Enantioselective degradation of indoxacarb in cabbage and soil under field conditions

The enantioselective degradation of indoxacarb in cabbage and soil has been investigated in Beijing and Anhui under open conditions. Indoxacarb enantiomers in samples were extracted with acetonitrile, cleaned up by florisil SPE column, separated on high performance liquid chromatography with a cellulose-tris-(3, 5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP), and determined by a photodiode array detector. The validation of the developed method by fortification rac-indoxcarb in cabbage and soil showed good accuracy and precision. The results of field trials indicated that the dissipation of indoxacarb enantiomers followed pseudo-first-order kinetics or first-order kinetics in cabbage and soil at two locations. The half-lives of two enantiomers in cabbage ranged from 2.8 to 4.6 d which were shorter than those in soil ranging from 23 to 35 d. The changes of enantiomeric fraction values proved that enantioselective degradation of indoxacarb happened in cabbage and soil. The (-)-indoxacarb showed faster degradation in the Beijing cabbage, whereas in the Anhui cabbage, (+)-indoxacarb preferentially degraded. In soil, preferential degradation of (+)-indoxacarb was observed at two locations.     

Chemical control of potato common scab disease under field conditions

The aim of this study was to evaluate certain fungicides against Streptomyces scabies (Thaxter), the main causal agent of common scab disease in potato and other crops, in vitro and in vivo. Fourteen isolates of S. scabies were isolated from naturally infected potato tubers showing common scab symptoms. All isolates were pathogenic to potato tubers and produced typical symptoms of common scab. Isolate (No. 11) caused highest disease index (DSI) followed by isolates 10, 8 and 5 (61.13%). Seven fungicides (Rizolex, Capitan, Moncut, Ridomil, Maxim, Topsin, and Oxyplus) were screened in vitro for their toxicity against the pathogen isolate (No. 11). Results showed that four of them (Rizolex, Capitan, Moncut, and Ridomil) exhibited inhibition zone ranging from 5.33 to 26.33?mm. Capitan, Ridomil, and Rizolex were able to reduce DSI under field condition but they varied in their effects. Capitan was the best fungicide which aids in the reduction of disease (33.8%) followed by Ridomil (31.5%) while Rizolex (21.2%) was the lowest one.     

Concentration-dependent degradation of three termiticides in soil under laboratory conditions and their bioavailability to eastern subterranean termites (Isoptera: Rhinotermitidae)

Degradation and bioavailability of imidacloprid, fipronil, and bifenthrin applied at label rates ([AI], wt:wt in soil) in the loamy soil of Nebraska were determined over a 6-mo duration. Based on the calculated half-lives of the three termiticides, it was concluded that the degradation rate was lowest when a termiticide was applied at the highest label rate. Bioassays of Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) conducted at 8, 31, 65, 90, 135, 160, and 180 d posttreatment showed an inverse relationship between the LT90 values and the variable concentrations. At day 180, exposures to all the termiticide-treated soil samples (concentration x termiticide) resulted in 100% mortality of R. flavipes workers. However, lower LT90 values were observed for termites exposed to soils treated with highest label rates even when the treated soils were aged in the lab for 6 mo. This suggested a higher bioavailability of these three termiticides when applied at higher application rates. Termite mortality was fastest for bifenthrin followed by fipronil and imidacloprid.     

Rapid degradation kinetics of amyloid fibrils under mild conditions by an archaeal chaperonin

Amyloid depositions containing exceptionally stable β-sheet rich protein aggregates, called fibrils are associated with prevalent and incurable neurodegenerative diseases. Chaperones are proteins that facilitate protein folding in both eukaryotes and prokaryotes. We found that a cold-adapted mutant ATP-dependant chaperonins (Hsp60) from a hyperthermophilic archaeon binds to and fragments insulin fibrils very rapidly with local targeted entry points. Individual fragments swell and the fibrillar β-sheet is quickly transformed into a mix of α-helical and unordered protein structures. After further incubation, the fragments coalesced, forming large amorphous aggregates with poly-disperse topologies. This finding represents a new approach to the disassembly of refractory protein aggregates under physiological conditions.     

