwell Publishing Ltd.

Research and management in a young northern red oak seedling seed orchard

Treesearch

S.E. Schlarbaum; J.L. McConnell; L.R. Barber; R.A. Cox; J.F. Grant; Paul P. Kormanik; T. La Farge; P.L. Lambdin; S.W. Oak; C.K. Proffitt; J.R. Rhea; T. Tibbs

1994-01-01

A northern red oak progeny test was thinned at age 15 to produce a seedling seed orchard. Studies were initiated to determine relationships between acorn production and seed source. Acorn production was observed in 1984-1986 and 1989-1992.Family differences were observed in reproductive maturity. Large differences in size of acorns from the same tree were observed...

Wildfire rehabilitation success with and without chaining on the Henry Mountains, Utah

Treesearch

Cristina Juran; Bruce A. Roundy; James N. Davis

2008-01-01

We sampled unchained and chained areas in 2004 and 2005 on the Henry Mountains that had been aerially seeded after the Bulldog Fire of 2003. Establishment of seeded grasses was high on unchained and chained areas although chaining increased seeded grass establishment on some sites. Western yarrow established well on unchained areas. Initially, high seedling emergence...

Integration of a waveguide self-electrooptic effect device and a vertically coupled interconnect waveguide

DOEpatents

Vawter, G Allen [Corrales, NM

2008-02-26

A self-electrooptic effect device ("SEED") is integrated with waveguide interconnects through the use of vertical directional couplers. Light initially propagating in the interconnect waveguide is vertically coupled to the active waveguide layer of the SEED and, if the SEED is in the transparent state, the light is coupled back to the interconnect waveguide.

Rapid assessment of rice seed availability for wildlife in harvested fields

USGS Publications Warehouse

Halstead, B.J.; Miller, M.R.; Casazza, Michael L.; Coates, P.S.; Farinha, M.A.; Benjamin, Gustafson K.; Yee, J.L.; Fleskes, J.P.

2011-01-01

Rice seed remaining in commercial fields after harvest (waste rice) is a critical food resource for wintering waterfowl in rice-growing regions of North America. Accurate and precise estimates of the seed mass density of waste rice are essential for planning waterfowl wintering habitat extents and management. In the Sacramento Valley of California, USA, the existing method for obtaining estimates of availability of waste rice in harvested fields produces relatively precise estimates, but the labor-, time-, and machineryintensive process is not practical for routine assessments needed to examine long-term trends in waste rice availability. We tested several experimental methods designed to rapidly derive estimates that would not be burdened with disadvantages of the existing method. We first conducted a simulation study of the efficiency of each method and then conducted field tests. For each approach, methods did not vary in root mean squared error, although some methods did exhibit bias for both simulations and field tests. Methods also varied substantially in the time to conduct each sample and in the number of samples required to detect a standard trend. Overall, modified line-intercept methods performed well for estimating the density of rice seeds. Waste rice in the straw, although not measured directly, can be accounted for by a positive relationship with density of rice on the ground. Rapid assessment of food availability is a useful tool to help waterfowl managers establish and implement wetland restoration and agricultural habitat-enhancement goals for wintering waterfowl. ?? 2011 The Wildlife Society.

Efficacy of Organic Soil Amendments for Management of Heterodera glycines in Greenhouse Experiments.

PubMed

Grabau, Zane J; Chen, Senyu

2014-09-01

In a repeated greenhouse experiment, organic soil amendments were screened for effects on population density of soybean cyst nematode (SCN), Heterodera glycines, and soybean growth. Ten amendments at various rates were tested: fresh plant material of field pennycress, marigold, spring camelina, and Cuphea; condensed distiller's solubles (CDS), ash of combusted CDS, ash of combusted turkey manure (TMA), marigold powder, canola meal, and pennycress seed powder. Soybeans were grown for 70 d in field soil with amendments and SCN eggs incorporated at planting. At 40 d after planting (DAP), many amendments reduced SCN egg population density, but some also reduced plant height. Cuphea plant at application rate of 2.9% (amendment:soil, w:w, same below), marigold plant at 2.9%, pennycress seed powder at 0.5%, canola meal at 1%, and CDS at 4.3% were effective against SCN with population reductions of 35.2%, 46.6%, 46.7%, 73.2%, and 73.3% compared with control, respectively. For Experiment 1 at 70 DAP, canola meal at 1% and pennycress seed powder at 0.5% reduced SCN population density 70% and 54%, respectively. CDS at 4.3%, ash of CDS at 0.2%, and TMA at 1% increased dry plant mass whereas CDS at 4.3% and pennycress seed powder at 0.1% reduced plant height. For Experiment 2 at 70 DAP, amendments did not affect SCN population nor plant growth. In summary, some amendments were effective for SCN management, but phytoxicity was a concern.

Efficacy of Organic Soil Amendments for Management of Heterodera glycines in Greenhouse Experiments

PubMed Central

Grabau, Zane J.; Chen, Senyu

2014-01-01

In a repeated greenhouse experiment, organic soil amendments were screened for effects on population density of soybean cyst nematode (SCN), Heterodera glycines, and soybean growth. Ten amendments at various rates were tested: fresh plant material of field pennycress, marigold, spring camelina, and Cuphea; condensed distiller’s solubles (CDS), ash of combusted CDS, ash of combusted turkey manure (TMA), marigold powder, canola meal, and pennycress seed powder. Soybeans were grown for 70 d in field soil with amendments and SCN eggs incorporated at planting. At 40 d after planting (DAP), many amendments reduced SCN egg population density, but some also reduced plant height. Cuphea plant at application rate of 2.9% (amendment:soil, w:w, same below), marigold plant at 2.9%, pennycress seed powder at 0.5%, canola meal at 1%, and CDS at 4.3% were effective against SCN with population reductions of 35.2%, 46.6%, 46.7%, 73.2%, and 73.3% compared with control, respectively. For Experiment 1 at 70 DAP, canola meal at 1% and pennycress seed powder at 0.5% reduced SCN population density 70% and 54%, respectively. CDS at 4.3%, ash of CDS at 0.2%, and TMA at 1% increased dry plant mass whereas CDS at 4.3% and pennycress seed powder at 0.1% reduced plant height. For Experiment 2 at 70 DAP, amendments did not affect SCN population nor plant growth. In summary, some amendments were effective for SCN management, but phytoxicity was a concern. PMID:25276000

Evaluating pollination deficits in pumpkin production in New York.

PubMed

Petersen, J D; Huseth, A S; Nault, B A

2014-10-01

Potential decreases in crop yield from reductions in bee-mediated pollination services threaten food production demands of a growing population. Many fruit and vegetable growers supplement their fields with bee colonies during crop bloom. The extent to which crop production requires supplementary pollination services beyond those provided by wild bees is not well documented. Pumpkin, Cucurbita pepo L., requires bee-mediated pollination for fruit development. Previous research identified the common eastern bumble bee, Bombus impatiens (Cresson), as the most efficient pumpkin pollinator. Two concomitant studies were conducted to examine pollination deficits in New York pumpkin fields from 2011 to 2013. In the first study, fruit weight, seed set, and B. impatiens visits to pumpkin flowers were compared across fields supplemented with B. impatiens colonies at a recommended stocking density of five colonies per hectare, a high density of 15 colonies per hectare, or not supplemented with bees. In the second study, fruit weight and seed set of pumpkins that received supplemental pollen through hand-pollination were compared with those that were open-pollinated by wild bees. Results indicated that supplementing pumpkin fields with B. impatiens colonies, regardless of stocking density, did not increase fruit weight, seed set, or B. impatiens visits to pumpkin flowers. Fruit weight and seed set did not differ between hand- and open-pollinated treatments. In general, we conclude that pumpkin production in central New York is not limited by inadequate pollination services provided by wild bees and that on average, supplementation with B. impatiens colonies did not improve pumpkin yield.

Effects of frugivore impoverishment and seed predators on the recruitment of a keystone palm

NASA Astrophysics Data System (ADS)

Fadini, Rodrigo F.; Fleury, Marina; Donatti, Camila I.; Galetti, Mauro

2009-03-01

Many plant species are threatened as a result of extinction of their large-bodied frugivores all over the world. Additionally, introduced herbivores and seed predators may cause severe pressure on early stages of plant recruitment. We studied the seed dispersal and seed predation of the keystone palm Euterpe edulis on a land-bridge island with a highly impoverished frugivore fauna and overabundant seed predators, and in a continuous Atlantic forest in Brazil. While the diversity of avian seed dispersers and predators was higher on the mainland, the abundance of seed dispersers was 4-fold higher on the island. Turdus flavipes was responsible for 72% and 96% of seeds removed in the island and mainland, respectively. However, the higher density of T. flaviceps on the island did not result in higher seed removal. In fact, seed removal rate was 1.7 times lower there than on the mainland, probably due to the aggressive behavior of the major seed disperser who defend palm fruits. Seed predation, on the other hand, was markedly higher on the island, where nearly 100% of seeds were preyed upon, but only 0.3% on the mainland. As a consequence of higher seed predation the population of E. edulis has few numbers of seedlings and saplings on the island. Therefore, management of the seed predator populations on the island is a key priority for recovering the natural population of this keystone palm and the frugivores that depend on its fruits.

Comparison of the quality of single-crystal diamonds grown on two types of seed substrates by MPCVD

NASA Astrophysics Data System (ADS)

Zhao, Yun; Guo, Yanzhao; Lin, Liangzhen; Zheng, Yuting; Hei, Lifu; Liu, Jinlong; Wei, Junjun; Chen, Liangxian; Li, Chengming

2018-06-01

Microwave plasma chemical vapor deposition (MPCVD) was used to grow single-crystal diamonds on two types of single-crystal diamond seed substrates prepared by high-pressure, high-temperature (HPHT) and chemical vapor deposition (CVD) methods. The quality of diamonds grown on the different seed substrates was compared. Fluorescence characteristics showed that the sectors of the HPHT seed substrates were obviously partitioned. Raman and absorption spectra showed that the CVD seed substrate produced higher-quality crystals with fewer nitrogen impurities. X-ray topography showed that the HPHT seed substrate had obvious growth sector boundaries, inclusions, dislocations, and stacking faults. The polarization characteristics of HPHT seed substrate were obvious, and the stress distribution was not uniform. When etching HPHT and CVD seed substrates using the same parameters, the etching morphology and extent of different growth sectors of the two substrates differed. Although extended defects were inevitably formed at the interface and propagated in the CVD layer, the dislocation density of a 1 mm-thick CVD layer grown on a CVD seed substrate was only half that of a 1 mm-thick CVD layer grown on an HPHT seed substrate. Therefore, the use of CVD seed substrate enabled the growth of a relatively higher-quality CVD single-crystal diamond.

Ecological patterns of seed microbiome diversity, transmission, and assembly.

PubMed

Shade, Ashley; Jacques, Marie-Agnès; Barret, Matthieu

2017-06-01

Seeds are involved in the transmission of microorganisms from one plant generation to another and consequently act as the initial inoculum for the plant microbiota. The purpose of this mini-review is to provide an overview of current knowledge on the diversity, structure and role of the seed microbiota. The relative importance of the mode of transmission (vertical vs horizontal) of the microbial entities composing the seed microbiota as well as the potential connections existing between seed and other plant habitats such as the anthosphere and the spermosphere is discussed. Finally the governing processes (niche vs neutral) involved in the assembly and the dynamics of the seed microbiota are examined. Copyright © 2017. Published by Elsevier Ltd.

Critical behavior of a two-step contagion model with multiple seeds

NASA Astrophysics Data System (ADS)

Choi, Wonjun; Lee, Deokjae; Kahng, B.

2017-06-01

A two-step contagion model with a single seed serves as a cornerstone for understanding the critical behaviors and underlying mechanism of discontinuous percolation transitions induced by cascade dynamics. When the contagion spreads from a single seed, a cluster of infected and recovered nodes grows without any cluster merging process. However, when the contagion starts from multiple seeds of O (N ) where N is the system size, a node weakened by a seed can be infected more easily when it is in contact with another node infected by a different pathogen seed. This contagion process can be viewed as a cluster merging process in a percolation model. Here we show analytically and numerically that when the density of infectious seeds is relatively small but O (1 ) , the epidemic transition is hybrid, exhibiting both continuous and discontinuous behavior, whereas when it is sufficiently large and reaches a critical point, the transition becomes continuous. We determine the full set of critical exponents describing the hybrid and the continuous transitions. Their critical behaviors differ from those in the single-seed case.

A small-scale dynamo in feedback-dominated galaxies - III. Cosmological simulations

NASA Astrophysics Data System (ADS)

Rieder, Michael; Teyssier, Romain

2017-12-01

Magnetic fields are widely observed in the Universe in virtually all astrophysical objects, from individual stars to entire galaxies, even in the intergalactic medium, but their specific genesis has long been debated. Due to the development of more realistic models of galaxy formation, viable scenarios are emerging to explain cosmic magnetism, thanks to both deeper observations and more efficient and accurate computer simulations. We present here a new cosmological high-resolution zoom-in magnetohydrodynamic (MHD) simulation, using the adaptive mesh refinement technique, of a dwarf galaxy with an initially weak and uniform magnetic seed field that is amplified by a small-scale dynamo (SSD) driven by supernova-induced turbulence. As first structures form from the gravitational collapse of small density fluctuations, the frozen-in magnetic field separates from the cosmic expansion and grows through compression. In a second step, star formation sets in and establishes a strong galactic fountain, self-regulated by supernova explosions. Inside the galaxy, the interstellar medium becomes highly turbulent, dominated by strong supersonic shocks, as demonstrated by the spectral analysis of the gas kinetic energy. In this turbulent environment, the magnetic field is quickly amplified via a SSD process and is finally carried out into the circumgalactic medium by a galactic wind. This realistic cosmological simulation explains how initially weak magnetic seed fields can be amplified quickly in early, feedback-dominated galaxies, and predicts, as a consequence of the SSD process, that high-redshift magnetic fields are likely to be dominated by their small-scale components.

Red grape seed extract improves lipid profiles and decreases oxidized low-density lipoprotein in patients with mild hyperlipidemia.

PubMed

Razavi, Seyed-Mostafa; Gholamin, Sharareh; Eskandari, Ali; Mohsenian, Nakta; Ghorbanihaghjo, Amir; Delazar, Abbas; Rashtchizadeh, Nadereh; Keshtkar-Jahromi, Maryam; Argani, Hassan

2013-03-01

Hyperlipidemia can lead to atherosclerosis by lipoprotein deposition inside the vessel wall and oxidative stress induction that leads to the formation of atherosclerotic plaque. Oxidized low-density lipoprotein particles (Ox-LDL) have a key role in the pathogenesis of atherosclerosis. The lipid-lowering properties and antioxidants of the grape seed can be beneficial in atherosclerosis prevention. We conducted a randomized double-blind placebo-controlled crossover clinical trial. Fifty-two mildly hyperlipidemic individuals were divided into two groups that received either 200 mg/day of the red grape seed extract (RGSE) or placebo for 8 weeks. After an 8-week washout period, the groups were crossed over for another 8 weeks. Lipid profiles and Ox-LDL were measured at the beginning and the end of each phase. RGSE consumption reduced total cholesterol (-10.68±26.76 mg/dL, P=.015), LDL cholesterol (-9.66±23.92 mg/dL, P=.014), and Ox-LDL (-5.47±12.12 mg/dL, P=.008). While triglyceride and very low-density lipoprotein cholesterol were decreased and high-density lipoprotein cholesterol was increased by RGSE, the changes were not statistically significant. RGSE consumption decreases Ox-LDL and has beneficial effects on lipid profile-consequently decreasing the risk of atherosclerosis and cardiovascular disorders-in mild hyperlipidemic individuals.

Elucidating the impacts of initial supersaturation and seed crystal loading on struvite precipitation kinetics, fines production, and crystal growth.

PubMed

Agrawal, Shantanu; Guest, Jeremy S; Cusick, Roland D

2018-04-01

To reduce intra-plant nutrient cycling, and recover phosphorus (P) fertilizers from nutrient-rich sidestreams, wastewater utilities increasingly elect to employ struvite precipitation processes without a clear understanding of the inherent tradeoffs associated with specific design and operating decisions. Specifically, the impact of reactor conditions on struvite crystallization rate, and distribution between formation of fines particles and secondary growth onto large diameter seed crystals represent critical knowledge gaps limiting the predictive capabilities of existing process models. In this work, the relative impacts of initial supersaturation (S i ), and seed loading, on P removal kinetics, and struvite solids distribution were investigated. In experiments conducted at different levels of initial supersaturation (1.7-2.4) and seed loading (0-25 g L -1 ), struvite fines represented the majority of phosphate solids formed in 10 of 12 conditions. While total P removal was dependent on S i , and primarily attributed to formation of fines, the concentration of struvite seed granules had a significant impact on the rate of P removal. Struvite seed granules increased the rate of precipitation by reducing induction time of primary nucleation of struvite fines. Secondary crystal growth represented the majority of struvite solids formed at high seed loading and low S i , but presented the tradeoff of low total removal and low rate of removal. To convey the significance of these findings on process modeling, we show how a prominent kinetic model with a first-order dependency on solid struvite concentration over-predicts P removal rate when total mass is dominated by large diameter seeds (0.9 mm). This works reveals the critical role of struvite fines in P removal, and highlights the need to account for their production and kinetic importance in struvite process design and operation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Rodent density and the landscape of fear in the Chihuahaun Desert

USDA-ARS?s Scientific Manuscript database

Small mammals in desert environments are important links in ecosystem energy flow, with their densities often effecting the abundance of their primarily predators. Granivorous small mammals also affect seed dispersal and can shape vegetation characteristics. Consequently, factors affecting small m...

Hybrid simulations of radial transport driven by the Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Delamere, P. A.; Stauffer, B. H.; Ma, X.

2017-12-01

Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability. In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016). We present a set of hybrid (kinetic ion / fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for Jupiter's inner and middle magnetosphere. A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions. Pressure balance is achieved by initializing two ion populations: one with fixed temperature, but varying density, and the other with fixed density, but a temperature gradient that offsets the density gradient from the first population and the centrifugal force (effective gravity). We first analyze two-dimensional results for the plane perpendicular to the magnetic field by comparing growth rates as a function of wave vector following Huba et al. (1998). Prescribed perpendicular wave modes are seeded with an initial velocity perturbation. We then extend the model to three dimensions, introducing a stabilizing parallel wave vector. Boundary conditions in the parallel direction prohibit motion of the magnetic field line footprints to model the eigenmodes of the magnetodisc's resonant cavity. We again compare growth rates based on perpendicular wave number, but also on the parallel extent of the resonant cavity, which fixes the size of the largest parallel wavelength. Finally, we search for evidence of strong guide field magnetic reconnection within the domain by identifying areas with large parallel electric fields or changes in magnetic field topology.

Process for preparation of large-particle-size monodisperse latexes

NASA Technical Reports Server (NTRS)

Vanderhoff, J. W.; Micale, F. J.; El-Aasser, M. S.; Kornfeld, D. M. (Inventor)

1981-01-01

Monodisperse latexes having a particle size in the range of 2 to 40 microns are prepared by seeded emulsion polymerization in microgravity. A reaction mixture containing smaller monodisperse latex seed particles, predetermined amounts of monomer, emulsifier, initiator, inhibitor and water is placed in a microgravity environment, and polymerization is initiated by heating. The reaction is allowed to continue until the seed particles grow to a predetermined size, and the resulting enlarged particles are then recovered. A plurality of particle-growing steps can be used to reach larger sizes within the stated range, with enlarge particles from the previous steps being used as seed particles for the succeeding steps. Microgravity enables preparation of particles in the stated size range by avoiding gravity related problems of creaming and settling, and flocculation induced by mechanical shear that have precluded their preparation in a normal gravity environment.

