Responses of microbial community in rhizosphere soils when ryegrass was subjected to stress from PCBs

Purpose  

The purpose of the present study was to investigate the composition and structure of microbial communities in rhizosphere soils in response to the presence of Aroclor 1242 with low (8 mg kg⁻¹ soil) and high (16 mg kg⁻¹ soil) concentrations in the hope to provide more information on potential dissipation of polychlorinated biphenyls (PCBs) at contaminated sites.     

聚类分析在黄瓜育种中的应用

本文提出在育种中通过聚类划分品系的新思想,对全部目标性状做聚类分析,同类者放入同一品系中选育较好,不同类者可放入同一品系或不同品系。通过聚类分析可清楚地看出目标性状间的关系,为制定育种方案提供客观、清晰的理论依据。供中国黄瓜科研工作者参考,并期望对提高国内黄瓜遗传研究与育种利用水平有所帮助。     

Desiccation tolerance of rhizobia when protected by synthetic polymers

Survival of rhizobia applied to the surface of legume seeds is poor due to factors such as desiccation. Poor survival of rhizobia results in poor nodulation and yield of legumes. Selecting polymeric adhesives for inoculation of legume seed with rhizobia that provide protection during desiccation may improve survival and increase the potential for maximum legume yields. Vacuum-drying cells after suspension in selected polymers proved an effective method for screening the potential of polymers to improve the desiccation tolerance of rhizobia. The effect of different polymers on survival of desiccated rhizobia could be attributed to their different chemical and physical properties. The specific protective properties of polymers have been difficult to determine due to the variation in the chemical nature of polymers often compared. In this research polyvinyl alcohol (PVA) with varying degrees of hydrolysis provided a useful range of measurable physical properties against which bacterial survival could be measured. PVA with a percent hydrolysis in the range 86.5-89% was better able to protect desiccated cells of a range of rhizobial strains than polymers with higher (98.5%) or lower (78.5-82%) degrees of hydrolysis. The percent hydrolysis affected the moisture properties of PVA and survival of rhizobia was not maximised with high moisture sorption or low water activity by the polymer but rather when moisture properties were at an intermediate level. In comparison, survival was poorest in highly hygroscopic polymers methyl cellulose (MC) and polyvinyl pyrrolidone (PVP). The survival profile of desiccated rhizobia stored at different relative humidities was altered when cells were embedded in different polymers and is probably related to moisture sorption by those polymers. The percent hydrolysis also affects the extent to which PVA is able to stabilise colloids against the precipitating action of KCl. The colloid-stabilising property and survival was highest at 86.5-89% indicating that this property may be manipulated to achieve better survival. There is an indication that highly stabilising PVA may lead to more evenly dispersed cells providing more colony forming units rather than better survival. However, survival was not strongly correlated to the colloid-stabilising properties of the other polymers and was very poor after suspension in highly stabilising MC indicating a strong interaction between factors. Synthetic polymers designed to improve survival of rhizobia exposed to desiccation stress should include properties that combine high stabilisation and optimum moisture sorption properties.     

矿化垃圾腐殖土在绿地中的应用研究进展

介绍了垃圾填埋场矿化垃圾的概念及性质,从矿化垃圾的有机质与营养物质含量、微生物、重金属以及基质配比等方面综述了矿化垃圾在绿地中应用研究现状,并结合目前研究的现状提出了展望。     

Testing for trends when there are changes in methods

Data from monitoring projects often include sampling or analytical changes that preclude trend analysis on the entire period of record. A modification of the nonparametric Kendall's test for monotonic trends, which accounts for such changes in the period of record, is described here. This approach blocks the data so that only data collected or analyzed under similar circumstances are compared. Alternatively, when appropriate data exist, data collected using the old method may be calibrated to values expected from the new method. Traditional trend tests may then be applied to resulting data sets. Results from simulations assessing both the power of the blocked test and the standard test performed on calibrated data are presented. The power of the blocked test exceeded the power of the calibration approach only when the calibration error was extremely large. Both the blocking and calibration approaches were applied to and compared for chemical data from Vermont lakes.     

农杆菌介导的抑制衰老的嵌合基因转化籼稻的研究

农杆菌介导的转化法是一种天然的遗传工程,具有诸多优越性.1993年Chan等首次利用农杆菌法成功地将外源基因转入水稻.随后又有一些实验室进行了农杆菌转化水稻的研究,并获得了较高的转化频率.但大部分的实验都是采用标记基因进行的,有用基因转化的报道则较少.同时,籼稻优良品种的转化也较困难.本实验采用抑制衰老的嵌合基因进行转化,以我国生产上的优良籼稻圭630为转化受体,力求获得有应用价值的转基因植株,为生产服务.     

