Spatial and Temporal Variability of Sorghum Grain Yield: Influence of Soil,Water, Pests,and Diseases Relationships     

Machado  S.  Bynum  E. D.  Archer  T. L.  Bordovsky  J.  Rosenow  D. T.  Peterson  C.  Bronson  K.  Nesmith  D. M.  Lascano  R. J.  Wilson  L. T.  Segarra  E. 《Precision Agriculture》2002,3(4):389-406

This study was conducted to determine relationships between biotic and abiotic factors and to generate information needed to improve the management of site-specific farming (SSF). The effects of water (80% evapotranspiration (ET) and 50% ET), hybrid (drought-tolerant and -susceptible), elevation, soil texture, soil NO₃--N, soil pH, and greenbugs (Schizaphis graminum) (Gb) on sorghum grain yield were investigated at Halfway, TX on geo-referenced locations on a 30-m grid in 1997, 1998, and 1999. Grain yields were influenced by interrelationships among many factors. Grain yields were consistently high under 80% ET treatment and in the upper slopes where the clay and silt fractions of the soil were high. Soil NO₃--N, rainfall, hybrid, and Gb effects on grain yields were seasonally unstable. Soil NO₃--N increased grain yield when water was abundant and depressed grain yields when water was limiting. Plant density effects on grain yield were confounded with hybrid responses to drought and Gb infestation. Managing seasonally unstable factors is a major challenge for farmers and better ways to monitor crop growth and diagnose causes of poor plant growth are needed. To improve the management of SSF, effects of the relationships between biotic and abiotic factors on crop yield must be integrated and evaluated as a system. Based on our study, information on seasonally stable factors like elevation and soil texture is useful in identifying management zones for water and fertilizer application. Water and fertilizers management should be complemented by in-season management of seasonally unstable factors like soil NO₃--N, rainfall, hybrid, and Gb effects on grain yield.  相似文献   

Kinetic isotope effects for the reactions of muonic helium and muonium with H2     

Fleming DG  Arseneau DJ  Sukhorukov O  Brewer JH  Mielke SL  Schatz GC  Garrett BC  Peterson KA  Truhlar DG 《Science (New York, N.Y.)》2011,331(6016):448-450

The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of ~4.1 atomic mass units ((4.1)H), because the negative muon almost perfectly screens one proton charge. We report the reaction rate of (4.1)H with (1)H(2) to produce (4.1)H(1)H + (1)H at 295 to 500 kelvin. The experimental rate constants are compared with the predictions of accurate quantum-mechanical dynamics calculations carried out on an accurate Born-Huang potential energy surface and with previously measured rate constants of (0.11)H (where (0.11)H is shorthand for muonium). Kinetic isotope effects can be compared for the unprecedentedly large mass ratio of 36. The agreement with accurate quantum dynamics is quantitative at 500 kelvin, and variational transition-state theory is used to interpret the extremely low (large inverse) kinetic isotope effects in the 10(-4) to 10(-2) range.  相似文献   

Structure-disrupting ions: detection of qualitative change in an enzyme   总被引：1，自引：0，他引：1  

J C Warren  D M Peterson 《Science (New York, N.Y.)》1966,152(726):1245-1246

Preparations of erythrocyte glucose-6-phosphate dehydrogenase from normal individuals show similar degrees of inhibition by neutral salts. Preparations from Caucasian subjects with different hereditary deficiency syndromes differ from each other and from normal subjects, indicating a qualitative difference in these specific "deficient" enzymes. Sensitivity to neutral salts may be a means of detecting an amino acid substitution.  相似文献   

Assisted colonization: Integrating conservation strategies in the face of climate change     

Scott R. Loss  Lauren A. Terwilliger  Anna C. Peterson 《Biological conservation》2011,(1):92-100

Global climate change poses an immense challenge for conservation biologists seeking to mitigate impacts to species and ecosystems. Species persistence will depend on geographic range shifts or adaptation in response to warming patterns as novel climates and community assemblages arise. Assisted colonization has been proposed as a method for addressing these challenges. This technique, which consists of transporting species to a new range that is predicted to be favorable for persistence under future climate scenarios, has become the subject of controversy and discussion in the conservation community due to its highly manipulative nature, questions about widespread feasibility, and uncertainty associated with the likelihood of translocated species becoming invasive. We reviewed the discussion and criticism associated with assisted colonization and sought to identify other conservation techniques that also display potential to promote the colonization and adaptation of species in response to climate change. We propose an integrated conservation strategy that includes management for habitat connectivity, conservation genetics, and when necessary, assisted colonization of species that are still unable to shift their ranges even given implementation of the above standard conservation approaches. We argue that this integrated approach will facilitate persistence for a larger proportion of species than is possible by solely using assisted colonization. Furthermore, a multi-faceted approach will likely reduce the uncertainty of conservation outcomes and will become increasingly necessary for conservation of biodiversity in a changing climate.  相似文献   

Soft palate cyst in a cat     

Peterson NW  Buote NJ 《Journal of Feline Medicine and Surgery》2011,13(8):594-596

A 17-month-old cat presented for frequent swallowing, occasional cough and stertor. Radiographic evaluation revealed a soft tissue mass at the level of the soft palate. Oral examination revealed a soft tissue mass within the soft palate. Surgical resection was performed. Histopathology was consistent with a large developmental cyst. Following surgical management the cat has remained clinically free of signs for 2 months.  相似文献   

