青藏高原东缘匍匐茎草本野草莓的分株种群特征及其沿海拔梯度的变化

对青藏高原东缘 5个不同海拔高度 ( 2 4 2 6m、2 75 0 m、32 0 0 m、3484m和 3944m)上旷地和林下遮荫条件下匍匐茎草本野草莓的分株种群特征进行了研究。结果显示 :无论在旷地或林下遮荫条件下 ,野草莓分株种群的密度随海拔升高显著减小 ,旷地条件下野草莓分株种群密度显著高于遮荫条件下的分株种群密度。不同海拔高度上 ,野草莓分株种群密度在不同光照条件下的变化存在显著差异。旷地条件下 ,随海拔升高其根冠比呈二次曲线变化。林下遮荫条件下 ,海拔 2 4 2 6m处的根冠比最低。光照条件的变化对野草莓分株种群的根冠比没有显著影响。运用空间自相关分析法 ( Moran` I)研究和 3944m处野草莓分株种群的空间分布格局 ,结果显示野草莓分株种群在多个尺度上呈现非随机分布格局 ,其中研究了海拔 348m处 d=1( 0 .2 m)尺度的集聚分布格局频率最高 ;与海拔 3484m相比 ,3944m处野草莓分株种群的集聚尺度更大。最后 ,结合克隆植物对环境的生态适应意义进行了讨论。     

内蒙古锡林河流域不同生境中羊草的克隆构型和分株种群特征

 克隆植物的形态可塑性在基株和种群水平上分别表现为克隆构型和分株种群特征的变化。研究对象为内蒙古锡林河流域草地、林地、沙地3种生境下的羊草(Leymus chinensis)种群,通过对羊草根茎节间长度、间隔子长度、分枝强度、分枝角度、株高和分株密度等指标的测定和分析,对这3种不同生境中羊草的克隆构型及分株种群特征进行了研究。结果表明羊草克隆构型相关特征,如,根茎节间长度,根茎节间长度频次分布格局、间隔子长度、间隔子长度频次分布格局,在不同生境差异较大。同时,羊草的分枝角度在不同生境间差异显著。而每间隔子所     

塔里木河流域胡杨和灰叶胡杨克隆分株空间分布格局

以叶尔羌河下游阿瓦提县天然胡杨和灰叶胡杨混交林、塔里木河上游农一师16团天然灰叶胡杨林和塔里木河中游轮台县天然胡杨林为对象,研究胡杨和灰叶胡杨克隆分株种群的空间分布格局.结果表明: 8种不同取样尺度(5 m×5 m、5 m×10 m、5 m×15 m、10 m×10 m、10 m×15 m、15 m×15 m、15 m×20 m、20 m×20 m)下,3个研究区2物种克隆分株种群的空间分布格局均表现为集群分布,表明集群分布是研究区胡杨和灰叶胡杨克隆分株种群空间分布格局的基本属性;在5 m×5 m尺度上,3个研究区2物种克隆分株种群均表现出负二项参数最小、Cassie指标和聚块性指标最大、聚集强度最大的分布特征.     

黑河中游荒漠草地地上和地下生物量的分配格局

草地生态系统中地上和地下生物量的分配方式对于研究生态系统碳储量和碳循环有着重要的意义.为了解黑河中游荒漠草地的地上和地下生物量分配格局,从群落和个体两个水平对黑河中游的地上和地下生物量进行了调查.结果表明:群落水平上地上生物量介于3.2-559.2 g·m-2之间,地下生物量介于3.3-188.2 g·m-2之间,个体水平上地上生物量介于6.1-489.0g·株-1之间,地下生物量介于2.4-244.2 g·株-1之间,群落水平上的根冠比(R/S)为0.10-2.49,个体水平上为0.07-1.55,地下生物量均小于地上生物量,群落水平上R/S值大于个体水平.群落和个体水平地上和地下生物量的拟合斜率分别为1.100 1和0.991 3,与1没有显著差异,说明地上与地下生物量呈等速生长关系.群落和个体水平土壤表层0-20 cm和0-30 cm的根系生物量分别占全部根系生物量的89.81％、96.95％和81.42％、93.62％,表明地下生物量主要集中在0-20cm和0-30cm土壤表层.     

亚高山暗针叶林不同林冠环境下华西箭竹的克隆可塑性

以亚高山暗针叶林3种林冠环境中以及暗针叶林林缘的华西箭竹（Fargesia nitida）为对象,对其无性系数量特征、无性系根茎特征、分株生物量以及分株形态特征进行了对比研究。结果表明：（1）林冠环境的差异导致了不同种群的基株密度和每基株分株数的显著差异,但林冠环境差异不影响分株密度。林冠郁闭度愈大,每基株分株数愈少,分株分布愈均匀。（2）不同林冠环境间。分株生物量、分株构件生物量和分株构件的生物量分配百分率均有显著差异。开敞的林冠环境有利于华西箭竹的生长和生物量积累。（3）随着林冠郁闭度的增加,华西箭竹通过增大分枝角度、叶生物量分配百分率、比叶面积和叶面积率以提高光能利用效率,有效适应弱光环境。（4）隔离者长度、隔离者直径和分枝强度在林缘和林窗环境中要显著大于林内环境;同级隔离者分枝角度随林冠郁闭度的增加而最大,其值在林下显著大于林窗和林缘,而异级隔离者分枝角度的变化则正好相反。研究表明,华西箭竹种群在不同的林冠环境中发生了明显的可塑性变化,这些可塑性变化是种群对林冠郁闭度差异的适应性反应的结果,有利于增强种群对环境中有限光资源的利用。     