清华大学钟毅课题组阐明果蝇短期记忆遗忘机理

新获取的记忆如果未经强化记忆通常会很快遗忘,这种记忆遗忘被认为是由于新获取记忆本身的不稳定性或随后获取信息的干扰所造成的.近日,来自清华大学钟毅课题组的研究人员在这种短期记忆遗忘机理研究上取得重大进展,该研究认为这种快速遗忘是一种主动行为,用以抹掉旧的记忆腾出空间来存储新的记忆.相关研究结果于2010年2月19日发表在(Cell)杂志上,并被列为同期的特色文章(Featured Article).     

Possible effects when two deficient essential elements are applied simultaneously

With assumptions of a possitive response of a plant to essential element “A”; and positive response also obtained when essential element “B”; is added without any application of element “A”; (either in soil medium or medium without absolute absence of both elements further assumed), five different types of responses are postulated and plotted. Additive, antagonistic and synergistic effects are included.     

Soil survey data needs when studying modern land use problems

Abstract. Modern land use problems in the Netherlands are now focused on striking a balance between agricultural production, environmental protection, and nature and landscape conservation by means of new laws on soil protection. Quantitative expressions for crucial land qualities for different land management scenarios are needed to obtain adequate input for the decision making process emphasizing not only actual, but particularly potential conditions. Computer simulation techniques are being applied in this context. Three case studies are reviewed, covering: (i) adsorption of excess phosphate from animal manure; (ii) effects of lowering of water deficits for crops, and (iii) effects of soil tillage and compaction on crucial land qualities for agricultural production. Lack of representative basic data for simulation models inhibits their widespread practical application. Derivation of such basic data from existing soil-survey databases is therefore being discussed in terms of using various types of transfer functions, which allow more effective use of available data. In addition, geographical information systems are needed to allow rapid output for areas of land as represented on soil maps.     

Response of three Sesbania species to salinity when grown hydroponically

The shoot and root growth response of three species of Sesbania to 0, 50 and 100 mM NaCl in a hydroponic culture was studied. Absorption and translocation of Na and Cl in 15 day old seedlings were studied using ²²Na and ³⁶Cl labelled NaCl. Shoot growth was significantly reduced at 100 mM NaCl in the nutrient solution for all three species. The salt tolerance of the three species was in the order S. rostrata > S. aculeata > S. speciosa. The transport of Na to stem and leaf was less compared to uptake in S. rostrata but greater proportion of the absorbed Cl was translocated to the shoot. Salinity reduced the nitrogen content in root and stem significantly.     

Verrucomicrobial elevational distribution was strongly influenced by soil pH and carbon/nitrogen ratio

Purpose

The bacterial phylum Verrucomicrobia plays important roles in biogeochemical cycling processes, while the ecology of this phylum is still unclear. Previous elevational studies mainly focused on whole bacterial communities, while no study exclusively picked out Verrucomicrobia. Our objectives were to investigate the abundance, diversity and community composition of soil Verrucomicrobia across an elevation gradient on Changbai Mountain.

Materials and methods

In total, 24 soil samples representing six elevation gradients were collected. Primer set 515F/806R was used for PCR amplifications and sequencing was conducted on an Illumina HiSeq2000 platform. Data sets comprising of Verrucomicrobial phylum were culled from all quality sequences for the further analyses of Verrucomicrobial diversity and community composition.

Results and discussion

The relative abundance of Verrucomicrobia accounted for ~20% of the total bacterial communities, and Spartobacteria and DA101 were the most dominant class and genus, respectively. Verrucomicrobia community composition differed significantly among elevations, while the Verrucomicrobia diversity showed no apparent trend along elevation although the richness of some classes or genera significantly changed with elevation. The Verrucomicrobial community composition, diversity, and relative abundance of specific classes or genera were significantly correlated with soil pH and carbon/nitrogen ratio (C:N ratio).

Conclusions

These results indicated that Verrucomicrobia were abundant in Changbai Mountain soils, and Verrucomicrobial elevational distribution was strongly influenced by soil pH and C:N ratio. Our results also provide potential evidence that the dominant genus DA101 occupies different ecological niches and performs oligotrophic life history strategy in soil environment.

     

水稻中抑制衰老的嵌合基因的基因枪转化和表达分析

利用基因枪法把抑制衰老的嵌合基因导入水稻恢复系HP121和偏籼型品系8706,经PCR、点杂交以及Southern杂交分析, 证明外源基因已整合到水稻基因组中.通过叶片细胞分裂素含量和叶绿素含量的测定以及形态观察,表明抑制衰老的嵌合基因在部分转基因水稻中表达,叶片衰老得到延迟.转基因植株后代符合3:1遗传规律.     