Rapid degradation of pyrogenic carbon

Pyrogenic carbon (PC‐ charcoal, biochar or black carbon) represents a poorly understood component of the global carbon (C) cycle, but one that has considerable potential to mitigate climate change through provision of long‐term soil C sequestration. Mass balance calculations suggest global PC production and stocks are not in balance, indicating a major gap in our understanding of the processes by which PC is re‐mineralized. We collected PC samples derived from the same wood material and exposed to natural environmental conditions for 1 and 11 years. We subjected these materials to repeated laboratory incubation studies at temperatures of up to 60 °C, as ground surface temperatures above 30 °C and up to 60 °C occur regularly over a significant area of the tropics and sub‐tropics. Mineralization rates were not different for the two samples and followed an exponential Arrhenius function that suggest an average turnover time of 67 years for conditions typical of a tropical savannah environment. Microbial biomass as measured by chloroform fumigation and DNA extractions was the same for the two samples, but abiotic CO₂ production was lower for the fresh PC sample than that for the aged sample. Nuclear magnetic resonance spectroscopy, hydrogen pyrolysis and scanning electron microscopy demonstrate that the measured CO₂ production originates dominantly from polycyclic aromatic compounds rather than any minor labile components. Therefore, rapid, sub‐centennial rates of re‐mineralization of PC on the soil surface in tropical and sub‐tropical environments may represent a major and hitherto unidentified mechanism for balancing the PC production at the global scale.     

Rapid protein release from Escherichia coli by chemical permeabilization under fermentation conditions

Overall protein release greater than 75% in less than 1 h can be attained by exposing exponentially growing Escherichia coli cells to 0.4 M guanidine plus 0.5% Triton X-100 at 37 degrees C in medium. Cell growth stops immediately upon addition of the chemicals, but the cells are not lysed. Guanidine concentrations lower than 0.2 M, in conjunction with 0.5% Triton X-100, do not release significant intracellular protein, nor do they inhibit cell growth. Under these conditions, the cells undergo an adaptation that confers resistance to protein release by further treatment with guanidine and Triton X-100. Cells treated with 0.2 M guanidine plus 0.5% Triton X-100 display intermediate behavior. Protein release is approximately 35%, and growth is temporarily interrupted by an extended lag phase. Subsequent resumption of cell growth results in resistant cells and no additional protein release. This resistance is shown to be reversible and is most likely due to physiological adaptation rather than genetic mutation.     

Fine root distribution and persistence under field conditions of three co-occurring Great Basin species of different life form

Fine roots of an annual grass, a perennial grass and a perennial shrub were examined. Based on life histories and tissue composition, we expected the greatest root persistence for the shrub and shortest for the annual grass. Roots were observed with minirhizotrons over 2 yr for number, length and diameter changes. A Cox proportional hazard regression correlated root persistence with soil water, depth, diameter and date of production. In 2001, grass roots had similar persistence times, but shrub roots had the shortest. In 2002, the annual had the longest median root persistence, the perennial grass intermediate and the perennial shrub had the shortest. All species responded similarly to the magnitude of seasonal precipitation; root numbers increased with favorable soil moisture and disappeared with drying; fewer, thinner roots at greater soil depths were found in the drier year (2001). Root persistence increased with soil moisture, diameter and earlier appearance in the spring. Plasticity in root morphology and placement was influenced by water availability, yet persistence was surprisingly contrary to expectations.     

Microbial degradation of lactate under methanogenic conditions

Summary A stable enrichment of bacteria capable of metabolizing lactate under methanogenic conditions was obtained from rumen contents. The methanogenic strains associated with lactate utilizers were identified asMethanosarcina sp. andMethanobacterium sp. The role of propionate as indicator of failure in the methanogenic phase is shown.

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Dégradation microbienne du lactate sous des conditions méthanigènes

Résumé Un enrichissement stable de bactéries capables de métaboliser le lactate dans des conditions méthanigènes a été isolé du contenu de rumen. Les souches méthanigènes, associées avec les utilisateurs de lactate, ont été identifiées comme appartenant aux genresMethanosarcina etMethanobacterium. Le rôle du propionate comme indicateur de la faillite de la phase méthanigène a été démontré.

