Characterization of recurrent somatic embryogenesis of alfalfa on auxin-free medium

Callus cultures from 300 genotypes of alfalfa (Medicago sativa L.) were initiated from leaf, petiole, and internode explants placed on Blaydes medium containing 10.74 M -naphthaleneacetic acid, 11.42 M indole-3-acetic acid, and 9.29 M kinetin. Five genotypes produced somatic embryos. Upon transfer of these embryos to growth regulator-free Murashige and Skoog medium with B₅ vitamins, new somatic embryos repeatedly formed directly on older somatic embryos without an intervening callus phase in a cycle lasting about 30 days. These cultures have been maintained for two years, during which time their embryogenic capacity has remained stable. New embryogenic cultures could be started repeatedly from these genotypes. The elimination of sugars from the medium could stop recurrent embryogenesis. Glucose, maltose, and fructose stimulated recurrent embryogenesis more effectively than sucrose. Sucrose was superior to lactose, while sorbitol and mannitol did not stimulate recurrent somatic embryogenesis. The absence of nicotinic acid in the medium, as long as sucrose was present, was lethal to embryos of three of the five tested genotypes. The ability of this system to propagate embryos exponentially offers potential for development of new gene transfer systems and application to artificial seed technology.Abbreviations NAA -naphthaleneacetic acid - RSE recurrent somatic embryogenesis     

Perspectives on environmental risk assessment

Risk is by no means a simple concept. Natural variability and definitional problems with the concept of probability complicate the measurement and use of risk as an analytical tool. Variability requires that risk assessment methods separate natural from total risk when attempting to estimate anthropogenic risk. Failure to do so results in the over estimation of anthropogenic risk and the eventual loss of credibility for risk assessment methodologies. The common frequentist approach to probability is not consistent with anything but a modelling approach to risk assessment. When combined with its ability to account for natural variability, incorporate laboratory-assay data and offer complete statistical and experimental control, modelling is a promising approach to risk assessment. Modelling, however, is not without its drawbacks. Initialization bias can result in the over, or under, estimation of both natural and anthropogenic risk. Furthermore, model estimates are time dependent. The convergence of natural and anthropogenic risk poses problems for modelling-based risk assessment and requires clear statements as to the importance of the time dimension in risk assessment. When combined, the drawbacks to modelling-based risk assessment argue that risk should never be stated as a scalar quantity. Instead, modelling-based risk assessment should provide estimates of the complete range of risk measures (total, natural, and anthropogenic) as well as indications of convergence time. Only then can the modelling-based approach be viewed as the most appropriate means of carrying out scientifically credible risk assessment.     

Evaluation of health risks from a buried mass of diesel fuel before and after bioremediation

Plans are being formulated for in situ bioremediation of a subsurface plume of diesel fuel No. 2 that resulted from an accidental fuel release. Raoult's law and the aqueous solubilities of the toxic components were used to estimate organic contaminant concentrations in leachate from the untreated fuel mass. Carcinogenic risks and noncarcinogenic hazard indices were calculated for undiluted leachate. An 80% decrease in hydrocarbon mass and increases in the average molecular weights of the component fractions were assumed to result from the treatment. Sample calculations are provided to show how to evaluate results of analyses for petroleum hydrocarbons after bioremediation.     

Extinction risk of Chinese angiosperms varies between woody and herbaceous species

Aim

Understanding how species' traits and environmental contexts relate to extinction risk is a critical priority for ecology and conservation biology. This study aims to identify and explore factors related to extinction risk between herbaceous and woody angiosperms to facilitate more effective conservation and management strategies and understand the interactions between environmental threats and species' traits.

Location

China.

Taxon

Angiosperms.

Methods

We obtained a large dataset including five traits, six extrinsic variables, and 796,118 occurrence records for 14,888 Chinese angiosperms. We assessed the phylogenetic signal and used phylogenetic generalized least squares regressions to explore relationships between extinction risk, plant traits, and extrinsic variables in woody and herbaceous angiosperms. We also used phylogenetic path analysis to evaluate causal relationships among traits, climate variables, and extinction risk of different growth forms.

