Physiological determinants of maize and sunflower grain yield as affected by nitrogen supply   总被引：1，自引：0，他引：1  

A.M. Massignam  S.C. Chapman  G.L. Hammer  S. Fukai   《Field Crops Research》2009,113(3):256-267

Utilisation of nitrogen (N) has been closely related to increases in crop productivity. However, not all crops respond similarly and the objective of this study is to identify physiological processes that determine responses to N supply for maize and sunflower. Grain yield in maize (range: 210–1255 g m⁻²) was greater and more responsive to N supply than in sunflower (106–555 g m⁻² in carbohydrate equivalents) over a wide range of total N uptake (3–>20 g N m⁻²). In maize, differences in grain yield among levels of N supply were associated more with variation in biomass than in harvest index. In sunflower, differences in grain yield (in carbohydrate equivalents) among levels of N supply were related similarly to variation in both biomass and harvest index. The decrease in biomass production with decreasing N supply was associated with decreases in both radiation interception and radiation use efficiency (RUE). Decreased interception was due to effects of N supply on reducing canopy leaf area, whereas the reduced RUE was associated with decreased SLN. Total biomass production in maize was more responsive to N supply than in sunflower. The major determinants of the differences in response of biomass accumulation to N supply found between maize and sunflower are: (i) sunflower tends to maintain SLN with increase in partitioning of N to leaves under N limitation whereas maize tends to maintain leaf area with increase in partitioning of biomass to leaves and (ii) the ability of maize to maintain N uptake following cessation of leaf production.  相似文献   

Africa’s wooden elephant: the baobab tree (Adansonia digitata L.) in Sudan and Kenya: a review     

Jens Gebauer  Yahia O. Adam  Aida Cuní Sanchez  Dietrich Darr  Muneer E. S. Eltahir  Kamal E. M. Fadl  Gabriele Fernsebner  Michael Frei  Tsige-Yohannes Habte  Karl Hammer  Mauricio Hunsche  Henry Johnson  Maha Kordofani  Michael Krawinkel  Florian Kugler  Eike Luedeling  Tarig E. Mahmoud  Anthony Maina  Dagmar Mithöfer  Chimuleke R. Y. Munthali  Georg Noga  Rabea North  Willis O. Owino  Kathleen Prinz  Freda K. Rimberia  Amina Saied  Martin Schüring  Anne Sennhenn  Martin A. Späth  Mohamed E. N. Taha  Andreas Triebel  Florian Wichern  Martin Wiehle  Nicole Wrage-Mönnig  Katja Kehlenbeck 《Genetic Resources and Crop Evolution》2016,63(3):377-399

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Gross Measurements of the Digestive Tract and Visceral Organs of Addax Antelope (Addax nasomaculatus) Following a Concentrate or Forage Feeding Regime          下载免费PDF全文

S. A. Tahas  O. Martin Jurado  S. Hammer  A. Arif  S. Reese  J.‐M. Hatt  M. Clauss 《Anatomia, histologia, embryologia》2017,46(3):282-293

Differences in macroscopic measurements of the gastrointestinal tract have been hypothesized to correlate with the browser–grazer continuum in the natural diet of ruminants. However, to what extent these characteristics represent species‐specific traits, or respond to the actually ingested diet, remains to be investigated. Twelve surplus addax antelope (Addax nasomaculatus) were divided into two groups and fed, for 3 months, either their usual diet, consisting of a concentrate feed with a limited amount of hay, or a diet of unlimited hay only. After culling, macroscopic measurements were compared between groups. The macroscopic anatomy of the addax showed many characteristics considered typical for grazing or ‘cattle‐type’ ruminants. While both diet groups had mesenteric, pericardial and perirenal adipose tissue, these depots were subjectively more pronounced in concentrate‐fed animals. Hay‐fed animals had significantly heavier filled forestomach compartments, with corresponding significantly longer linear measurements. Masseter muscles and the surface of first‐order omasal leaves were significantly more prominent in hay‐fed animals, reflecting possible adaptations to overcome resistance of grass forage and to reabsorb fluid from increased rumination, but differences were not as distinct as reported between ‘cattle‐type’ and ‘moose‐type’ ruminants. Some measurements such as reticular crests and empty foregut mass remained stable between groups, indicating possibly genetically pre‐defined characteristics less prone to change in adult life. The results emphasize the adaptability of ruminant digestive tract anatomy in adult animals even after a short period of time, but also suggest limits to this adaptability that reveals a species‐specific anatomy regardless of the diet actually consumed.  相似文献   