Adenosine Phosphates in Germinating Radish (Raphanus sativus L.) Seeds 1

PubMed Central

Moreland, Donald E.; Hussey, Griscelda G.; Shriner, Carole R.; Farmer, Fred S.

1974-01-01

Changes in concentrations of adenosine phosphates (AMP, ADP, and ATP), oxygen utilization, and fresh weights were measured during the first 48 hours after imbibition of water by quiescent radish seeds (Raphanus sativus L.) at 22.5 C. The changes in ATP concentrations, oxygen utilization, and fresh weights followed a triphasic time course, characterized by a rapid initial increase, which extended from 0 to approximately 1.5 hours, a lag phase from 1.5 to 16 hours, and a sharp linear increase from 16 to 48 hours. In unimbibed seeds, the concentrations of ATP, ADP, and AMP were <0.1, 0.9, and 2.2 nmoles/seed, respectively. After imbibition of water by the quiescent seeds, for 1 hour, the ATP concentration had increased to 2.5, and ADP and AMP concentrations had decreased to 0.3 and 0.1 nmole/seed, respectively. These early changes occurred also in seeds maintained under anaerobic conditions (argon), or when treated with either 5 mm fluoroacetate, or 5 mm iodoacetate. The concentrations of ADP and AMP did not change significantly from 1 to 48 hours. The termination of the lag phase at 16 hours correlated with radicle emergence. Cell division in the radicles was initiated at approximately 28 hours. ATP concentrations in seeds maintained under argon or treated with fluoroacetate remained relatively constant from approximately 2 to 48 hours. In contrast, the ATP concentration of iodoacetate-treated seeds decreased curvilinearly from 4 to 48 hours. Oxidative phosphorylation was estimated to have contributed 15, 20, and 65% of the pool ATP at 1.5, 16, and 48 hours, respectively. PMID:16658928

The influence of pulsed electric fields and microwave pretreatments on some selected physicochemical properties of oil extracted from black cumin seed.

PubMed

Bakhshabadi, Hamid; Mirzaei, HabibOllah; Ghodsvali, Alireza; Jafari, Seid Mahdi; Ziaiifar, Aman Mohammad

2018-01-01

Application of novel technologies such as microwave and pulsed electric fields (PEF) might increase the speed and efficiency of oil extraction. In the present research, PEF (3.25 kV/cm electric field intensity and 30 pulse number) and microwave (540 W for 180 s) pretreatments were used to study the process of oil extraction from black cumin ( Nigella sativa ) seeds. After applying the selected pretreatments, the oil of seeds was extracted with the use of a screw press and the extraction efficiency, refractive index, oil density, color index, oxidative stability, and chemical components of oil and protein of meal were evaluated. The achieved results expressed that PEF and microwave pretreatments increased the oil extraction efficiency and its oxidative stability. Different pretreatments didn't have any significant influence on the refractive index of black cumin seed oil ( p >.05). When microwave and PEF were used, the oil density showed an enhancement as the following: 1.51% and 0.96%, respectively in comparison with the samples with no pretreatments. Evaluation of the extracted oils, using GC/MS analysis indicated that thymoquinone was the dominant phenolic component in the black cumin oil. Finally, the SEM analysis revealed that microwave and PEF can be useful in the extraction of oil from black cumin seeds since these treatments damaged cell walls and facilitated the oil extraction process.

Consumer preference for seeds and seedlings of rare species impacts tree diversity at multiple scales.

PubMed

Young, Hillary S; McCauley, Douglas J; Guevara, Roger; Dirzo, Rodolfo

2013-07-01

Positive density-dependent seed and seedling predation, where herbivores selectively eat seeds or seedlings of common species, is thought to play a major role in creating and maintaining plant community diversity. However, many herbivores and seed predators are known to exhibit preferences for rare foods, which could lead to negative density-dependent predation. In this study, we first demonstrate the occurrence of increased predation of locally rare tree species by a widespread group of insular seed and seedling predators, land crabs. We then build computer simulations based on these empirical data to examine the effects of such predation on diversity patterns. Simulations show that herbivore preferences for locally rare species are likely to drive scale-dependent effects on plant community diversity: at small scales these foraging patterns decrease plant community diversity via the selective consumption of rare plant species, while at the landscape level they should increase diversity, at least for short periods, by promoting clustered local dominance of a variety of species. Finally, we compared observed patterns of plant diversity at the site to those obtained via computer simulations, and found that diversity patterns generated under simulations were highly consistent with observed diversity patterns. We posit that preference for rare species by herbivores may be prevalent in low- or moderate-diversity systems, and that these effects may help explain diversity patterns across different spatial scales in such ecosystems.

Patterns of food abundance for breeding waterbirds in the san luis valley of Colorado

USGS Publications Warehouse

Gammonley, J.H.; Laubhan, M.K.

2002-01-01

We measured the amount and distribution of macroinvertebrates and seeds in four wetland habitats (short emergent, seasonal open water, semipermanent/permanent open water, and saltgrass [Distichlis spicata]) used by breeding ducks and shorebirds at a wetland complex in the San Luis Valley, Colorado, USA. Density of macroinvertebrates did not differ among habitats or sampling periods (P = 0.45), but dry mass, crude protein, and gross energy production were greater (P < 0.05) in short emergent than in other habitats. These differences were largely due to the greater dry mass of gastropods in short emergent than in other habitats. Total seed density, dry mass, crude protein, and gross energy differed among habitats and periods with interaction effects (P <0.01). Although seed abundance varied among habitats and sampling periods, abundance was greatest in short emergent during all sampling periods. Breeding waterbirds consumed a variety of macroinvertebrates and seeds on the study area. Patterns of abundance among habitats of macroinvertebrates and seeds consumed by six waterbird species were not consistent with patterns of foraging habitat use by most ducks and shorebirds at this wetland complex. Our results indicate that estimates of food or nutrient abundance are useful in assessing the functional role of broad habitat types, but factors other than food abundance also influence avian selection of wetland foraging habitats. ?? 2002, The Society of Wetland Scientists.

Dynamic Seeding of Perfusing Human Umbilical Vein Endothelial Cells (HUVECs) onto Dual-Function Cell Adhesion Ligands: Arg-Gly-Asp (RGD)-Streptavidin and Biotinylated Fibronectin

PubMed Central

Anamelechi, Charles C.; Clermont, Edward C.; Novak, Matthew T.; Reichert, William M.

2014-01-01

Surfaces decorated with high affinity ligands can be used to facilitate rapid attachment of endothelial cells; however, standard equilibrium cell detachment studies are poorly suited for assessing these initial adhesion events. Here, a dynamic seeding and cell retention method was used to examine the initial attachment of perfusing human umbilical vein endothelial cells (HUVECs) to bare Teflon-AF substrates, substrates pre-adsorbed with fibronectin alone, or substrates co-pre-adsorbed with two dual-function cell-adhesion ligands: biotinylated fibronectin (bFN) and RGD-streptavidin mutant (RGD-SA). Cell attachment was evaluated as a function of cell trypsinization (integrin digestion), surface protein formulation, and cell perfusion rate. Surfaces co-pre-adsorbed with bFN and RGD-SA showed the highest density of attached cells after 8 min of perfusion and the highest percent retention when subjected to shear flow at 60 dynes/cm2 for 2 min. Surfaces with no ligand treatment showed the lowest cell attachment and retention under flow in all cases. HUVECs trypsinized with mild 0.025% trypsin/ethylenediaminetetraacetic acid (EDTA) showed greater cell adhesion after perfusion and higher percent retention after shear flow than those trypsinized using harsher 0.05% trypsin/EDTA. The preferential affinities of the two dual-function ligands for α5β1 and αvβ3 integrins were also examined by surface plasmon resonance (SPR) spectroscopy. The dynamic cell seeding studies confirmed that the dual-function ligand system promotes HUVEC adhesion and retention at short time points when tested using a perfusion assay. SPR studies showed that the two ligands exhibited equal affinity for both α5β1 and αvβ3 integrins but that the combined ligands bound more total integrins than the two ligands tested separately. PMID:19348476

Shining in the dark: the spectral evolution of the first black holes

NASA Astrophysics Data System (ADS)

Pacucci, Fabio; Ferrara, Andrea; Volonteri, Marta; Dubus, Guillaume

2015-12-01

Massive black hole (MBH) seeds at redshift z ≳ 10 are now thought to be key ingredients to explain the presence of the supermassive (109-10 M⊙) black holes in place <1 Gyr after the big bang. Once formed, massive seeds grow and emit copious amounts of radiation by accreting the left-over halo gas; their spectrum can then provide crucial information on their evolution. By combining radiation-hydrodynamic and spectral synthesis codes, we simulate the time-evolving spectrum emerging from the host halo of a MBH seed with initial mass 105 M⊙, assuming both standard Eddington-limited accretion, or slim accretion discs, appropriate for super-Eddington flows. The emission occurs predominantly in the observed infrared-submm (1-1000 μm) and X-ray (0.1-100 keV) bands. Such signal should be easily detectable by JWSTaround ˜ 1 μm up to z ˜ 25, and by ATHENA (between 0.1 and 10 keV, up to z ˜ 15). Ultra-deep X-ray surveys like the Chandra Deep Field South could have already detected these systems up to z ˜ 15. Based on this, we provide an upper limit for the z ≳ 6 MBH mass density of ρ• ≲ 2.5 × 102 M⊙ Mpc-3 assuming standard Eddington-limited accretion. If accretion occurs in the slim disc mode the limits are much weaker, ρ• ≲ 7.6 × 103 M⊙ Mpc-3 in the most constraining case.

Density and Refractive Index Measurements of Peanut Oil to Determine Oleic and Linoleic Acid Content

USDA-ARS?s Scientific Manuscript database

Peanut seed are approximately 50% oil of which > 80% is either oleic or linoleic acid. The oleic/linoleic acid (O/L) ratio largely influences oxidative stability and hence peanut shelf life. Traditional peanut seed have O/L ratios near 2.5; however, many new cultivars are “high oleic” with O/L rat...

Refractive Index and Density Measurements of Peanut Oil for Determining Oleic and Linoleic Acid Contents

USDA-ARS?s Scientific Manuscript database

Peanut seed are approximately 50% oil of which > 80% is either oleic or linoleic acid. The oleic/linoleic acid (O/L) ratio largely influences oxidative stability and hence peanut shelf life. Traditional peanut seed have O/L ratios near 1.5-2.0; however, many new cultivars are “high oleic” with O/L...

Straw mulch prevents loss of fall-sown seeds to cold temperatures and wildlife predation

Treesearch

J. Wichman; R. Hawkins; P.M. Pijut

2005-01-01

A combination of cover crops and straw mulch effectively protect fall-sown hardwood seeds from cold temperature damage and predation at our nursery in central Indiana. Before using this treatment, we experienced 30% to 90% crop losses on a regular basis, but now our seedbed densities are consistently at target and the resulting seedlings are larger. Specialized...

phenoSeeder - A Robot System for Automated Handling and Phenotyping of Individual Seeds.

PubMed

Jahnke, Siegfried; Roussel, Johanna; Hombach, Thomas; Kochs, Johannes; Fischbach, Andreas; Huber, Gregor; Scharr, Hanno

2016-11-01

The enormous diversity of seed traits is an intriguing feature and critical for the overwhelming success of higher plants. In particular, seed mass is generally regarded to be key for seedling development but is mostly approximated by using scanning methods delivering only two-dimensional data, often termed seed size. However, three-dimensional traits, such as the volume or mass of single seeds, are very rarely determined in routine measurements. Here, we introduce a device named phenoSeeder, which enables the handling and phenotyping of individual seeds of very different sizes. The system consists of a pick-and-place robot and a modular setup of sensors that can be versatilely extended. Basic biometric traits detected for individual seeds are two-dimensional data from projections, three-dimensional data from volumetric measures, and mass, from which seed density is also calculated. Each seed is tracked by an identifier and, after phenotyping, can be planted, sorted, or individually stored for further evaluation or processing (e.g. in routine seed-to-plant tracking pipelines). By investigating seeds of Arabidopsis (Arabidopsis thaliana), rapeseed (Brassica napus), and barley (Hordeum vulgare), we observed that, even for apparently round-shaped seeds of rapeseed, correlations between the projected area and the mass of seeds were much weaker than between volume and mass. This indicates that simple projections may not deliver good proxies for seed mass. Although throughput is limited, we expect that automated seed phenotyping on a single-seed basis can contribute valuable information for applications in a wide range of wild or crop species, including seed classification, seed sorting, and assessment of seed quality. © 2016 American Society of Plant Biologists. All Rights Reserved.

phenoSeeder - A Robot System for Automated Handling and Phenotyping of Individual Seeds1[OPEN

PubMed Central

Roussel, Johanna; Kochs, Johannes; Huber, Gregor; Scharr, Hanno

2016-01-01

The enormous diversity of seed traits is an intriguing feature and critical for the overwhelming success of higher plants. In particular, seed mass is generally regarded to be key for seedling development but is mostly approximated by using scanning methods delivering only two-dimensional data, often termed seed size. However, three-dimensional traits, such as the volume or mass of single seeds, are very rarely determined in routine measurements. Here, we introduce a device named phenoSeeder, which enables the handling and phenotyping of individual seeds of very different sizes. The system consists of a pick-and-place robot and a modular setup of sensors that can be versatilely extended. Basic biometric traits detected for individual seeds are two-dimensional data from projections, three-dimensional data from volumetric measures, and mass, from which seed density is also calculated. Each seed is tracked by an identifier and, after phenotyping, can be planted, sorted, or individually stored for further evaluation or processing (e.g. in routine seed-to-plant tracking pipelines). By investigating seeds of Arabidopsis (Arabidopsis thaliana), rapeseed (Brassica napus), and barley (Hordeum vulgare), we observed that, even for apparently round-shaped seeds of rapeseed, correlations between the projected area and the mass of seeds were much weaker than between volume and mass. This indicates that simple projections may not deliver good proxies for seed mass. Although throughput is limited, we expect that automated seed phenotyping on a single-seed basis can contribute valuable information for applications in a wide range of wild or crop species, including seed classification, seed sorting, and assessment of seed quality. PMID:27663410

A study on seed characteristics and seed bank of Spartina alterniflora at saltmarshes in the Yangtze Estuary, China

NASA Astrophysics Data System (ADS)

Xiao, Derong; Zhang, Liquan; Zhu, Zhenchang

2009-06-01

Since Spartina alterniflora was introduced into the Chongming Dongtan Nature Reserve in 1995, there has been a rapid expansion of this species, seriously threatening the overall biodiversity. In this study, the seed production, germination characteristics and soil seed bank of S. aterniflora were studied at the nature reserve along an intertidal gradient where this invasive species distributed and spread. The results showed that the middle intertidal zone (MIT) had the largest seed production and higher viability than those of lower (LIT) and higher (HIT) intertidal zones. The differences in seed production among these sites were largely dependent on the higher percentage of fruiting culms, longer spike and higher seed number per spike. The differences in seed viability among these sampling sites seemed largely dependent on the higher seed weight at the site MIT. The chilling treatment (at low temperature and in moist conditions) could significantly enhance the germinability of S. alterniflora seeds and shorten the time of onset seed germination. The seeds from the site MIT had much higher germinability than the sites LIT and HIT. The highest density of soil seed bank was recorded at the site of MIT, where had the highest seed production. By July, before there was any replenishment with fresh seeds from the current year, the soil seed bank was completely exhausted and the persistent time of soil seed bank for S. alterniflora was less than 9 months, which is in agreement with that of the transient seed bank. The results from this study indicated that the seed propagation could have an important attribution to the spreading of this invasive plant and the implications in terms of controlling and managing the invasion of S. alterniflora at the nature reserve were discussed.

Identification and Management of Multiple Threats to Rare and Endangered Plant Species

DTIC Science & Technology

2013-07-30

Glynn et. al., 2003), affect fruit removal (Schaefer et. al., 2003) and change the palatability of plants to slugs (Albrectsen et. al., 2004...persistent seed bank. Initial seed bank composition should not be affected by the fence, as we detected no initial difference in flowering or fruiting ...and secondary compounds affect fruit removal. Oikos 102, 318-328. Sessions, L., Kelly, D., 2002. Predator mediated apparent competition between an

Predictive modelling of JT-60SA high-beta steady-state plasma with impurity accumulation

NASA Astrophysics Data System (ADS)

Hayashi, N.; Hoshino, K.; Honda, M.; Ide, S.

2018-06-01

The integrated modelling code TOPICS has been extended to include core impurity transport, and applied to predictive modelling of JT-60SA high-beta steady-state plasma with the accumulation of impurity seeded to reduce the divertor heat load. In the modelling, models and conditions are selected for a conservative prediction, which considers a lower bound of plasma performance with the maximum accumulation of impurity. The conservative prediction shows the compatibility of impurity seeding with core plasma with high-beta (β N  >  3.5) and full current drive conditions, i.e. when Ar seeding reduces the divertor heat load below 10 MW m‑2, its accumulation in the core is so moderate that the core plasma performance can be recovered by additional heating within the machine capability to compensate for Ar radiation. Due to the strong dependence of accumulation on the pedestal density gradient, high separatrix density is important for the low accumulation as well as the low divertor heat load. The conservative prediction also shows that JT-60SA has enough capability to explore the divertor heat load control by impurity seeding in high-beta steady-state plasmas.

Supplementing seed banks to rehabilitate disturbed Mojave Desert shrublands: where do all the seeds go?

USGS Publications Warehouse

DeFalco, Lesley A.; Esque, Todd C.; Nicklas, Melissa B.; Kane, Jeffrey M.

2012-01-01

Revegetation of degraded arid lands often involves supplementing impoverished seed banks and improving the seedbed, yet these approaches frequently fail. To understand these failures, we tracked the fates of seeds for six shrub species that were broadcast across two contrasting surface disturbances common to the Mojave Desert—sites compacted by concentrated vehicle use and trenched sites where topsoil and subsurface soils were mixed. We evaluated seedbed treatments that enhance soil-seed contact (tackifier) and create surface roughness while reducing soil bulk density (harrowing). We also explored whether seed harvesting by granivores and seedling suppression by non-native annuals influence the success of broadcast seeding in revegetating degraded shrublands. Ten weeks after treatments, seeds readily moved off of experimental plots in untreated compacted sites, but seed movements were reduced 32% by tackifier and 55% through harrowing. Harrowing promoted seedling emergence in compacted sites, particularly for the early-colonizing species Encelia farinosa, but tackifier was largely ineffective. The inherent surface roughness of trenched sites retained three times the number of seeds than compacted sites, but soil mixing during trench development likely altered the suitability of the seedbed thus resulting in poor seedling emergence. Non-native annuals had little influence on seed fates during our study. In contrast, the prevalence of harvester ants increased seed removal on compacted sites, whereas rodent activity influenced removal on trenched sites. Future success of broadcast seeding in arid lands depends on evaluating disturbance characteristics prior to seeding and selecting appropriate species and seasons for application.