     

Radiocarbon--a low-impact tool to study nutrient transport by soil fungi under field conditions

Here, we present a new in-situ method to study the uptake of amino acids by soil fungi. We injected 14C-labeled glycine into a marshland soil and measured the rate and the 14C signature of CO2 respired from sporocarps of Pholiota terrestris over 53.5 h and 2 m. We also determined the incorporation of glycine-C into sporocarp tissue. The 14C signature of the CO2 and tissue was quantified by accelerator mass spectrometry. After the label application, the rate of CO2 flux and its 14C signature from chambers with sporocarps were significantly higher than from chambers without sporocarps, and then declined with time. Postlabel, the 14C signature of the sporocarp tissue increased by 35 per thousand. We show that this approach can be used to study below-ground food webs on an hourly time-scale while minimizing the perturbation of competitive relationships among soil microorganisms and between plants and soil microorganisms. Additionally we show that care must be taken to avoid confounding effects of sporocarp senescence on rates and radiocarbon signatures of respired CO2.     

辽河下游平原不同水分条件下稻田氨挥发

应用通气密闭室法,研究了辽河下游平原不同水分条件下潮棕壤稻田生态系统施用氮肥后的NH3挥发.结果表明稻田施用氮肥后有明显NH3挥发损失,整个生长期间总挥发量为11.64～34.01 kg N·hm-2,占施氮量的4.66%～11.66%;不同施肥时期的损失量为分蘖期＞孕穗期＞移栽前,挥发高峰出现在施氮肥后的2～4 d内.稻田水分状况对NH3挥发损失具有重要影响,田面积水条件下NH3挥发总量和肥料氮损失率都较大,且不同施氮水平间差异显著(P＜0.05),挥发量随施氮量的增加而增加;田面不积水条件下NH3挥发量相对较小.氮肥用量、田面水NH4 浓度和pH是影响NH3挥发的重要因素;氮肥用量为180 kg N·hm-2时,不同磷水平对NH3挥发的影响不显著.     

Root structure and arbuscular mycorrhizal colonization of the palm Serenoa repens under field conditions

Serenoa repens (Bartr.) Small is a palm native to the southeastern USA. It is a common understory plant in pine communities on both acid sands and alkaline limestone. Roots have only primary growth and range in thickness from 8.0 mm (first order roots from the stem) to 0.8–2.9 mm (ultimate roots of third to fifth order). The thickest roots occur at soil depths >20 cm; fine roots (<1.2 mm) occur at all depths (1–60 cm). Some second and third order roots are negatively geotropic and grow up to the mineral soil surface. The epidermis of all roots has a thick, eventually lignified outer wall. Except for the thinnest, all roots have a single-layered, thick-walled exodermis, which is first suberized and later lignified. Root hairs are never present. A hypodermis composed of several layers of lignified cells (up to 8-cells-thick) is next to the exodermis and forms the outer cortex. Radial series of thin walled and slightly lignified cells sporadically occur in the outer cortex of the thinnest roots, but there are no passage cells in the exodermis, which is continuous. The remaining inner cortex is composed of unlignified parenchyma with air canals and a completely lignosuberized endodermis in old roots. Passage cells were seen the the endodermis of the some of the thinnest roots. Arbuscular mycorrhizal (AM) fungi occur in the outer one-third of the cortical parenchyma adjacent to the hypodermis. Fungal coils, arbuscules and vesicles are found most frequently in the thinnest roots, but also occur sporadically in all root orders. Cells a few mm from the apical meristem are sometimes colonized. At sites of appressoria, coils of AM hyphae occur within an epidermal cell and exodermal and hypodermal cells beneath. Intercellular hyphae with intracellular branch arbuscules (Arum-type) are common in the inner cortex. There is evidence of a dieback of the highest order roots during the winter dry season. Profiles of soil and roots have the highest density of AM spores in the surface 10 cm layer. Total AM spore density ranged from 130 to 1100 spores per 50 g soil in different samples. Glomus spp. dominated followed by Gigaspora spp. The findings are related to a more general understanding of growth and AM colonization in long-lived roots of tropical woody monocotyledons. Palm roots, in particular, are slow growing and are protected by massive hypodermal layers. This revised version was published online in June 2006 with corrections to the Cover Date.     

