应用多种生物类群评价白洋淀水环境质量变化

白洋淀是华北平原最大的浅水湖泊。近几十年来,白洋淀上游耗水增加,天然入淀水量急剧减少,使白洋淀水位明显降低;同时,随着淀泊周边农村生活污水的排入,白洋淀发生了严重的富营养化。2017年雄安新区设立,白洋淀环境治理工作的重要性空前提高。近几年通过上游水库和跨流域生态补水,白洋淀水位明显抬升,同时淀中和淀边农村实施了生活污水收集。为了解白洋淀当前水环境状况,对前期补水和治污的效果进行评估,2019年8月对白洋淀水体理化指标及水生生物进行调查,采用水质、浮游植物、浮游动物、底栖动物指标评价白洋淀水环境质量,并与2010年的调查数据进行对比,辅以沉水植物指标评价水体生态状况。结果表明: 白洋淀2019年总磷达到优于Ⅲ类水平,总氮优于Ⅱ类水平,水环境状况比2010年有较大改善。其中,总磷浓度下降了88.6%,总氮浓度下降了83.9%,叶绿素a浓度下降了47.8%,透明度增大了43.4%;浮游动物、底栖动物等生物多样性明显提高,浮游植物密度显著降低,优势种从普遍的重富营养型转变为富营养型;沉水植物清洁型种类分布范围缩小。这说明沉水植物物种评价法不适于白洋淀水环境质量评价,浮游动物多样性评价方法也不适用于当前白洋淀水环境质量评价。早期,由于污染源集中在西部,白洋淀西部水质差于东部;现在,由于自西、北、南多方向补水,淀区的水动力条件发生显著改变,加之西部实施治污工程,淀区水质呈现空间均一化的特点。     

生态阈值确定方法综述

生态系统在环境条件变化时表现出的剧变或阈值现象是当前生态学研究的热点,但是生态阈值定量检测的困难阻碍了这一主题的研究与应用。本文从典型案例入手,通过分析潜在生态阈值的S型曲线式、补给-压力式和跃迁式驱动-响应机理,归纳了局部加权回归散点平滑法、分段回归、高斯模型、拐点分析软件、稳态转换检测软件、指示种阈值分析和系统动力学仿真模型7种生态阈值确定方法,并评述了其优缺点和适用性,以期为生态阈值的定量分析研究提供方法借鉴。     

内生真菌感染对宿主羽茅及邻生植物抗病性的影响

Epichloë内生真菌能够影响宿主植物的抗病性, 但目前关于内生真菌感染对宿主邻生植物抗病性影响的研究很少。该研究首先调查了内蒙古呼伦贝尔天然草地中植物病害发生情况, 发现在常见牧草中禾本科植物病害最为严重, 其中感染内生真菌的羽茅(Achnatherum sibiricum)的总病情指数最低。进一步比较了与羽茅邻生及非邻生植物的病害差异, 结果显示羽茅显著降低了邻生羊草(Leymus chinensis)、狼针草(Stipa baicalensis)和冰草(Agropyron cristatum)的褐斑病病情指数。为探究羽茅对邻生植物病害的影响是否与其内生真菌有关, 分别从内生真菌发酵液、离体叶片和植株层面进行了室内验证试验。结果表明: 羽茅的2种内生真菌Epichloë gansuensis和Epichloë sibiricum发酵液显著抑制了新月弯孢(Curvularia lunata)、根腐离蠕孢(Bipolaris sorokiniana)、核盘菌(Sclerotinia sclerotioru)和三叶草核盘菌(Sclerotinia trifoliorum)的生长; 对于离体叶片, E. gansuensis和E. sibiricum显著减小了宿主叶片受4种病原真菌侵染后的病斑长度。在新月弯孢和根腐离蠕孢的植株接种条件下, 内生真菌显著降低了宿主羽茅及邻生植物羊草的病害程度。该研究首次发现并验证了羽茅内生真菌对邻生禾草抵御褐斑病有一定的增益作用。     