Paths of water entry and structures involved in the breaking of seed dormancy of Lupinus.

PubMed

Robles-Díaz, Erika; Flores, Joel; Yáñez-Espinosa, Laura

2016-03-15

Physical dormancy is the water impermeability of the seed coat caused by one or more palisade cell layer(s) called macrosclereids. The specialised structure for water entry sites is the water gap, which serves as a detector of environmental cues for germination. In Fabaceae, the water gap is the lens, although another seed structure for water entry could exist. In this study, we identified the initial site of water entry, observed the hydration of a cushion-like structure near the radicle, described the anatomy of the water gap, and analysed the association of anatomical seed traits with the initial site of water entry and the imbibition velocity of six species of Lupinus from the state of Jalisco, Mexico. Dye tracking with a toluidine blue solution was used to identify the initial site of water entry. The anatomical description was performed using conventional microtechnique and a light microscope. The entry of the toluidine solution into seeds of L. montanus was observed after 6h, followed by L. exaltatus and L. mexicanus after 18h and L. elegans, L. reflexus and L. rotundiflorus after 48h. The site of water entry was the lens in L. elegans, L. exaltatus, L. reflexus and L. rotundiflorus and the micropyle in L. mexicanus and L. montanus. The cushion-like structure was responsible for water accumulation in embryo imbibition. Significant differences among anatomical seed traits such as thickness in the hilar region, the counter-palisade layer, cushion-like structure, epidermis, hypodermis, and innermost parenchyma layer were found among the species. Copyright © 2016 Elsevier GmbH. All rights reserved.

Frugivory and seed dispersal by tapirs: an insight on their ecological role.

PubMed

O'Farrill, Georgina; Galetti, Mauro; Campos-Arceiz, Ahimsa

2013-03-01

Tapirs are one of the last extant megafauna species that survived the Pleistocene extinctions. Given their size and digestive system characteristics, tapirs might be the last potential seed disperser of plant species that were previously dispersed by other large mammal species that are now extinct. We compiled evidence from 39 published scientific studies showing that tapirs have a key role as seed dispersers and seed predators. Tapirs play an important role either through seed predation or by facilitating the recruitment of seeds over long distances, therefore influencing the diversity of plant species in the ecosystem. Neotropical tapirs might have a unique role as long-distance seed dispersers of large seeds (<20 mm) because they are capable of depositing viable large seeds in favorable places for germination that even large-bodied primates cannot disperse. Given the high diversity of seed species found in tapir diet, more information is needed on the identification of seed traits that allow the survival of seeds in the tapir's gut. Moreover, further studies are necessary on the role of tapirs as seed dispersers and predators; in particular considering spatial patterns of dispersed seeds, seed viability, effect of dung, and seed density in tapir latrines, and the effect of deposition sites on germination and seedling survival. Because all tapir species are highly threatened, it is paramount to identify gaps in our knowledge on the ecological role of tapirs and, in particular, on critical and endangered plant-tapir interactions to avoid possible trophic cascading effects on ecosystem function. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

GEOMETRIC, VOLUMETRIC, COLOUR AND FRICTIONAL PROPERTIES OF SELECTED SALVIA SPECIES OF TURKEY.

PubMed

Bayram, Mustafa; Altuntas, Ebubekir; Yilar, Melih

2017-01-01

Salvia seeds are promite to dietary and healthy oils because they contain essential fatty acids. Salvia seeds frequently produce mucilage on soaking, and this mucilage is used for the treatment of eye diseases in eastern countries. Salvia species studied for medicine, food and cosmetics, have the potential to be used in the various fields. In the present study, selected engineering (geometrical, volumetrical, colour and frictional) properties of 6 Salvia species seeds were determined and compared. This study was performed on selected engineering properties of seeds of 6 Salvia species ( Salvia viridis L., Salvia aethiopis L., Salvia cryptantha Montbert & Aucher ex Benthan., Salvia tomentosa Mill ., Salvia sclarea L., Salvia virgata Jacq.,) cultivated in Turkey. Plants were collected during the vegetation in 2012-2013 (May-Agust). The seeds were cleaned from foreign matter, dirt and broken seeds manually. The average length, width and thickness were found in the range of 2.61 to 3.53 mm, 1.59 to 2.92 mm and 1.14 to 2.52 mm, respectively. Salvia viridis L. specie had the lowest geometric mean diameter and surface area, whereas Salvia cryptantha L. had the least values among these 6 Salvia species for these properties. The bulk density, true density and the porosity were between 296.83 and 702.80 kg m -3 , 285.69 and 718.08 kg m -3 , 10.27 and 44.05%, respectively. The volume of unit seed and sphericity ranged between 2.56 and 13.64 mm 3 , 62.90 and 90.40%, respectively. The coefficient of friction of salvia species were largely influenced by the friction surfaces studied, and highest values were found for polywood in the Salvia crytantha L.. In the study, the static friction coefficient and the angle of repose of salvia species changed from 0.477 to 0.955, and from 14.09 to 23.57°, respectively. Determination of geometric, volumetric, colour and frictional properties of Salvia spp. seeds may increase their economic value.

Effects of Thiamethoxam-Treated Seed on Mexican Bean Beetle (Coleoptera: Coccinellidae), Nontarget Arthropods, and Crop Performance in Southwestern Virginia Snap Beans.

PubMed

Nottingham, L; Kuhar, T P; Kring, T; Herbert, D A; Arancibia, R; Schultz, P

2017-12-08

Thiamethoxam is a neonicotinoid insecticide commonly applied directly to the seeds (seed-treatment) of commercial snap beans, Phaseolus vulgaris L. While previous studies have examined target and nontarget effects of thiamethoxam seed-treatments in snap beans and other crops, to our knowledge, none have been conducted in agroecosystems predominated by the pest Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae). This study examined the effects of thiamethoxam-treated snap beans on E. varivestis, other arthropods, and crop performance in southwestern Virginia. Greenhouse experiments were conducted to evaluate residual toxicity of treated snap beans to E. varivestis and a key predator, Podisus maculiventris (Say) (Hemiptera: Pentatomidae). Treated plants were highly toxic to E. varivestis at 13 d, moderately toxic from 16 to 20 d, and minimally toxic at 24 d. P. maculiventris was unaffected by exposure to treated plants or by feeding on E. varivestis that consumed treated plants. Small plot field experiments in 2014 and 2015 showed no significant effects of thiamethoxam seed-treatments on E. varivestis densities, other arthropods, crop injury, or yield. In 2016, planting was delayed by persistent rain, resulting in early E. varivestis colonization. In this year, thiamethoxam-treated plants had significantly lower densities and feeding injury from E. varivestis, followed by significantly higher yields. Natural enemies were unaffected by seed-treatments in all field experiments. These experiments demonstrated that thiamethoxam seed-treatments provide control of E. varivestis when beetles infest fields within 2 to 3 wk after planting; but otherwise provide negligible advantages. Negative effects from thiamethoxam seed-treatments on nontarget arthropods appear minimal for snap beans in this region. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Influence of Old World bluestem (Bothrichloa ischaemum) monocultures on breeding density of three grassland songbirds in Oklahoma

USGS Publications Warehouse

George, Andrew D.; O'Connell, Timothy J.; Hickman, Karen R.; Leslie, David M.

2009-01-01

Despite persistent and widespread declines of grassland birds in North America, few studies have assessed differences between native grasslands and seeded monocultures as songbird habitat. In the Great Plains, many fields enrolled in the Conservation Reserve Program have been seeded to Old World bluestems (OWB), but there is evidence to suggest that OWB may not provide suitable conditions for several grassland bird species. Our objectives were to investigate the influence of OWB monocultures on vegetation structure, composition, and breeding densities of three common grassland bird species. In 2007, we used distance sampling to survey breeding songbirds in 6 native mixed grass prairie and 6 OWB fields in Garfield, Grant, and Alfalfa counties, Oklahoma. Native mixed grass prairie supported taller and denser vegetation, as well as greater forb cover than OWB fields. Breeding density of Grasshopper Sparrow (Ammodramus savannarum) was higher in OWB monocultures, while density of Dickcissel (Spiza americana) and Eastern Meadowlark (Sturnella magna) was similar among field types.

Effect of laser irradiation on the early-stage seed formation of laser-induced submicrometer-scale silica spheres

NASA Astrophysics Data System (ADS)

Kim, H. J.; Ha, S. Y.; Hong, Y. J.; Nam, S.; Oh, S. Y.; Lim, C.

2014-04-01

We describe the effect of irradiation on the early-stage seed formation of submicrometer-scale (SS) SiO2 spheres by a laser-induced process. A quartz cell containing chemical reagents was exposed to a pulsed laser (Nd:YAG, 532 nm) tuned to various energy densities, while SiO2 SS spheres are synthesized in the quartz cell by the Stöber, Fink, and Bohn method. Higher laser energy densities typically produce wider size distributions. In particular, bidisperse SiO2 spheres were obtained when the laser energy density was 1.15 J/cm2. The size distributions were widest with 1.15 J/cm2 and narrowest with 0.33 J/cm2 laser energy density. However, the compositions of the SiO2 SS spheres were not affected by laser irradiation, and we observed by the energy-dispersive X-ray spectroscopy that the compositions of the irradiated and nonirradiated SiO2 SS spheres were the same.

Who I Am Is the Text. Who I Become Is the Purpose

ERIC Educational Resources Information Center

Arbisi-Kelm, Heidi; Clay, Jasmine P.; Lin, Mariko M.; Horikawa, Rodney; Clifton, William H.; Kapani, Seema

2013-01-01

Student SEED (Seeking Educational Equity and Diversity) is a grassroots, social justice course in which participants actively engage in dialogue about diversity and social identity. This chapter examines Student SEED as a multicultural initiative.

Ion beam inertial confinement target

DOEpatents

Bangerter, Roger O.; Meeker, Donald J.

1985-01-01

A target for implosion by ion beams composed of a spherical shell of frozen DT surrounded by a low-density, low-Z pusher shell seeded with high-Z material, and a high-density tamper shell. The target has various applications in the inertial confinement technology. For certain applications, if desired, a low-density absorber shell may be positioned intermediate the pusher and tamper shells.

Controlled cell-seeding methodologies: a first step toward clinically relevant bone tissue engineering strategies.

PubMed

Impens, Saartje; Chen, Yantian; Mullens, Steven; Luyten, Frank; Schrooten, Jan

2010-12-01

The repair of large and complex bone defects could be helped by a cell-based bone tissue engineering strategy. A reliable and consistent cell-seeding methodology is a mandatory step in bringing bone tissue engineering into the clinic. However, optimization of the cell-seeding step is only relevant when it can be reliably evaluated. The cell seeding efficiency (CSE) plays a fundamental role herein. Results showed that cell lysis and the definition used to determine the CSE played a key role in quantifying the CSE. The definition of CSE should therefore be consistent and unambiguous. The study of the influence of five drop-seeding-related parameters within the studied test conditions showed that (i) the cell density and (ii) the seeding vessel did not significantly affect the CSE, whereas (iii) the volume of seeding medium-to-free scaffold volume ratio (MFR), (iv) the seeding time, and (v) the scaffold morphology did. Prolonging the incubation time increased the CSE up to a plateau value at 4 h. Increasing the MFR or permeability by changing the morphology of the scaffolds significantly reduced the CSE. These results confirm that cell seeding optimization is needed and that an evidence-based selection of the seeding conditions is favored.

Post-dispersal seed removal by ground-feeding rodents in tropical peatlands, Central Kalimantan, Indonesia

PubMed Central

Blackham, Grace V.; Corlett, Richard T.

2015-01-01

Forested tropical peatlands in Southeast Asia are being rapidly converted to agriculture or degraded into non-forest vegetation. Although large areas have been abandoned, there is little evidence for subsequent forest recovery. As part of a study of forest degradation and recovery, we used seed removal experiments and rodent surveys to investigate the potential role of post-dispersal seed predation in limiting the regeneration of woody plants. Two 14-day seed removal trials were done in deforested and forested peatland habitat in Central Kalimantan, Indonesia. Seeds of Nephelium lappaceum, Syzygium muelleri, Artocarpus heterophyllus (all animal-dispersed) and Combretocarpus rotundatus (wind-dispersed) were tested. Significantly more seeds (82.8%) were removed in forest than non-forest (38.1%) and Combretocarpus had the lowest removal in both habitats. Most handled seeds were eaten in situ and little caching was observed. Six species of rodents were captured in forest and five in non-forest. The most trapped taxa were three Maxomys spp. in forest (85.5% of individuals) and Rattus tiomanicus in non-forest (74.8%). Camera traps confirmed that rodents were responsible for seed removal. Seed predation in deforested areas, which have a much lower seed rain than forest, may contribute to the low density and diversity of regenerating forest. PMID:26369444

Post-dispersal seed removal by ground-feeding rodents in tropical peatlands, Central Kalimantan, Indonesia.

PubMed

Blackham, Grace V; Corlett, Richard T

2015-09-15

Forested tropical peatlands in Southeast Asia are being rapidly converted to agriculture or degraded into non-forest vegetation. Although large areas have been abandoned, there is little evidence for subsequent forest recovery. As part of a study of forest degradation and recovery, we used seed removal experiments and rodent surveys to investigate the potential role of post-dispersal seed predation in limiting the regeneration of woody plants. Two 14-day seed removal trials were done in deforested and forested peatland habitat in Central Kalimantan, Indonesia. Seeds of Nephelium lappaceum, Syzygium muelleri, Artocarpus heterophyllus (all animal-dispersed) and Combretocarpus rotundatus (wind-dispersed) were tested. Significantly more seeds (82.8%) were removed in forest than non-forest (38.1%) and Combretocarpus had the lowest removal in both habitats. Most handled seeds were eaten in situ and little caching was observed. Six species of rodents were captured in forest and five in non-forest. The most trapped taxa were three Maxomys spp. in forest (85.5% of individuals) and Rattus tiomanicus in non-forest (74.8%). Camera traps confirmed that rodents were responsible for seed removal. Seed predation in deforested areas, which have a much lower seed rain than forest, may contribute to the low density and diversity of regenerating forest.

A comparative study of Rayleigh-Taylor and Richtmyer-Meshkov instabilities in 2D and 3D in tantalum

NASA Astrophysics Data System (ADS)

Sternberger, Z.; Maddox, B. R.; Opachich, Y. P.; Wehrenberg, C. E.; Kraus, R. G.; Remington, B. A.; Randall, G. C.; Farrell, M.; Ravichandran, G.

2017-01-01

Driving a shock wave through the interface between two materials with different densities can result in the Richtmyer-Meshkov or Rayleigh-Taylor instability and initial perturbations at the interface will grow. If the shock wave is sufficiently strong, the instability will lead to plastic flow at the interface. Material strength will reduce the amount of plastic flow and suppress growth. While such instabilities have been investigated in 2D, no studies of this phenomena have been performed in 3D on materials with strength. Initial perturbations to seed the hydrodynamic instability were coined into tantalum recovery targets. Two types of perturbations were used, two dimensional (2D) perturbations (hill and valley) and three-dimensional (3D) perturbations (egg crate pattern). The targets were subjected to dynamic loading using the Janus laser at the Jupiter Laser Facility. Shock pressures ranged from 50 GPa up to 150 GPa and were calibrated using VISAR drive targets.

Mask-Assisted Seeded Growth of Segmented Metallic Heteronanostructures

DOE PAGES

Crane, Cameron C.; Tao, Jing; Wang, Feng; ...

2014-12-04

Controlling the deposition of exotic metals in the seeded growth of multi-metal nanostructures is challenging. This work describes a seeded growth method assisted by a mask for synthesis of segmented binary or ternary metal nanostructures. Silica is used as a mask to partially block the surface of a seed and a second metal is subsequently deposited on the exposed area, forming a bimetallic heterodimer. The initial demonstration was carried out on a Au seed, followed by deposition of Pd or Pt on the seed. It was found that Pd tends to spread out laterally on the seed while Pt inclinesmore » to grow vertically into branched topology on Au. Without removal of the SiO₂ mask, Pt could be further deposited on the unblocked Pd of the Pd-Au dimer to form a Pt-Pd-Au trimer. The mask-assisted seeded growth provides a general strategy to construct segmented metallic nanoarchitectures.« less

SU-F-T-20: Novel Catheter Lumen Recognition Algorithm for Rapid Digitization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dise, J; McDonald, D; Ashenafi, M

Purpose: Manual catheter recognition remains a time-consuming aspect of high-dose-rate brachytherapy (HDR) treatment planning. In this work, a novel catheter lumen recognition algorithm was created for accurate and rapid digitization. Methods: MatLab v8.5 was used to create the catheter recognition algorithm. Initially, the algorithm searches the patient CT dataset using an intensity based k-means filter designed to locate catheters. Once the catheters have been located, seed points are manually selected to initialize digitization of each catheter. From each seed point, the algorithm searches locally in order to automatically digitize the remaining catheter. This digitization is accomplished by finding pixels withmore » similar image curvature and divergence parameters compared to the seed pixel. Newly digitized pixels are treated as new seed positions, and hessian image analysis is used to direct the algorithm toward neighboring catheter pixels, and to make the algorithm insensitive to adjacent catheters that are unresolvable on CT, air pockets, and high Z artifacts. The algorithm was tested using 11 HDR treatment plans, including the Syed template, tandem and ovoid applicator, and multi-catheter lung brachytherapy. Digitization error was calculated by comparing manually determined catheter positions to those determined by the algorithm. Results: he digitization error was 0.23 mm ± 0.14 mm axially and 0.62 mm ± 0.13 mm longitudinally at the tip. The time of digitization, following initial seed placement was less than 1 second per catheter. The maximum total time required to digitize all tested applicators was 4 minutes (Syed template with 15 needles). Conclusion: This algorithm successfully digitizes HDR catheters for a variety of applicators with or without CT markers. The minimal axial error demonstrates the accuracy of the algorithm, and its insensitivity to image artifacts and challenging catheter positioning. Future work to automatically place initial seed positions would improve the algorithm speed.« less

Proanthocyanidin-rich date seed extract protects against chemically induced hepatorenal toxicity.

PubMed

Ahmed, Atallah F; Al-Qahtani, Jawaher H; Al-Yousef, Hanan M; Al-Said, Mansour S; Ashour, AbdelKader E; Al-Sohaibani, Mohammed; Rafatullah, Syed

2015-03-01

A hydroacetone extract was prepared from seeds of Phoenix dactylifera L. var. Khalas, which is an industrial by-product of date processing. The proanthocyanidin nature of the extract (coded as DTX) was characterized by phytochemical and nuclear magnetic resonance (NMR) analyses. The total phenol/proanthocyanidin content and antioxidant activity of DTX were estimated by Folin-Ciocalteu, vanillin-sulfuric acid, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, respectively. The hepatorenal protective activity of DTX was evaluated using CCl4-induced toxicity model in rats, in comparison with silymarin (SYL). Results of the histopathological examination and measurements of various hepatorenal serum indices and tissue biochemical markers demonstrated that DTX displayed marked protective potential against CCl4-induced liver and kidney injury at 100 mg/kg/rat. Relative to the control CCl4-intoxicated group, pretreatment with DTX significantly (P<.001) suppressed the elevated serum levels of alanine aminotransferase and aspartate aminotransferase (ALT and AST), alkaline phosphatase (ALP), γ-glutamyl transferase (GGT), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), bilirubin, creatinine, and calcium, whereas it significantly (P<.001) increased the diminished serum levels of high-density lipoprotein cholesterol (HDL-C) and total protein (TP). Moreover, DTX significantly decreased malondialdehyde (MDA) formation and increased TP synthesis in hepatorenal tissues compared with the intoxicated control. The improvement in biochemical parameters by DTX was observed in a dose-dependent manner and confirmed by restoration of normal histological features. The acute toxicity test of DTX in rats revealed safety of the extract. This study reveals that DTX enhances the recovery from xenobiotics-induced toxicity initiated by free radicals.

