刈割冬牧70黑麦地上生物量动态与草群再生效应的研究

通过刈割冬牧70黑麦研究一、二茬草地上生物量动态特征及草群的再生效应,结果表明:从返青至初夏(6月7日)的生长期内,冬牧70黑麦可收获两茬草,地上最高总生物量可达1004.20g/m²,表明其具有强的光合生产效率。通过一、二茬草生产性能比较可以看出,在最高总生物量中,二茬草占57.11%,生长天数占总生长天数的42.06%;一茬草鲜干比相对较大,茎叶比则相对较低,说明一茬草更适合用作青饲或制备青绿饮食品,二茬草则更利于制备干草饲用或纤维食品。AGR与RGR的比较可进一步证明一茬草后期的管理对草群总生物量的形成具有重要的作用。本研究为最大限度发挥冬牧70黑麦生产性能及实施高效生态农业工程提供理论依据。     

基于光周期和温度的物候模型对华北平原刺槐始花期的模拟

光周期和温度是影响木本植物开花的两大关键气象因素。基于我国华北平原1963-2018年57个站点的刺槐始花期实测数据,构建了6种基于气温或光周期驱动的春季物候过程模型(积温模型、光周期模型、光周期-温度顺序模型、温度-光周期顺序模型、光周期-温度平行模型、光周期-温度乘法模型),并进行了参数率定和模型比较优选,以期明确刺槐开花的主导驱动因子以及潜在的光温作用机制。根据内部模拟的赤池信息准则(AIC)判定光周期-温度顺序模型的表现最佳,模拟值与观测值的相关系数(r)为0.86,均方根误差(RMSE)为4.81d,纳什效率系数(NSE)达到0.74,说明刺槐始花期的发生同时受到光周期和温度的作用。同时,在华北平原14个代表性站点上,光周期-温度顺序模型的表现普遍优于均值模型。基于光周期-温度顺序模型的参数率定结果,以下限温度6.5℃和下限日长4.5h来统计刺槐开花的实际有效积温量和实际有效日长累积量的年际变化情况,结果表明56年来刺槐开花的实际有效积温量呈现显著递增趋势,平均每10年增加4.5℃ · d(P ＜ 0.05),而实际有效日长累积量却呈现极显著递减趋势,平均每10年减少23.9h · d(P ＜ 0.01),这说明在气候变暖背景下,刺槐开花的热量需求会更快速完成,引起刺槐开花日期的提前,但自然光周期的年内变化只与地理位置有关,日长累积需求则需要更长的时间完成,因此会在一定程度上抑制春季升温引起的开花日期提前。     

西安和宝鸡木本植物花期物候变化及温度敏感度对比

植物物候是指示生态系统对气候变化响应的重要证据。已有研究多基于代表性站点的物候观测数据研究物候特征及其对气候变化的响应规律。同一气候区内,不同站点的物候变化及对温度变化响应的敏感度是否一致仍需深入探讨。本文选择同属于暖温带湿润区汾渭平原气候区的西安和宝鸡为研究区,利用"中国物候观测网"在两个站点21个共有物种的开花始期和开花末期数据,比较了1987—2016年两站点各植物花期物候变化特征及其对温度变化响应的敏感度差异。结果表明,西安和宝鸡各物种的开花始期和开花末期均以提前趋势为主。大部分物种开花始期在西安的提前趋势(平均趋势-0.57 d/a)明显强于在宝鸡的提前趋势(平均趋势-0.29 d/a),但开花末期趋势差异不显著。除紫薇和迎春的敏感度差异较大外,其他物种开花始期和开花末期的温度敏感度在两站点间非常接近,无显著差异。由此可见,在同一气候区的不同站点,因增温幅度不同,植物的始花期变化存在较大差异,不能用单站点的物候变化反映整个气候区的物候变化。但同一植物在单站点的温度敏感度可以较好的反映同一气候区其他站点的植物物候-气候关系。本文研究结果可为利用有限站点的物候观测数据分析区域物候...     

高校生物化学首堂课教学方法探索与实践

生物化学作为医学、生命科学等专业学生必修的一门学科基础课程,理论性强、概念抽象、内容较多、逻辑关系复杂,是教学难度相对较大的一门课程。本文通过阐述在首堂课授课过程中,从任课教师如何塑造良好的自身形象,如何形象生动地引入生物化学的研究内容,如何通过展现生物化学的魅力来激发学生的学习热情和兴趣,如何使用巧妙的方法学好这门课程,以及如何将课程思政理念融入到生物化学课程中等诸多方面,探讨了在授课过程中的一些教学方法和实践,以期改变生物化学课堂不受学生喜爱的现状,为生物化学课程教学改革提供一些思路和参考。     