猴头菌UDP-葡萄糖-4-差向异构酶基因克隆表达及酶学性质

通过实验室前期对诱变菌株猴头菌321的多组学分析结果,获得了一个多糖合成过程中起关键作用的UDP-葡萄糖-4-差向异构酶基因（UDP-glucose-4-epimerase,UGE）,并在大肠杆菌E. coli BL21（DE3）中进行了异源表达。通过筛选最优的目的蛋白诱导表达条件后,通过镍柱亲和层析纯化后获得高纯度目的蛋白,并对目的蛋白进行了酶学性质的研究,明确了其生物学性质和动力学参数,为其开发利用提供理论参考。     

黑鲷ELO基因编码蛋白结构与功能的生物信息学分析

黑鲷是一种抗逆性强的海水经济鱼类,但在长江以北无法在室外自然越冬,每年进行室内越冬又耗时耗力。为了培育黑鲷耐低温品系,探究黑鲷低温耐受的分子机制,研究了黑鲷脂肪酸延长酶（fatty acid elongase,ELO）基因编码蛋白的结构和功能。首先,运用DNAman 8软件对黑鲷、金头鲷、鱖鱼、斜带石斑鱼、鲤鱼等5种鱼类的ELO蛋白进行氨基酸序列比对,分析其同源性和进化关系;随后,利用生物信息学工具对黑鲷ELO蛋白的理化性质、亚细胞定位、信号肽、跨膜区、剪切位点、蛋白磷酸化、糖基化、二级结构、结构域、分子功能及蛋白质相互作用等进行分析,并进行同源建模与三维结构预测。氨基酸序列比对结果显示,黑鲷与其他鱼类之间序列的同源性较高,在所分析的5种鱼类中,黑鲷与金头鲷亲缘关系最近,与鲤科鱼类亲缘关系最远。生物信息学分析结果表明,ELO蛋白为碱性、小分子、稳定、非分泌型亲水蛋白质,亚细胞定位于细胞质、细胞核和线粒体;该蛋白质中存在22个剪切位点、19个磷酸化位点和 9个赖氨酸糖化作用位点,没有糖基化位点和信号肽;其包含多种二级结构,其中以α-螺旋为主,存在1个结构域及7个跨膜区域;ELO蛋白与其他10个蛋白质可能存在直接的相互作用关系,有可能影响雌激素合成。通过对黑鲷ELO基因编码蛋白结构与功能的生物信息学分析,初步判定其与低温耐受相关。研究结果为黑鲷耐低温品系选育提供了基础理论依据。     

不同来源家蝇幼虫蛋白粉的水解与抗氧化性

本研究比较不同来源、不同酶解物浓度的家蝇幼虫蛋白及其抗氧化活性。以来自猪粪源和鸡粪源家蝇幼虫为原料制备蛋白粉,用胰蛋白酶水解蛋白粉制备水解产物,以·OH和O_2~-·清除率为指标评价两种蛋白酶解物的抗氧化活性。结果显示,家蝇幼虫蛋白水解物在4 h达水解度最高值,其水解物的·OH清除率在5 h达到最大为59.02%,其水解物的O_2~-·清除率在4 h达到最大为73.24%;随着两种水解物浓度增加,其抗氧化效果越强,当猪粪源和鸡粪源家蝇幼虫酶解物浓度为10 mg/mL时,两者O_2~-·清除率达到最大分别为70%和80%;·OH清除率分别为45%和52%。由此可见,家蝇幼虫酶水解物对超氧阴离子、羟自由基均有清除能力,鸡粪源家蝇幼虫酶解物优于猪粪源。     

悬铃木方翅网蝽发生为害调查与防治

悬铃木方翅网蝽是一种外来入侵害虫,该虫近几年在石家庄发生普遍,为害严重.调查了悬铃木方翅网蝽在石家地区的寄主植物、为害特点和发生规律,观察描述了其形态特征、生活史和生活习性,测试分析了树冠喷施不同药剂对悬铃木方翅网蝽的防效.     

