Influence of soil moisture stress and soil bulk density on the imbibition of corn seeds in a sandy soil     

G. Collins  E. Stibbe  B. Kroesbergen 《Soil & Tillage Research》1984,4(4):361-370

The imbibition of corn seeds (Zea mays L.) was examined in a sandy soil compacted to simulate the effect that might be expected from pressure wheels behind a planting machine.Water uptake was found to be exponential and to be the only factor contributing to the increase in volume of the seed during imbibition. Changes in bulk density of the soil over the range from 0.90 to 1.31 Mg cm^?3 produced no significant effects on water uptake.It was therefore concluded that the degree of contact between seed coat and soil particles is not an important factor in influencing the rate of imbibition of corn seeds under the specific conditions which were examined.Water flux into the seeds was calculated to be several orders of magnitude lower than bulk soil water flux at all soil water potentials tested. Estimates of seed coat permeability suggest that, for corn, this factor is the major restriction on entry of water into the seed during imbibition.At a field level, the widespread use of pressure wheels behind corn planters as a means of increasing seed/soil contact appears not to be necessary in sandy soils.  相似文献   

Laboratory studies of crust development in Irish and Iraqi soils. III. Micromorphological observations of artificially-formed crusts     

J. F. Collins  G. W. Smillie

S. M. Hussain 《Soil & Tillage Research》1986,6(4):337-350

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Crop and soil response to subsoil loosening, deep incorporation of phosphorus and potassium fertilizer and subsequent soil management on a range of soil types.: Part 2: Soil structural conditions   总被引：2，自引：0，他引：2  

G.C. Soane  R.J. Godwin  MJ. Marks  G. Spoor 《Soil Use and Management》1987,3(3):123-130

Abstract. In a series of experiments on 16 sites both a power-driven rotary-tine Wye Double Digger and a rigid tine winged subsoiler produced significant subsoil loosening and fissuring. The Double Digger consistently produced the greatest clod breakdown together with the least soil bulk densities and cone penetration resistances. Management strategies after loosening had an important influence on the longevity of the loosening effect. The rate of recompaction was least with controlled traffic and bed systems and increased with random traffic and with the growing of root crops. No significant differences in crop response were monitored between the two loosening treatments, yield response depending largely on the extent of moisture stress experienced by the crop. Loosening on silty soils reduced yields in wet seasons and this was associated with soil structural instability. Visual soil profile examination is necessary to support bulk density and cone penetration resistance measurements when assessing soil compaction.  相似文献   

Soil microbial, fungal, and nematode responses to soil fumigation and cover crops under potato production     

H. P. Collins  A. Alva  R. A. Boydston  R. L. Cochran  P. B. Hamm  A. McGuire  E. Riga 《Biology and Fertility of Soils》2006,42(3):247-257

Sodium N-methyldithiocarbamate (metam sodium) and 1,3 dichloropropene are widely used in potato production for the control of soil-borne pathogens, weeds, and plant parasitic nematodes that reduce crop yield and quality. Soil fumigation with metam sodium has been shown in microcosm studies to significantly reduce soil microbial populations and important soil processes such as C and N mineralization. However, few published data report the impact of metam sodium on microbial populations and activities in potato production systems under field conditions. Fall-planted white mustard (Brassica hirta) and sudangrass (Sorghum sudanense) cover crops may serve as an alternative to soil fumigation. The effect of metam sodium and cover crops was determined on soil microbial populations, soil-borne pathogens (Verticillium dahliae, Pythium spp., and Fusarium spp.), free-living and plant-parasitic nematodes, and C and N mineralization potentials under potato production on five soil types in the Columbia Basin of Eastern Washington. Microbial biomass C was 8–23% greater in cover crop treatments compared to those fumigated with metam sodium among the soil types tested. Replacing fumigation with cover crops did not significantly affect C or N mineralization potentials. Cumulative N mineralized over a 49-day laboratory incubation averaged 18 mg NO₃-N kg⁻¹ soil across all soil types and treatments. There was a general trend for N mineralized from fumigated treatments to be lower than cover-cropped treatments. Soil fungal populations and free-living nematode levels were significantly lowered in fumigated field trials compared to cover-cropped treatments. Fumigation among the five soil types significantly reduced Pythium spp. by 97%, Fusarium spp. by 84%, and V. dahliae by 56% compared to the mustard cover crop treatment. The percentage of bacteria and fungi surviving fumigation was greater for fine- than coarse-textured soils, suggesting physical protection of organisms within the soil matrix or a reduced penetration and distribution of the fumigants. This suggests the potential need for a higher rate of fumigant to be used in fine-textured soils to obtain comparable reductions in soil-borne pathogens.  相似文献   

Influence of a probiotic adjunct culture of Enterococcus faecium on the quality of cheddar cheese   总被引：1，自引：0，他引：1  

Gardiner GE  Ross RP  Wallace JM  Scanlan FP  Jägers PP  Fitzgerald GF  Collins JK  Stanton C 《Journal of agricultural and food chemistry》1999,47(12):4907-4916

Cheddar cheese has previously been shown to be an effective vehicle for delivery of viable cells of a probiotic Enterococcus faecium strain to the gastrointestinal tract. The particular strain, E. faecium PR88, has proven efficacy in the treatment of irritable bowel syndrome, and in this study it was evaluated for suitability as a starter adjunct for Cheddar cheese manufacture. When added to cheesemilk at an inoculum of 2 x 10(7) cfu/mL, the enterococcal adjunct maintained viability in Cheddar cheese at levels of up to 3 x 10(8) cfu/g during 9 months of ripening. Increased proteolysis and higher levels of some odor-active volatile compounds were observed in Cheddar cheeses containing the PR88 adjunct compared with the control throughout the ripening period. In addition, the enterococcal adjunct strain did not affect cheese composition. Although sensory evaluation showed no significant difference in flavor/aroma and body/texture scores between control and experimental cheeses, repeated comments by the commercial grader consistently described the cheeses containing PR88 as 'more advanced than the control' and as having 'better flavor'. These findings indicate that the presence of the PR88 adjunct strain in Cheddar cheese at levels of >/=10(8) cfu/g may positively influence Cheddar flavor.  相似文献   