Characterization of a PCR‐based lymphocyte clonality assay as a complementary tool for the diagnosis of feline lymphoma          下载免费PDF全文

S. E. Hammer  S. Groiss  A. Fuchs‐Baumgartinger  N. Nedorost  V. Gress  N. Luckschander‐Zeller  A. Saalmüller  I. Schwendenwein  B. C. Rütgen 《Veterinary and comparative oncology》2017,15(4):1354-1369

Differentiation between resident mature lymphocyte populations and small cell lymphoma cannot be made by cytological review alone and remains challenging in histopathological review. These cases warrant application of complementary tools like PCR‐based immunoglobulin (IG) and T‐cell receptor (TCR) clonality testing for confirmation. In this prospective study, diagnostic sensitivity and specificity of different primer sets for routine diagnosis of feline TCR gamma (TCRG) and complete IG heavy chain (IGH) gene rearrangements were assessed. Fine needle aspirates from 20 feline lymphoma cases and lymph node material from 10 cats without hematopoietic neoplasia were subjected to clonality testing. Feline lymphoma cell lines and previously confirmed patient material served as positive control. Detection limits for clonal populations within a polyclonal background was 90% for B‐cells and 50% for T‐cells. Diagnostic sensitivity and specificity of the clonality assay were 70% and 90%. Overall diagnostic accuracy was 77%, positive predictive value 93% and negative predictive value 60%.  相似文献   

Current distribution of older and deciduous forests as legacies from historical use patterns in a Swedish boreal landscape (1725–2007)     

Sofia Eriksson  Helle Skånes  Monica Hammer  Mikael Lönn 《Forest Ecology and Management》2010

We combine historical maps and satellite derived data to reconstruct the development of a Swedish boreal landscape over the past 300 years. The aim is to understand legacies from past use patterns in present-day forest composition and consequences for conservation objectives from a landscape perspective. We analyze landscape development in cross-tabulation matrixes, building change trajectories. These trajectories are tested in linear models to explain the distribution of present-day landscape composition of coniferous, mixed, and deciduous forests >110 years. Of 49 tested change trajectories, 11 showed a significant association. Associations for mixed and coniferous forests were similar and linked to characteristics such as forest continuity, which characterized the studied landscape. Deciduous older forests did not show any association to forest continuity but were more likely to occur on areas that specifically shifted from forests with grazing in the 1720s to open impediment (likely indicating low tree coverage) in the 1850s. There were large shifts and spatial redistribution in ownerships over time. Use patterns and legacies varied between small- and large-scale ownership categories as well as within small-scale categories. The legacies found in the study indicate a complex origin of heterogeneous landscape elements such as older deciduous forests. Additionally, the origin of the legacies indicates a potential need to diversify conservation management based on the influence of past use patterns. Despite large inconsistencies in historical and contemporary data we argue that this type of analysis could be used to further understand the distribution of landscape elements important for conservation objectives.  相似文献   

