EDWARD BRADFORD TITCHENER     

Warren HC 《Science (New York, N.Y.)》1927,66(1705):208-209

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Path analysis of genotype-environment interactions of potatoes exposed to increasing warm-climate constraints     

George C. C. Tai  David Levy  Warren K. Coleman 《Euphytica》1994,75(1-2):49-61

Summary Twenty potato cultivars were tested in replicated trials in three seasons. The weather gradually changed from relatively high humidity and cold air temperatures in February to dry and hot in July. Fresh and dry weights, sucrose, reducing sugar and starch contents were recorded on tubers sequentially harvested over four stages during the growing period of each of the three trials. The data were analyzed for genotype-environment interactions by a path regression model which is composed of a main effect and four multiplicative effects. The model fitted well to the observed data for all traits but reducing sugar. Results of dry tuber weight were used to calculate a heat susceptibility index for each of the cultivars. Four components of the index were identified based on the path model. Comparison of sizes of the components provided information on the degree of response to the environmental stress of each of the cultivars during successive stages of growth. High yielding and heat tolerant cultivars were identified based on the experimental results.  相似文献   

How does P affect photosynthesis and metabolite profiles of Eucalyptus globulus?     

Warren CR 《Tree physiology》2011,31(7):727-739

Phosphorus (P) has multiple effects on plant metabolism, but there are many unresolved questions especially for evergreen trees. For example, we do not know the general effects of P on metabolism, or if P affects photosynthesis via the internal conductance to CO(2) transfer from sub-stomatal cavities to chloroplast or amounts of Rubisco. This study investigates how P?deficiency affects seedlings of the evergreen tree Eucalyptus globulus grown for 2.5 months with four nutrient solutions differing in P concentration. To determine why photosynthesis was affected by P supply, Rubisco was quantified by capillary electrophoresis, internal conductance was quantified from gas exchange and carbon isotope discrimination, and biochemical parameters of photosynthesis were estimated from A/C(c) responses. Additional insights into the effect of P on metabolism were provided by gas chromatography-mass spectrometry (GC-MS) metabolite profiling. Larger concentrations of P in the nutrient solution led to significantly faster rates of photosynthesis. There was no evidence that stomatal or internal conductances contributed to the effect of P supply on photosynthesis. The increase in photosynthesis with P supply was correlated with V(cmax), and amounts of P, phosphate and fructose 6-phosphate (6-P). Phosphorous supply affected approximately one-third of the 90 aqueous metabolites quantified by GC-MS, but the effect size was generally smaller than reported for experiments on herbaceous species. Phosphorus deficiency decreased concentrations of phosphate, glucose 6-P and fructose 6-P more than it decreased photosynthesis, suggesting faster turnover of smaller pools of phosphate and phosphorylated intermediates. The effect of P supply on most amino acids was small, with the exception of arginine and glutamine, which increased dramatically under P deficiency. P deficiency had small or non-significant effects on carbohydrates and organic acids of the tricarboxylic acid (TCA) cycle. The small effect of P on carbohydrates, organic acids and (most) amino acids likely reflects a functional homeostasis among C metabolism (glycolysis, TCA and pentose P cycles), rates of photosynthesis and growth. The strong functional homeostasis in E. globulus may reflect a conservative, long-term growth and metabolic strategy of evergreen trees.  相似文献   

Elevated CO₂ enhances leaf senescence during extreme drought in a temperate forest     

Warren JM  Norby RJ  Wullschleger SD 《Tree physiology》2011,31(2):117-130

In 2007, an extreme drought and acute heat wave impacted ecosystems across the southeastern USA, including a 19-year-old Liquidambar styraciflua L. (sweetgum) tree plantation exposed to long-term elevated (E(CO(2))) or ambient (A(CO(2))) CO(2) treatments. Stem sap velocities were analyzed to assess plant response to potential interactions between CO(2) and these weather extremes. Canopy conductance and net carbon assimilation (A(net)) were modeled based on patterns of sap velocity to estimate indirect impacts of observed reductions in transpiration under E(CO(2)) on premature leaf senescence. Elevated CO(2) reduced sap flow by 28% during early summer, and by up to 45% late in the drought during record-setting temperatures. Modeled canopy conductance declined more rapidly in E(CO(2)) plots during this period, thereby directly reducing carbon gain at a greater rate than in A(CO(2)) plots. Indeed, pre-drought canopy A(net) was similar across treatment plots, but declined to ～40% less than A(net) in A(CO(2)) as the drought progressed, likely leading to negative net carbon balance. Consequently, premature leaf senescence and abscission increased rapidly during this period, and was 30% greater for E(CO(2)). While E(CO(2)) can reduce leaf-level water use under droughty conditions, acute drought may induce excessive stomatal closure that could offset benefits of E(CO(2)) to temperate forest species during extreme weather events.  相似文献   

Retention capacities of immiscible chemicals in unsaturated soils     

Selma E. Guigard  Warren H. Stiver  Richard G. Zytner 《Water, air, and soil pollution》1996,89(3-4):277-289

Retention capacities were measured in the laboratory for n-hexane and tetrachloroethylene (PCE) in three soils at varying soil water contents. Two experimental techniques were used; 1) saturation/drainage experiments where the soil columns were saturated with the chemical and allowed to drain freely for 24 h, and 2) spill simulations where a known amount of chemical was spilled on the surface of the soil column and allowed to infiltrate for one hour. Results show that the retention capacities on a volume basis were independent of chemical type. However, the retention capacities did decrease with decreasing porosity and increasing soil water content. The decrease of retention capacity with respect to soil water content was significant, with the decreases ranging from 38% to 94%. The implication of this decrease is rapid chemical penetration into the subsurface. Retention capacities obtained from spill simulations were consistently lower than those obtained by the saturation/drainage experiments due to hysteresis.  相似文献   