Grain and flour quality of wheat genotypes grown under heat stress

Heat stress during the grain-filling period is the main abiotic stress factor limiting grain yield and quality in wheat (Triticum aestivum L.). In this study, 64 wheat genotypes were exposed to heat stress during reproduction caused by delayed sowing in two growing seasons. Grain yield, 1000 grain weight (GW), grain hardness (GH), and grain-quality related traits were investigated. Heat stress caused a significant decrease in GW through reducing starch content (SC) and a non-compensating rise in protein content (PC), and thereby resulted in lower yield. In addition, significant increases in flour water absorption (WA), Zeleny sedimentation volume (ZT), ash content (AC), lipid content (LC), loaf volume (LV), wet gluten content (WG), dry gluten content (DG), gluten index (GI), and amylopectin content (APC) were found following heat stress. In contrast, decreases in grain moisture content (MC) and amylose content (AMC) induced by heat stress were observed. The heat-tolerant genotypes were superior in grain yield, GW, SC, AMC, and MC. While the sensitive genotypes contained higher PC, LV, GI and AMP. A group of wheat genotypes characterized with a higher yield, AMC, GW, and SC as well as lower PC, WA, GH, ZT, and LV; and was found to be the most heat tolerant by principal component analysis. Lighter weight and smaller grains produce a smaller starchy endosperm with lower quality (less amylose) and higher grain protein content in heat stress compared to normal conditions. Heat stress caused by delayed sowing improves some of the baking-quality related traits.     

Reproduction and survival of Glaucous Gulls breeding in an Arctic seabird colony

ABSTRACT.   Despite being widespread and easily observed, little is known about the life history of Glaucous Gulls ( Larus hyperboreus ). From 1984 to 2007, we examined their breeding biology and demography at Coats Island, Nunavut, Canada, where they nest alongside a colony of 30,000 pairs of Thick-billed Murres ( Uria lomvia ). The gulls fed mainly on murre eggs and chicks and by scavenging adult carcasses. The median age at first breeding was 5 yr, and the mean age was 4.8 ± 0.9 yr. Adult survival was estimated as 0.84 ± 0.03 (SE). The mean clutch size was 2.56 eggs and the mean number of young reared per year was 1.6 (range = 0.9–2.2). Birds reared at the colony provided 40% of recruits. Assuming that survival of locally reared chicks that emigrated was similar to that of chicks that returned to the colony, about 22% of the young gulls survived to breeding age. The timing of breeding by Glaucous Gulls appeared related to the timing of laying by murres. Although the demographic characteristics of Glaucous Gulls in our study were similar to those of populations of other large gulls, adult survival was at the lower end of the range for populations of large Larus gulls. There is some evidence that Glaucous Gulls exhibit lower survival than large gulls breeding in temperate areas, possibly because of contaminant burdens. In general, however, the demographic characteristics of large gulls show little variation and are probably a product of their common phylogeny.     

First record of the western black widow spider Latrodectus hesperus Chamberlin & Ivie, 1935 (Araneae: Theridiidae) in South Korea

Two individuals of Latrodectus hesperus Chamberlin & Ivie were newly found in munitions storage at military facilities in Daegu, South Korea. A female was first discovered on August 31, 2018, and followed by another female along with three egg sacs on September 20, 2018. These spiders were identified based on morphological characters and DNA barcode sequence analysis. Additional surveys were made around the initial detection site to examine the range and spread of this species, but no additional individuals were found.     

Molecular insights into Aβ42 protofibril destabilization with a fluorinated compound D744: A molecular dynamics simulation study

The aggregation of amyloid β‐peptide (Aβ₄₂) into toxic oligomers, fibrils, has been identified as a key process in Alzheimer's disease (AD) progression. The role of halogen‐substituted compounds have been highlighted in the disassembly of Aβ protofibril. However, the underlying inhibitory mechanism of Aβ₄₂ protofibril destabilization remains elusive. In this regard, a combined molecular docking and molecular dynamics (MD) simulations were performed to elucidate the inhibitory mechanism of a fluorinated compound, D744 , which has been reported previously for potential in vitro and in vivo inhibitory activity against Aβ₄₂ aggregation and reduction in the Aβ‐induced cytotoxicity. The molecular docking analysis highlights that D744 binds and interacts with chain A of the protofibril structure with hydrophobic contacts and orthogonal multipolar interaction. MD simulations reveal destabilization of the protofibril structure in the presence of D744 due to the decrease in β‐sheet content and a concomitant increase of coil and bend structures, increase in the interchain D23‐K28 salt bridge distance, decrease in the number of backbone hydrogen bonds, increase in the average distance between Cα atoms, and decrease in the binding affinity between chains A and B of the protofibril structure. The binding free‐energy analysis between D744 and the protofibril structure with Molecular Mechanics Poisson‐Boltzmann Surface Area (MM‐PBSA) reveal that residues Leu17, Val18, Phe19, Phe20, Ala21, Glu22, Asp23, Leu34, Val36, Gly37, and Gly38 of chain A of the protofibril structure contribute maximum towards binding free energy (ΔG _binding  = −44.87 kcal/mol). The insights into the underlying inhibitory mechanism of small molecules that show potential in vitro anti‐aggregation activity against Aβ₄₂ will be beneficial for the current and future AD therapeutic studies.