外源水杨酸对盐胁迫下非洲菊抗氧化酶活性和生理特性的影响(英文)

以非洲菊(Gerbera jamesonii L.)品种Amaretto'为试材,研究外源水杨酸(SA)对缓解非洲菊生殖生长期因盐胁迫引起的过氧化伤害作用.在开花前分别用0、0.5和1.0mmol L-1SA对非洲菊植株进行预处理,3d后用100mmol L-1NaCl灌溉,持续2周;对照植株未经NaCl和SA处理.结果表明:盐胁迫处理后,叶片的超氧化物歧化酶(SOD)和过氧化物酶(POD)活性增加,丙二醛(MDA)含量、电解质外渗率和脯氨酸含量提高;外源SA预处理显著降低了盐胁迫植株叶片的MDA含量和电解质外渗率;在外源0.5mmol L-1SA预处理后,植株SOD和POD活性分别是对照的1.4倍和2.4倍;SA预处理后与植株耐盐性相关的生理生化指标呈显著相关,以0.5mmol L-1SA处理增强植株盐胁迫耐性的效果更好.说明外源SA处理能够诱导盐胁迫下非洲菊植株的抗氧化反应,水杨酸将是一种提高园艺作物耐盐性的有效物质.     

Aerobic soil metabolism of a new herbicide,LGC-42153

To elucidate the fate of a new sulfonylurea herbicide, LGC-42153 [N-((4,6-dimethoxypyrimidin-2-yl)aminocarbonyl)-2-(1-methoxyacetoxy-2-fluoropropyl)-3-pyridinesulfonamide], in soil, an aerobic soil metabolism study was carried out for 120 days with [(14)C]LGC-42153 applied to a loamy soil. The material balance ranged from 90.7 to 101.5% of applied herbicide. The half-life of [(14)C]LGC-42153 was calculated to be approximately 9.0 days. The degradation products resulted from the cleavage of the sulfonylurea bridge. The metabolites identified during the study were N-((4,6-dimethoxypyrimidin-2-yl)aminocarbonyl)-2-(1-hydroxy-2-fluoropropyl)-3-pyridinesulfonamide, 2-(1-hydroxy-2-fluoropropyl)-3-pyridinesulfonamide, and 4,6-dimethoxy-2-aminopyrimidine. No significant volatile products or [(14)C]carbon dioxide was observed during the study. Nonextractable (14)C-residue reached 14.4-30.5% of applied material at 120 days after treatment, and radioactivity was distributed mostly in the humin and fulvic acid fractions.     

Carbon nanotubes with temperature-invariant viscoelasticity from -196 degrees to 1000 degrees C

Viscoelasticity describes the ability of a material to possess both elasticity and viscosity. Viscoelastic materials, such as rubbers, possess a limited operational temperature range (for example, for silicone rubber it is -55° to 300°C), above which the material breaks down and below which the material undergoes a glass transition and hardens. We created a viscoelastic material composed from a random network of long interconnected carbon nanotubes that exhibited an operational temperature range from -196° to 1000°C. The storage and loss moduli, frequency stability, reversible deformation level, and fatigue resistance were invariant from -140° to 600°C. We interpret that the thermal stability stems from energy dissipation through the zipping and unzipping of carbon nanotubes at contacts.     

Grain composition of Virginia winter barley and implications for use in feed,food, and biofuels production

Grain compositional components impacting barley (Hordeum vulgare L.) use in food, feed and fuel products, must be combined with improved agronomic traits to produce a commercially viable barley cultivar. Little current information is available on grain composition and variability among winter barley genotypes. This study was conducted to determine the variability among modern hulled and hulless winter barley genotypes in grain composition. Barley types varied significantly in grain and kernel weight, starch, beta-glucan, oil and ash content, but not in protein concentration. Hulless barley had significantly higher grain test weight and starch concentration than hulled and malting types, and significantly higher beta-glucan than malting barley. Hulless barley had significantly lower kernel weights, oil, and ash concentrations than hulled and malting types. Higher starch and lower fiber and ash in grain of hulless barley versus hulled feed or malting type barley are characteristics that increase hulless barley desirability. Selection for high starch concentration among all barley types is feasible and will facilitate development of barley cultivars better suited for use in feed, malt, and ethanol production.     

Uptake and nutrient balance of nitrogen,sulfur, and boron for optimal canola production in eastern Canada

Balanced plant nutrition is essential to achieve high yields of canola (Brassica napus L.) and get the best economic return from applied fertilizers. A field study was conducted at nine site‐years across eastern Canada to investigate the effects of nitrogen (N), sulfur (S) and boron (B) fertilization on canola nutrient uptake, nutrient balance, and their relationship to canola yields. The factorial experiment consisted of four N rates of 0 (N0), 50 (N50), 100 (N100), and 150 (N150) kg ha^?1, two S rates of 0 (S0) and 20 (S20) kg ha^?1, and three B treatments of 0 (B0), 2 kg ha^?1 at preplant (B2.0P), and 0.5 kg B ha^?1 foliar‐applied at early flowering stage (B0.5F). Each site‐year used the same experimental design and assigned treatments in a randomized complete block design with four replications. Fertilizer S application greatly improved seed yields at six out of nine site‐years, and the highest N use efficiency was in the N150+S20 treatment. Sulfur application generally increased seed S concentration, seed S removal, and plant total S uptake, while B fertilization mainly elevated straw B concentration and content, with minimal effect on seed yields. At the early flowering stage, plant tissue S ranged from 2.2 to 6.6 mg S g^?1, but the N : S ratio was over or close to the critical value of 12 in the N150+S0 combination at five site‐years. On average across nine site‐years, canola reached a plateau yield of 3580 kg ha^?1 when plants contained 197 kg N ha^?1, 33 kg S ha^?1 and 200 g B ha^?1, with a seed B content of 60 g B ha^?1. The critical N, S, and B values identified in this work and their potential for a posteriori nutrient diagnosis of canola should be useful to validate fertilizer requirements for canola production in eastern Canada.     