Results

The phylogenetic signal of extinction risk differed among woody and herbaceous species. Angiosperm extinction risk was mainly affected by growth form, altitude, mean annual temperature, normalized difference vegetation index, and precipitation change from 1901 to 2020. Woody species' extinction risk was strongly affected by height and precipitation, whereas extinction risk for herbaceous species was mainly affected by mean annual temperature rather than plant traits.

Main conclusions

Woody species were more likely to have higher extinction risks than herbaceous species under climate change and extinction threat levels varied with both plant traits and extrinsic variables. The relationships we uncovered may help identify and protect threatened plant species and the ecosystems that rely on them.     

好氧反硝化细菌及其在微污染水源水修复中的应用研究进展

相比于氨氮,天然水体中的硝酸盐氮通常更稳定,导致更难将其从水中去除。由于好氧反硝化可以在有氧环境下进行反硝化作用去除硝酸盐氮,该过程对含有较高溶解氧的天然水体中硝酸盐氮处理有重要作用。本文综述了好氧反硝化菌的分离纯化现状、微生物代谢机制和环境影响因子,并介绍了功能菌群在微污染饮用水源水生物修复的应用研究进展。与一般的厌氧反硝化类似,好氧反硝化菌的种属分布较广,常见的如假单胞菌属(Pseudomoas)、产碱杆菌属(Alcaligenes)、副球菌属(Paracoccus)和芽孢杆菌属(Bacillus)等所属部分微生物均有好氧反硝化能力。大部分好氧反硝化菌株在最佳生长条件下(25–37℃、溶解氧浓度为3–5mg/L、pH为7–8、碳氮比为5–10)具有高效的脱氮效率。但目前好氧反硝化作用在微污染饮用水源水的生物修复方面的应用仍有着脱氮性能不稳定、菌剂流失等不足。此外,目前较少相关中试及实际工程应用的研究,需要进一步的深入探究。     

Framework for validation and implementation of in vitro toxicity tests

Summary The development and application of in vitro alternatives designed to reduce or replace the use of animals, or to lessen the distress and discomfort of laboratory animals, is a rapidly developing trend in toxicology. However, at present there is no formal administrative process to organize, coordinate, or evaluate validation activities. A framework capable of fostering the validation of new methods is essential for the effective transfer of new technologic developments from the research laboratory into practical use. This committee has identified four essential validation resources: chemical bank(s), cell and tissue banks, a data bank, and reference laboratories. The creation of a Scientific Advisory Board composed of experts in the various aspects and endpoints of toxicity testing, and representing the academic, industrial, and regulatory communities, is recommended. Test validation acceptance is contingent on broad buy-in by disparate groups in the scientific community—academics, industry, and government. This is best achieved by early and frequent communication among parties and agreement on common goals. It is hoped that the creation of a validation infrastructure composed of the elements described in this report will facilitate scientific acceptance and utilization of alternative methodologies and speed implementation of replacement, reduction, and refinement alternatives in toxicity testing.     

Trusting the Health System and COVID 19 Restriction Compliance

We examine the extent to which exposure to higher relative COVID-19 mortality (RM), influences health system trust (HST), and whether changes in HST explain the perceived ease of compliance with pandemic restrictions during the COVID-19 pandemic. Drawing on evidence from two representative surveys covering all regions of 28 European countries before and after the first COVID-19 wave, and using a difference in differences strategy together with Coarsened Exact Matching (CEM), we document that living in a region with higher RM during the first wave of the pandemic increased HST. However, the positive effect of RM on HST is driven by individuals over 45 years of age, and the opposite effect is found among younger cohorts. Furthemore, we find that a higher HST reduces the costs of complying with COVID-19 restrictions, but only so long as excess mortality does not exceed the average by more than 20%, at which point the ease of complying with COVID-19 restrictions significantly declines, offsetting the positive effect of trust in the healthcare system. Our interpretation of these estimates is that a higher RM is interpreted as a risk signal among those over 45, and as a signal of health-care system failure among younger age individuals.     