Dose range finding study for the efficacy of meloxicam administered prior to sodium urate-induced synovitis in cats     

Carroll GL  Narbe R  Kerwin SC  Taylor L  Peterson K  Hartsfield SM 《Veterinary anaesthesia and analgesia》2011,38(4):394-406

ObjectiveTo determine the lowest efficacious dose of oral meloxicam for relieving pain in cats with a sodium urate (SU)-induced acute inflammatory synovitis.Study designRandomized, blinded, controlled, and four-way crossover study.AnimalsEight surgically neutered cats (four males, four females) paired according to sex.MethodsEach pair of cats was treated with 0 (placebo), 0.025, 0.05, or 0.075 mg kg^?1 oral meloxicam once daily for 4 days prior to injection, into alternating stifles, of 1 mL of 20 mg mL^?1 SU crystals, beginning with the right stifle. Each cat received each of the four treatments, separated by at least 21 days. Analgesic efficacy was evaluated based on objective (e.g., pressure mat data total force, contact pressure, and contact area) and subjective (e.g., scores for Analgesia Scale [AS], Lameness Scale [LS], and Visual Analog Scale [VAS]) outcome measures for pain assessment. All outcome measures were recorded before and during 30 hours after SU injection. The pre-defined primary outcome measure was the area under the response–time curve (AUC_0–30 hours) of the total force of the injected limb. Data were analyzed by analysis of variance. A sequential test procedure was applied and the test sequence stopped in case of a nonsignificant result.ResultsMeloxicam at doses of 0.05 and 0.075 mg kg^?1 day^?1 PO was significantly different from placebo for the pre-defined primary outcome measure (i.e., AUC_0–30 hours of total force). All tested meloxicam doses were lower than placebo for the subjective outcome measures (i.e., AUC_0–30 hours of AS, LS, and VAS).Conclusions and clinical relevanceThe lowest efficacious dose of meloxicam for relieving pain in cats with an SU-induced synovitis was 0.05 mg kg^?1 day^?1 PO according to the pre-defined primary outcome measure. However, lower doses may also be effective as seen in the subjective outcome measures.  相似文献   

Genetic diversity within a range of cultivars and landraces of flax (Linum usitatissimum L.) as revealed by RAPDs   总被引：1，自引：0，他引：1  

Yong-Bi Fu  Axel Diederichsen  K.W. Richards  Gregory Peterson 《Genetic Resources and Crop Evolution》2002,49(2):167-174

Analysis of the extent and distribution of genetic diversity incrop plants is essential for optimizing sampling and breedingstrategies. We used random amplified polymorphic DNA (RAPD)markers to assess genetic diversity and relationships in 22 Canadiancultivars, 29 selected world cultivars and 10 landraces of flax(Linum usitatissimum L.). RAPDvariation was generally low and more variation was detected among,than within, the investigated flax accessions. Based on 53 variableRAPD loci observed for the 61 accessions, the landraces had a lowerproportion of fixed recessive RAPD loci (0.427) (i.e.,more genetic variation) than all of the flax cultivars examined(0.492). The linseed cultivars had a lower proportion ofrecessive loci (0.469) than the fiber flax cultivars(0.529). Canadian linseed cultivars had a lower proportionof recessive loci (0.465) than the selected world flaxcultivars (0.512). A trend was also observed that the rateof loss in genetic variation in Canadian flax breeding programs overthe last fifty years was approximately two variable loci per 100 lociper 10 years. Clustering analyses based on similarity estimatesshowed that the fiber cultivars were more related (or similar toeach other) and were classified as a homogeneous group. All ofthe linseed cultivars were clustered in diverse groups with the ninelandrace accessions. Implications of these findings for flax breedingand germplasm management are discussed.  相似文献   

Sorghums of the Sudan: analysis of regional diversity and distribution   总被引：1，自引：0，他引：1  

C. Grenier  P.J. Bramel  J.A. Dahlberg  A. El-Ahmadi  M. Mahmoud  G.C. Peterson  D.T. Rosenow  G. Ejeta 《Genetic Resources and Crop Evolution》2004,51(5):489-500

Sorghum [Sorghum bicolor (L.) Moench] is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums.  相似文献   

On the potential of documenting decadal-scale avifaunal change from before-and-after comparisons of museum and observational data across North America     

Fernando Machado-Stredel  Benedictus Freeman  Daniel Jiménez-Garcia  Marlon E.Cobos  Claudia Nu?ez-Penichet  Laura Jiménez  Ed Komp  Utku Perktas  Ali Khalighifar  Kate Ingenloff  Walter Tapondjou  Thilina de Silva  Sumudu Fernando  Luis Osorio-Olvera  A.Townsend Peterson 《中国鸟类》2022,(1):1-10

Studies of biodiversity dynamics have been cast on either long(systematics)or short(ecology)time scales,leaving a gap in coverage for moderate time scales of de...  相似文献   

Jefferson's yeoman farmer as frontier hero a self defeating mythic structure     

Tarla Rai Peterson 《Agriculture and Human Values》1990,7(1):9-19

American agrarianism, as informed by the frontier myth, has provided fundamental inventional resources for agricultural rhetoric. These myths have deflected farmers from positive adaptation, reinforcing instead the self-image of a hero victimized by circumstances. Critical examination of these independent myths reveals their literalized status as well as inconsistencies with fundamental agricultural goals.  相似文献