Allochrony as a potential driver for reproductive isolation in adaptive radiations of European whitefish ecomorphs

In northern Fennoscandian lakes, monophylogenetic lineages of postglacial fishes are radiating into several adaptive forms, but the speciation process is still at an incipient stage. The speciation process has received increased attention over the years, but the underlying mechanisms and drivers are still debated and poorly understood. European whitefish (Coregonus lavaretus [L.]) is the most abundant fish species in these lakes and has evolved into several ecomorphs adapted to different trophic niches and habitats. Genetic divergence has been observed among these ecomorphs, but the mechanism(s) responsible for the ongoing build-up of reproductive isolation has still to be revealed. As these systems are young in evolutionary time (<10 kyr), prezygotic and postzygotic extrinsic isolation mechanisms are thought to be more likely to contribute to the reproductive isolation than intrinsic isolation mechanisms. We determined the gonadosomatic index (GSI) of three ecomorphs in two replicated lake systems and used GSI as a proxy to investigate the prezygotic isolation mechanism, allochrony, as a driving factor of divergence in this adaptive radiation of whitefish. We found that the three ecomorphs differed in GSI values within and between lakes, suggesting different spawning times of the ecomorphs. We also show that males of one ecomorph had equal onset of maturity as another ecomorph, giving novel insights into the ongoing gene flow observed between ecomorphs. The result supports allochrony as a driver for the divergence process of whitefish ecomorphs, but more evidence is still needed to rule out that the three ecomorphs make use of different spawning grounds.     

Interactions between arbuscular mycorrhizal fungi and fungivorous nematodes on the growth and arsenic uptake of tobacco in arsenic-contaminated soils

The effects of inoculation with two AM fungi (M1, Glomus caledonium; M2, Glomus spp. and Acaulospora spp.) and a fungivorous nematode Aphelenchoides sp. on growth and arsenic (As) uptake of Nicotiana tabacum L. were investigated in soils contaminated with a range of As. The reproduction of Aphelenchoides sp. was triggered by the co-inoculation of AM fungi regardless of AM fungal isolates and As levels. Stimulative effects of Aphelenchoides sp. on the development of mycorrhiza, slightly different between two AM fungi, were found particularly at the lowest As level. Irrespective of mycorrhizal inoculi, increasing soil As level decreased plant growth, but increased plant As uptake. Co-inoculation of AM fungi and Aphelenchoides sp. led plants to achieving further growth and greater As accumulation at the lowest As level. Results showed that the interactions between AM fungi and fungivorous nematodes were important in plant As tolerance and phytoextraction at low level As-polluted soil.     

森林土壤有机氮的X光吸收近边结构光谱技术测定

本研究通过采用氮的K边X光吸收近边结构(XANES)技术来了解森林土壤有机氮,以此深入研究土壤中有机氮种类与其转化的定量关系。土壤样品采自台湾中部的云杉、铁杉林与草地。结果表明,氮的 XANES 可以揭示样品中不同的氮的种类。在土壤腐植质、可溶性氮及本体土壤中胺态及吡咯氮占了主要的比率。然而不同处理及植被下的土壤样品氮的种类分布是不同的。云杉与铁杉土壤可溶性有机氮在402.3 eV 能量处有显著的差异。在A层土壤中,吡啶类氮含量要显著高于O层土壤,说明氮在不同土层中的转化率存在极大的差异,这种变化对于氮在森林土壤中的循环将起重要作用。图3表1参8。     

坛紫菜中铝的形态分析及风险性评价

应用化学连续萃取法结合电感耦合等离子体质谱(ICP-MS)法对紫菜中铝的存在形态进行了初步研究,并对紫菜中铝食用安全性进行了评价。所测30份紫菜样品中铝的总含量范围为74.3~1 479 mg/kg,紫菜中铝的形态存在难溶态>有机态>无机态>水溶性游离态的分布规律。约75%的铝以难溶态存在。可溶态的铝主要以有机铝的形态存在,有机铝占总可溶态铝的72%左右。无机铝主要以Al(OH)₃的形态存在,水溶性游离态铝占无机铝的18.5%。通过模拟胃肠消化环境测定紫菜中铝的溶出率,结果表明,模拟胃液可溶出的铝占总铝的1.38%～6.80%,说明大部分铝在人体消化过程中不易溶出,对人体的潜在危害并不大。     

Mechanisms of cadmium accumulation in rice grains and molecular breeding for its reduction