Aerosol and precipitation chemistry relationships at big bend national park     

Michele R. Derrick  Jarvis L. Moyers  Keith A. Yarborough  Mike Warren 《Water, air, and soil pollution》1984,21(1-4):171-181

Aerosol chemistry, precipitation and visibility parameters are currently being measured at Big Bend National Park in Texas. This is part of a large-scale air resource evaluation program which the National Park Service is sponsoring in several southwestern national parks and monuments to determine the potential impact of local and distant pollutant sources on the environmental quality within these areas. Analysis of aerosol samples collected at six sites in the Southwest indicates that soil-derived components, organic materials and the acid-base ions of sulfate, nitrate, and ammonium are the major constituents of suspended airborne particulate matter in the remote areas of the arid region. Comparison of particulate matter chemistry and precipitation chemistry data at Big Bend National Park shows consistent features which indicate that the airborne alkaline soil material and NH₃ largely neutralize the atmospheric acidic species of H₂SO₄ and HNO₃. Given the similarity of the particulate matter composition and loading at the other monitoring sites, it is suggested that the trace chemical composition of precipitation will be similar in many remote regions of the Southwest.  相似文献   

Improved cleanup for liquid chromatographic analysis and fluorescence detection of aflatoxins M1 and M2 in fluid milk products   总被引：1，自引：0，他引：1  

J Ferguson-Foos  J D Warren 《Journal of the Association of Official Analytical Chemists》1984,67(6):1111-1114

A rapid method is described for extraction and cleanup of raw and processed milk for determination of aflatoxins M1 and M2 by using a C18 Sep-Pak/silica gel cleanup column combination. Aflatoxins are separated by normal phase liquid chromatography and their concentrations are determined by fluorescence detection in a silica gel-packed flow cell. Recoveries ranged from 99 to 103% with coefficients of variation less than 2% for M1 levels of 0.117-1.17 ng/mL added to raw milk. Similar recoveries were obtained for M2. The coefficient of variation for analysis of 5 subsamples of naturally contaminated milk was less than 1%. Agreement with the official method is satisfactory. Each sample requires less than 25 mL solvent and 10 min actual handling time. Sample chromatograms show no interferences in the M1-M2 elution region and no late-eluting peaks, which permits spacing injections at 13-20 min intervals. Aflatoxin levels as low as 0.03 ppb may be determined by this procedure. Extracts have also been analyzed by thin layer chromatography.  相似文献   

Protozoan bioassays of soil amended with sewage sludge and heavy metals,using the common soil ciliate Colpoda steinii     

T. A. Forge  M. L. Berrow  J. F. Darbyshire  A. Warren 《Biology and Fertility of Soils》1993,16(4):282-286

The common soil protozoan Colpoda steinii was used to study the toxicity of sulphate solutions of Ni, Cd, Cu, and Zn. The growth of C. steinii was reduced by 50% in the presence of 0.10, 0.22, 0.25, and 0.85 mg litre^-1 of Ni, Cd, Cu and Zn, respectively, during 24 h of incubation at 25°C, as calculated from a regression analysis of probit-transformed data. The same growth assay was used to assess the toxicity of soil solution extracted by centrifugation from soil samples of field plots of a grass/clover ley on a sandy loam treated with sewage sludge spiked with additional Cd, Cu, Cr, Ni, Pb, or Zn at concentrations either equivalent to or twice the limits for heavy metals recommended in recent EC guidelines (Commission of European Communities directive 86/278/EEC). The toxicity of these soil solutions varied with the season of the year. None of the soil solutions extracted in winter (February 1991) inhibited the growth of C. steinii. In summer (July 1991), the growth was reduced in solutions extracted from plots that were amended with sludge plus additional Zn or Ni at twice the maxima recommended by the EC. The changes in toxicity to C. steinii of the soil solutions between February and July were positively correlated with increases in heavy metal concentrations of Zn and Ni between winter and summer. These preliminary results suggest that regular protozoan bioassays may be used to monitor the biological availability of heavy metals in soils, especially when combined with other microbial assays and with chemical analyses of soil solutions.  相似文献   

Golgin tethers define subpopulations of COPI vesicles     

Malsam J  Satoh A  Pelletier L  Warren G 《Science (New York, N.Y.)》2005,307(5712):1095-1098

Coiled-coil proteins of the golgin family have been implicated in intra-Golgi transport through tethering coat protein complex I (COPI) vesicles. The p115-golgin tether is the best studied, and here we characterize the golgin-84-CASP tether. The vesicles bound by this tether were strikingly different from those bound by the p115-golgin tether in that they lacked members of the p24 family of putative cargo receptors and contained enzymes instead of anterograde cargo. Microinjected golgin-84 or CASP also inhibited Golgi-enzyme transport to the endoplasmic reticulum, further implicating this tether in retrograde transport. These and other golgins may modulate the flow patterns within the Golgi stack.  相似文献   

THE CENTRIOLE IN RADIATED TUMOR TISSUE     

Fogg LC  Warren S 《Science (New York, N.Y.)》1940,91(2370):528-529

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