When is Commuting Desirable to the Individual?     

David T. Ory  Patricia L. Mokhtarian  Lothlorien S. Redmond  Ilan Salomon  Gustavo O. Collantes  Sangho Choo 《Growth and change》2004,35(3):334-359

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Variation of Phyllosphere Microflora of Different Rice Varieties in Sri Lanka and its Relationship to Leaf Anatomical and Physiological Characters   总被引：2，自引：0，他引：2  

D. M. De Costa  R. M. P. S. Rathnayake  W. A. J. M. De Costa  W. M. D. Kumari  D. M. N. Dissanayake 《Journal of Agronomy and Crop Science》2006,192(3):209-220

Anatomical and physiological characters of the leaf surface and its physico‐chemical environment substantially influence the density and diversity of phyllosphere‐inhabiting microorganisms, which may include natural antagonists of important pathogens. The objective of this investigation was to quantify the phyllosphere (i.e. leaf surface) microbial population in a range of rice varieties grown in Sri Lanka and to identify the leaf anatomical and physiological characters that determine the density and diversity of phyllosphere microbes. Fifteen rice varieties including both traditional and new high‐yielding varieties were used in a planthouse experiment and a field experiment in two consecutive seasons to quantify the phyllosphere microbial population and measure leaf characters that may influence it. There were highly significant intervarietal variations in the density and diversity of epiphytic bacterial, fungal and total microbial populations under both planthouse and field conditions. However, there was no difference between traditional and new, high‐yielding varieties in their capacity to harbour epiphytic microbes in the phyllosphere. Total microbial density (TMD) under both conditions showed positive correlations with leaf hair density, stomatal density and transpiration rate. Under planthouse conditions, TMD was also positively correlated with leaf hair length and negatively correlated with leaf temperature. These correlations can be explained in terms of providing favourable microsites on the phylloplane for epiphytic microbial growth.  相似文献   

Breeding Panicum maximum in Brazil. 1. Genetic resources,modes of reproduction and breeding procedures     

Y. H. Savidan  L. Jank  J. C. G. Costa  C. B. do Valle 《Euphytica》1989,41(1-2):107-112

Summary Apomixis is widely distributed among tropical forage grasses, and has long been merely regarded as an impediment to breeding. Panicum maximum is presented as the first opportunity for Brazilian geneticists to develop and test original breeding schemes adapted to an apomictic species.A large and representative germplasm of P. maximum has been introduced and is currently being evaluated. Basic knowledges on biology and reproduction are also available, which demonstrate an easy manipulation of apomixis and sexuality. Several limiting traits have already been detected during evaluation, which justify breeding attempts. An ideal scheme is given to transfer new qualities to already selected varieties.  相似文献   

Interaction of the mutant genes B,og c,hp and t in the coloring of tomato fruit     

Thiago Matos Andrade  Wilson Roberto Maluf  Celso Mattes de Oliveira  Luiz Antônio Augusto Gomes  Daniela Costa Santos  Regis de Castro Carvalho  Ranoel José de Sousa Gonçalves  Álvaro Carlos Gonçalves Neto 《Euphytica》2015,205(3):773-783

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Grain weight responses to post-anthesis spikelet-trimming in an old and a modern wheat under Mediterranean conditions     

Julia Cartelle  Anna Pedr  Roxana Savin  Gustavo A. Slafer 《European Journal of Agronomy》2006,25(4):365-371

Average grain weight is a major yield component contributing to its variation, especially in Mediterranean regions where grain weight is frequently exposed to terminal stresses affecting grain growth. Most of the literature agrees that wheat grain growth is hardly limited by the source. However, no source–sink ratios studies seem to have been conducted in the Mediterranean region to determine to what degree wheat grain growth is actually limited by the source in these particular regions. We conducted two field experiments in Catalonia (north-eastern Spain), where an old cultivar (Anza) and a more recently released one (Soissons) were sown in a range of different nitrogen and water availabilities and sowing dates. This was to analyse the degree of source limitation for grain growth. Sink size was modified by removing half of the spikelets c. 10 days after anthesis, virtually doubling the availability of assimilates per grain effectively growing.