ABSTRACT

Cadmium (Cd) has an important impact on agriculture, as the excessive consumption of this element from contaminated food crops leads to toxicity in humans. Rice is the greatest source of dietary Cd intake in populations consuming rice as a staple food. Therefore, reducing the Cd concentration of rice grains for diminishing the potential risk of Cd for human health is a major challenge. This review summarizes the main achievements on Cd accumulation in rice by our research group. Using a positron-emitting tracer imaging system, we succeeded to visualize differences in real-time Cd dynamics from roots to panicles in rice varieties with different Cd accumulation abilities. Several loci or genes responsible for Cd accumulation in rice were found through quantitative trait loci (QTLs) analysis. Using the QTL qCdp7 responsible for efficiently extracting Cd from paddy soils, practical rice varieties for Cd-phytoextraction were developed by DNA marker-assisted breeding. A rice variety named ‘Koshihikari Kan No.1? carrying a mutant allele of OsNramp5 for reducing Cd concentration in rice grains was produced by mutant breeding with ion-beams, and breeding programs have been implemented to transfer this allele into many Japanese rice varieties by DNA marker-assisted breeding. Growing low-Cd varieties aerobically would be a feasible way to simultaneously reduce inorganic arsenic and Cd concentrations in rice grains. These results provide basis for reducing Cd concentration in rice through breeding new varieties.     

Mechanisms of arsenite elimination by Thiomonas sp. isolated from Carnoulès acid mine drainage

Weathering of the arsenopyrite-rich tailings of the Carnoulès abandoned mining site (Gard, France) results in the formation of acid mine waters heavily loaded with arsenic. Dissolved arsenic present in the seepage waters is precipitated within a few meters from the bottom of the tailing dam by microorganisms. From these effluents, we have isolated and characterized a Gram negative bacterium involved in this bioremediation process. This bacterium, which belongs to the Thiomonas genus, is very efficient in removing arsenite from contaminated acidic waters by oxidizing it to arsenate, which precipitates.     

土壤中砷的来源及迁移释放影响因素研究进展

砷是一种高致癌风险的类金属,自然环境中高砷(As)含量可对人类和生态系统构成直接的健康威胁。研究自然环境中砷的来源、存在形式及影响因素有助于进一步理解环境中砷的迁移转化规律,降低人体摄入砷的风险。对文献的分析表明,铁锰氧化物矿物的还原性溶解、黄铁矿及其他硫化物矿物的氧化溶解、铝氢氧化物表面的砷还原、有机质抑制砷吸附以及Eh降低和pH升高是造成砷向环境迁移的主要原因。本文综述了环境中砷的来源及其向环境迁移的多种影响因素,分析了这些因素与砷之间的作用机制,以期为加强砷污染治理提供科学依据。     

Mobility and phytoavailability of arsenic in an abandoned mining area

The mobility and phytoavailability of arsenic in an area affected by the abandoned exploitation of an arsenical tungsten-tin deposit was studied to establish the current and eventual environmental risks and to propose possible remediation practices. Soil and plant samples were collected at different distances from the polluting sources and analyzed for their As content and distribution. Critical soil total concentrations of As were found, with values in the range 175-2300 mg kg^− 1. The readily labile As contents represent < 0.2% of the total concentrations, whereas the As contents more prone to be mobilized could rise up to 25%. Different phytostabilizing plants were identified, namely, Agrostis castellana (Boiss. & Reut.), Centaurea jacea L., Eryngium campestre L. and Scirpus holoschoenus L.. Such plants show important root bioaccumulation factor values in relation to the labile As contents (up to 197, 58, 201 and 88, respectively) and low translocation factor values (down to 0.170, 0.032, 0.173 and 0.036, respectively). Additionally to promote the revegetation with these plants, the species Rumex acetosella L. should be eliminated as this behaves as an index plant, reaching above-ground As concentrations up to 218 mg kg^− 1.     

双道原子荧光光谱同时测定土壤中砷、汞的方法研究

研究了土壤中总As、总Hg的同时测定方法,并对消化体系进行了筛选,利用正交试验设计法对测试条件进行了优化.建立了用王水消解样品,在10%盐酸溶液中用双道原子荧光光度计同时测定土壤中As、Hg的新方法.方法线性范围宽(As 0～200μg/L;Hg 0～10μg/L);检出限低(As 0.05μg/L;Hg 0.007μg/L);As的回收率为96.0%～101.0%,Hg的回收率为97.0%～103.7%;相对标准偏差(RSD)As为2.7%,Hg为4.5%.该方法准确、简便、快速,结果令人满意.     

砷污染土壤的蜈蚣草修复研究进展

本文评述了As污染土壤的蜈蚣草植物修复及其对As的解毒机制的研究进展,内容着重包括蜈蚣草对As的富集特征,As在蜈蚣草中的赋存形态、迁移及其转化,土壤以及土壤中P、Ca和K等元素对蜈蚣草吸收、转运As的影响等方面。