青藏高原东部高寒灌丛生物量分配对模拟增温的响应

植物生物量分配特征的变化反映了不同环境条件下植物的适应策略,全球气候变暖正在改变青藏高原高寒生态系统植被动态和生物量分配格局。然而,到目前为止,有关青藏高原高寒灌丛生物量分配特征对气候变暖的响应研究较少。为了探究气候变暖对高寒灌丛生物量分配的影响,以青藏高原东部典型的窄叶鲜卑花高寒灌丛为研究对象,分析了高寒灌丛灌木层、草本层和群落水平生物量分配特征对开顶式生长室（OTC）模拟增温的响应。研究结果表明：整个生长季节,模拟增温使空气温度和表层土壤温度分别升高0.6℃和1.2℃,使表层土壤水分含量下降2.7%。模拟增温使草本层和群落地上生物量显著增加57.8%和7.2%,使灌木层、草本层和群落根系生物量显著增加42.5%、105.6%和45.6%。然而,模拟增温没有显著影响灌木层地上生物量。同时,模拟增温使灌木层、草本层和群落总生物量显著增加25.6%、85.7%和28.4%,使灌木层、草本层和群落根冠比显著增加33.2%、30.4%和36.0%。由此可见,模拟增温在促进高寒灌丛生物量生产的同时将显著提高向地下根系部分的分配比例。Pearson相关分析表明,高寒灌丛生物量分配与空气温度、土壤温度和土壤硝态氮含量呈显著正相关关系;多元线性回归分析结果也表明,空气温度、土壤温度和土壤硝态氮含量解释了高寒灌丛生物量分配变异的50.8%以上。这些结果表明,青藏高原东部高寒灌丛植被能够通过调节生物量分配模式应对未来气候变暖。     

Highly Sensitive Resonance Scattering Detection of DNA Hybridization Using Aptamer-Modified Gold Nanopaticle as Catalyst

Gold nanoparticle particles in size of 10 nm were used to label the thiol-modified single-stranded DNA aptamer (SH-ssDNA) to obtain an aptamer-modified gold nanoparticle probe (AussDNA) for target DNA (tDNA). In pH 7.4 NaH₂PO₄–Na₂HPO₄ buffer solution, the hybridization reaction between AussDNA and tDNA took place to form larger aptamer-modified gold nanoparticle cluster complex. The excess aptamer-modified gold nanoparticle probe in the supernatant solutions was obtained by centrifuging and can be used as nanocatalyst for the 0.276 mmol/L CuSO₄-65.4 mmol/L potassium-sodium tartrate-0.37 mmol/L glucose system at 70 °C. The cubic Cu₂O particles generated by the nanocatalytic reducing exhibit a strong resonance scattering (RS) peak at 620 nm. In the selected conditions, the RS intensity at 620 nm decreased with addition of tDNA, and the decreased intensity ΔI _{620 nm} is proportional to tDNA concentration (C _tDNA) from 0.12 to 72 pM, with regress equation of ΔI _620 nm = 1.29C _tDNA + 4.05, correlation coefficient of 0.9917, and detection limit of 0.084 pM tDNA.     

Post‐metamorphic allometry in the earliest acrotretoid brachiopods from the lower Cambrian (Series 2) of South China,and its implications

The earliest growth of post‐metamorphic (post‐larval) shells in two species of Eohadrotreta is described from the Cambrian Shuijingtuo Formation of South China. Two different growth patterns can be observed by quantifying developmental variations in size and shape of successive stages of post‐metamorphic shell growth (including the pedicle foramen forming stage, pedicle foramen enclosing stage and intertrough increasing stage) of Eohadrotreta zhenbaensis and Eohadrotreta ? zhujiahensis . The pedicle foramen is never enclosed within the metamorphic shell of E. zhenbaensis , while the enclosed pedicle foramen of E .? zhujiahensis is located directly outside the metamorphic shell after the pedicle foramen enclosing stage. A strongly allometric growth pattern of E. zhenbaensis is demonstrated by the early enclosure of the pedicle foramen; an accelerated lengthening of the ventral intertrough is associated with the development of a more complex dorsal median septum during the intertrough increasing stage. By contrast, E .? zhujiahensis demonstrates possible paedomorphic development by delayed enclosure of pedicle foramen and an associated decreased lengthening of ventral intertrough during the intertrough increasing stage. This ontogenetic developmental sequence represents the marginal accretionary formation and growth of the pedicle foramen, which resembles that of linguloid brachiopods. Furthermore, the developmental process of the pedicle foramen of Eohadrotreta seems to recapitulate the likely evolutionary transition from the Botsfordiidae, with open delthyrium, to the Acrotheloidea, with an enclosed foramen. This study provides a unique opportunity to obtain a complete understanding of the ontogenetic development of the earliest acrotretoids, and casts new light on the phylogeny of lingulate brachiopods.     

