The effect of physiological age and planting date on the response of potatoes to applied nitrogen and on levels of residual nitrogen post-harvest     

Patrick A. Johnson  Frances Seeney  Diana Williams 《Potato Research》1996,39(4):561-569

Summary Experiments were conducted on sandy and deep silty soils to assess the effect of physiological age of seed tubers and planting date on the response of potatoes to nitrogen fertiliser. Nitrogen optima commonly had large standard errors which made interpretation of the data difficult. On the sandy soil with cv. Record, early planting increased yield in two years but had no effect on mean N optimum (303 kg ha⁻¹, NOpt). Mean NOpt was less on the silty soil where the cv. Pentland Squire was grown, and was reduced from 273 kg ha⁻¹ to 241 kg ha⁻¹ when planting was delayed by 4 weeks. Physiological age had no effect on NOpt. On the sandy soil, residual soil mineral nitrogen (RSMN) increased by 0.05 kg ha⁻¹ per kg N fertiliser applied; on the silty soil the increase was four times as large. RSMN was larger following the late planted crop on the silty soil in one year.  相似文献   

Correlations among species distributions, human density and human infrastructure across the high biodiversity tropical mountains of Africa   总被引：1，自引：0，他引：1  

Neil D. Burgess  Andrew Balmford  Jon Fjeldså  Carsten Rahbek  Jörn P.W. Scharlemann  Paul H. Williams 《Biological conservation》2007,134(2):164-177

This paper explores whether spatial variation in the biodiversity values of vertebrates and plants (species richness, range-size rarity and number or proportion of IUCN Red Listed threatened species) of three African tropical mountain ranges (Eastern Arc, Albertine Rift and Cameroon-Nigeria mountains within the Biafran Forests and Highlands) co-vary with proxy measures of threat (human population density and human infrastructure). We find that species richness, range-size rarity, and threatened species scores are all significantly higher in these three tropical African mountain ranges than across the rest of sub-Saharan Africa. When compared with the rest of sub-Saharan Africa, human population density is only significantly higher in the Albertine Rift mountains, whereas human infrastructure is only significantly higher in the Albertine Rift and the Cameroon-Nigeria mountains. Statistically there are strong positive correlations between human density and species richness, endemism and density or proportion of threatened species across the three tropical African mountain ranges, and all of sub-Saharan Africa. Kendall partial rank-order correlation shows that across the African tropical mountains human population density, but not human infrastructure, best correlates with biodiversity values. This is not the case across all of sub-Saharan Africa where human density and human infrastructure both correlate almost equally well with biodiversity values. The primary conservation challenge in the African tropical mountains is a fairly dense and poor rural population that is reliant on farming for their livelihood. Conservation strategies have to address agricultural production and expansion, in some cases across the boundaries and into existing reserves. Strategies also have to maintain, or finalise, an adequate protected area network. Such strategies cannot be implemented in conflict with the local population, but have to find ways to provide benefits to the people living adjacent to the remaining forested areas, in return for their assistance in conserving the forest habitats, their biodiversity, and their ecosystem functions.  相似文献   

Using a nonlinear mixed effects model to characterize cholinesterase activity in rats exposed to Aldicarb     

C.?A.?ClaytonEmail author  T.?B.?Starr  R.?L.?Sielken  R.?L.?Williams  P.?-G.?Pontal  A.?J.?Tobia 《Journal of Agricultural, Biological & Environmental Statistics》2003,8(4):420-437

A statistical mixed effects model was applied to data from a two-phased experiment in which cholinesterase activity (CA) in red blood cells (RBCs) of rats was monitored following single-and double-gavagead ministrations of the carbamate pesticide, Aldicarb. Our goals were to develop and estimate a nonlinear mixed effects model for describing the inhibition and recovery pattern of CA as a continuous function of time and Aldicarb dose, and to use the results to characterize both the typical-animal CA response and its variability across animals. The Phase 1 experiment involved adult male CD® rats randomly assigned to a control and two dose groups. Blood samples were taken via jugular cannula prior to exposure and at 11 post-dose time points (over six hours) for determination of RBC CA. The Phase II experiment was similar, but involved a second administration approximately 4.5 hours after the first. An open, one-compartment model with first-order kinetics appeared to provide an adequate structural basis for the statistical nonlinear mixed effects model, which was fit to the RBC data of the 26 treatment-group rats from both phases. For the “typical” animal, the model predicts that about a 20% (40%) maximal reduction in activity will occur for the low (high) dose group and that recovery to 90% of the baseline level will occur in 105 minutes (179 minutes) for the low (high) dose group. Based on simulated distributions derived from the model’s variance-covariance matrix of random effects, we estimated that about 99% of animals are expected to require less than 143 minutes (267 minutes) to recover to 90% of their baseline level for the low (high) dose group. Because virtually all animals had returned to near pre-exposure, levels by the time of the second administration, the level of the first dosing had little impact on the CA patterns following the second dose.  相似文献   

The retention, distribution, excretion, and metabolism of dibutyl phthalate-7-14 C in the rat.     