Seed and Germination Characteristics of 20 Amazonian Liana Species

PubMed Central

Roeder, Mareike; Ferraz, Isolde D. K.; Hölscher, Dirk

2013-01-01

Lianas are an important component of tropical forests, and may reach their highest densities in disturbed areas. However, information on seed and germination characteristics is scarce. Twenty Amazon liana species were screened for their germination characteristics, including light dependence, tolerance of desiccation and of alternating temperatures; these characteristics are considered important for the germination success in areas with relatively open canopies. Between 31–1,420 seeds per species were available, as 15 species seeds came from one mother plant. We studied seed biometry and conducted germination trials with fresh seeds (12 h light daily, or dark) and desiccated seeds at 25 °C. Germination at alternating temperatures (20/30 °C, 15/35 °C) was analyzed for nine species. Of the 20 species, eight species with the largest seeds had desiccation sensitive seeds; this is the first record for species of four genera and one family, where only desiccation tolerant seeds are otherwise recorded. Light-dependent germination was found in three species (0.01–0.015 g) and is the first record for two; however, results were based on seeds from one plant per species. Alternating temperatures of 15/35 °C decreased final germination of four out of nine species, and response to 20/30 °C cycles varied compared to constant 25 °C. Seed and germination characteristics of the species ranged from pioneer to climax traits indicating that establishment of lianas from seeds may be confined to species specific niches. PMID:27137363

Kinetic studies of adsorption of Cu (II) from aqueous solution by coriander seeds (Coriandrum Sativum)

NASA Astrophysics Data System (ADS)

Kadiri, L.; Lebkiri, A.; Rifi, E. H.; Ouass, A.; Essaadaoui, Y.; Lebkiri, I.; Hamad, H.

2018-05-01

The adsorption of copper ions Cu2+ by Coriandrum Sativum seeds (CSS) from aqueous solution was studied in order to highlight the importance of coriander seeds as a potential tool in the treatment of wastewaters containing heavy metals. The kinetic studies of adsorption of Cu (II) were discussed using the spectroscopic technique "Inducting Coupled Plasma" (ICP). The effects of initial copper ion concentration and contact time were determined. All results show that coriander seeds have, over their culinary and medicinal benefits, a significant adsorbent power of copper ions.

The effect of altitude on breaking seed dormancy and stimulation of seed germination of Persian hogweed (Heracleum persicum).

PubMed

Salehani, M Khajavi; Mahmoudi, J; Mahdavi, S Kh; Habibzadeh, R

2013-01-01

Persian hogweed is a perennial herb and aromatic plant which has pharmaceutical and fodder values, and the main propagation method of this species is seed. The goal of this study was to investigate the effect of altitude on breaking dormancy and stimulate seed germination of this species. The study was designed and carried out using the test of seed analysis. For our purpose, seeds were collected from three different altitudes (1700, 2200, 2700 masl) in Kojoor area. After initial purification, germination percent (GP) and speed (GS) of each elevation were determined by cold stratification compared to control. According to results, control seeds did not germinate, showing that the seeds of this species need to be treated. Statistical analysis of results showed that there are significant differences between GP and GS of each elevation, as seeds of higher elevation had slower and less germination in longer periods. So, changes in elevation are an effective factor on seed germination characteristics of this species and this factor has to be considered in seed preparation and restoration with this species.

Analysis of the NMI01 marker for a population database of cannabis seeds.

PubMed

Shirley, Nicholas; Allgeier, Lindsay; Lanier, Tommy; Coyle, Heather Miller

2013-01-01

We have analyzed the distribution of genotypes at a single hexanucleotide short tandem repeat (STR) locus in a Cannabis sativa seed database along with seed-packaging information. This STR locus is defined by the polymerase chain reaction amplification primers CS1F and CS1R and is referred to as NMI01 (for National Marijuana Initiative) in our study. The population database consists of seed seizures of two categories: seed samples from labeled and unlabeled packages regarding seed bank source. Of a population database of 93 processed seeds including 12 labeled Cannabis varieties, the observed genotypes generated from single seeds exhibited between one and three peaks (potentially six alleles if in homozygous state). The total number of observed genotypes was 54 making this marker highly specific and highly individualizing even among seeds of common lineage. Cluster analysis associated many but not all of the handwritten labeled seed varieties tested to date as well as the National Park seizure to our known reference database containing Mr. Nice Seedbank and Sensi Seeds commercially packaged reference samples. © 2012 American Academy of Forensic Sciences.

Journey to the MBH-σ relation: the fate of low-mass black holes in the Universe

NASA Astrophysics Data System (ADS)

Volonteri, Marta; Natarajan, Priyamvada

2009-12-01

In this paper, we explore the establishment and evolution of the empirical correlation between black hole mass (MBH) and velocity dispersion (σ) with redshift. We trace the growth and accretion history of massive black holes (MBHs) starting from high-redshift seeds that are planted via physically motivated prescriptions. Two seeding models are explored in this work: `light seeds', derived from Population III remnants, and `heavy seeds', derived from direct gas collapse. Even though the seeds themselves do not satisfy the MBH-σ relation initially, we find that the relation can be established and maintained at all times if self-regulating accretion episodes are associated with major mergers. The massive end of the MBH-σ relation is established early, and lower mass MBHs migrate on to it as hierarchical merging proceeds. How MBHs migrate towards the relation depends critically on the seeding prescription. Light seeds initially lie well below the MBH-σ relation, and MBHs can grow via steady accretion episodes unhindered by self-regulation. In contrast, for the heavy seeding model, MBHs are initially over-massive compared to the empirical correlation, and the host haloes assemble prior to kick-starting the growth of the MBH. We find that the existence of the MBH-σ correlation is purely a reflection of the merging hierarchy of massive dark matter haloes. The slope and scatter of the relation however appear to be a consequence of the seeding mechanism and the self-regulation prescription. We expect flux limited active galactic nucleus surveys to select MBHs that have already migrated on to the MBH-σ relation. Similarly, the Laser Interferometer Space Antenna (LISA) is also likely to be biased towards detecting merging MBHs that preferentially inhabit the MBH-σ. These results are a consequence of major mergers being more common at high redshift for the most massive, biased, galaxies that host MBHs which have already migrated on to the MBH-σ relation. We also predict the existence of a large population of low-mass `hidden' MBHs at high redshift which can easily escape detection. Additionally, we find that if MBH seeds are massive, ~105Msolar, the low-mass end of the MBH-σ flattens towards an asymptotic value, creating a characteristic `plume'.

Conductive Au nanowires regulated by silk fibroin nanofibers

NASA Astrophysics Data System (ADS)

Dong, Bo-Ju; Lu, Qiang

2014-03-01

Conductive Au-biopolymer composites have promising applications in tissue engineering such as nerve tissue regeneration. In this study, silk fibroin nanofibers were formed in aqueous solution by regulating silk self-assembly process and then used as template for Au nanowire fabrication. We performed the synthesis of Au seeds by repeating the seeding cycles for several times in order to increase the density of Au seeds on the nanofibers. After electroless plating, densely decorated Au seeds grew into irregularly shaped particles following silk nanofiber to fill the gaps between particles and finally form uniform continuous nanowires. The conductive property of the Au-silk fibroin nanowires was studied with current-voltage ( I-V) measurement. A typical ohmic behavior was observed, which highlighted their potential applications in nerve tissue regeneration.

Prostate implant nomograms for the North American scientific {sup 103}Pd seed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jay J.; Stevens, Ritchie N

Palladium-103-({sup 103}Pd) seed has been increasingly used in prostate implantation as either definitive or boost therapy because of its shorter half-life and higher initial dose rate. Because a growing number of radiation oncologists prefer real-time implantation in the operating room, it will be helpful if the total activity of the seeds can be determined based on the gland size before the patient is taken to the operating room. Based on our clinic data, nomograms have therefore been developed for one of the widely used {sup 103}Pd seeds, the MED3633 seed, which is produced by North American Scientific, Inc. (NASI). Themore » total activities for implant volume ranging from 15 cc to 55 cc are provided for both seed 'monotherapy' and seed boost.« less

Effects of hypobaria and hypoxia on seed germination of six plant species

NASA Astrophysics Data System (ADS)

Tang, Yongkang; Gao, Feng; Guo, Shuangsheng; Li, Fang

2014-10-01

Hypobaria (low pressure) is typically associated with hypoxia (low oxygen partial pressure). There are several advantages of growing higher plants under hypobaria in the moon or mars habitat. The objectives of this research were to investigate the seed germination of six plant species under hypobaric and ambient total pressure conditions. Seeds were sown and germinated under three levels of total atmospheric pressure (101, 30 and 10 kPa) and three levels of oxygen partial pressures (21, 6 and 2 kPa) in an 8-day study. Hypoxia (6 or 2 kPa) significantly inhibited all seed germination under three levels of total atmospheric pressure by increasing the electrical conductivity and the optical density, decreasing the seed germination percentage and seed dehydrogenase activity and inhibiting the growth of the shoots and roots. Hypobaria (30 or 10 kPa) markedly improved seed germination and root growth by enhancing the oxygen diffusion rate under hypoxic conditions (6 or 2 kPa). The seeds of three dicot plants (lettuce, Chinese cabbage and cucumber) were more sensitive to hypoxia caused by hypobaria than were those of three monocot plants (maize, wheat and rice); lettuce and cucumber seeds had the highest sensitivity, whereas rice seeds had the lowest sensitivity. This research demonstrates that six experimental seeds can germinate normally under hypobaria (30 kPa), but the oxygen partial pressure should not be less than 6 kPa.

[Dynamics of Quercus variabilis seed rain and soil seed bank in different habitats on the north slope of Qinling Mountains].

PubMed

Wu, Min; Zhang, Wen-Hui; Zhou, Jian-Yun; Ma, Chuang; Ma, Li-Wei

2011-11-01

In order to explore the dynamics of Quercus variabilis seed rain and soil seed bank in different habitats on the north slope of Qinling Mountains, three kinds of micro-habitats (understory, forest gap, and forest edge) were selected, with the seed rain quantity and quality of Q. variabilis, seed amount and viability in soil seed bank, as well as the seedling development of Q. variabilis studied. The seed rain of Q. variabilis started from mid August, reached the peak in mid September-early October, and ended at the beginning of November, and there existed differences in the dissemination process, occurrence time, and composition of the seed rain among the three micro-habitats. The seed rain had the maximum intensity (39.55 +/- 5.56 seeds x m(-2)) in understory, the seeds had the earliest landing time, the longest lasting duration, and the highest viability in forest gap, and the mature seeds had the largest proportion in forest edge, accounting for 58.7% of the total. From the ending time of seed rain to next August, the total reserve of soil seed bank was the largest in understory and the smallest in forest edge. In the three habitats, the amount of mature and immature seeds, that of seeds eaten by animals, and the seed viability in soil seed bank all decreased with time. In contrast, the number of moldy seeds increased. The seeds were mainly concentrated in litter layer, a few of them were in 0-2 cm soil layer, and few were in 2-5 cm soil layer. The density of the seedlings varied with habitats, being the largest in forest gap, followed by in forest edge, and the least in understory, which suggested that forest gap was more suitable for the seed germination and seedling growth of Q. variabilis, and thus, appropriate thinning should be taken to increase forest gap to provide favorable conditions for the natural regeneration of Q. variabilis forest.

Estimating mast production: an evaluation of visual surveys and comparison with seed traps using white oaks

Treesearch

Roger W. Perry; Ronald E. Thill

1999-01-01

Perry and Thill compared five types of visual mast surveyed with seed trap data from 105 white oaks (Quercus alba L.) during 1996-1997 in the Ouachita Mountains of Arkansas. They also evaluated these visual survey methods for their usefulness in detecting differences in acorn density among areas. Indices derived from all five methods were highly...

Effect of seed position and media on germination of black walnut and northern red oak: implications for nursery production and direct seeding

Treesearch

Anthony S. Davis; Barrett C. Wilson; Douglass F. Jacobs

2004-01-01

Germination of black walnut (Juglans nigra L.) and northern red oak (Quercus rubra L.) prior to sowing into containers or bareroot nursery beds can help maintain desired crop density and reduce nursery costs. Recommended techniques for germination of black walnut are labor intensive and require that walnuts be completely covered...

A Stem Cell-Seeded Nanofibrous Scaffold for Auditory Nerve Replacement

DTIC Science & Technology

2015-10-01

guinea pigs . Initial results show improved electrically-evoked auditory brainstem responses in cell-seeded implants compared to control, cell-free...scaffold’s conduit, but the IAM of the guinea pig and limits imposed by the surgical approach make this difficult. Alternatives are being pursued...transplantation of the seeded nanofibrous scaffold Task 13. Group 1: Pilot deafening. Confirm efficacy of ß-bungarotoxin in guinea pig and time point of

Fire timing in relation to masting: an important determinant of post-fire recruitment success for the obligate-seeding arid zone soft spinifex (Triodia pungens).

PubMed

Wright, Boyd R; Fensham, Roderick J

2018-01-25

Plant species with fire-triggered germination are common in many fire-prone ecosystems. For such plants, fire timing in relation to the timing of reproduction may strongly influence post-fire population regeneration if: (a) flowering occurs infrequently (e.g. plants are mast seeders); and (b) seed survival rates are low and input from the current year's flowering therefore contributes a large proportion of the viable dormant seedbank. The role of fire timing in relation to masting as a driver of post-fire recruitment has rarely been examined directly, so this study tested the hypothesis that fires shortly after masting trigger increased recruitment of the obligate-seeding arid zone spinifex, Triodia pungens R. Br., an iteroparous masting grass with smoke-cued germination. Phenological monitoring of T. pungens was conducted over 5 years, while a longitudinal seedbank study assessed the influence of seeding events on soil-stored seedbank dynamics. Concurrently, a fire experiment with randomized blocking was undertaken to test whether T. pungens hummocks burnt shortly after masting have greater post-fire recruitment than hummocks burnt when there has not been recent input of seeds. Triodia pungens flowered in all years, though most flowerings were characterized by high rates of flower abortion. A mast flowering with high seed set in 2012 triggered approx. 200-fold increases in seedbank densities, and seedbank densities remained elevated for 24 months after this event. The fire experiment showed significantly higher recruitment around hummocks burnt 6 months after the 2012 mast event than around hummocks that were burnt but prevented from masting by having inflorescences clipped. Fires shortly after masting trigger mass recruitment in T. pungens because such fires synchronize an appropriate germination cue (smoke) with periods when seedbank densities are elevated. Interactions between natural fire regimes, seedbank dynamics and fire management prescriptions must be considered carefully when managing fire-sensitive masting plants such as T. pungens. © The Author(s) 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Yam bean seed poisoning mimicking cyanide intoxication.

PubMed

Hung, Y-M; Hung, S-Y; Olson, K R; Chou, K-J; Lin, S-L; Chung, H-M; Tung, C-N; Chang, J-C

2007-02-01

Yam bean is a common food in southern Taiwan. However, its seeds are rarely consumed. We describe five patients of yam bean seed poisoning in Taiwan, one of them life-threatening. The five patients presented with perioral numbness, nausea and vomiting after eating a same soup made from yam bean seeds. One of them, a 54-year-old woman, had difficulty breathing and lost consciousness. Physical examination showed dilated pupils and coma with no focal neurological signs. The initial blood pressure was normal. Laboratory data showed a severe anion gap metabolic acidosis, with a serum lactate level of 185 mg/dL. An initial diagnosis of cyanide intoxication was considered and she was given sodium nitrite and sodium thiosulfate i.v. Hypotension ensued shortly afterwards and pulmonary artery catheterization showed a decreased cardiac index. Aggressive fluid and inotropic therapy were given and the patient eventually recovered. The other four patients suffered only minor gastrointestinal and neurological symptoms and received supportive treatment. Cyanide levels were negative in all five patients. Yam bean seed poisoning can cause acute metabolic acidosis and altered mental status, which could be confused with acute cyanide intoxication from a cyanogenic glycoside-containing plant. To our knowledge, this is the first outbreak of yam bean seed poisoning reported in the English published work.

How mammalian predation contributes to tropical tree community structure.

PubMed

Paine, C E Timothy; Beck, Harald; Terborgh, John

2016-12-01

The recruitment of seedlings from seeds is the key demographic transition for rain forest trees. Though tropical forest mammals are known to consume many seeds, their effects on tree community structure remain little known. To evaluate their effects, we monitored 8,000 seeds of 24 tree species using exclosure cages that were selectively permeable to three size classes of mammals for up to 4.4 years. Small and medium-bodied mammals removed many more seeds than did large mammals, and they alone generated beta diversity and negative density dependence, whereas all mammals reduced diversity and shaped local species composition. Thus, small and medium-bodied mammals more strongly contributed to community structure and promoted species coexistence than did large mammals. Given that seedling recruitment is seed limited for most species, alterations to the composition of the community of mammalian seed predators is expected to have long-term consequences for tree community structure in tropical forests. © 2016 by the Ecological Society of America.

Microbunching-instability-induced sidebands in a seeded free-electron laser

DOE PAGES

Zhang, Zhen; Lindberg, Ryan; Fawley, William M.; ...