Neodymium-142 evidence for Hadean mafic crust

Neodymium-142 data for rocks from the Nuvvuagittuq greenstone belt in northern Quebec, Canada, show that some rock types have lower 142Nd/144Nd ratios than the terrestrial standard (epsilon142Nd = -0.07 to -0.15). Within a mafic amphibolite unit, 142Nd/144Nd ratios correlate positively with Sm/Nd ratios and produce a 146Sm-142Nd isochron with an age of 4280(-81)(+53) million years. These rocks thus sample incompatible-element-enriched material formed shortly after Earth formation and may represent the oldest preserved crustal section on Earth.     

The feasibility of oyster raft culture in east coast estuaries

Styrofoam-floated oyster rafts were used to study the feasibility of raft culture in typical American east coast estuaries. Rafts were placed in Delaware Bay and several tidal tributaries in the state of Delaware. Four types of cultch were tested for resistance to the environment and utilization by setting spat. Hatchery-spawned oysters were reared on rafts and their growth and mortality were monitored. A special raft with moveable trays was designed to study the effectiveness of air drying in controlling fouling.Rafts withstood the environmental conditions in small tidal rivers but were severely damaged by waves in Delaware Bay. Although spat set was too low for commercial purposes in the rivers, sets approaching commercial density were obtained in the bay by putting bundles of strings on the oyster beds during setting. Oysters grown on rafts reached market size in approximately 2 years in two of the rivers: slower growth was noted in the other rivers. It was shown that fouling could be controlled effectively by air drying for 4 h each week.An economic analysis of raft culture for this area was conducted at the conclusion of the study, which showed that relatively high prices would be necessary to maintain a raft-based industry at this time.     

The response of cylindrocladium conidia to soil fungistasis

Direct observation of washed conidia of Cylindrocladium scoparium on non-sterile soils, air dried and rewetted immediately before deposition of conidia, indicated that peak germination (33–58%) occurred after 24 h incubation at 26°C. Peak germination on continually moist soils was lower (18–26%) than on rewetted soils. Lysis of germ tubes and germinating conidia on continually moist soils at 26°C was evident with 48 h. Conidia did not germinate on continually moist soils at 6°C and lysis did not become apparent until 168 h. Conidia germinated at a high level (93–99%) in axenic culture in the absence of exogenous C and N sources. The inhibition of conidial germination on soils may be attributed, in part, to the presence of soil volatiles. Germination of conidia placed on washed agar disks and exposed to volatiles from four soils ranged from 51 to 86% of the no-soil controls. Addition of carbon (13 ng C per conidium as glucose) and nitrogen (65 pg N ng^?1 C as NH₄C1) nullified the inhibitory effect of the soil volatiles. Germinability assayed on a selective medium at 26°C of conidia in artificially infested soils (approximately 10⁴ conidia g^?1 soil) decreased progressively during incubation at 26°C from 1 week to 4 months. No germinable conidia were recovered from artificially infested soils after 2 months incubation at 6°C. Conidia of C. floridanum and C. crotalariae responded similarly to C. scoparium in many assays.     

Frequency of urinary tract infection in catheterized dogs and comparison of bacterial culture and susceptibility testing results for catheterized and noncatheterized dogs with urinary tract infections

OBJECTIVE: To determine frequency of urinary tract infections (UTIs) in catheterized dogs that had intervertebral disk disease (IVDD) or disease other than IVDD and compare bacterial culture and susceptibility testing results for catheterized and noncatheterized dogs with UTIs. DESIGN: Retrospective cohort study. ANIMALS: 147 catheterized dogs (105 with IVDD and 42 with other diseases) and 99 noncatheterized dogs with UTIs. PROCEDURES: Medical records were reviewed for signalment, history, clinical problem, duration of urinary tract catheterization, administration of drugs, and urine bacterial culture and susceptibility testing results. RESULTS: Forty-two percent (44/105) of dogs with IVDD and 55% (23/42) of dogs with other diseases had UTIs; this difference was not significant. For catheterized dogs, the odds of UTI were increased by 20% for each year increase in age, 27% for each day increase in duration of catheterization, and 454% with antimicrobial administration. Escherichia coli and Proteus spp were more frequently isolated from noncatheterized dogs, whereas Enterobacter spp and Staphylococcus spp were more frequently isolated from catheterized dogs. There was no significant difference in frequency of 1, 2, or 3 isolates between groups. Proportions of antimicrobials to which the most frequently isolated bacteria were resistant were not significantly different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that urinary tract catheterization is a reasonable alternative for management of dogs with urinary bladder dysfunction, but that duration of catheterization should be minimized and indiscriminate antimicrobial administration to dogs with indwelling urinary catheters should be avoided.