Vegetative phase change among sweet corn (Zea mays L.) hybrids varying for reaction to common rust (Puccinia sorghi Schw.)     

M. A. Chandler    W. F. Tracy 《Plant Breeding》2007,126(6):569-573

In maize, timing of vegetative phase change has been implicated in the response to certain pests and environmental stresses. Common rust is the most serious disease of sweet corn in the north central United States. Sweet corn hybrids differing for resistance to common rust were evaluated for vegetative phase change traits. There were significant differences among hybrids for all vegetative phase change traits measured, as well as resistance to common rust. Certain hybrids displayed rapid transition (within two leaves) from juvenile to adult vegetation, while others displayed prolonged transition (within four leaves). There were no significant correlations between vegetative phase change traits and common rust severity among the commercial sweet corn hybrids evaluated in this experiment.  相似文献   

Book reviews     

Geoffrey Abers  Robert D. Cicerone  Douglas J. Galpin  William Power  Tracy Rushmer  et al. 《Euphytica》1990,51(3):281-284

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THE INFLUENCE OF CLIMATE AND SOIL ON THE TRANSMITTING POWER OF SEEDS     

Tracy WW 《Science (New York, N.Y.)》1904,19(488):738-740

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Paleoindian seafaring, maritime technologies, and coastal foraging on California's Channel Islands     

Erlandson JM  Rick TC  Braje TJ  Casperson M  Culleton B  Fulfrost B  Garcia T  Guthrie DA  Jew N  Kennett DJ  Moss ML  Reeder L  Skinner C  Watts J  Willis L 《Science (New York, N.Y.)》2011,331(6021):1181-1185

Three archaeological sites on California's Channel Islands show that Paleoindians relied heavily on marine resources. The Paleocoastal sites, dated between ~12,200 and 11,200 years ago, contain numerous stemmed projectile points and crescents associated with a variety of marine and aquatic faunal remains. At site CA-SRI-512 on Santa Rosa Island, Paleocoastal peoples used such tools to capture geese, cormorants, and other birds, along with marine mammals and finfish. At Cardwell Bluffs on San Miguel Island, Paleocoastal peoples collected local chert cobbles, worked them into bifaces and projectile points, and discarded thousands of marine shells. With bifacial technologies similar to those seen in Western Pluvial Lakes Tradition assemblages of western North America, the sites provide evidence for seafaring and island colonization by Paleoindians with a diversified maritime economy.  相似文献   

CO2-forced climate and vegetation instability during Late Paleozoic deglaciation     

Montañez IP  Tabor NJ  Niemeier D  Dimichele WA  Frank TD  Fielding CR  Isbell JL  Birgenheier LP  Rygel MC 《Science (New York, N.Y.)》2007,315(5808):87-91

The late Paleozoic deglaciation is the vegetated Earth's only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent ice-free world.  相似文献   

Restoration of tolerance in lupus by targeted inhibitory receptor expression     

McGaha TL  Sorrentino B  Ravetch JV 《Science (New York, N.Y.)》2005,307(5709):590-593

Lupus, a multigenic autoimmune condition in which a breakdown of tolerance results in the development of autoantibodies, leads to a variety of pathologic outcomes. Despite the heterogeneity of factors influencing disease susceptibility, we demonstrate that the partial restoration of inhibitory Fc receptor (FcgRIIB) levels on B cells in lupus-prone mouse strains is sufficient to restore tolerance and prevent autoimmunity. FcgRIIB regulates a common B cell checkpoint in genetically diverse lupus-prone mouse strains, and modest changes in its expression can result in either tolerance or autoimmunity. Therefore, increasing FcgammaRIIB levels on B cells may be an effective way to treat autoimmune diseases.  相似文献   

Perspectives on linear heat transfer     

Strunk TH  Tracy CR  Kleiber M 《Science (New York, N.Y.)》1973,181(4095):184-186

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Stable RNA/DNA hybrids in the mammalian genome: inducible intermediates in immunoglobulin class switch recombination     

Tracy RB  Hsieh CL  Lieber MR 《Science (New York, N.Y.)》2000,288(5468):1058-1061

Although it is well established that mammalian class switch recombination is responsible for altering the class of immunoglobulins, the mechanistic details of the process have remained unclear. Here, we show that stable RNA/DNA hybrids form at class switch sequences in the mouse genome upon cytokine-specific stimulation of class switch in primary splenic B cells. The RNA hybridized to the switch DNA is transcribed in the physiological orientation. Mice that constitutively express an Escherichia coli ribonuclease H transgene show a marked reduction in RNA/DNA hybrid formation, an impaired ability to generate serum immunoglobulin G antibodies, and significant inhibition of class switch recombination in their splenic B cells. These data provide evidence that stable RNA/DNA hybrids exist in the mammalian nuclear genome, can serve as intermediates for physiologic processes, and are mechanistically important for efficient class switching in vivo.  相似文献   

Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa   总被引：1，自引：0，他引：1  

Thompson LG  Mosley-Thompson E  Davis ME  Henderson KA  Brecher HH  Zagorodnov VS  Mashiotta TA  Lin PN  Mikhalenko VN  Hardy DR  Beer J 《Science (New York, N.Y.)》2002,298(5593):589-593

Six ice cores from Kilimanjaro provide an approximately 11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: approximately 8.3, approximately 5.2, and approximately 4 thousand years ago (ka). The latter is coincident with the "First Dark Age," the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between approximately 11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased approximately 80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020.  相似文献   

Modelling and mapping the suitability of European forest formations at 1-km resolution     

Stefano Casalegno  Giuseppe Amatulli  Annemarie Bastrup-Birk  Tracy Houston Durrant  Anssi Pekkarinen 《European Journal of Forest Research》2011,130(6):971-981

Proactive forest conservation planning requires spatially accurate information about the potential distribution of tree species. The most cost-efficient way to obtain this information is habitat suitability modelling i.e. predicting the potential distribution of biota as a function of environmental factors. Here, we used the bootstrap-aggregating machine-learning ensemble classifier Random Forest (RF) to derive a 1-km resolution European forest formation suitability map. The statistical model use as inputs more than 6,000 field data forest inventory plots and a large set of environmental variables. The field data plots were classified into different forest formations using the forest category classification scheme of the European Environmental Agency. The ten most dominant forest categories excluding plantations were chosen for the analysis. Model results have an overall accuracy of 76%. Between categories scores were unbalanced and Mesophitic deciduous forests were found to be the least correctly classified forest category. The model’s variable ranking scores are used to discuss relationship between forest category/environmental factors and to gain insight into the model’s limits and strengths for map applicability. The European forest suitability map is now available for further applications in forest conservation and climate change issues.  相似文献