Stress wave velocity,basic density,and compressive strength in 34-year-old <Emphasis Type="Italic">Pinus merkusii</Emphasis> planted in Indonesia     

Futoshi Ishiguri  Kazuko Makino  Imam Wahyudi  Yuya Takashima  Kazuya Iizuka  Shinso Yokota  Nobuo Yoshizawa 《Journal of Wood Science》2011,57(6):526-531

The relationship between the growth speed and wood properties of Pinus merkusii was investigated using 34-year-old trees planted in Indonesia in an attempt to promote the establishment of plantation of this species. The trees in the test plot were categorized as fast, middle, or slow growing according to the mean stem diameter and standard deviation in the plot. Five trees were selected from each category to investigate the effects of the growth rate on the wood properties [basic density (BD) and compressive strength parallel to the grain in a 5-mm-diameter core sample (CS)]. No significant correlation was recognized between the stem diameter and the stress wave velocity of trees. Clearly lower values of BD and CS were found in slow-growing trees than in fast- and middle-growing trees. The BD of xylem near the pith was reduced by extraction with organic solvent. BD after extraction and CS gradually increased from pith to bark. The results obtained in this study clarified that an early selection of trees with high BD is possible by using the BD after extraction at 4 cm from the pith.  相似文献   

High-Energy Charged Particles in the Innermost Jovian Magnetosphere     

HM Fischer  E Pehlke  G Wibberenz  LJ Lanzerotti  JD Mihalov 《Science (New York, N.Y.)》1996,272(5263):856-858

The energetic particles investigation carried by the Galileo probe measured the energy and angular distributions of the high-energy particles from near the orbit of Io to probe entry into the jovian atmosphere. Jupiter's inner radiation region had extremely large fluxes of energetic electrons and protons; intensities peaked at approximately2.2RJ (where RJ is the radius of Jupiter). Absorption of the measured particles was found near the outer edge of the bright dust ring. The instrument measured intense fluxes of high-energy helium ions (approximately62 megaelectron volts per nucleon) that peaked at approximately1.5RJ inside the bright dust ring. The abundances of all particle species decreased sharply at approximately1.35RJ; this decrease defines the innermost edge of the equatorial jovian radiation.  相似文献   

Evidence for Glacial Control of Rapid Sea Level Changes in the Early Cretaceous   总被引：2，自引：0，他引：2  

HM Stoll  DP Schrag 《Science (New York, N.Y.)》1996,272(5269):1771-1774

Lower Cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves. Strontium data from an interval spanning 7 million years in the Berriasian-Valanginian imply that global sea level fluctuated about 50 meters over time scales of 200,000 to 500,000 years, which is in agreement with the Exxon sea level curve. Oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes. If glaciation caused all the rapid sea level changes in the Cretaceous that are indicated by the Exxon curve, then an Antarctic ice sheet may have existed despite overall climatic warmth.  相似文献   

Gene expression during the life cycle of Drosophila melanogaster     

Arbeitman MN  Furlong EE  Imam F  Johnson E  Null BH  Baker BS  Krasnow MA  Scott MP  Davis RW  White KP 《Science (New York, N.Y.)》2002,297(5590):2270-2275

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Screening wheat germplasm for seedling root architectural traits under contrasting water regimes: potential sources of variability for drought adaptation     

Jafar Ahmadi  Alireza Pour-Aboughadareh  Sedigheh Fabriki-Ourang  Ali-Ashraf Mehrabi  Kadambot HM Siddique 《Archives of Agronomy and Soil Science》2018,64(10):1351-1365

In this study, we selected 180 accessions from different wild relatives of wheat (Aegilops–Triticum species) and tested them in the presence of a tolerant and a sensitive control variety under well-watered and drought-stressed conditions. The results of analysis of variance for dry masses and all measured root traits showed that water regimes, accession and species main effects were highly significant. Drought stress significantly declined shoot dry mass (59.42%), root length (37.85%) and the total number of branch roots (36.25%), but increased the root-to-shoot ratio (75.00%), specific root length (64.19%) and root tissue density (29.46%). Principal component analysis for 182 individuals and 12 species groups identified two components that explained 75.67 and 82.39% of the total variation in dry mass and root traits under drought-stressed conditions, respectively. Taking together, our results identified 12 accessions with superior tolerance to drought stress. Remarkably, four species of wild relatives – Ae. cylindrica (DC genome), Ae. neglecta (UM genome), Ae. speltoides (B genome) and Ae. tauschii (D genome) – responded well to drought stress. The potential of these species could be used for molecular analysis such as marker assisted selection and gene mapping, ultimately aimed at breeding for root traits with improved adaptation to drought environments.  相似文献