Determination of grain number in sorghum   总被引：1，自引：0，他引：1  

E.J. van Oosterom  G.L. Hammer 《Field Crops Research》2008

Grain number is an important component of grain yield in sorghum. Research in wheat and maize has indicated a dependency of grain number on the crop or panicle growth rate around anthesis (CGR_a and PGR_a respectively), but little quantitative information is available for sorghum. The aim of this paper was firstly to quantify the effect of CGR_a and PGR_a on grain number and secondly, to identify other parameters that could be used as substitutes for PGR_a. Analyses included data from a number of experiments, covering a range in nitrogen and drought treatments and including both tall (single dwarf) and short (triple dwarf) hybrids. CGR_a and SGR_a (stem growth rate) were calculated from the derivative of a curvilinear function fitted to experimental data, and PGR_a was obtained by subtraction of SGR_a from CGR_a. Results indicated a linear relationship between grain number and CGR_a, but the slope differed for tall and short hybrids. This was due to a difference in the proportion of dry matter allocated to the reproductive organs around anthesis (P_r), as PGR_a was closely related to grain number, irrespective of crop height. Since panicle dry mass at maturity (excluding grain) was closely correlated with reproductive biomass shortly after anthesis, this indicator represents an integration of panicle growth during the critical period for yield determination in sorghum (i.e. flag leaf until start of grain filling). Panicle biomass at maturity (excluding grain) was thus also linearly related to grain number, and the relationship was independent of crop height and of the timing, severity, or type of stress. Our results indicate that panicle mass at maturity could provide an alternative to PGR_a for the estimation of grain number.  相似文献   

Penny ice cap cores, baffin island, canada, and the wisconsinan foxe dome connection: two states of hudson bay ice cover     

DA Fisher  RM Koerner  JC Bourgeois  G Zielinski  C Wake  CU Hammer  HB Clausen  N Gundestrup  S Johnsen  K Goto-Azuma  T Hondoh  E Blake  M Gerasimoff 《Science (New York, N.Y.)》1998,279(5351):692-695

Ice cores from Penny Ice Cap, Baffin Island, Canada, provide continuous Holocene records of oxygen isotopic composition (delta18O, proxy for temperature) and atmospheric impurities. A time scale was established with the use of altered seasonal variations, some volcanic horizons, and the age for the end of the Wisconsin ice age determined from the GRIP and GISP2 ice cores. There is pre-Holocene ice near the bed. The change in delta18O since the last glacial maximum (LGM) is at least 12.5 per mil, compared with an expected value of 7 per mil, suggesting that LGM ice originated at the much higher elevations of the then existing Foxe Dome and Foxe Ridge of the Laurentide Ice Sheet. The LGM delta18O values suggest thick ice frozen to the bed of Hudson Bay.  相似文献   

Design of a surface alloy catalyst for steam reforming   总被引：1，自引：0，他引：1  

F Besenbacher  I Chorkendorff  BS Clausen  B Hammer  AM Molenbroek  JK Norskov  I Stensgaard 《Science (New York, N.Y.)》1998,279(5358):1913-1915

Detailed studies of elementary chemical processes on well-characterized single crystal surfaces have contributed substantially to the understanding of heterogeneous catalysis. Insight into the structure of surface alloys combined with an understanding of the relation between the surface composition and reactivity is shown to lead directly to new ideas for catalyst design. The feasibility of such an approach is illustrated by the synthesis, characterization, and tests of a high-surface area gold-nickel catalyst for steam reforming.  相似文献   

The infraspecific taxa of coriander (Coriandrum sativum L.)     

A. Diederichsen  K. Hammer 《Genetic Resources and Crop Evolution》2003,50(1):33-63

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Morphological spike diversity of Omani wheat     

S. Al Khanjari  A. A. Filatenko  K. Hammer  A. Buerkert 《Genetic Resources and Crop Evolution》2008,55(8):1185-1195

Little is known about the diversity of field crops in Oman. The objective of this study therefore was to characterize wheat accessions from this country using individual spikes collected from different wheat cultivation areas. The phenotypic assessment of 15 qualitative and 17 quantitative characters showed variations among Omani wheat landraces. The standardized phenotypic diversity index (H′) was with 0.66 higher for quantitative characters than for qualitative characters (0.52) in tetraploid wheats and with 0.63 and 0.62, respectively, in hexaploid wheats. Overall, the morphological data revealed a surprisingly high diversity among landraces and showed that simple morphological characters can be used for an effective characterization of diversity in Omani wheat.  相似文献