2016-05-02

Measurements of the multishot-averaged, soft x-ray, self-seeding spectrum at the LCLS free-electron laser often have a pedestal-like distribution around the seeded wavelength, which limits the spectral purity and can negatively affect some user applications not employing a post-undulator monochromator. In this paper, we study the origins of such pedestals, focusing on longitudinal phase space modulations produced by the microbunching instability upstream of the free-electron laser (FEL) undulator. Furthermore, we show from theory and numerical simulation that both energy and density modulations can induce sidebands in a high-gain, seeded FEL whose fractional strength typically grows as the square of the undulatormore » length. The results place a tight constraint on the longitudinal phase space uniformity of the electron beam for a seeded FEL, possibly requiring the amplitude of long-wavelength modulations to be much smaller than the typical incoherent energy spread if the output sideband power is to remain only a couple percent or less of the amplified seed power.« less

Soil physical and X-ray computed tomographic measurements to investigate small-scale structural differences under strip tillage compared to mulch till and no-till

NASA Astrophysics Data System (ADS)

Pöhlitz, Julia; Rücknagel, Jan; Schlüter, Steffen; Vogel, Hans-Jörg

2017-04-01

In recent years there has been an increasing application of conservation tillage techniques where the soil is no longer turned, but only loosened or left completely untilled. Dead plant material remains on the soil surface, which provides environmental and economic benefits such as the conservation of water, preventing soil erosion and saving time during seedbed preparation. There is a variety of conservation tillage systems, e.g. mulch till, no-till and strip tillage, which is a special feature. In strip tillage, the seed bed is divided into a seed zone (strip-till within the seed row: STWS) and a soil management zone (strip-till between the seed row: STBS). However, each tillage application affects physical soil properties and processes. Here, the combined application of classical soil mechanical and computed tomographic methods is used on a Chernozem (texture 0-30 cm: silt loam) to show small-scale structural differences under strip tillage (STWS, STBS) compared to no-till (NT) and mulch till (MT). In addition to the classical soil physical parameters dry bulk density and saturated conductivity (years: 2012, 2014, 2015) at soil depths 2-8 and 12-18 cm, stress-strain tests were carried out to map mechanical behavior. The stress-strain tests were performed for a load range from 5-550 kPa at 12-18 cm depth (year 2015). Mechanical precompression stress was determined on the stress-dry bulk density curves. Further, CT image cross sections and computed tomographic examinations (average pore size, porosity, connectivity, and anisotropy) were used from the same soil samples. For STBS and NT, a significant increase in dry bulk density was observed over the course of time compared to STWS and MT, which was more pronounced at 2-8 cm than at 12-18 cm depth. Despite higher dry bulk density, STBS displayed higher saturated conductivity in contrast to STWS, which can be attributed to higher earthworm abundance. In strip tillage, structural differences were identified. Mechanical precompression stress was significantly higher for STBS (141 kPa) than STWS (38 kPa). In addition, the CT image cross sections and the computed tomographic parameters confirmed the mechanically more stable soil structure observed under STBS with a higher initial average pore size but lower porosity and connectivity values compared to STWS. The reason for this is the lack of tillage. On the other hand, tillage at STWS created a loosened, porous and connective substrate. For all variants, the increasing load application led to progressive homogenization processes of the soil structure. At the same time, as stress application increased in all variants, the increase in dry bulk density led to a decrease in average pore size, porosity, and connectivity, while anisotropy increased. It was possible to confirm that strip tillage combines the advantages of no-till and a deeper conservation primary tillage, since on the one hand MT and STWS and on the other hand STBS and NT showed very similar soil structures. The computed tomographic parameters therefore provide valuable information about the impact of tillage on microscopic pore space attributes that improve our understanding about soil functional behavior at much larger scales.

Volume three-dimensional flow measurements using wavelength multiplexing.

PubMed

Moore, Andrew J; Smith, Jason; Lawson, Nicholas J

2005-10-01

Optically distinguishable seeding particles that emit light in a narrow bandwidth, and a combination of bandwidths, were prepared by encapsulating quantum dots. The three-dimensional components of the particles' displacement were measured within a volume of fluid with particle tracking velocimetry (PTV). Particles are multiplexed to different hue bands in the camera images, enabling an increased seeding density and (or) fewer cameras to be used, thereby increasing the measurement spatial resolution and (or) reducing optical access requirements. The technique is also applicable to two-phase flow measurements with PTV or particle image velocimetry, where each phase is uniquely seeded.

Effects of resource availability and propagule supply on native species recruitment in sagebrush ecosystems invaded by Bromus tectorum

USGS Publications Warehouse

Mazzola, Monica B.; Chambers, Jeanne C.; Blank, Robert R.; Pyke, David A.; Schupp, Eugene W.; Allcock, Kimberly G.; Doescher, Paul S.; Nowak, Robert S.

2011-01-01

Resource availability and propagule supply are major factors influencing establishment and persistence of both native and invasive species. Increased soil nitrogen (N) availability and high propagule inputs contribute to the ability of annual invasive grasses to dominate disturbed ecosystems. Nitrogen reduction through carbon (C) additions can potentially immobilize soil N and reduce the competitiveness of annual invasive grasses. Native perennial species are more tolerant of resource limiting conditions and may benefit if N reduction decreases the competitive advantage of annual invaders and if sufficient propagules are available for their establishment. Bromus tectorum, an exotic annual grass in the sagebrush steppe of western North America, is rapidly displacing native plant species and causing widespread changes in ecosystem processes. We tested whether nitrogen reduction would negatively affect B. tectorum while creating an opportunity for establishment of native perennial species. A C source, sucrose, was added to the soil, and then plots were seeded with different densities of both B. tectorum (0, 150, 300, 600, and 1,200 viable seeds m-2) and native species (0, 150, 300, and 600 viable seeds m-2). Adding sucrose had short-term (1 year) negative effects on available nitrogen and B. tectorum density, biomass and seed numbers, but did not increase establishment of native species. Increasing propagule availability increased both B. tectorum and native species establishment. Effects of B. tectorum on native species were density dependent and native establishment increased as B. tectorum propagule availability decreased. Survival of native seedlings was low indicating that recruitment is governed by the seedling stage.

On the ability of plant life-history strategies to shape bio-geomorphologic interactions

NASA Astrophysics Data System (ADS)

Schwarz, Christian; van Belzen, Jim; Zhu, ZhenChang; Bouma, Tjeerd; van de Koppel, Johan; Gourgue, Olivier; Temmerman, Stijn

2017-04-01

Previous work studying bio-geomorphologic interactions in intertidal habitats underlined the importance of wetland vegetation shaping their environment (e.g. tidal channel networks). Up to this point the potential of wetland vegetation to shape their environment was linked to their physical plant properties, such as stiffness, stem diameter or stem density. However the effect of life-history strategies, i.e. the mode of plant proliferation such as sexual reproduction from seeds, non-sexual lateral expansion or a combination of the former two was hitherto ignored. We present numerical experiments based on a wetland ecosystem present in the Western Scheldt Estuary (SW, the Netherlands) showing the importance of life-history strategies shaping bio-geomorphologic interactions. We specifically compare two extremes in life-history strategies, (1) one species solely establishing from seeds and relying on their mass recruitment (Salicornia europea); And a second species (Spartina anglica) which relies on a mixed establishment strategy consisting of seed dispersal and asexual lateral expansion through tillering, with a very low seed recruitment success per year. Based on conducted numerical experiments using TELEMAC2D we show that the Spartina-case facilitates relative low channel densities with pronounced channel networks, whereas the Salicornia-case favors high channel densities with less pronounced intertidal channels. The conducted numerical experiments are the first indication showing that plant proliferation strategies exert a major control on emerging patterns in bio-geomorphologic systems. This provides a deeper understanding in the constraining factors and dynamics shaping the emergence and resilience of bio-geomorphologic systems.

Application of paclobutrazol affect maize grain yield by regulating root morphological and physiological characteristics under a semi-arid region.

PubMed

Kamran, Muhammad; Wennan, Su; Ahmad, Irshad; Xiangping, Meng; Wenwen, Cui; Xudong, Zhang; Siwei, Mou; Khan, Aaqil; Qingfang, Han; Tiening, Liu

2018-03-19

A field experiment was conducted to investigate the effects of paclobutrazol on ear characteristics and grain yield by regulating root growth and root-bleeding sap of maize crop. Seed-soaking at rate of 0 (CK1), 200 (S1), 300 (S2), and 400 (S3) mg L -1 , and seed-dressing at rate of 0 (CK2), 1.5 (D1), 2.5 (D2), and 3.5 (D3) g kg -1 were used. Our results showed that paclobutrazol improved the ear characteristics and grain yield, and were consistently higher than control during 2015-2016. The average grain yield of S1, S2 and S3 were 18.9%, 61.3%, and 45.9% higher, while for D1, D2 and D3 were 20.2%, 33.3%, and 45.2%, compared to CK, respectively. Moreover, paclobutrazol-treated maize had improved root-length density (RLD), root-surface area density (RSD) and root-weight density (RWD) at most of the soil profiles (0-70 cm for seed-soaking, 0-60 cm for seed-dressing) and was attributed to enhancing the grain yield. In addition, root-activity, root-bleeding sap, root dry weight, diameter and root/shoot ratio increased by paclobutrazol, with highest values achieved in S2 and D3 treatments, across the whole growth stages in 2015-2016. Our results suggested that paclobutrazol could efficiently be used to enhance root-physiological and morphological characteristics, resulting in higher grain yield.

Fabric pilling measurement using three-dimensional image

NASA Astrophysics Data System (ADS)

Ouyang, Wenbin; Wang, Rongwu; Xu, Bugao

2013-10-01

We introduce a stereovision system and the three-dimensional (3-D) image analysis algorithms for fabric pilling measurement. Based on the depth information available in the 3-D image, the pilling detection process starts from the seed searching at local depth maxima to the region growing around the selected seeds using both depth and distance criteria. After the pilling detection, the density, height, and area of individual pills in the image can be extracted to describe the pilling appearance. According to the multivariate regression analysis on the 3-D images of 30 cotton fabrics treated by the random-tumble and home-laundering machines, the pilling grade is highly correlated with the pilling density (R=0.923) but does not consistently change with the pilling height and area. The pilling densities measured from the 3-D images also correlate well with those counted manually from the samples (R=0.985).

2D motility tracking of Pseudomonas putida KT2440 in growth phases using video microscopy

PubMed Central

Davis, Michael L.; Mounteer, Leslie C.; Stevens, Lindsey K.; Miller, Charles D.; Zhou, Anhong

2011-01-01

Pseudomonas putida KT2440 is a gram negative motile soil bacterium important in bioremediation and biotechnology. Thus, it is important to understand its motility characteristics as individuals and in populations. Population characteristics were determined using a modified Gompertz model. Video microscopy and imaging software were utilized to analyze two dimensional (2D) bacteria movement tracks to quantify individual bacteria behavior. It was determined that inoculum density increased the lag time as seeding densities decreased, and that the maximum specific growth rate decreased as seeding densities increased. Average bacterial velocity remained relatively similar throughout exponential growth phase (~20.9 µm/sec), while maximum velocities peak early in exponential growth phase at a velocity of 51.2 µm/sec. Pseudomonas putida KT2440 also favor smaller turn angles indicating they often continue in the same direction after a change in flagella rotation throughout the exponential growth phase. PMID:21334971

Antibacterial activity of essential oil components and their potential use in seed disinfection.

PubMed

Lo Cantore, Pietro; Shanmugaiah, Vellasamy; Iacobellis, Nicola Sante

2009-10-28

Among the main (> or = 0.7%) components of some essential oils, considerable antibacterial activity was shown by terpenoid and phenylpropanoid derivatives containing phenol and alcohol functionalities. A reduced or no activity was shown by those derivatives containing ketones, aldehydes, ethers, and ester functionalities as well as the remaining terpenoids. Eugenol emulsion treatments (1-8 mg/mL) of bean seeds bearing about 2.6 x 10(6) cfu/seed of strain ICMP239 of Xanthomonas campestris pv. phaseoli var. fuscans determined a highly significant reduction of the bacteria on seeds. In particular, eugenol at 4 mg/mL disinfect seeds bearing about 7.0 x 10(2) cfu/seed and lower densities. However, after 72 h, incubation treatments with 2, 4, and 8 mg/mL of eugenol caused germination reduction of 3%, 7%, and 16%, respectively, which was significantly different from the controls. No effect on germination was observed with 1 mg/mL eugenol emulsion treatment. These data indicate eugenol as potentially useful for bean seed disinfection from X. campestris pv. phaseoli var. fuscans. Further studies on the effects on seed vitality and on formulation of essential oils are needed.

Supplementing seed banks to rehabilitate disturbed Mojave Desert shrublands: Where do all the seeds go?

USGS Publications Warehouse

DeFalco, L.A.; Esque, T.C.; Nicklas, M.B.; Kane, J.M.

2012-01-01

Revegetation of degraded arid lands often involves supplementing impoverished seed banks and improving the seedbed, yet these approaches frequently fail. To understand these failures, we tracked the fates of seeds for six shrub species that were broadcast across two contrasting surface disturbances common to the Mojave Desert-sites compacted by concentrated vehicle use and trenched sites where topsoil and subsurface soils were mixed. We evaluated seedbed treatments that enhance soil-seed contact (tackifier) and create surface roughness while reducing soil bulk density (harrowing). We also explored whether seed harvesting by granivores and seedling suppression by non-native annuals influence the success of broadcast seeding in revegetating degraded shrublands. Ten weeks after treatments, seeds readily moved off of experimental plots in untreated compacted sites, but seed movements were reduced 32% by tackifier and 55% through harrowing. Harrowing promoted seedling emergence in compacted sites, particularly for the early-colonizing species Encelia farinosa, but tackifier was largely ineffective. The inherent surface roughness of trenched sites retained three times the number of seeds than compacted sites, but soil mixing during trench development likely altered the suitability of the seedbed thus resulting in poor seedling emergence. Non-native annuals had little influence on seed fates during our study. In contrast, the prevalence of harvester ants increased seed removal on compacted sites, whereas rodent activity influenced removal on trenched sites. Future success of broadcast seeding in arid lands depends on evaluating disturbance characteristics prior to seeding and selecting appropriate species and seasons for application. ?? 2010 Society for Ecological Restoration International.

Spatial heterogeneity in soil microbes alters outcomes of plant competition.

PubMed

Abbott, Karen C; Karst, Justine; Biederman, Lori A; Borrett, Stuart R; Hastings, Alan; Walsh, Vonda; Bever, James D

2015-01-01

Plant species vary greatly in their responsiveness to nutritional soil mutualists, such as mycorrhizal fungi and rhizobia, and this responsiveness is associated with a trade-off in allocation to root structures for resource uptake. As a result, the outcome of plant competition can change with the density of mutualists, with microbe-responsive plant species having high competitive ability when mutualists are abundant and non-responsive plants having high competitive ability with low densities of mutualists. When responsive plant species also allow mutualists to grow to greater densities, changes in mutualist density can generate a positive feedback, reinforcing an initial advantage to either plant type. We study a model of mutualist-mediated competition to understand outcomes of plant-plant interactions within a patchy environment. We find that a microbe-responsive plant can exclude a non-responsive plant from some initial conditions, but it must do so across the landscape including in the microbe-free areas where it is a poorer competitor. Otherwise, the non-responsive plant will persist in both mutualist-free and mutualist-rich regions. We apply our general findings to two different biological scenarios: invasion of a non-responsive plant into an established microbe-responsive native population, and successional replacement of non-responders by microbe-responsive species. We find that resistance to invasion is greatest when seed dispersal by the native plant is modest and dispersal by the invader is greater. Nonetheless, a native plant that relies on microbial mutualists for competitive dominance may be particularly vulnerable to invasion because any disturbance that temporarily reduces its density or that of the mutualist creates a window for a non-responsive invader to establish dominance. We further find that the positive feedbacks from associations with beneficial soil microbes create resistance to successional turnover. Our theoretical results constitute an important first step toward developing a general understanding of the interplay between mutualism and competition in patchy landscapes, and generate qualitative predictions that may be tested in future empirical studies.

Spatial Heterogeneity in Soil Microbes Alters Outcomes of Plant Competition

PubMed Central

Abbott, Karen C.; Karst, Justine; Biederman, Lori A.; Borrett, Stuart R.; Hastings, Alan; Walsh, Vonda; Bever, James D.

2015-01-01

Plant species vary greatly in their responsiveness to nutritional soil mutualists, such as mycorrhizal fungi and rhizobia, and this responsiveness is associated with a trade-off in allocation to root structures for resource uptake. As a result, the outcome of plant competition can change with the density of mutualists, with microbe-responsive plant species having high competitive ability when mutualists are abundant and non-responsive plants having high competitive ability with low densities of mutualists. When responsive plant species also allow mutualists to grow to greater densities, changes in mutualist density can generate a positive feedback, reinforcing an initial advantage to either plant type. We study a model of mutualist-mediated competition to understand outcomes of plant-plant interactions within a patchy environment. We find that a microbe-responsive plant can exclude a non-responsive plant from some initial conditions, but it must do so across the landscape including in the microbe-free areas where it is a poorer competitor. Otherwise, the non-responsive plant will persist in both mutualist-free and mutualist-rich regions. We apply our general findings to two different biological scenarios: invasion of a non-responsive plant into an established microbe-responsive native population, and successional replacement of non-responders by microbe-responsive species. We find that resistance to invasion is greatest when seed dispersal by the native plant is modest and dispersal by the invader is greater. Nonetheless, a native plant that relies on microbial mutualists for competitive dominance may be particularly vulnerable to invasion because any disturbance that temporarily reduces its density or that of the mutualist creates a window for a non-responsive invader to establish dominance. We further find that the positive feedbacks from associations with beneficial soil microbes create resistance to successional turnover. Our theoretical results constitute an important first step toward developing a general understanding of the interplay between mutualism and competition in patchy landscapes, and generate qualitative predictions that may be tested in future empirical studies. PMID:25946068

Effects of high-frequency understorey fires on woody plant regeneration in southeastern Amazonian forests

PubMed Central

Balch, Jennifer K.; Massad, Tara J.; Brando, Paulo M.; Nepstad, Daniel C.; Curran, Lisa M.

2013-01-01

Anthropogenic understorey fires affect large areas of tropical forest, yet their effects on woody plant regeneration post-fire remain poorly understood. We examined the effects of repeated experimental fires on woody stem (less than 1 cm at base) mortality, recruitment, species diversity, community similarity and regeneration mode (seed versus sprout) in Mato Grosso, Brazil. From 2004 to 2010, forest plots (50 ha) were burned twice (B2) or five times (B5), and compared with an unburned control (B0). Stem density recovered within a year after the first burn (initial density: 12.4–13.2 stems m−2), but after 6 years, increased mortality and decreased regeneration—primarily of seedlings—led to a 63 per cent and 85 per cent reduction in stem density in B2 and B5, respectively. Seedlings and sprouts across plots in 2010 displayed remarkable community similarity owing to shared abundant species. Although the dominant surviving species were similar across plots, a major increase in sprouting occurred—almost three- and fourfold greater in B2 and B5 than in B0. In B5, 29 species disappeared and were replaced by 11 new species often present along fragmented forest edges. By 2010, the annual burn regime created substantial divergence between the seedling community and the initial adult tree community (greater than or equal to 20 cm dbh). Increased droughts and continued anthropogenic ignitions associated with frontier land uses may promote high-frequency fire regimes that may substantially alter regeneration and therefore successional processes. PMID:23610167

Modelling injection rates of PUIs from photoionization using kinetic simulations of interstellar neutrals traversing the heliosphere

NASA Astrophysics Data System (ADS)

Keilbach, D.; Drews, C.; Taut, A.; Wimmer-Schweingruber, R. F.

2016-12-01

Recent studies of the inflow direction of the local insterstellar medium from PUI density distributions have shown that the extrema of the longitudinal distribution of PUI velocities (with respect to the solar wind speed) can be attributed to the radial velocity of the interstellar neutral seed population and is symmetric around the inflow direction of the local interstellar medium. This work is aimed to model pickup ion injection rates from photoionization (which is the main process of interstellar PUI production) throughout the heliosphere. To that end a seed population of interstellar neutrals is injected into a model heliosphere at 60 AU distance from the sun, whereas each particle's initial speed is given by a maxwellian distribution at a temperature of 1 eV and an inflow speed of 22 km/s. Then the density of the interstellar neutrals is integrated over the model heliosphere, while the movement of the neutrals is simulated using timestep methods. To model the focusing of the interstellar neutral trajectories from the sun's gravitational potential the model heliosphere contains a central gravitational potential.Each neutral test particle can be ionized via photoionization with a per-timestep probability antiproportional to the neutral's distance to the sun squared. By tracking the ionization rate location-dependently, PUI injection rates have been determined. Therefore using these simulations the density distributions of different species of interstellar neutrals have been calculated. In addition location-dependent injection rates of different species of PUIs have been calculated, which show an increased rate of PUI production in the focusing cone region (e.g. for He+ PUIs), but also in the crescent region (e.g. for O+ PUIs).Furthermore the longitudinal distribution of the neutrals' velocity at 1 AU is calculated from the simulation's results in order to estimate the PUI cut-off as a function of ecliptic longitude. Figure: Simulated He neutral density (left) and simulated He PUI production rates from photoionization (right). The sun is located at 0 AU at both x-and y-axes.