Behaviourally structured populations persist longer under harsh environmental conditions

The factors and mechanisms that enhance population persistence in a fragmented habitat and/or under harsh environmental conditions are of significant current interest. We consider the dynamics of a population in an isolated habitat surrounded by an unfavourable environment subject to different behavioural responses between the individuals. We assume that there are two responses available: one of them is aggression in its extreme form, the other is its contrary when an individual takes flight in order to avoid any contact with its conspecific. We show that a behaviourally structured population consisting of individuals with fixed behavioural responses is intrinsically less prone to extinction under harsh environmental condition than a population where the individuals can ‘choose’ between the two given behaviours. We also show that, contrary to an intuitively expected negative impact of aggression on population persistence, the optimal conditions for population persistence are reached when a considerable proportion of the individuals exhibit aggressive behaviour.     

Foraging speed and precision of arbuscular mycorrhizal fungi under field conditions: An experimental approach

To better understand the ecology of arbuscular mycorrhizal (AM) symbiosis, we need to measure functional traits of individual fungal virtual taxa under field conditions. The efficiency of AM fungi in locating nutrient‐rich patches in soil space is one of their central traits in this symbiotic relationship. We used plots of a long‐term field experiment in grassland with manipulated functional group composition of host plant community to establish ingrowth patches with substrate free of roots and fungi and with varying nutrient availability. Comparison of the original AM fungal community before patch creation with that present 9 weeks after patch establishment enabled us to estimate relative hyphal foraging speed for 41 fungal taxa, and a comparison of the fungal community in neighbouring patches differing in nutrient availability provided estimates of hyphal foraging precision for 22 taxa. Members of two dominant fungal families, Glomeraceae and Claroideoglomeraceae, differed in their foraging speed and precision. Glomeraceae taxa responded more slowly, but with a higher focus on enriched patches. We further demonstrated the usefulness of the obtained fungal functional traits by testing the differences between grass and dicotyledonous plant hosts using a data set obtained in another experiment at the same plots. Grass species hosted AM fungal communities with higher foraging speed, but lower foraging precision than the dicotyledonous species. Our study results support the use of field experiments for measuring comparative characteristics of AM fungi, which are highly elusive (or misrepresented) under controlled conditions.     

Persistence of the nematophagous fungus Paecilomyces lilacinus strain 251 in soil under controlled conditions

The persistence of the nematophagous fungus Paecilomyces lilacinus Samson strain 251 (PL251) and the effect of application rate, substrate type, as well as the presence of the nematode host on its dynamics after application to the soil were investigated under controlled conditions. In all experiments, increase of P. lilacinus colony forming units after application was not found. In contrast, a gradual decline in fungal densities over time was observed. Application rate had no significant effect on the dynamics of the fungal population. Likewise, P. lilacinus density decline in soil was not significantly affected by the presence of the nematode host. Substrate type had a significant effect on P. lilacinus persistence in soil. The fungal agent persisted longer in silty loam and clay soil, with reduced persistence when sand was added to field soil. Conversely, when organic substrate was added to pure sand, persistence was significantly increased. Although persistence of fungal biocontrol agents in soil depends on various biotic and abiotic conditions, baseline data on persistence such as those reported in this study are helpful for biocontrol and environmental risk assessment and merit further study.     