Generating solitons by phase engineering of a bose-einstein condensate     

Denschlag J  Simsarian JE  Feder DL  Clark CW  Collins LA  Cubizolles J  Deng L  Hagley EW  Helmerson K  Reinhardt WP  Rolston SL  Schneider BI  Phillips WD 《Science (New York, N.Y.)》2000,287(5450):97-101

Quantum phase engineering is demonstrated with two techniques that allow the spatial phase distribution of a Bose-Einstein condensate (BEC) to be written and read out. A quantum state was designed and produced by optically imprinting a phase pattern onto a BEC of sodium atoms, and matter-wave interferometry with spatially resolved imaging was used to analyze the resultant phase distribution. An appropriate phase imprint created solitons, the first experimental realization of this nonlinear phenomenon in a BEC. The subsequent evolution of these excitations was investigated both experimentally and theoretically.  相似文献   

Construction of a general human chromosome jumping library, with application to cystic fibrosis   总被引：22，自引：0，他引：22  

F S Collins  M L Drumm  J L Cole  W K Lockwood  G F Vande Woude  M C Iannuzzi 《Science (New York, N.Y.)》1987,235(4792):1046-1049

In many genetic disorders, the responsible gene and its protein product are unknown. The technique known as "reverse genetics," in which chromosomal map positions and genetically linked DNA markers are used to identify and clone such genes, is complicated by the fact that the molecular distances from the closest DNA markers to the gene itself are often too large to traverse by standard cloning techniques. To address this situation, a general human chromosome jumping library was constructed that allows the cloning of DNA sequences approximately 100 kilobases away from any starting point in genomic DNA. As an illustration of its usefulness, this library was searched for a jumping clone, starting at the met oncogene, which is a marker tightly linked to the cystic fibrosis gene that is located on human chromosome 7. Mapping of the new genomic fragment by pulsed field gel electrophoresis confirmed that it resides on chromosome 7 within 240 kilobases downstream of the met gene. The use of chromosome jumping should now be applicable to any genetic locus for which a closely linked DNA marker is available.  相似文献   

Increased insulin sensitivity and obesity resistance in mice lacking the protein tyrosine phosphatase-1B gene   总被引：1，自引：0，他引：1  

Elchebly M  Payette P  Michaliszyn E  Cromlish W  Collins S  Loy AL  Normandin D  Cheng A  Himms-Hagen J  Chan CC  Ramachandran C  Gresser MJ  Tremblay ML  Kennedy BP 《Science (New York, N.Y.)》1999,283(5407):1544-1548

Protein tyrosine phosphatase-1B (PTP-1B) has been implicated in the negative regulation of insulin signaling. Disruption of the mouse homolog of the gene encoding PTP-1B yielded healthy mice that, in the fed state, had blood glucose concentrations that were slightly lower and concentrations of circulating insulin that were one-half those of their PTP-1B+/+ littermates. The enhanced insulin sensitivity of the PTP-1B-/- mice was also evident in glucose and insulin tolerance tests. The PTP-1B-/- mice showed increased phosphorylation of the insulin receptor in liver and muscle tissue after insulin injection in comparison to PTP-1B+/+ mice. On a high-fat diet, the PTP-1B-/- and PTP-1B+/- mice were resistant to weight gain and remained insulin sensitive, whereas the PTP-1B+/+ mice rapidly gained weight and became insulin resistant. These results demonstrate that PTP-1B has a major role in modulating both insulin sensitivity and fuel metabolism, thereby establishing it as a potential therapeutic target in the treatment of type 2 diabetes and obesity.  相似文献   

Boron-toxicity tolerance in barley arising from efflux transporter amplification   总被引：1，自引：0，他引：1  

Sutton T  Baumann U  Hayes J  Collins NC  Shi BJ  Schnurbusch T  Hay A  Mayo G  Pallotta M  Tester M  Langridge P 《Science (New York, N.Y.)》2007,318(5855):1446-1449

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Evolution of supergene families associated with insecticide resistance   总被引：5，自引：0，他引：5  

Ranson H  Claudianos C  Ortelli F  Abgrall C  Hemingway J  Sharakhova MV  Unger MF  Collins FH  Feyereisen R 《Science (New York, N.Y.)》2002,298(5591):179-181

The emergence of insecticide resistance in the mosquito poses a serious threat to the efficacy of many malaria control programs. We have searched the Anopheles gambiae genome for members of the three major enzyme families- the carboxylesterases, glutathione transferases, and cytochrome P450s-that are primarily responsible for metabolic resistance to insecticides. A comparative genomic analysis with Drosophila melanogaster reveals that a considerable expansion of these supergene families has occurred in the mosquito. Low gene orthology and little chromosomal synteny paradoxically contrast the easily identified orthologous groups of genes presumably seeded by common ancestors. In A. gambiae, the independent expansion of paralogous genes is mainly a consequence of the formation of clusters among locally duplicated genes. These expansions may reflect the functional diversification of supergene families consistent with major differences in the life history and ecology of these organisms. These data provide a basis for identifying the resistance-associated enzymes within these families. This will enable the resistance status of mosquitoes, flies, and possibly other holometabolous insects to be monitored. The analyses also provide the means for identifying previously unknown molecules involved in fundamental biological processes such as development.  相似文献