Trimming the spikes did not produce significant changes in grain growth rate or duration of grain filling. Consequently, grain weight did not respond noticeably to the reduction in sink demand and any eventual response has been far from representing a strong competition among grains during grain filling.  相似文献   

Absorption of calcium fumarate salts is equivalent to other calcium salts when measured in the rat model   总被引：3，自引：0，他引：3  

Weaver CM  Martin BR  Costa NM  Saleeb FZ  Huth PJ 《Journal of agricultural and food chemistry》2002,50(17):4974-4975

Calcium absorption from fumarate salts (calcium fumarate and calcium malate fumarate), which have recently been considered for use as sources for food and beverage enrichment, was compared to that from calcium citrate malate, calcium citrate, and calcium carbonate. Salts were instrinsically labeled with 45Ca and orally administered to Sprague-Dawley rats. Fractional absorption of calcium from each salt was determined using the femur uptake model. Fractional absorption from the five salts (0.30-0.27) was not significantly different (p > 0.05). Thus, when measured in the rat model, calcium from calcium fumarate and calcium malate fumarate is absorbed equally well as compared to other salts, which are common calcium sources in many foods, beverages, and supplements.  相似文献   

Heavy Metal Contamination in Sediments of Lake Nahuel Huapi,Nahuel Huapi National Park,Northern Patagonia,Argentina     

Ribeiro Guevara  Sergio  Massaferro  Julieta  Villarosa  Gustavo  Arribére  María  Rizzo  Andrea 《Water, air, and soil pollution》2002,137(1-4):21-44

Trace metals (Sb, As, Br, Cs, Co, Cr, Ag and Hg), rare earth elements (Ce, Eu, La, Lu, Sm, Tb and Yb), and Sc. were analysed in suspended load and in two sediment cores from Lake Nahuel Huapi, Nahuel Huapi National Park, Patagonia, Argentina, by using Instrumental Neutron Activation Analysis. The core activity profiles of ²¹⁰Pb and ¹³⁷Cs were measured to estimate the age of the sediments. Silver was enriched in the upper layers of both cores, and correlated with the strong growthof the population of Bariloche City in the last 50 yr. Concentrations are higher in the core sampled near Bariloche, andindicate some transport in the water body. Silver concentrationsmeasured in the suspended load were 4.58±0.36 and 3.46±0.40 μg g^-1 in the southern margin of the lake, near San Carlos de Bariloche City, whereas in the northern margin the concentrations were 1.68±0.18 and 1.88±0.23 μg g^-1. Concentration ratio for silver in suspended load and upper core layers were equal in both sampling points. These facts suggest that Ag contents correspond to inputs associated with human activities. Bromine concentrations show a strong increase abovebase line values, similar to silver. In contrast, caesium, chromium, and cobalt concentrations do not differ from base linevalues. The metalloids antimony and arsenic show little variationwith regard to base line concentration. Noticeable, the mercurycontents found in the suspended load.  相似文献   

Observation of X-ray lines from a gamma-ray burst (GRB991216): evidence of moving ejecta from the progenitor     

Piro L  Garmire G  Garcia M  Stratta G  Costa E  Feroci M  Mészáros P  Vietri M  Bradt H  Frail D  Frontera F  Halpern J  Heise J  Hurley K  Kawai N  Kippen RM  Marshall F  Murakami T  Sokolov VV  Takeshima T  Yoshida A 《Science (New York, N.Y.)》2000,290(5493):955-958

We report on the discovery of two emission features observed in the x-ray spectrum of the afterglow of the gamma-ray burst (GRB) of 16 December 1999 by the Chandra X-ray Observatory. These features are identified with the Ly(alpha) line and the narrow recombination continuum by hydrogenic ions of iron at a redshift z = 1.00 +/- 0.02, providing an unambiguous measurement of the distance of a GRB. Line width and intensity imply that the progenitor of the GRB was a massive star system that ejected, before the GRB event, a quantity of iron approximately 0.01 of the mass of the sun at a velocity approximately 0.1 of the speed of light, probably by a supernova explosion.  相似文献   

A molecular basis for natural selection at the timeless locus in Drosophila melanogaster     

Sandrelli F  Tauber E  Pegoraro M  Mazzotta G  Cisotto P  Landskron J  Stanewsky R  Piccin A  Rosato E  Zordan M  Costa R  Kyriacou CP 《Science (New York, N.Y.)》2007,316(5833):1898-1900

Diapause is a protective response to unfavorable environments that results in a suspension of insect development and is most often associated with the onset of winter. The ls-tim mutation in the Drosophila melanogaster clock gene timeless has spread in Europe over the past 10,000 years, possibly because it enhances diapause. We show that the mutant allele attenuates the photosensitivity of the circadian clock and causes decreased dimerization of the mutant TIMELESS protein isoform to CRYPTOCHROME, the circadian photoreceptor. This interaction results in a more stable TIMELESS product. These findings reveal a molecular link between diapause and circadian photoreception.  相似文献   

The ubiquitin ligase SCFFbw7 antagonizes apoptotic JNK signaling     

Nateri AS  Riera-Sans L  Da Costa C  Behrens A 《Science (New York, N.Y.)》2004,303(5662):1374-1378

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