An approach for estimating when soils will reach maximum nitrogen storage

Abstract. Net accumulation of organic nitrogen in soil is constrained by the amount of organic matter and its minimum C:N ratio. Our objective was to estimate the potential for New Zealand soils to continue accumulating nitrogen within the soil organic pool. We calculated total carbon and nitrogen in the top metre of 138 representative soil profiles from the New Zealand National Soils Database. Carbon in these mainly pasture soils was assumed to be at steady state. The maximum nitrogen storage capacity was estimated by calculating the amount of nitrogen stored under assumed minimum soil C:N ratios of either 9, 10 or 11. The storage capacity remaining was determined as the difference between the amount of nitrogen currently stored and the maximum storage capacity. The length of time before a soil profile will reach the maximum capacity for nitrogen storage was calculated assuming net accumulation of 20, 50 and 100 kg N ha⁻¹ yr⁻¹. A C:N ratio of 9 (giving most storage capacity) and a conservative accumulation rate of 20 kg N ha⁻¹ yr⁻¹ showed that 12% of these soils would be at maximum storage within 40 years. A C:N ratio of 10 and a storage rate of 50 kg N ha⁻¹ yr⁻¹ would result in 54% of the soils reaching maximum storage within the next 40 years. As the capacity for nitrogen storage in soils declines, nitrate leaching is likely to increase with associated risk to the environment.     

Factors contributing to guidance performance when using a camera-based guidance aid

A guidance aid is a device that provides guidance information to the driver rather than replacing the driver. With a camera-based guidance aid, the view seen by a forward-looking video camera is displayed on a monitor situated within the operator station of the vehicle. As the vehicle moves forward, images of the ground scroll vertically across the monitor. The rate at which the image scrolls, the image velocity, is related to the forward velocity of the vehicle, the placement of the camera (height and tilt angle), and the optical characteristics of the guidance camera. When tested with a tractor at forward velocities between 1.6 and 12.8 km/h, lateral error increased linearly as image velocity increased. Driver self-confidence decreased linearly as image velocity increased. Based on subjective feedback, drivers preferred a camera tilt angle of 20 degrees (over either 30 degrees or 40 degrees) because it yielded the greatest look-ahead distance. Statistically, a tilt angle of 30 degrees was best for a camera with a narrow field of view (narrow FOV, 20 degrees in the lateral direction). For a camera with a wide field of view (wide FOV, 39 degrees in the lateral direction), there was no statistical difference. For the narrow FOV camera, a camera height of 1.1 m yielded statistically smaller lateral errors than a camera height of 1.5 m. There was no statistical difference for the wide FOV camera. Overall, the lateral error was statistically smaller for the narrow FOV camera than for the wide FOV camera due to the difference in the lateral ratio for each camera, where the lateral ratio is the ratio of the lateral field of view of the camera to the fixed monitor width.     

Fumonisin B-glucose reaction products are less toxic when fed to swine

The effects of fumonisin B-glucose reaction products in swine diets was examined. Pigs were fed diets containing 528 micromol of total fumonisin B/kg (FB), 528 micromol of total FB-glucose adducts/kg (FB-G, 122 micromol of unreacted FB/kg), or 0 micromol of total FB/kg for 15 days to test the efficacy of the FB-G reaction products in detoxifying FB. Weight gain in FB pigs was lower than in FB-G or controls, which was correlated with feed intake reduction in FB pigs. Serum aspartate aminotransferase, gamma-glutamyltransferase, and total bilirubin in FB pigs were higher than in FB-G or control pigs. Serum sphinganine/shingosine ratios in FB pigs were higher than in FB-G or control pigs. Microscopic examination of tissues from FB pigs showed generalized liver necrosis and apoptosis with marked cellular pleomorphism and disorganized hepatic cords. The liver and kidneys in the FB-G group appeared to be normal. Tissues of controls were free of lesions. Results suggest that dietary FB-G products are less toxic to swine and may provide an detoxification approach in instances of widespread FB grain contamination (p < 0.05).     

Digested Ara h 1 loses sensitizing capacity when separated into fractions

The major peanut allergen Ara h 1 is an easily digestible protein under physiological conditions. The present study revealed that pepsin digestion products of Ara h 1 retained the sensitizing potential in a Brown Norway rat model, while this sensitizing capacity was lost by separating the digest into fractions by gel permeation chromatography. Protein chemical analysis showed that the peptide composition as well as the aggregation profiles of the fractions of Ara h 1 digest differed from that of the whole pool. These results indicate that the sensitizing capacity of digested Ara h 1 is a consequence of the peptides being in an aggregated state resembling the intact molecule or that most peptides of the digests need to be present in the same solution, having a synergistic or adjuvant effect and thereby augmenting the immune response against other peptides.     

植物硅测定中损失硅的确定

植物中的Si主要以蛋白石形式(无定形水合二氧化硅SiO2nH2O,也有报道认为以α-石英石形式)存在[1].无定形二氧化硅在不同介质中有不同的溶解表现,其溶解度在25℃时为70～150 mg/kg[2].如此大的差异是由于SiO2粒子大小、内部水合状态、杂质含量等情况的不同造成的.诸多测定方法中,经典碱熔融法仍然具有不可替代的优点,即共熔使Si转化为可溶性硅酸盐[3].