纳米硒对岢岚绒山羊妊娠母羊及胎儿抗氧化性、硒蛋白表达及生长发育的影响

为研究纳米硒对岢岚绒山羊妊娠母羊及胎儿抗氧化能力、硒蛋白表达和生长发育的影响。选择体重相近的岢岚妊娠绒山羊80只,随机分为2组,分别喂以基础日粮和添加0.5mg/kg DM纳米硒的饲粮,实验期110d。结果表明:日粮中纳米硒的添加极显著(P<0.01)地提高了母羊及胎儿血清中GSH-Px、SOD的活性;极显著(P<0.01)提高了母羊及胎儿肝、胎盘组织中GSH-Px、SOD的活性;极显著(P<0.01)降低了母羊及胎儿血清与胎盘组织中MDA的浓度。在日粮中添加纳米硒后,母羊及胎儿肝、肾组织中cGPx1 mRNA的表达显著提高(P<0.05);胎盘组织中的cGPx、SeP、Trx1 mRNA的表达极显著提高(P<0.01)。妊娠母羊的基础日粮中加入纳米硒,极显著(P<0.01)提高了妊娠母羊及胎儿血清、肝、胎盘组织中IGF-1的含量和IGF-1mRNA表达量,显著增加了胎盘、胎儿及胎儿肝、肾组织的重量(P<0.05)。日粮中添加0.5mg/kg DM纳米硒,增强了妊娠母羊及胎儿的抗氧化能力,提高了IGF-1、cGPx1、SeP和Trx1 mRNA的表达量,进一步促进了胎儿的生长发育。     

Hydraulic failure and tree dieback are associated with high wood density in a temperate forest under extreme drought

Catastrophic hydraulic failure will likely be an important mechanism contributing to large‐scale tree dieback caused by increased frequency and intensity of droughts under global climate change. To compare the susceptibility of 22 temperate deciduous tree and shrub species to hydraulic failure during a record drought in the southeastern USA, we quantified leaf desiccation, native embolism, wood density, stomatal conductance and predawn and midday leaf water potential at four sites with varying drought intensities. At the two driest sites, there was widespread leaf wilting and desiccation, and most species exhibited predawn leaf water potentials of ≤3 MPa and >60% loss of xylem conductivity in branches. Although species with high wood density were more resistant to cavitation, they had higher levels of native embolism and greater canopy dieback than species with low wood density. This unexpected result can be explained by the failure of species with dense wood to avert a decline in water potential to dangerous levels during the drought. Leaf water potential was negatively correlated with wood density, and the relationship was strongest under conditions of severe water deficit. Species with low wood density avoided catastrophic embolism by relying on an avoidance strategy that involves partial drought deciduousness, higher sensitivity of stomata to leaf water potential and perhaps greater rooting depth. These species therefore maintained water potential at levels that ensured a greater margin of safety against embolism. These differences among species may mediate rapid shifts in species composition of temperate forests if droughts intensify due to climate change.     

Reduced N cycling in response to elevated CO2, warming,and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

Field‐scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a seminatural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO₂), warming, and extended summer drought in all combinations. Here, we report on the short‐term responses of the nitrogen (N) cycle after 2 years of treatments. Elevated CO₂ significantly affected aboveground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co‐dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Belowground, elevated CO₂ had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH₄⁺ consumption, gross mineralization, potential nitrification, denitrification and N₂O emissions. Drought reduced belowground gross N mineralization and decreased fauna N mass and fauna N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue in response to elevated CO₂, as well as drought‐induced decreases in litter N production and fauna N mineralization prevailed in the full treatment combination. Overall, the simulated future climate scenario therefore lead to reduced N turnover, which could act to reduce the potential growth response of plants to elevated atmospheric CO₂ concentration.