The distribution of Vallisneria americana seeds and seedling light requirements in the upper Mississippi River

USGS Publications Warehouse

Kimber, A.; Korschgen, C.E.; Van Der Valk, A.G.

1995-01-01

Vallisneria americana declined in backwaters of the Upper Mississippi River, U.S.A., after a drought in 1988. To determine whether viable seeds of V. americana occurred in the seed bank of navigation pool 7, Lake Onalaska, the upper 5 cm of sediment was collected from 103 sites in May 1990. These sediment samples were kept in pots at a depth of 0.4, 0.8, and 1.2 m in an outdoor pond for 12 weeks. Vallisneria americana seeds germinated from sites throughout the lake, and some seedlings produced overwintering buds by the end of the study. Seeds, spores, or fragments of 12 other species of aquatic plants also germinated. Seed germination trials with fresh and stored seeds in both greenhouse and ponds in which light availability was reduced with shade cloths indicated that seed germination was insensitive to light level. To determine the tight requirements for seedling survival and bud production, sediment from Lake Onalaska was incubated in ponds under neutral density shade screens reducing light to 2, 5, 9, and 25% of full sun. Seeds germinated under all shade treatments but survival was significantly higher in the 9 and 25% light treatments, and bud production was restricted to these light levels.

Human dental pulp stem cell adhesion and detachment in polycaprolactone electrospun scaffolds under direct perfusion

PubMed Central

Paim, A.; Braghirolli, D.I.; Cardozo, N.S.M.; Pranke, P.; Tessaro, I.C.

2018-01-01

Cell adhesion in three-dimensional scaffolds plays a key role in tissue development. However, stem cell behavior in electrospun scaffolds under perfusion is not fully understood. Thus, an investigation was made on the effect of flow rate and shear stress, adhesion time, and seeding density under direct perfusion in polycaprolactone electrospun scaffolds on human dental pulp stem cell detachment. Polycaprolactone scaffolds were electrospun using a solvent mixture of chloroform and methanol. The viable cell number was determined at each tested condition. Cell morphology was analyzed by confocal microscopy after various incubation times for static cell adhesion with a high seeding density. Scanning electron microscopy images were obtained before and after perfusion for the highest flow rate tested. The wall pore shear stress was calculated for all tested flow rates (0.005–3 mL/min). An inversely proportional relationship between adhesion time with cell detachment under perfusion was observed. Lower flow rates and lower seeding densities reduced the drag of cells by shear stress. However, there was an operational limit for the lowest flow rate that can be used without compromising cell viability, indicating that a flow rate of 0.05 mL/min might be more suitable for the tested cell culture in electrospun scaffolds under direct perfusion. PMID:29590258

Transcriptional effect of an Aframomum angustifolium seed extract on human cutaneous cells using low-density DNA chips.

PubMed

Bonnet-Duquennoy, Mathilde; Dumas, Marc; Debacker, Adeline; Lazou, Kristell; Talbourdet, Sylvie; Franchi, Jocelyne; Heusèle, Catherine; André, Patrice; Schnebert, Sylvianne; Bonté, Frédéric; Kurfürst, Robin

2007-06-01

Studying photoexposed and photoprotected skin biopsies from young and aged women, it has been found that a specific zone, composed of the basal layers of the epidermis, the dermal epidermal junction, and the superficial dermis, is major target of aging and reactive oxygen species. We showed that this zone is characterized by significant variations at a transcriptional and/or protein levels. Using low-density DNA chip technology, we evaluated the effect of a natural mixture of Aframomum angustifolium seed extract containing labdane diterpenoids on these aging markers. Expression profiles of normal human fibroblasts (NHF) were studied using a customized cDNA macroarray system containing genes covering dermal structure, inflammatory responses, and oxidative stress defense mechanisms. For normal human keratinocyte (NHK) investigations, we chose OLISA technique, a sensitive and quantitative method developed by BioMérieux specifically designed to investigate cell death, proliferation, epidermal structure, differentiation, and oxidative stress defense response. We observed that this extract strongly modified gene expression profiles of treated NHK, but weakly for NHF. This extract regulated antioxidant defenses, dermal-epidermal junction components, and epidermal renewal-related genes. Using low-density DNA chip technology, we identified new potential actions of A. angustifolium seed extract on skin aging.

Adhesion of a monolayer of fibroblast cells to fibronectin under sonic vibrations in a bioreactor.

PubMed

Titze, Ingo R; Klemuk, Sarah A; Lu, Xiaoying

2012-06-01

We examined cell adhesion to a surface under vibrational forces approximating those of phonation. A monolayer of human fibroblast cells was seeded on a fibronectin-coated glass coverslip, which was attached to either the rotating part or the stationary part of a rheometer-bioreactor. The temperature, humidity, carbon dioxide level, nutrients, and cell seeding density were controlled. The cell density was on the order of 1,000 to 5,000 cells per square millimeter. Target stresses above 1 kPa at an oscillatory frequency of 100 Hz were chosen to reflect conditions of vocal fold tissue vibration. Fibronectin coating provided enough adhesion to support at least 2 kPa of oscillating stress, but only about 0.1 kPa of steady rotational shear. For stresses exceeding those limits, the cells were not able to adhere to the thin film of fibronectin. Cells will adhere to a planar surface under stresses typical of phonation, which provide a more stringent test than adherence in a 3-dimensional matrix. The density of cell seeding on the coverslip played a role in cell-extracellular matrix adhesion, in that the cells adhered to each other more than to the fibronectin coating when the cells were nearly confluent.

Aqueous seed extract of Hunteria umbellata (K. Schum.) Hallier f. (Apocynaceae) palliates hyperglycemia, insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome in rats.

PubMed

Ajiboye, T O; Hussaini, A A; Nafiu, B Y; Ibitoye, O B

2017-02-23

Hunteria umbellata is used in the management and treatment of diabetes and obesity in Nigeria. This study evaluates the effect of aqueous seed extract of Hunteria umbellata on insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome MATERIALS AND METHODS: Rats were randomized into seven groups (A-G). Control (group A) and group C rats received control diet for nine weeks while rats in groups B, D - G were placed on high-fructose diet for 9 weeks. In addition to the diets, groups C - F rats orally received 400, 100, 200 and 400mg/kg body weight aqueous seed extract of Hunteria umbellata for 3 weeks starting from 6th - 9th week. High-fructose diet (when compared to control rats) mediated a significant (p<0.05) increase in body weight, body mass index and abdominal circumference. Similarly, levels of blood glucose, insulin, leptin, adiponectin and insulin resistance were increased. It also caused a significant increase in the levels of cholesterol, triglycerides, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, atherogenic index, cardiac index and coronary artery index while high-density lipoprotein cholesterol was decreased significantly. Levels of proinflammatory factor, tumour necrosis factor-α, interleukin-6 and 8 were also increased by the high fructose diet. Moreover, it mediated decrease in activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose 6-phosphate dehydrogenase and level of glutathione reduced. Conversely, levels of malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl and fragmented DNA were elevated. Aqueous seed extract of Hunteria umbellata significantly ameliorated the high fructose diet-mediated alterations. From this study, it is concluded that aqueous seed extract of Hunteria umbellata possesses hypoglycemic, hypolipidemic and antioxidants abilities as evident from its capability to extenuate insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome rats. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

A model for multiseasonal spread of verticillium wilt of lettuce.

PubMed

Wu, B M; Subbarao, K V

2014-09-01

Verticillium wilt, caused by Verticillium dahliae, is a destructive disease in lettuce, and the pathogen is seedborne. Even though maximum seed infestation rates of <5% have been detected in commercial lettuce seed lots, it is necessary to establish acceptable contamination thresholds to prevent introduction and establishment of the pathogen in lettuce production fields. However, introduction of inoculum into lettuce fields for experimental purposes to determine its long term effects is undesirable. Therefore, we constructed a simulation model to study the spread of Verticillium wilt following pathogen introduction from seed. The model consists of four components: the first for simulating infection of host plants, the second for simulating reproduction of microsclerotia on diseased plants, the third for simulating the survival of microsclerotia, and the fourth for simulating the dispersal of microsclerotia. The simulation results demonstrated that the inoculum density-disease incidence curve parameters and the dispersal gradients affect disease spread in the field. Although a steep dispersal gradient facilitated the establishment of the disease in a new field with a low inoculum density, a long-tail gradient allowed microsclerotia to be dispersed over greater distances, promoting the disease spread in fields with high inoculum density. The simulation results also revealed the importance of avoiding successive lettuce crops in the same field, reducing survival rate of microsclerotia between crops, and the need for breeding resistance against V. dahliae in lettuce cultivars to lower the number of microsclerotia formed on each diseased plant. The simulation results, however, suggested that, even with a low seed infestation rate, the pathogen would eventually become established if susceptible lettuce cultivars were grown consecutively in the same field for many years. A threshold for seed infestation can be established only when two of the three drivers of the disease-(i) low microsclerotia production per diseased plant, (ii) long-tail dispersal gradient, and (iii) low microsclerotia survival between lettuce crops-are present.

Seed distribution of four co-occurring grasses around Artemisia halodendron shrubs in a sandy habitat

NASA Astrophysics Data System (ADS)

Li, Feng-Rui; Zhao, Wen-Zhi; Kang, Ling-Fen; Liu, Ji-Liang; Huang, Zhi-Gang; Wang, Qi

2009-05-01

In a natural population of the perennial semi-shrub Artemisia halodendron in a shifting sandy habitat in the Horqin Desert of eastern Inner Mongolia, six isolated adult A. halodendron individuals of similar canopy size were chosen as target plants. The density of seeds in the top 5 cm soil depth around shrubs was measured using transects aligned to the four main wind directions and at different distances from the shrub base on both the windward and leeward sides. The effects of shrub presence on seed distribution of four co-occurring grasses were examined by linking seed distribution to seed traits. Of the four species, Setaris viridis and Eragrostis pilosa had small but similar seed mass, while Chloris virgata and Aristida adscensionis had large but similar seed mass. The species were grouped into two cohorts: small-seeded vs. large-seeded cohorts, and shrub presence effects on seed distribution of both cohorts were examined. We found marked difference in the seed distribution pattern among species, especially between the small-seeded and large-seeded cohorts. The small-seeded cohort had significantly higher seed accumulation on the windward than the leeward sides in the most and least prevailing wind directions and much higher seed accumulation on the leeward than the windward sides in the second and third most prevailing wind directions, while opposite patterns occurred in the large-seeded cohort. Four species also showed marked variation in the seed distribution pattern among transects and between windward and leeward sides of each transect. This study provided further evidence that shrubs embedded in a matrix of herbaceous plants is a key cause of spatial heterogeneity in seed availability of herbaceous species. However, seed distribution responses to the presence of shrubs will vary with species as well as with wind direction, sampling position (windward vs. leeward sides of the shrub) and distance from the shrub.

SU-F-BRA-03: Integrating Novel Electromagnetic Tracking Hollow Needle Assistance in Permanent Implant Brachytherapy Procedures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Racine, E; Hautvast, G; Binnekamp, D

Purpose: To report on the results of a complete permanent implant brachytherapy procedure assisted by an electromagnetic (EM) hollow needle possessing both 3D tracking and seed drop detection abilities. Methods: End-to-end in-phantom EM-assisted LDR procedures were conducted. The novel system consisted of an EM tracking apparatus (NDI Aurora V2, Planar Field Generator), a 3D US scanner (Philips CX50), a hollow needle prototype allowing 3D tracking and seed drop detection and a specially designed treatment planning software (Philips Healthcare). A tungsten-doped 30 cc spherical agarose prostate immersed in gelatin was used for the treatment. A cylindrical shape of 0.8 cc wasmore » carved along its diameter to mimic the urethra. An initial plan of 26 needles and 47 seeds was established with the system. The plan was delivered with the EM-tracked hollow needle, and individual seed drop locations were recorded on the fly. The phantom was subsequently imaged with a CT scanner from which seed positions and contour definitions were obtained. The DVHs were then independently recomputed and compared with those produced by the planning system, both before and after the treatment. Results: Of the 47 seeds, 45 (96%) were detected by the EM technology embedded in the hollow needle design. The executed plan (from CT analysis) differed from the initial plan by 2%, 14% and 8% respectively in terms of V100, D90 and V150 for the prostate, and by 8%, 7% and 10% respectively in terms of D5, V100 and V120 for the urethra. Conclusion: The average DVH deviations between initial and executed plans were within a 5% tolerance imposed for this proof-of-concept assessment. This relatively good concordance demonstrates the feasibility and potential benefits of combining EM tracking and seed drop detection for real-time dosimetry validation and assistance in permanent implant brachytherapy procedures. This project has been entirely funded by Philips Healthcare.« less

Can the Results of Biodiversity-Ecosystem Productivity Studies Be Translated to Bioenergy Production?

DOE PAGES

Dickson, Timothy L.; Gross, Katherine L.

2015-09-11

Biodiversity experiments show that increases in plant diversity can lead to greater biomass production, and some researchers suggest that high diversity plantings should be used for bioenergy production. However, many methods used in past biodiversity experiments are impractical for bioenergy plantings. For example, biodiversity experiments often use intensive management such as hand weeding to maintain low diversity plantings and exclude unplanted species, but this would not be done for bioenergy plantings. Also, biodiversity experiments generally use high seeding densities that would be too expensive for bioenergy plantings. Here we report the effects of biodiversity on biomass production from two studiesmore » of more realistic bioenergy crop plantings in southern Michigan, USA. One study involved comparing production between switchgrass (Panicum virgatum) monocultures and species-rich prairie plantings on private farm fields that were managed similarly to bioenergy plantings. The other study was an experiment where switchgrass was planted in monoculture and in combination with increasingly species-rich native prairie mixtures. Overall, we found that bioenergy plantings with higher species richness did not produce more biomass than switchgrass monocultures. The lack of a positive relationship between planted species richness and production in our studies may be due to several factors. Non-planted species (weeds) were not removed from our studies and these non-planted species may have competed with planted species and also prevented realized species richness from equaling planted species richness. Also, we found that low seeding density of individual species limited the biomass production of these individual species. Finally, production in future bioenergy plantings with high species richness may be increased by using a high density of inexpensive seed from switchgrass and other highly productive species, and future efforts to translate the results of biodiversity experiments to bioenergy plantings should consider the role of seeding density.« less

Can the Results of Biodiversity-Ecosystem Productivity Studies Be Translated to Bioenergy Production?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickson, Timothy L.; Gross, Katherine L.

Biodiversity experiments show that increases in plant diversity can lead to greater biomass production, and some researchers suggest that high diversity plantings should be used for bioenergy production. However, many methods used in past biodiversity experiments are impractical for bioenergy plantings. For example, biodiversity experiments often use intensive management such as hand weeding to maintain low diversity plantings and exclude unplanted species, but this would not be done for bioenergy plantings. Also, biodiversity experiments generally use high seeding densities that would be too expensive for bioenergy plantings. Here we report the effects of biodiversity on biomass production from two studiesmore » of more realistic bioenergy crop plantings in southern Michigan, USA. One study involved comparing production between switchgrass (Panicum virgatum) monocultures and species-rich prairie plantings on private farm fields that were managed similarly to bioenergy plantings. The other study was an experiment where switchgrass was planted in monoculture and in combination with increasingly species-rich native prairie mixtures. Overall, we found that bioenergy plantings with higher species richness did not produce more biomass than switchgrass monocultures. The lack of a positive relationship between planted species richness and production in our studies may be due to several factors. Non-planted species (weeds) were not removed from our studies and these non-planted species may have competed with planted species and also prevented realized species richness from equaling planted species richness. Also, we found that low seeding density of individual species limited the biomass production of these individual species. Finally, production in future bioenergy plantings with high species richness may be increased by using a high density of inexpensive seed from switchgrass and other highly productive species, and future efforts to translate the results of biodiversity experiments to bioenergy plantings should consider the role of seeding density.« less

Observation of dual-mode, Kelvin-Helmholtz instability vortex merger in a compressible flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, W. C.; Malamud, Guy; Shimony, A.

Here, we report the first observations of Kelvin-Helmholtz vortices evolving from well-characterized, dual-mode initial conditions in a steady, supersonic flow. The results provide the first measurements of the instability's vortex merger rate and supplement data on the inhibition of the instability's growth rate in a compressible flow. These experimental data were obtained by sustaining a shockwave over a foam-plastic interface with a precision-machined seed perturbation. This technique produced a strong shear layer between two plasmas at high-energy-density conditions. The system was diagnosed using x-ray radiography and was well-reproduced using hydrodynamic simulations. Experimental measurements imply that we observed the anticipated vortexmore » merger rate and growth inhibition for supersonic shear flow.« less

Observation of dual-mode, Kelvin-Helmholtz instability vortex merger in a compressible flow

DOE PAGES

Wan, W. C.; Malamud, Guy; Shimony, A.; ...

2017-04-25

Here, we report the first observations of Kelvin-Helmholtz vortices evolving from well-characterized, dual-mode initial conditions in a steady, supersonic flow. The results provide the first measurements of the instability's vortex merger rate and supplement data on the inhibition of the instability's growth rate in a compressible flow. These experimental data were obtained by sustaining a shockwave over a foam-plastic interface with a precision-machined seed perturbation. This technique produced a strong shear layer between two plasmas at high-energy-density conditions. The system was diagnosed using x-ray radiography and was well-reproduced using hydrodynamic simulations. Experimental measurements imply that we observed the anticipated vortexmore » merger rate and growth inhibition for supersonic shear flow.« less

Characterization of the PTW SourceCheck ionization chamber with the Valencia lodgment for (125)I seed verification.