国家公园农户对野生动物肇事保险购买意愿及其影响因素——以大熊猫国家公园为例

国家公园内人与野生动物冲突严重,建立野生动物肇事保险机制是减缓冲突的重要举措。以大熊猫国家公园周边社区为例,分析建立国家公园以及农户风险偏好对野生动物肇事保险购买意愿的影响,并探讨冲突程度和制度信任的中介效应。研究结果表明建立国家公园显著增加了农户野生动物肇事保险购买意愿,而农户风险偏好对保险购买意愿会产生负向显著影响。冲突程度和制度信任是重要的中介变量,冲突程度和制度信任均对农户保险购买意愿产生正向显著影响。建立国家公园显著增加了人与野生动物冲突严重程度,进而对保险购买意愿产生正向影响。此外,建立国家公园显著降低了农户制度信任,进而对保险购买意愿产生负向影响。农户风险偏好对野生动物肇事损失程度产生正向显著影响,进而对保险购买意愿产生正向影响。农户风险偏好对制度信任影响并不显著。基于此,研究提出吸纳社会资本参与,拓宽野生动物肇事保险资金来源,开展社区共管、地役权补偿等措施提升社区信任以及建立基于农户自主防护行为的野生动物肇事保险机制等政策建议。     

城市建筑屋顶光伏发电潜力评估方法和模型

建筑屋顶作为闲置的土地资源已成为光伏发电重要的潜在空间,屋顶光伏发电是脱碳电力供应的主要方式,将在实现城市碳中和进程中发挥重要作用。对建筑屋顶光伏发电潜力进行精确评估将有助于分布式光伏的科学规划和合理布局,提升土地利用效率。旨在对建筑屋顶光伏发电潜力影响因素和评估方法,以及光伏发电潜力主要评估模型进行系统性阐述,比较分析不同评估方法的优缺点,总结未来研究的重点方向。现有研究表明,建筑屋顶光伏发电潜力评估已从经验取值发展为定量空间分析,评估尺度、评估精度和评估成本已经成为不同评估方法综合权衡的重点。现有三种评估方法中,采样法计算成本和数据成本较低,但评估结果不确定性较大、精度较低;全面评估法评估精度较高,但数据获取成本和计算成本较高;机器学习法能够高效挖掘大数据潜力,且算法性能显著提升,因而相较于其他方法更适宜大尺度建筑屋顶光伏发电潜力评估。当前建筑屋顶光伏发电潜力评估仍然存在大尺度精细评估缺乏、评估结果不确定性大以及评估模型计算量大等问题。未来研究重点应关注三个方面：1)建立适宜不同区域的高精度简化模型并完善技术潜力评估模型;2)阐明建筑屋顶光伏发电潜力的影响因素,为代表性建筑分类体系...     

Cucumber mosaic virus genome is encapsidated in alfalfa mosaic virus coat protein expressed in transgenic tobacco plants

The expression of viral coat protein (CP) in transgenic plants has been shown to be very effective in virus plant protection. However, the introduction of CP genes into plants presents the potential risk of the encapsidation of a superinfecting viral genome in the transgenic protein, an event which could change the epidemiology of the disease. To detect the potential heterologous encapsidation of the cucumber mosaic virus (CMV) genome by alfalfa mosaic virus (AIMV) CP expressed in transgenic tobacco plants, a system of immunocapture (IC) and amplification by polymerase chain reaction (PCR) was optimized. This provided high sensitivity and reliable selection of the heterologously encapsidated CMV genome in the presence of natural CMV particles. As little as 2 pg of virus could be detected by immunocapture/polymerase chain reaction (IC/PCR) technique. Evidence for heterologous encapsidation of the CMV genome was found in 11 of the 33 transgenic plants tested two weeks after CMV inoculation. This demonstrates a significant rate of heterologous encapsidation events between two unrelated viruses in transgenic plants. Since CP is involved in the interactions of the virus particle with its vector, the release in the field of such transgenic plants could alter the transmission properties of some important viruses.