罗汉果染色体组型的研究

本文采用根尖和组织培养材料,观察了罗汉果四个品种染色体数日和形态。结果表明,罗汉果体细胞染色体数目为2n=28染色体小,长度在1．4μm以下而又不易分辩着丝点,不同品种的染色体形态有所不同,染色体长度比为2．00-2.46之间。对罗汉果的归属问题进行了讨论。     

小秦岭自然保护区秦岭冷杉死亡原因

小秦岭国家级自然保护区濒危植物秦岭冷杉(Abies chensiensis)近几年出现了不明原因的衰败死亡现象,并有不断扩展的趋势,分析研究就地保护这一珍稀植物资源迫在眉睫。在对小秦岭全部秦岭冷杉定位监测的基础上,通过对活树、死树分布和结构的对比分析,并采用相关分析、偏相关分析和结构等式模型(Structural Equation Models,SEM)结合环境因子,探讨了秦岭冷杉的生存状况和死亡原因。结果如下:(1)枯死树与活树分布基本相一致,活树个体中小树和大树相对较少,死亡个体主要为小树和中龄树;(2)秦岭冷杉的生长与海拔、坡度、土壤含水量和土壤温度呈显著的相关性;(3)SEM分析结果显示,秦岭冷杉活树与土壤含水量和温度呈明显的正相关系,而死树却表现出负相关关系,枯死树与空间位置和地形表现出的负相关关系要明显大于活树。上述结果说明,秦岭冷杉幼苗和小树较少,更新能力差,秦岭冷杉的死亡不是个别现象和局部环境变化所造成的;秦岭冷杉的生长与海拔、坡度、土壤含水量和土壤温度关系密切;土壤含水量和温度对秦岭冷杉生长具有促进作用,是影响秦岭冷杉死亡和衰败的重要环境因素。在今后秦岭冷杉经营保护过程中要注意微环境的变化,减少人为因素对环境的干扰。     

小秦岭自然保护区苔藓植物群落数量分类、排序及多样性垂直格局

苔藓物种多样性沿海拔梯度呈什么样的分布格局?基于53个20 m×20 m样地,采集并鉴定了样地内所有生境中的苔藓物种;采用多元回归树(multivariate regression trees,MRT)对苔藓植物进行分类;采用典范对应分析(canonical correspondence analysis,CCA)进行排序分析;用广义线性模型(Generalized Linear Model,GLM)研究苔藓物种多样性沿海拔的分布格局。结果如下:(1)采集的1378份苔藓植物标本经过鉴定,共有33科89属240种,其中藓类226种,苔类14种;(2)经交叉验证认为本区苔藓植物可分为4类,Ⅰ长肋青藓(Brachythecium populeum)+大叶匐灯藓(Plagiomnium succulentum)+圆叶匐灯藓(Plagiomnium vesicatum)群落,Ⅱ灰白青藓(Brachythecium albicans)+宽叶青藓(Brachythecium curtum)+短肋羽藓(Thuidium kanedae)+平肋提灯藓(Mnium laevinerve)群落,Ⅲ短肋羽藓(Thuidium kanedae)+光萼叶苔(Jungermannia leiantha)+薄罗藓(Leskea polycarpa)+叉肋藓(Trachyphyllum inflexum)群落,Ⅳ宽叶青藓(Brachythecium curtum)+垂蒴棉藓(Plagiothecium nemorale)+全缘匐灯藓(Plagiomnium integrum)群落;(3)海拔、坡度和坡向对苔藓物种分布的解释量为7.29%;(4)苔藓物种多样性随海拔的变化成明显的上升格局。通过研究了解了小秦岭国家级自然保护区苔藓物种组成、群丛划分以及每种苔藓植物的海拔分布范围;苔藓物种多样性随海拔的上升呈显著的上升格局,与乔木、灌木和草本的分布格局不同。希望此研究能为苔藓植物生态学研究和物种多样性保护提供参考。     