Rapid cold hardening in the olive fruit fly Bactrocera oleae under laboratory and field conditions

A rapid cold hardening response was studied in females and males of the olive fruit fly Bactrocera (Dacus) oleae. When laboratory-reared females and males were transferred and maintained from the rearing temperature of 24 °C for 2 h to –6.5 °C approximately 5% survived. However, conditioning of both females and males for 2 h at various temperatures from 0 to 10 °C before their exposure for 2 h to –6.5 °C increased survival to 80 to 92%. A similar rapid cold hardening response in both females and males was also induced through gradual cooling of the flies at a rate of approximately 0.4 °C per min. The rapid increase in cold tolerance after prior conditioning of the flies to low temperatures, was rapidly lost when they returned to a higher temperature of 24 °C. In the field, in late February and early March, females and males were capable of a rapid cold hardening response. After exposure to the critical temperature they suffered a high mortality when tested in the afternoon and low mortality early in the morning on consecutive days, probably because of differences in the prevailing field temperatures a few hours before testing. This plasticity of cold tolerance gained through rapid cold hardening may allow the flies to survive during periods of the year with great fluctuation in circadian temperatures.     

Rapid purification of recombinant anthrax-protective antigen under nondenaturing conditions

White adipose tissue development is regulated by many factors, including the energy content of food and the genetic background. Nevertheless, little is known about possible differential effects of high-fat palatable diets when fed for short or long-time periods. Thus, the expression of certain genes involved with lipid metabolism (peroxisome proliferator-activated receptor gamma, PPARgamma2; retinoic receptors; fatty acid binding protein, aP2 and uncoupling proteins, UCP) may be affected by those dietary manipulations (high-energy-yielding diet and time duration of feeding). High-fat feeding for 8 days decreased mRNA UCP3 levels compared to control fed animals, while feeding for 30 days increased them over controls. Similar findings occurred for PPARgamma2 and aP2. Furthermore, statistically significant associations were found among PPARgamma2, aP2 and UCP3 mRNA levels. These data suggest a physiological time-dependent response seeking to prevent excessive fat deposition when animals are fed for short-term with a high amount of dietary fat, which was followed by an adaptive period to the high-energy content of diet throughout a coregulation among certain lipid metabolism related genes: PPARgamma2, aP2, UCP3.     

茂兰喀斯特森林不同地形植物多样性与土壤理化特征研究

为探讨不同地形植物群落物种多样性与土壤理化特征之间的相互关系。该文以茂兰喀斯特森林为研究对象,分析了不同地形植物多样性与土壤理化特征以及两者之间的相互关系。结果表明:(1)不同地形木本植物的物种组成存在差异,坡地木本植物有35科65属78种,槽谷木本植物有38科64属89种,漏斗木本植物有35科61属84种。同时,丰富度指数、多样性指数、均匀度指数大小表现为槽谷>漏斗>坡地;优势度指数大小表现为坡地>漏斗>槽谷。(2)不同地形土壤物理性质差异性显著(P<0.05),其中土壤容重和非毛管孔隙度表现为坡地>槽谷>漏斗,自然含水量、田间持水量、总孔隙度、毛管孔隙度等指标均表现为漏斗>槽谷>坡地。(3)除全K外,大多数土壤养分指标表现为漏斗显著高于槽谷、坡地,即漏斗>槽谷>坡地。(4)冗余分析表明,植物多样性与土壤理化性质具有相关性,不同地形植物多样性指数受土壤理化性质的影响明显。以上结果旁证了茂兰喀斯特森林地形条件的复杂性和土壤理化性质的差异性是该区小生境多样、物种组成丰富的原因之一,为喀斯特森林物种多样性维持机制提供了科学依...     

Inoculation of potatoes with microorganisms under field conditions

The effect of inoculation of potatoes with isolates ofPseudomonas putida andTrichoderma sp. suspension and in preparations with kaolin and peat carriers on growth of potatoes, yields and physiological proporties of tubers was investigated on seven locations of the potato-rye and sugar-beet regions. In 57.5% of experiments increased yields could be detected. More favorable results were obtained in the sugar-beet region and on commercially utilized fields when using suspensions of the isolates. Variability of the results can be partially explained by soil-climatic factors affecting colonization of the rhizosphere by the microorganisms and their effect on the environment. Physiological properties and the quality of the harvested tubers were comparable with those of the control. The results are discussed from the point of view of a possible inoculation of potatoes with rhizobacteria and, in the presence ofTrichoderma sp., improvement of their growth and yields.