D T Williams  B J Blanchfield 《Journal of agricultural and food chemistry》1975,23(5):854-858

  相似文献   

52-Week oral gavage chronic toxicity study with ubiquinone in rats with a 4-week recovery     

Williams KD  Maneke JD  AbdelHameed M  Hall RL  Palmer TE  Kitano M  Hidaka T 《Journal of agricultural and food chemistry》1999,47(9):3756-3763

Potential ubiquinone (CoQ10; a natural fermentation product) toxicity was assessed in rats administered CoQ(10) by oral gavage for 1 year at 100, 300, 600, and 1200 mg/(kg day). No adverse changes in mortality, clinical signs, body weight, food consumption, or clinical pathology results occurred. CoQ(10) had elimination half-lives ranging from 10.7 to 15.2 h. At 1200 mg/(kg day), a high incidence of orange, granular, lumenal exudate in nasal turbinates occurred; microscopically, findings similar to those in the turbinates were occasionally observed in small granulomas within lung alveoli. A dose-related increased incidence of vacuolated macrophages (mesenteric lymph nodes) and vacuolated hepatic periportal cells was noted. Neither were associated with tissue damage or organ dysfunction, so they were not considered to be adverse. The nasal turbinate and lung findings were probably secondary to incidental exposure to crystallized test material. Overall, CoQ(10) was well tolerated by male and female rats at dose levels up to 1200 mg/(kg day).  相似文献   

Determination of halogenated phenols in raw and potable water by selected ion gas chromatography-mass spectrometry     

B B Sithole  D T Williams  C Lastoria  J L Robertson 《Journal of the Association of Official Analytical Chemists》1986,69(3):466-473

Pentafluorobenzylation and in situ acetylation are compared in the determination of phenol and halogenated phenols in water samples. The latter technique is considered superior to the former for determining phenols at the ng/L level because of less background interference and better recoveries (80% or better except for pentachlorophenol and trichloroguaiacol which had recoveries of about 60%). Further evaluation of the in situ technique by electron capture gas chromatography and gas chromatography-mass spectrometry shows that the latter, in the selected ion monitoring mode, is more suitable because, unlike GC-ECD, it can confirm and quantitate all phenols. In particular, GC-ECD could not detect even high levels of phenol and the monohalogenated phenols. Phenols at 5-473 ng/L were detected in some Canadian drinking water supplies by the in situ acetylation technique combined with GC-MS.  相似文献   

STUDIES ON THE ROOT DEVELOPMENT OF HERBAGE PLANTS     

T. E. Williams  H. K. Baker 《Grass and Forage Science》1957,12(1):49-55

Various methods of root sampling are reviewed and discussed in relation to the type of information required. The root sampling techniques at the Grassland Research Institute are described and examples of sampling errors are given. Details of a root washing machine are given.  相似文献   

Introgression and stabilization oferwinia tuber soft rot resistance into potato after somatic hybridization ofsolanum tuberosum ands. brevidens     

J. Mitchell McGrath  Christie E. Williams  Geraldine T. Haberlach  Susan M. Wielgus  Thomas F. Uchytil  John P. Helgeson 《American Journal of Potato Research》2002,79(1):19-24

Resistance to potato tuber soft rot caused byErwinia carotovora was transferred fromSolanum brevidens to the cultivated potato over the course of four backcross generations originating from a somatic hybrid. Soft rot reactions were determined via a tuber plug inoculation method developed during the course of these experiments. Soft rot resistance was highest in the somatic hybrid (only ca. 20% of tubers and plugs showed evidence of severe rotting) and lowest among progeny of control potato x potato crosses (ca. 80% of tuber plugs showed severe rot). Backcross generations involving somatic hybrids were intermediate in their reaction, and resistance stabilized to about 60% of tuber plugs showing severe rot in the BC₂ through the BC₄. Reciprocal crosses showed no difference in the inheritance of soft rot resistance, indicating that neitherS. brevidens norS. tuberosum donor cytoplasm had a significant effect on the expression of resistance. Crosses between BC₃ siblings where noS. brevidens genetic markers were detected but resistance was segregating demonstrated a dosage effect for soft rot resistance. We conclude that introgression of soft rot resistance has occurred and that at least one locus responsible for resistance inS. brevidens now resides in theS. tuberosum genome.  相似文献   

Leaf mineral nutrient concentrations or media pH affect Georgia Jet sweetpotato transplant number,length, and weight 1     

J. M. Dangler  J. E. Brown  G. E. Boyhan  J. C. Williams 《Journal of plant nutrition》2013,36(7):1459-1469

The results of four experiments were combined to determine the relationships between leaf mineral nutrients or media pH and sweetpotato transplant production. The relative number of transplants and the relative mean transplant lengths or weights were determined by comparing the values obtained with unamended aged pine sawdust, a traditional medium. These values were regressed against leaf mineral concentrations and media pH. There was no relationship between relative transplant production and leaf nitrogen (N), potassium (K), or manganese (Mn) concentrations. Compared to sufficiency ranges for nearly mature sweetpotatoes, concentrations of N and K were low and Mn was sufficient. An upper value of 1210 mg/L leaf iron (Fe) was obtained for relative mean transplant weight, but concentrations of this mineral were not associated with relative transplant numbers or relative mean transplant lengths. Leaf calcium (Ca) and magnesium (Mg) concentrations were related to all three transplant characteristics directly, or indirectly through possible effects on leaf phosphorus (P) concentration or media pH. Compared to the established sufficiency ranges for nearly mature sweetpotato plants, Ca and Mg concentrations were low, P and Fe concentrations were sufficient, and zinc (Zn) concentrations were high.  相似文献   

Review of The Chinese Medicinal Herb Farm     

Debby Williams 《Journal Of Agricultural & Food Information》2013,14(1):87-88

Collaborative ventures between industry and professional association represent a strategy to maximize resources for a mutual goal. As a cooperative venture, The American Dietetic Association co-sponsored with Kraft General Foods, Inc. and The Good Housekeeping Institute a survey on American's diet and nutrition habits. The survey findings focused on consumer's behaviors, attitudes, knowledge and obstacles toward diet and nutrition. The results from the survey are being used to create and expand nutrition education campaings to the public.  相似文献