毛乌素沙地根茎灌木羊柴的基株特征和不同生境中的分株种群特征

通过对毛乌素沙地常见的豆科根茎灌木羊柴的基株的分株种群的调查研究,揭示植物的克隆生长的生态适应意义。研究表明：１）根茎灌木羊柴具有合轴型分枝类型和游击型基株构型。多年生根茎在沙基质中形成多层密集网络结构。２）固定沙丘的羊柴分株种群与半固定沙丘比具有较大的密度和较长的根状茎节间,较小的平均株距,但两种生境中的分株高度是相似的。固定沙丘的种群生物量和对根茎与花果生物量的投资也高于半固定沙丘上的种群。本     

华西雨屏区白夹竹分株种群的点格局分析

采用点格局分析方法对华西雨屏区白夹竹分株种群的分布格局以及不同龄级分株之间的相互关系进行分析.结果表明:白夹竹分株种群在0～0.32 m空间尺度上呈集群分布,0.64～4.48 m空间尺度上呈均匀分布,＞4.48 m空间尺度上呈随机分布.各龄级分株种群在0～8.00m空间尺度上主要呈随机分布,龄级间略有差别.其中,Ⅰ龄级与Ⅱ、Ⅲ龄级分别在1.76～4.16 m、0.32～4.16 m尺度上接近或达到空间负关联,与Ⅳ龄级在0.32～3.04m尺度上呈显著空间负关联,表现为随着龄级差距的加大,幼龄分株与高龄级分株的空间负关联增加.白夹竹分株种群的空间格局及不同龄级分株之间的相互关系由尺度、分株龄级及环境因素其同决定.     

不同光照条件下聚花过路黄的克隆构型和分株种群特征

以都江堰灵岩山常绿阔叶林林下、林缘和林缘旷地3种不同光照环境中匍匐茎草本聚花过路黄(Lysimachla congestiflora)为对象,对其匍匐茎节间长、分枝强度、分枝角度、分株种群密度、分株种群生物量等指标进行了测定和分析．结果表明,聚花过路黄的匍匐茎节间长、分枝强度、分株种群密度和分株种群生物量在3种生境间差异显著．Kruskal Wallis检验表明,匍匐茎节间长度和分枝角度的频次分布在3种生境间差异显著．3种生境中匍匐茎节间长度分布偏斜度(skewness)的大小分别为：林缘旷地>林缘>林下．林缘旷地与林缘和林下生境在分枝角度、分株种群高度和分株种群根冠比差异显著,而且林缘旷地生境中分枝角度分布偏斜度最小．林缘和林下生境在分枝角度、分株种群高度和分株种群根冠比差异不显著．从林缘旷地、林缘到林下,聚花过路黄的克隆构型和分株种群特征发生了相应改变．结合克隆植物对资源的利用对策,讨论了不同生境中聚花过路黄克隆构型和分株种群特征可塑性的生态适应意义．     

荒漠绿洲区芦苇种群构件生物量与地下水埋深关系

在野外调查的基础上 ,利用 Pearson关联分析法研究了河西荒漠绿洲区不同生境中芦苇种群构件生物量与地下水埋深的关系 ,结果表明 :地下水埋深对芦苇种群的影响明显 ,主要体现在 :在湿地和地下水埋深小于 0 .5 m的生境中 ,芦苇种群表现为高的种群密度、低的种群高度、低的地上生物量和高的地下生物量 ;在地下水埋深为 1 .5 m左右的生境中 ,芦苇种群地上生物量最高 ,生长最旺盛。随着地下水埋深的增加 ,垂直根茎生物量对芦苇种群地上生物量的影响加强 ,而水平根茎生物量对芦苇种群生物量的影响呈随机型 ,这可能是造成芦苇种群呈不连续、斑块状分布的主要原因。在地下水埋深 1 .5 m左右的生境中 ,芦苇的垂直根茎对种群生物量影响十分显著 ( P<0 .0 1 ) ;在地下水埋深 1 .5～ 4.0 m的生境中 ,影响显著 ( P<0 .0 5 ) ,但在地下水埋深 4m以上的生境中影响不显著 ,这表明在河西荒漠绿洲区 ,芦苇垂直根茎的最大水力提升高度 4m左右     

青藏高原东缘葡匐茎草本野草莓的分株种群特征及其沿海拔梯度的变化

对青藏高原东缘5个不同海拔高度（2426m,2750m,3200m,3484m和3944m）上旷地和林下遮荫条件下葡匐茎草本野草莓的分株种群特征进行了研究。结果显示,无论在旷地或林下遮荫条件下,野草莓分株种群的密度随海拔升高显著减小,旷地条件下野草莓分株种群密度显著高于遮荫条件下的分株种群密度。不同海拔高度上,野草莓分株种群密度在不同光照条件下的变化存在显著差异,旷地条件下,随海拔升高其根冠比呈二次曲线变化。林下遮荫条件下,海拔2426m处的根冠比最低。光照条件的变化对野草莓分株种群的根冠比没有显著影响。运用空间自相关分析法（Moran′I）研究和3944m处野草梅分株种群的空间分布格局,结果显示野草莓分株群在多个尺度上呈现非随机分布格局,其中研究了海拔348m处d=1（0.2m）尺度的集聚分布格局频率最高;与海拔3484m相比,3944m处野草莓分株种群的集聚尺度更大,最后,结论克隆植物对环境的生态适应意义进行了讨论。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).