Seed Germination in Ginkgo biloba L. I. Influences of Cold Treatment, Gibberellic Acid and Red Light

The influences of cold treatment, gibberellic acid and red light treatment on rate of germination of seeds of Ginkgo biloba L. were followed for a 12-wk period. Dispersal units were collected, and the outer fleshy layer was removed soon after harvest. Of water-imbibed, non-cold-treated seeds, 50% of those which germinated did so within 11 wk after planting. A single application of red light accelerated the 50% germination time by 3 wk. Imbibition in GA3 solution did not appear to accelerate germination. With 4-wk cold treatment the 50% germination time was accelerated 6 wk in water-imbibed seeds. Both red light and GA3 treated seeds also were accelerated 6 wk by cold treatment. An 8-wk cold treatment accelerated the 50% germination time 7 wk for all three treatment groups. The influence of red light observed on non-cold-treated seeds was not seen with seeds receiving a cold treatment prior to irradiation. A 12-wk cold treatment period delayed germination in all treated groups. Dry storage of seeds for 4mo at 25 C also delayed germination regardless of red light, GA3 or cold treatment

Disjunct Lake Michigan Populations of Two Atlantic Coast Spiders, \u3ci\u3eDisembolus Bairdi\u3c/i\u3e and \u3ci\u3eGrammonota Pallipes\u3c/i\u3e (Araneae: Linyphiidae)

Two species of linyphiid spiders, Disembolus bairdi Edwards, 1999 and Grammonota pallipes Banks, 1895, were discovered along the southwestern coast of Lake Michigan in Lake County, Illinois representing an Atlantic Coastal Plain disjunct distribution. A brief discussion of known collection sites, habitat preferences, and possible modes of dispersal are given

Towards an exact reconstruction of a time-invariant model from time series data

Dynamic processes in biological systems may be profiled by measuring system properties over time. One way of representing such time series data is through weighted interaction networks, where the nodes in the network represent the measurables and the weighted edges represent interactions between any pair of nodes. Construction of these network models from time series data may involve seeking a robust data-consistent and time-invariant model to approximate and describe system dynamics. Many problems in mathematics, systems biology and physics can be recast into this form and may require finding the most consistent solution to a set of first order differential equations. This is especially challenging in cases where the number of data points is less than or equal to the number of measurables. We present a novel computational method for network reconstruction with limited time series data. To test our method, we use artificial time series data generated from known network models. We then attempt to reconstruct the original network from the time series data alone. We find good agreement between the original and predicted networks

Segmentation Analysis of Grocery Shoppers in Alabama

Using survey responses from over 500 responses, this paper conducts a market segmentation of grocery shoppers in Alabama. By employing cluster analysis technique, Alabama grocery shoppers are segmented into three different groups based on the relative importance of factors that describe their shopping experiences.Food Consumption/Nutrition/Food Safety,

Investigating Behavioral Responses to Positive Inducements for Filing Tax Returns

A significant amount of non-compliance associated with the personal income tax is due to the taxpayers who are not “in the system,” not having filed a tax return in the recent past or perhaps ever. We use experimental laboratory methods to examine two types of positive incentives for filing tax returns: tax credits and social safety net benefits, both of which are conditional on tax filing. Our experimental design captures the essential features of the voluntary income reporting and tax assessment system used in many countries. Human participants in a controlled laboratory environment earn income through their performance in a task. The participants must then decide whether to file a tax return and, conditional upon filing, how much income to report. Taxes are paid on reported income only. Unreported income of filers may be discovered via a random audit, and the participant must then pay the owed taxes plus a fine based on the unpaid taxes; non-filers are not subject to an audit. Inducements for filing are introduced in several alternative treatments. In one treatment we introduce a social safety net (e.g., unemployment replacement income) that is conditional on past filing behavior. In a second treatment we introduce tax credits that are available either to low income participants or to all income levels, but again only to those who file a tax return. Our results suggest that a tax credit increases filing but only if the credit is targeted to low income earners. The provision of a social safety net via unemployment benefits also has a positive, albeit indirect, impact on participation. Key Words:

Magnetic collimation of protostellar winds into bipolar outflows

Researchers describe self-consistent 2-D magnetohydrodynamic (MHD) simulations of the collimation of an isotropic protostellar wind into bipolar outflows by magnetic stresses in the ambient medium. A variety of ambient field strengths, wind luminosities, and density profiles were studied. Collimation occurs when the energy of the magnetic field swept up by the expanding bubble approaches the bubble thermal energy. Measured axial and radial expansion rates are in good agreement with the analytical predictions of Konigl (1982)

Clonal Interference, Multiple Mutations, and Adaptation in Large Asexual Populations

Two important problems affect the ability of asexual populations to accumulate beneficial mutations, and hence to adapt. First, clonal interference causes some beneficial mutations to be outcompeted by more-fit mutations which occur in the same genetic background. Second, multiple mutations occur in some individuals, so even mutations of large effect can be outcompeted unless they occur in a good genetic background which contains other beneficial mutations. In this paper, we use a Monte Carlo simulation to study how these two factors influence the adaptation of asexual populations. We find that the results depend qualitatively on the shape of the distribution of the effects of possible beneficial mutations. When this distribution falls off slower than exponentially, clonal interference alone reasonably describes which mutations dominate the adaptation, although it gives a misleading picture of the evolutionary dynamics. When the distribution falls off faster than exponentially, an analysis based on multiple mutations is more appropriate. Using our simulations, we are able to explore the limits of validity of both of these approaches, and we explore the complex dynamics in the regimes where neither are fully applicable.Comment: 24 pages, 5 figure

The Functions of the Multiproduct and Rapidly Evolving \u3cem\u3edec-1\u3c/em\u3e Eggshell Gene Are Conserved Between Evolutionarily Distant Species of Drosophila

The Drosophila dec-1 gene encodes multiple proteins that are required for female fertility and proper eggshell morphogenesis. Genetic and immunolocalization data suggest that the different DEC-1 proteins are functionally distinct. To identify regions within the proteins with potential biological significance, we cloned and sequenced the D. yakuba and D. virilis dec-1 homologs. Interspecies comparisons of the predicted translation products revealed rapidly evolving sequences punctuated by blocks of conserved amino acids. Despite extensive amino acid variability, the proteins produced by the different dec-1 homologs were functionally interchangeable. The introduction of transgenes containing either the D. yakuba or the D. virilis dec-1 open reading frames into a D. melanogaster DEC-1 protein null mutant was sufficient to restore female fertility and wild-type eggshell morphology. Normal expression and extracellular processing of the DEC-1 proteins was correlated with the phenotypic rescue. The nature of the conserved features highlighted by the evolutionary comparison and the molecular resemblance of some of these features to those found in other extracellular proteins suggests functional correlates for some of the multiple DEC-1 derivatives