宝天曼自然保护区不同针叶树径向生长对气候的响应

树木年轮资料能够提供区域内过去长时间的环境和气候信息,成为获取过去气候变化信息的重要手段之一。利用采自宝天曼自然保护区的两种针叶树种油松和华山松树木年轮样本分别建立了油松和华山松树轮宽度标准年表PT和PA,并将油松和华山松样本合并建立了联合树种的区域年表(RC)。3种年表分别与不同气候要素(月平均气温、月平均最高气温、月平均最低气温、月降水量)及其不同月份组合进行相关分析,结果表明,油松年表PT和华山松年表PA都包含较高的气候信息,且都和生长季不同月份温度显著负相关和降水显著正相关。其中,油松和华山松都与当年4月和5月降水显著正相关,油松还与当年5月的平均最高温度和上年11月最低温显著负相关,与当年3月平均最低气温显著正相关;华山松与上年10月和当年4月的平均最高温度显著负相关,与上年12月和当年7月平均最低温度显著正相关;联合年表RC包含了单个年表PT和PA共同的气候信息,与当年4—5月降水和3月最低温显著正相关,与当年7月最低温和4、5月最高温显著负相关。不同年表与生长季(3—8月)内气候要素月份组合的相关分析也表明联合年表RC包含和单物种年表PT、PA相似的气候信息并加强了PT、PA受当年生长季气候变化影响的公共信号。可见,同一地区的多树种联合年表一定程度上能体现出区域性树木生长对气候变化响应的生态生理特征,为同地区建成多树种联合年表来探讨当地区域性气候变化提供了可行性的理论基础和一定的参考作用.     

2010秋季东海今生颗石藻的空间分布

根据2010年11月东海29站位所采集108个样品偏光镜检分析结果显示:调查区共发现26种今生颗石藻,优势种为赫氏艾密里藻(Emiliania huxleyi)、大洋桥石藻(Gephyrocapsa oceanica)、卡特螺旋球藻(Helicosphaera carteri)和粗壮环翼球(Algirosphaera robusta)等.水体中今生颗石藻丰度为0-76.562个/mL,平均值为18.641个/mL;颗石粒丰度0-4506.47个/mL,平均值为613.44个/mL,今生颗石藻在表层和底层均呈斑块状分布,海盆区站位丰度较近岸站位下降明显,但物种丰富度明显增多;颗石球丰度最大值站位发生在硅藻水华站位.将研究区域划分为3个断面进行分析:PN断面、沿岸流断面和黑潮断面.比较显示,PN断面的空间分布差异性较大,赫氏艾密里藻具有最高丰度的颗石粒和颗石球.沿岸流断面颗石粒/颗石球、黑潮断面中颗石粒(除底层外),自表至底随水深增加有轻微增加趋势,黑潮断面颗石球丰度高值区集中于25-80 m之间.结合历史环境资料,分析得出东海调查期水体混合、泥沙再悬浮以及硝酸盐浓度是控制今生颗石藻物种丰富度与物种特异分布的主要因子;今生颗石藻在不同环境中具有不同的生活策略,其空间分布特征随取样季节和海区不同有较大变化.     

Metagenomic next-generation sequencing as a diagnostic tool for toxoplasmic encephalitis

Background

More than 100 different pathogens can cause encephalitis. Testing of all the neurological pathogens by conventional methods can be difficult. Metagenomic next-generation sequencing (NGS) could identify the infectious agents in a target-independent manner. The role of this novel method in clinical diagnostic microbiology still needs to be evaluated. In present study, we used metagenomic NGS to search for an infectious etiology in a human immunodeficiency virus (HIV)-infected patient with lethally diffuse brain lesions. Sequences mapping to Toxoplasma gondii were unexpectedly detected.

Case presentation

A 31-year-old HIV-infected patient presented to hospital in a critical ill condition with a Glasgow coma scale score of 3. Brain magnetic resonance imaging showed diffuse brain abnormalities with contrast enhancement. Metagenomic NGS was performed on DNA extract from 300 μL patient’s cerebrospinal fluid (CSF) with the BGISEQ-50 platform. The sequencing detection identified 65,357 sequence reads uniquely aligned to the Toxoplasma gondii genome. Presence of Toxoplasma gondii genome in CSF was further verified by Toxoplasma gondii-specific polymerase chain reaction and Sanger sequencing. Altogether, those results confirmed the diagnosis of toxoplasmic encephalitis.

Conclusions

This study suggests that metagenomic NGS may be a useful diagnostic tool for toxoplasmic encephalitis. As metagenomic NGS is able to identify all pathogens in a single run, it may be a promising strategy to explore the clinical causative pathogens in central nervous system infections with atypical features.

     

转基因食品安全性研究进展

转基因食品的安全性在世界范围内备受关注,近年来,已经成为公众争论的焦点。本文简要综述了转基因食品的现状和安全性,并介绍了我国政府对转基因食品的态度。此外,还对转基因食品的发展前景作了简要展望。