PubMed

Tornero-López, Ana M; Torres Del Río, Julia; Ruiz, Carmen; Perez-Calatayud, Jose; Guirado, Damián; Lallena, Antonio M

2015-12-01

In brachytherapy using (125)I seed implants, a verification of the air kerma strength of the sources used is required. Typically, between 40 and 100 seeds are implanted. Checking all of them is unaffordable, especially when seeds are disposed in sterile cartridges. Recently, a new procedure allowing the accomplishment of the international recommendations has been proposed for the seedSelectron system of Elekta Brachytherapy. In this procedure, the SourceCheck ionization chamber is used with a special lodgment (Valencia lodgment) that allows to measure up to 10 seeds simultaneously. In this work we analyze this procedure, showing the feasibility of the approximations required for its application, as well as the effect of the additional dependence with the air density that shows the chamber model used. Uncertainty calculations and the verification of the approximation needed to obtain a calibration factor for the Valencia lodgment are carried out. The results of the present work show that the chamber dependence with the air density is the same whether the Valencia lodgment is used or not. On the contrary, the chamber response profile is influenced by the presence of the lodgment. The determination of this profile requires various measurements due to the nonnegligible variability found between different experiments. If it is considered, the uncertainty in the determination of the air-kerma strength increases from 0.5% to 1%. Otherwise, a systematic additional uncertainty of 1% would occur. This could be relevant for the comparison between user and manufacturer measurements that is mandatory in the case studied here. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Stability Study of Algerian Nigella sativa Seeds Stored under Different Conditions

PubMed Central

Ahamad Bustamam, Muhammad Safwan; Hadithon, Kamarul Arifin; Rukayadi, Yaya; Lajis, Nordin

2017-01-01

In a study to determine the stability of the main volatile constituents of Nigella sativa seeds stored under several conditions, eight storage conditions were established, based on the ecological abiotic effects of air, heat, and light. Six replicates each were prepared and analyzed with Headspace-Gas Chromatography-Mass Spectrometry (HS-GC-MS) for three time points at the initial (1st day (0)), 14th (1), and 28th (2) day of storage. A targeted multivariate analysis of Principal Component Analysis revealed that the stability of the main volatile constituents of the whole seeds was better than that of the ground seeds. Exposed seeds, whole or ground, were observed to experience higher decrement of the volatile composition. These ecofactors of air, heat, and light are suggested to be directly responsible for the loss of volatiles in N. sativa seeds, particularly of the ground seeds. PMID:28255502

Imbibition of wheat seeds: Application of image analysis

NASA Astrophysics Data System (ADS)

Lev, Jakub; Blahovec, Jiří

2017-10-01

Image analysis is widely used for monitoring seeds during germination, and it is often the final phase of germination that is subjected to the greatest attention. However, the initial phase of germination (the so-called imbibition) also exhibits interesting behaviour. This work shows that image analysis has significant potential in the imbibition. Herein, a total of 120 seeds were analysed during germination tests, and information about seed size and shape was stored and analysed. It was found that the imbibition can be divided into two newly defined parts. The first one (`abrupt imbibition') consists mainly of the swelling of the seed embryo part and lasts approximately one hour. The second one, referred to as `main imbibition', consists mainly of spatial expansion caused by imbibition in the other parts of the seed. The results presented are supported by the development of seed cross area and shape parameters, and by direct observation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crane, Cameron C.; Tao, Jing; Wang, Feng

Controlling the deposition of exotic metals in the seeded growth of multi-metal nanostructures is challenging. This work describes a seeded growth method assisted by a mask for synthesis of segmented binary or ternary metal nanostructures. Silica is used as a mask to partially block the surface of a seed and a second metal is subsequently deposited on the exposed area, forming a bimetallic heterodimer. The initial demonstration was carried out on a Au seed, followed by deposition of Pd or Pt on the seed. It was found that Pd tends to spread out laterally on the seed while Pt inclinesmore » to grow vertically into branched topology on Au. Without removal of the SiO₂ mask, Pt could be further deposited on the unblocked Pd of the Pd-Au dimer to form a Pt-Pd-Au trimer. The mask-assisted seeded growth provides a general strategy to construct segmented metallic nanoarchitectures.« less

Pesticide seed dressings can affect the activity of various soil organisms and reduce decomposition of plant material.

PubMed

Zaller, Johann G; König, Nina; Tiefenbacher, Alexandra; Muraoka, Yoko; Querner, Pascal; Ratzenböck, Andreas; Bonkowski, Michael; Koller, Robert

2016-08-17

Seed dressing with pesticides is widely used to protect crop seeds from pest insects and fungal diseases. While there is mounting evidence that especially neonicotinoid seed dressings detrimentally affect insect pollinators, surprisingly little is known on potential side effects on soil biota. We hypothesized that soil organisms would be particularly susceptible to pesticide seed dressings as they get in direct contact with these chemicals. Using microcosms with field soil we investigated, whether seeds treated either with neonicotinoid insecticides or fungicides influence the activity and interaction of earthworms, collembola, protozoa and microorganisms. The full-factorial design consisted of the factor Seed dressing (control vs. insecticide vs. fungicide), Earthworm (no earthworms vs. addition Lumbricus terrestris L.) and collembola (no collembola vs. addition Sinella curviseta Brook). We used commercially available wheat seed material (Triticum aesticum L. cf. Lukullus) at a recommended seeding density of 367 m(-2). Seed dressings (particularly fungicides) increased collembola surface activity, increased the number of protozoa and reduced plant decomposition rate but did not affect earthworm activity. Seed dressings had no influence on wheat growth. Earthworms interactively affected the influence of seed dressings on collembola activity, whereas collembola increased earthworm surface activity but reduced soil basal respiration. Earthworms also decreased wheat growth, reduced soil basal respiration and microbial biomass but increased soil water content and electrical conductivity. The reported non-target effects of seed dressings and their interactions with soil organisms are remarkable because they were observed after a one-time application of only 18 pesticide treated seeds per experimental pot. Because of the increasing use of seed dressing in agriculture and the fundamental role of soil organisms in agroecosystems these ecological interactions should receive more attention.

A large scale laboratory cage trial of Aedes densonucleosis virus (AeDNV).

PubMed

Wise de Valdez, Megan R; Suchman, Erica L; Carlson, Jonathan O; Black, William C

2010-05-01

Aedes aegypti (L.) (Diptera: Culicidae) the primary vector of dengue viruses (DENV1-4), oviposit in and around human dwellings, including sites difficult to locate, making control of this mosquito challenging. We explored the efficacy and sustainability of Aedes Densonucleosis Virus (AeDNV) as a biocontrol agent for Ae. aegypti in and among oviposition sites in large laboratory cages (> 92 m3) as a prelude to field trials. Select cages were seeded with AeDNV in a single oviposition site (OPS) with unseeded OPSs established at varied distances. Quantitative real-time polymerase chain reaction was used to track dispersal and accumulation of AeDNV among OPSs. All eggs were collected weekly from each cage and counted. We asked: (1) Is AeDNV dispersed over varying distances and can it accumulate and persist in novel OPSs? (2) Are egg densities reduced in AeDNV treated populations? AeDNV was dispersed to and sustained in novel OPSs. Virus accumulation in OPSs was positively correlated with egg densities and proximity to the initial infection source affected the timing of dispersal and maintenance of viral titers. AeDNV did not significantly reduce Ae. aegypti egg densities. The current study documents that adult female Ae. aegypti oviposition behavior leads to successful viral dispersal from treated to novel containers in large-scale cages; however, the AeDNV titers reached were not sufficient to reduce egg densities.

QTLs for Seed Vigor-Related Traits Identified in Maize Seeds Germinated under Artificial Aging Conditions

PubMed Central

Han, Zanping; Ku, Lixia; Zhang, Zhenzhen; Zhang, Jun; Guo, ShuLei; Liu, Haiying; Zhao, Ruifang; Ren, Zhenzhen; Zhang, Liangkun; Su, Huihui; Dong, Lei; Chen, Yanhui

2014-01-01

High seed vigor is important for agricultural production due to the associated potential for increased growth and productivity. However, a better understanding of the underlying molecular mechanisms is required because the genetic basis for seed vigor remains unknown. We used single-nucleotide polymorphism (SNP) markers to map quantitative trait loci (QTLs) for four seed vigor traits in two connected recombinant inbred line (RIL) maize populations under four treatment conditions during seed germination. Sixty-five QTLs distributed between the two populations were identified and a meta-analysis was used to integrate genetic maps. Sixty-one initially identified QTLs were integrated into 18 meta-QTLs (mQTLs). Initial QTLs with contribution to phenotypic variation values of R2>10% were integrated into mQTLs. Twenty-three candidate genes for association with seed vigor traits coincided with 13 mQTLs. The candidate genes had functions in the glycolytic pathway and in protein metabolism. QTLs with major effects (R2>10%) were identified under at least one treatment condition for mQTL2, mQTL3-2, and mQTL3-4. Candidate genes included a calcium-dependent protein kinase gene (302810918) involved in signal transduction that mapped in the mQTL3-2 interval associated with germination energy (GE) and germination percentage (GP), and an hsp20/alpha crystallin family protein gene (At5g51440) that mapped in the mQTL3-4 interval associated with GE and GP. Two initial QTLs with a major effect under at least two treatment conditions were identified for mQTL5-2. A cucumisin-like Ser protease gene (At5g67360) mapped in the mQTL5-2 interval associated with GP. The chromosome regions for mQTL2, mQTL3-2, mQTL3-4, and mQTL5-2 may be hot spots for QTLs related to seed vigor traits. The mQTLs and candidate genes identified in this study provide valuable information for the identification of additional quantitative trait genes. PMID:24651614

QTLs for seed vigor-related traits identified in maize seeds germinated under artificial aging conditions.

PubMed

Han, Zanping; Ku, Lixia; Zhang, Zhenzhen; Zhang, Jun; Guo, Shulei; Liu, Haiying; Zhao, Ruifang; Ren, Zhenzhen; Zhang, Liangkun; Su, Huihui; Dong, Lei; Chen, Yanhui

2014-01-01

High seed vigor is important for agricultural production due to the associated potential for increased growth and productivity. However, a better understanding of the underlying molecular mechanisms is required because the genetic basis for seed vigor remains unknown. We used single-nucleotide polymorphism (SNP) markers to map quantitative trait loci (QTLs) for four seed vigor traits in two connected recombinant inbred line (RIL) maize populations under four treatment conditions during seed germination. Sixty-five QTLs distributed between the two populations were identified and a meta-analysis was used to integrate genetic maps. Sixty-one initially identified QTLs were integrated into 18 meta-QTLs (mQTLs). Initial QTLs with contribution to phenotypic variation values of R(2)>10% were integrated into mQTLs. Twenty-three candidate genes for association with seed vigor traits coincided with 13 mQTLs. The candidate genes had functions in the glycolytic pathway and in protein metabolism. QTLs with major effects (R(2)>10%) were identified under at least one treatment condition for mQTL2, mQTL3-2, and mQTL3-4. Candidate genes included a calcium-dependent protein kinase gene (302810918) involved in signal transduction that mapped in the mQTL3-2 interval associated with germination energy (GE) and germination percentage (GP), and an hsp20/alpha crystallin family protein gene (At5g51440) that mapped in the mQTL3-4 interval associated with GE and GP. Two initial QTLs with a major effect under at least two treatment conditions were identified for mQTL5-2. A cucumisin-like Ser protease gene (At5g67360) mapped in the mQTL5-2 interval associated with GP. The chromosome regions for mQTL2, mQTL3-2, mQTL3-4, and mQTL5-2 may be hot spots for QTLs related to seed vigor traits. The mQTLs and candidate genes identified in this study provide valuable information for the identification of additional quantitative trait genes.

A Genome-wide Combinatorial Strategy Dissects Complex Genetic Architecture of Seed Coat Color in Chickpea

PubMed Central

Bajaj, Deepak; Das, Shouvik; Upadhyaya, Hari D.; Ranjan, Rajeev; Badoni, Saurabh; Kumar, Vinod; Tripathi, Shailesh; Gowda, C. L. Laxmipathi; Sharma, Shivali; Singh, Sube; Tyagi, Akhilesh K.; Parida, Swarup K.

2015-01-01

The study identified 9045 high-quality SNPs employing both genome-wide GBS- and candidate gene-based SNP genotyping assays in 172, including 93 cultivated (desi and kabuli) and 79 wild chickpea accessions. The GWAS in a structured population of 93 sequenced accessions detected 15 major genomic loci exhibiting significant association with seed coat color. Five seed color-associated major genomic loci underlying robust QTLs mapped on a high-density intra-specific genetic linkage map were validated by QTL mapping. The integration of association and QTL mapping with gene haplotype-specific LD mapping and transcript profiling identified novel allelic variants (non-synonymous SNPs) and haplotypes in a MATE secondary transporter gene regulating light/yellow brown and beige seed coat color differentiation in chickpea. The down-regulation and decreased transcript expression of beige seed coat color-associated MATE gene haplotype was correlated with reduced proanthocyanidins accumulation in the mature seed coats of beige than light/yellow brown seed colored desi and kabuli accessions for their coloration/pigmentation. This seed color-regulating MATE gene revealed strong purifying selection pressure primarily in LB/YB seed colored desi and wild Cicer reticulatum accessions compared with the BE seed colored kabuli accessions. The functionally relevant molecular tags identified have potential to decipher the complex transcriptional regulatory gene function of seed coat coloration and for understanding the selective sweep-based seed color trait evolutionary pattern in cultivated and wild accessions during chickpea domestication. The genome-wide integrated approach employed will expedite marker-assisted genetic enhancement for developing cultivars with desirable seed coat color types in chickpea. PMID:26635822

Long-term development of regeneration under longleaf pine seedtree and shelterwood stands

Treesearch

William D. Boyer

1993-01-01

Well-stocked mature longleaf pine (Pinus palustris Mill.) stands were cut tofive residual basal areas in 1957, namely 9,18,2 7.36, and 45 ft2 per ac, to observe the effect of stand density on seed production and seedling establishment. Seedlings, mainly from the 195.5 or 1961 seed crops, were established in treated stands. All pines on net 0.9 ac...

The influence of cattle grazing and grass seeding on coniferous regeneration after shelterwood cutting in eastern Oregon.

Treesearch

K.W. Seidel; J. Michael Geist; Gerald S. Strickler

1990-01-01

Natural regeneration was abundant, regardless of grazing and grass seeding treatments,after shelterwood cutting to three overstory densities (27, 73, and 119 square feet of basal area per acre) in mixed conifer stands in the Starkey Experimental Forest and Range in eastern Oregon. After 6 years, the number of tree seedlings ranged from about 3,800 per acre on the low-...

Fibroblast contractility and growth in plastic compressed collagen gel scaffolds with microstructures correlated with hydraulic permeability.

PubMed

Serpooshan, Vahid; Muja, Naser; Marelli, Benedetto; Nazhat, Showan N

2011-03-15

Scaffold microstructure is hypothesized to influence physical and mechanical properties of collagen gels, as well as cell function within the matrix. Plastic compression under increasing load was conducted to produce scaffolds with increasing collagen fibrillar densities ranging from 0.3 to above 4.1 wt % with corresponding hydraulic permeability (k) values that ranged from 1.05 to 0.03 μm², as determined using the Happel model. Scanning electron microscopy revealed that increasing the level of collagen gel compression yielded a concomitant reduction in pore size distribution and a slight increase in average fibril bundle diameter. Decreasing k delayed the onset of contraction and significantly reduced both the total extent and the maximum rate of contraction induced by NIH3T3 fibroblasts seeded at a density of either 6.0 x 10⁴ or 1.5 x 10⁵ cells mL⁻¹. At the higher cell density, however, the effect of k reduction on collagen gel contraction was overcome by an accelerated onset of contraction which led to an increase in both the total extent and the maximum rate of contraction. AlamarBlue™ measurements indicated that the metabolic activity of fibroblasts within collagen gels increased as k decreased. Moreover, increasing seeded cell density from 2.0 x 10⁴ to 1.5 x 10⁵ cells mL⁻¹ significantly increased NIH3T3 proliferation. In conclusion, fibroblast-matrix interactions can be optimized by defining the microstructural properties of collagen scaffolds through k adjustment which in turn, is dependent on the cell seeding density. Copyright © 2011 Wiley Periodicals, Inc.

Activation of Arabidopsis Seed Hair Development by Cotton Fiber-Related Genes

PubMed Central

Pang, Mingxiong; Shi, Xiaoli; Stelly, David M.; Chen, Z. Jeffrey

2011-01-01

Each cotton fiber is a single-celled seed trichome or hair, and over 20,000 fibers may develop semi-synchronously on each seed. The molecular basis for seed hair development is unknown but is likely to share many similarities with leaf trichome development in Arabidopsis. Leaf trichome initiation in Arabidopsis thaliana is activated by GLABROUS1 (GL1) that is negatively regulated by TRIPTYCHON (TRY). Using laser capture microdissection and microarray analysis, we found that many putative MYB transcription factor and structural protein genes were differentially expressed in fiber and non-fiber tissues. Gossypium hirsutum MYB2 (GhMYB2), a putative GL1 homolog, and its downstream gene, GhRDL1, were highly expressed during fiber cell initiation. GhRDL1, a fiber-related gene with unknown function, was predominately localized around cell walls in stems, sepals, seed coats, and pollen grains. GFP:GhRDL1 and GhMYB2:YFP were co-localized in the nuclei of ectopic trichomes in siliques. Overexpressing GhRDL1 or GhMYB2 in A. thaliana Columbia-0 (Col-0) activated fiber-like hair production in 4–6% of seeds and had on obvious effects on trichome development in leaves or siliques. Co-overexpressing GhRDL1 and GhMYB2 in A. thaliana Col-0 plants increased hair formation in ∼8% of seeds. Overexpressing both GhRDL1 and GhMYB2 in A. thaliana Col-0 try mutant plants produced seed hair in ∼10% of seeds as well as dense trichomes inside and outside siliques, suggesting synergistic effects of GhRDL1 and GhMYB2 with try on development of trichomes inside and outside of siliques and seed hair in A. thaliana. These data suggest that a different combination of factors is required for the full development of trichomes (hairs) in leaves, siliques, and seeds. A. thaliana can be developed as a model a system for discovering additional genes that control seed hair development in general and cotton fiber in particular. PMID:21779324

Papaya Seeds as A Low-Cost Sorbent for Removing Cr(VI) from The Aqueous Solution

NASA Astrophysics Data System (ADS)

Rahmawati, Atik; Marwoto, Putut; Karunia Z, Anita

2016-08-01

The presence of chromium (VI) contaminants and their toxicity in aqueous streams important environmental problems. Adsorption is one of the effective techniques that can be used for removing metal from wastewater. This research was initiated by preparing sorbent from papaya seeds and determining its functional group contents by using FT-IR. The adsorption process was carried out in a batch method. The study of adsorption aspects involved the pH, initial Cr (VI) concentration and contact time between Cr (VI) and sorbent. FT IR analysis results showed that the main functional groups are carbonyl, hydroxyl, and carboxylic. It was also found that the effective pH for Cr (VI) uptake is 2.0 and increasing contact time would increase the Cr (VI) uptake. In addition, the equilibrium was reached after 40 minutes interaction and the increase of initial chromium (VI) concentration would increase the sorbent uptake percentage. All these results indicated that papaya seed is a potential sorbent for removing Cr (VI) from aqueous solutions.

Study on small molecular organic compounds pyrolysed from rubber seed oil and its sodium soap.

PubMed

Fernando, T L D; Prashantha, M A B; Amarasinghe, A D U S

2016-01-01

Rubber seed oil (RSO) and its sodium soap were pyrolysed in a batch reactor to obtain low molar mass organic substances. The pyrolitic oil of RSO was redistilled and the distillates were characterized by GC-MS and FTIR. Density, acid value, saponification value and ester values were also measured according to the ASTM standard methods. A similar analysis was done for samples taken out at different time intervals from the reaction mixture. Industrially important low molar mass alkanes, alkenes, aromatics, cyclic compounds and carboxylic acids were identified in the pyrolysis process of rubber seed oil. However, pyrolysis of the sodium soap of rubber seed oil gave a mixture of hydrocarbons in the range of C14-C17 and hence it has more applications as a fuel.

Quinoa seeds leach phytoecdysteroids and other compounds with anti-diabetic properties

PubMed Central

Graf, Brittany L.; Poulev, Alexander; Kuhn, Peter; Grace, Mary H.; Lila, Mary Ann; Raskin, Ilya

2014-01-01

Quinoa (Chenopodium quinoa Willd.) contains high levels of biologically active phytoecdysteroids, which have been implicated in plant defense from insects, and have shown a range of beneficial pharmacological effects in mammals. We demonstrated that the most prevalent phytoecdysteroid, 20-hydroxyecdysone (20HE), was secreted (leached) from intact quinoa seeds into water during the initial stages of seed germination. Leaching efficiency was optimized by ethanol concentration (70% ethanol), temperature (80°C), time (4 h), and solvent ratio (5 ml/g seed). When compared to extraction of macerated seeds, the leaching procedure released essentially all the 20HE available in the seeds (491 μg/g seed). The optimized quinoa leachate (QL), containing 0.86% 20HE, 1.00% total phytoecdysteroids, 2.59% flavonoid glycosides, 11.9% oil, and 20.4% protein, significantly lowered fasting blood glucose in obese, hyperglycemic mice. Leaching effectively releases and concentrates bioactive phytochemicals from quinoa seeds, providing an efficient means to produce a food-grade mixture that may be useful for anti-diabetic applications. PMID:24912714

Influence of Poly(L-Lactic Acid) Nanofibers and BMP-2–Containing Poly(L-Lactic Acid) Nanofibers on Growth and Osteogenic Differentiation of Human Mesenchymal Stem Cells

PubMed Central

Schofer, Markus D.; Fuchs-Winkelmann, Susanne; Gräbedünkel, Christian; Wack, Christina; Dersch, Roland; Rudisile, Markus; Wendorff, Joachim H.; Greiner, Andreas; Paletta, Jürgen R. J.; Boudriot, Ulrich

2008-01-01

The aim of this study was to characterize synthetic poly-(L-lactic acid) (PLLA) nanofibers concerning their ability to promote growth and osteogenic differentiation of stem cells in vitro, as well as to test their suitability as a carrier system for growth factors. Fiber matrices composed of PLLA or BMP-2–incorporated PLLA were seeded with human mesenchymal stem cells and cultivated over a period of 22 days under growth and osteoinductive conditions, and analyzed during the course of culture, with respect to gene expression of alkaline phosphatase (ALP), osteocalcin (OC), and collagen I (COL-I). Furthermore, COL-I and OC deposition, as well as cell densities and proliferation, were analyzed using fluorescence microscopy. Although the presence of nanofibers diminished the dexamethasone-induced proliferation, there were no differences in cell densities or deposition of either COL-I or OC after 22 days of culture. The gene expression of ALP, OC, and COL-I decreased in the initial phase of cell cultivation on PLLA nanofibers as compared to cover slip control, but normalized during the course of cultivation. The initial down-regulation was not observed when BMP-2 was directly incorporated into PLLA nanofibers by electrospinning, indicating that growth factors like BMP-2 might survive the spinning process in a bioactive form. PMID:19112539

Dynamic chromatin changes associated with de novo centromere formation in maize euchromatin.

PubMed

Su, Handong; Liu, Yalin; Liu, Yong-Xin; Lv, Zhenling; Li, Hongyao; Xie, Shaojun; Gao, Zhi; Pang, Junling; Wang, Xiu-Jie; Lai, Jinsheng; Birchler, James A; Han, Fangpu

2016-12-01

The inheritance and function of centromeres are not strictly dependent on any specific DNA sequence, but involve an epigenetic component in most species. CENH3, a centromere histone H3 variant, is one of the best-described epigenetic factors in centromere identity, but the chromatin features required during centromere formation have not yet been revealed. We previously identified two de novo centromeres on Zea mays (maize) minichromosomes derived from euchromatic sites with high-density gene distributions but low-density transposon distributions. The distribution of gene location and gene expression in these sites indicates that transcriptionally active regions can initiate de novo centromere formation, and CENH3 seeding shows a preference for gene-free regions or regions with no gene expression. The locations of the expressed genes detected were at relatively hypomethylated loci, and the altered gene expression resulted from de novo centromere formation, but not from the additional copy of the minichromosome. The initial overall DNA methylation level of the two de novo regions was at a low level, but increased substantially to that of native centromeres after centromere formation. These results illustrate the dynamic chromatin changes during euchromatin-originated de novo centromere formation, which provides insight into the mechanism of de novo centromere formation and regulation of subsequent consequences. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Seeding method influences warm-season grass abundance and distribution but not local diversity in grassland restoration

USGS Publications Warehouse

Yurkonis, Kathryn A.; Wilsey, Brian J.; Moloney, Kirk A.; Drobney, Pauline; Larson, Diane L.

2010-01-01

Ecological theory predicts that the arrangement of seedlings in newly restored communities may influence future species diversity and composition. We test the prediction that smaller distances between neighboring seeds in drill seeded grassland plantings would result in lower species diversity, greater weed abundance, and larger conspecific patch sizes than otherwise similar broadcast seeded plantings. A diverse grassland seed mix was either drill seeded, which places seeds in equally spaced rows, or broadcast seeded, which spreads seeds across the ground surface, into 24 plots in each of three sites in 2005. In summer 2007, we measured species abundance in a 1 m2 quadrat in each plot and mapped common species within the quadrat by recording the most abundant species in each of 64 cells. Quadrat-scale diversity and weed abundance were similar between drilled and broadcast plots, suggesting that processes that limited establishment and controlled invasion were not affected by such fine-scale seed distribution. However, native warm-season (C4) grasses were more abundant and occurred in less compact patches in drilled plots. This difference in C4 grass abundance and distribution may result from increased germination or vegetative propagation of C4 grasses in drilled plots. Our findings suggest that local plant density may control fine-scale heterogeneity and species composition in restored grasslands, processes that need to be further investigated to determine whether seed distributions can be manipulated to increase diversity in restored grasslands.

Seeding Method Influences Warm-Season Grass Abundance and Distribution but not Local Diversity in Grassland Restoration

USGS Publications Warehouse

Yurkonis, K.A.; Wilsey, B.J.; Moloney, K.A.; Drobney, P.; Larson, D.L.

2010-01-01

Ecological theory predicts that the arrangement of seedlings in newly restored communities may influence future species diversity and composition. We test the prediction that smaller distances between neighboring seeds in drill seeded grassland plantings would result in lower species diversity, greater weed abundance, and larger conspecific patch sizes than otherwise similar broadcast seeded plantings. A diverse grassland seed mix was either drill seeded, which places seeds in equally spaced rows, or broadcast seeded, which spreads seeds across the ground surface, into 24 plots in each of three sites in 2005. In summer 2007, we measured species abundance in a 1 m2 quadrat in each plot and mapped common species within the quadrat by recording the most abundant species in each of 64 cells. Quadrat-scale diversity and weed abundance were similar between drilled and broadcast plots, suggesting that processes that limited establishment and controlled invasion were not affected by such fine-scale seed distribution. However, native warm-season (C4) grasses were more abundant and occurred in less compact patches in drilled plots. This difference in C4 grass abundance and distribution may result from increased germination or vegetative propagation of C4 grasses in drilled plots. Our findings suggest that local plant density may control fine-scale heterogeneity and species composition in restored grasslands, processes that need to be further investigated to determine whether seed distributions can be manipulated to increase diversity in restored grasslands. ?? 2010 Society for Ecological Restoration International.

Multipotent Mesenchymal Stromal Stem Cell Expansion by Plating Whole Bone Marrow at a Low Cellular Density: A More Advantageous Method for Clinical Use

PubMed Central

Mareschi, Katia; Rustichelli, Deborah; Calabrese, Roberto; Gunetti, Monica; Sanavio, Fiorella; Castiglia, Sara; Risso, Alessandra; Ferrero, Ivana; Tarella, Corrado; Fagioli, Franca

2012-01-01

Mesenchymal stem cells (MSCs) are a promising source for cell therapy due to their pluripotency and immunomodulant proprieties. As the identification of “optimal” conditions is important to identify a standard procedure for clinical use. Percoll, Ficoll and whole bone marrow directly plated were tested from the same sample as separation methods. The cells were seeded at the following densities: 100 000, 10 000, 1000, 100, 10 cells/cm2. After reaching confluence, the cells were detached, pooled and re-plated at 1000, 500, 100, and 10 cells/cm2. Statistical analyses were performed. Cumulative Population Doublings (PD) did not show significant differences for the separation methods and seeding densities but only for the plating density. Some small quantity samples plated in T25 flasks at plating densities of 10 and 100 cells/cm2 did not produce any expansion. However, directly plated whole bone marrow resulted in a more advantageous method in terms of CFU-F number, cellular growth and minimal manipulation. No differences were observed in terms of gross morphology, differentiation potential or immunophenotype. These data suggest that plating whole bone marrow at a low cellular density may represent a good procedure for MSC expansion for clinical use. PMID:23715383

Thieving rodents as substitute dispersers of megafaunal seeds.

PubMed

Jansen, Patrick A; Hirsch, Ben T; Emsens, Willem-Jan; Zamora-Gutierrez, Veronica; Wikelski, Martin; Kays, Roland

2012-07-31

The Neotropics have many plant species that seem to be adapted for seed dispersal by megafauna that went extinct in the late Pleistocene. Given the crucial importance of seed dispersal for plant persistence, it remains a mystery how these plants have survived more than 10,000 y without their mutualist dispersers. Here we present support for the hypothesis that secondary seed dispersal by scatter-hoarding rodents has facilitated the persistence of these large-seeded species. We used miniature radio transmitters to track the dispersal of reputedly megafaunal seeds by Central American agoutis, which scatter-hoard seeds in shallow caches in the soil throughout the forest. We found that seeds were initially cached at mostly short distances and then quickly dug up again. However, rather than eating the recovered seeds, agoutis continued to move and recache the seeds, up to 36 times. Agoutis dispersed an estimated 35% of seeds for >100 m. An estimated 14% of the cached seeds survived to the next year, when a new fruit crop became available to the rodents. Serial video-monitoring of cached seeds revealed that the stepwise dispersal was caused by agoutis repeatedly stealing and recaching each other's buried seeds. Although previous studies suggest that rodents are poor dispersers, we demonstrate that communities of rodents can in fact provide highly effective long-distance seed dispersal. Our findings suggest that thieving scatter-hoarding rodents could substitute for extinct megafaunal seed dispersers of tropical large-seeded trees.

Polyhouse cultivation of invitro raised elite Stevia rebaudiana Bertoni: An assessment of biochemical and photosynthetic characteristics

USDA-ARS?s Scientific Manuscript database

Polyhouse cultivated Stevia rebaudiana Bertoni plants, initially raised from synthetic seeds, were assessed for biochemical and photosynthetic characteristics and compared with their mother plant. Synthetic seeds were produced using nodal segments containing single axillary buds excised from in vitr...

Removal of Malachite Green Dye by Mangifera indica Seed Kernel Powder

NASA Astrophysics Data System (ADS)

Singh, Dilbagh; Sowmya, V.; Abinandan, S.; Shanthakumar, S.

2017-11-01

In this study, batch experiments were carried out to study the adsorption of Malachite green dye from aqueous solution by Mangifera indica (mango) seed kernel powder. The mango seed kernel powder was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Effect of various parameters including pH, contact time, adsorbent dosage, initial dye concentration and temperature on adsorption capacity of the adsorbent was observed and the optimized condition for maximum dye removal was identified. Maximum percentage removal of 96% was achieved with an adsorption capacity of 22.8 mg/g at pH 6 with an initial concentration of 100 mg/l. The equilibrium data were examined to fit the Langmuir and Freundlich isotherm models. Thermodynamic parameters for the adsorption process were also calculated.

Development of resting membrane potentials in differentiating murine neuroblastoma cells (N1E-115) evaluated by flow cytometry.

PubMed

Kisaalita, W S; Bowen, J M

1997-09-01

With the aid of a voltage-sensitive oxonol dye, flow cytometry was used to measure relative changes in resting membrane potential (V(m)) and forward angle light scatter (FALS) profiles of a differentiating/differentiated murine neuroblastoma cell line (N1E-115). Electrophysiological differentiation was characterized by V(m) establishment. The (V(m))-time profile was found to be seed cell concentration-dependent for cell densities of less than 2 × 10(4) cells/cm(2). At higher initial cell densities, under differentiating culture conditions, V(m) development commenced on day 2 and reached a steady-state on day 12. The relative distribution of differentiated cells between low and high FALS has been proposed as a potential culture electrophysiological differentiation state index. These experiments offer a general methodology to characterize cultured excitable cells of nervous system origin, with respect to electrophysiological differentiation. This information is valuable in studies employing neuroblastoma cells as in vitro screening models for safety/hazard evaluation and/or risk assessment of therapeutical and industrial chemicals under development.

Proteomic analysis of the seed development in Jatropha curcas: from carbon flux to the lipid accumulation.

PubMed

Liu, Hui; Wang, Cuiping; Komatsu, Setsuko; He, Mingxia; Liu, Gongshe; Shen, Shihua

2013-10-08

To characterize the metabolic signatures of lipid accumulation in Jatropha curcas seeds, comparative proteomic technique was employed to profile protein changes during the seed development. Temporal changes in comparative proteome were examined using gels-based proteomic technique at six developmental stages for lipid accumulation. And 104 differentially expressed proteins were identified by MALDI-TOF/TOF tandem mass spectrometry. These protein species were classified into 10 functional categories, and the results demonstrated that protein species related to energy and metabolism were notably accumulated and involved in the carbon flux to lipid accumulation that occurs primarily from early to late stage in seed development. Glycolysis and oxidative pentose phosphate pathways were the major pathways of producing carbon flux, and the glucose-6-phosphate and triose-phosphate are the major carbon source for fatty acid synthesis. Lipid analysis revealed that fatty acid accumulation initiated 25days after flowering at the late stage of seed development of J. curcas. Furthermore, C16:0 was initially synthesized as the precursor for the elongation to C18:1 and C18:2 in the developing seeds of J. curcas. Together, the metabolic signatures on protein changes in seed development provide profound knowledge and perspective insights into understanding lipid network in J. curcas. Due to the abundant oil content in seeds, Jatropha curcas seeds are being considered as the ideal materials for biodiesel. Although several studies had carried out the transcriptomic project to study the genes expression profiles in seed development of J. curcas, these ESTs hadn't been confirmed by qRT-PCR. Yet, the seed development of J. curcas had been described for a pool of developing seeds instead of being characterized systematically. Moreover, cellular metabolic events are also controlled by protein-protein interactions, posttranslational protein modifications, and enzymatic activities which cannot be described by transcriptional profiling approaches alone. In this study, within the overall objective of profiling differential protein abundance in developing J. curcas seeds, we provide a setting of physiological data with dynamic proteomic and qRT-PCR analysis to characterize the metabolic pathways and the relationship between mRNA and protein patterns from early stage to seed filling during the seed development of J. curcas. The construction of J. curcas seed development proteome profiles will significantly increase our understanding of the process of seed development and provide a foundation to examine the dynamic changes of the metabolic network during seed development process and certainly suggest some clues to improve the lipid content of J. curcas seeds. © 2013. Published by Elsevier B.V. All rights reserved.

Mechanical properties of high density polyethylene--pennycress press cake composites

USDA-ARS?s Scientific Manuscript database

Pennycress press cake (PPC) is evaluated as a bio-based fiber reinforcement. PPC is a by-product of crop seed oil extraction. Composites with a high density polyethylene (HDPE) matrix are created by twin screw compounding of 25% by weight of PPC and either 0% or 5% by weight of maleated polyethyle...

Density gradients at hydrogel interfaces for enhanced cell penetration.

PubMed

Simona, B R; Hirt, L; Demkó, L; Zambelli, T; Vörös, J; Ehrbar, M; Milleret, V

2015-04-01

We report that stiffness gradients facilitate infiltration of cells through otherwise cell-impermeable hydrogel interfaces. By enabling the separation of hydrogel manufacturing and cell seeding, and by improving cell colonization of additively manufactured hydrogel elements, interfacial density gradients present a promising strategy to progress in the creation of 3D tissue models.

Numerical analysis of thermal stress and dislocation density distributions in large size multi-crystalline silicon ingots during the seeded growth process

NASA Astrophysics Data System (ADS)

Nguyen, Thi Hoai Thu; Chen, Jyh-Chen; Hu, Chieh; Chen, Chun-Hung; Huang, Yen-Hao; Lin, Huang-Wei; Yu, Andy; Hsu, Bruce

2017-06-01

In this study, a global transient numerical simulation of silicon growth from the beginning of the solidification process until the end of the cooling process is carried out modeling the growth of an 800 kg ingot in an industrial seeded directional solidification furnace. The standard furnace is modified by the addition of insulating blocks in the hot zone. The simulation results show that there is a significant decrease in the thermal stress and dislocation density in the modified model as compared to the standard one (a maximal decrease of 23% and 75% along the center line of ingot for thermal stress and dislocation density, respectively). This modification reduces the heating power consumption for solidification of the silicon melt by about 17% and shortens the growth time by about 2.5 h. Moreover, it is found that adjusting the operating conditions of modified model to obtain the lower growth rate during the early stages of the solidification process can lower dislocation density and total heater power.

Polarity reversals and tilt of the Earth's magnetic dipole

NASA Technical Reports Server (NTRS)

Dolginov, A. Z.

1993-01-01

There is evidence that the terrestrial magnetic field is connected with the Earth's mantle: (1) there are magnetic anomalies that do not take part in the westward drift of the main field, but are fixed with respect to the mantle; (2) the geomagnetic pole position flips in a particular way by preferred meridional paths during a reversal; and (3) magnetic polarity reversals are correlated with the activations of geological processes. These facts may be explained if we take into account that a significant horizontal temperature gradient can exist in the top levels of the liquid core because of the different thermoconductivity of the different areas of the core-mantle boundary. These temperature inhomogeneities can penetrate the core because fluxes along the core boundary (the thermal wind) can be strongly suppressed by a small redistribution of the chemical composition in the top of the core. The nonparallel gradients of the temperature, density, and composition on the top of the core create a curled electric field that produces a current and a magnetic field. This seed-field can be amplified by motions in the core. The resulting field does not forget the seed-field distribution and in this way the field on the Earth surface (that can be created only in regions with high conductivity, i.e. in the core) is connected with the core-mantle boundary. Contrary to the usual approach to the dynamo problem, we will take into account that the seed field of thermoelectric origin is acting not only at some initial moment of time but permanently.

Physicochemical Properties of Defatted Rambutan (Nephelium lappaceum) Seed Flour after Alkaline Treatment.

PubMed

Eiamwat, Jirawat; Wanlapa, Sorada; Kampruengdet, Sukit

2016-03-31

Rambutan seeds were subjected to SC-CO₂ extraction at 35 MPa, 45 °C to obtain defatted rambutan seed flour. Its physicochemical properties before and after treatment with alkali solution using 0.075 N NaOH were investigated. Alkali-treated flour had a significant increment in bulk density, swelling power, water adsorption capacity, emulsion capacity and stability but a reduction in turbidity, solubility and oil absorption capacity. Pasting measurements showed peak viscosity, breakdown, setback and final viscosity increased significantly for the alkali-treated flour, while pasting temperature decreased. The alkaline treatment decreased the least gelation concentration, but increased the apparent viscosity.