西沟煤矿煤火废弃地土壤种子库与地上植被关系研究

采用种子萌发法和地表植被调查法, 研究了西沟煤矿煤火废弃地及留存原有植被的对照山体土壤种子库与地表植被之间的关系。结果表明: 研究区地表植被分属22 科58 属77 种, 优势科主要为蔷薇科、禾本科、菊科和豆科。地表植被的物种生活型, 以生长周期短、适应性强的多年生草本为主。地表植被物种丰富度指数、多样性指数和均匀度指数都以草本层为最高。研究区土壤种子库中共有40 种物种, 以多年生草本为主。土壤种子库的物种丰富度指数、多样性指数和均匀度指数与地表植被具有一致性, 相比地表植被物种多样性变化不明显。土壤种子库与地表植被共有物种为38种, 二者Sorensen 相似性系数为0.65。表明研究区土壤种子库与地表植被间相似性较高, 这与长期煤矿开采和放牧等人为活动有很大关系。     

荒漠草原土壤种子库对草地管理方式的响应

以宁夏中部不同封育年限(封育1a、3a、5a和7a)、不同放牧方式(中等强度自由放牧、中等强度4区轮牧)、补播改良(2006年补播沙打旺Astragalus adsurgens和紫花苜蓿Alfalfa stiva)及未封育等管理方式下的荒漠草原为研究对象,采用空间梯度代替时间梯度法,于2012年3月下旬用样线法采集土壤样品,采用温室萌发法,统计土壤种子库物种组成和种子数,研究了不同草地管理方式下的种子库与地上植被相似性、多样性等特征。结果表明:1)宁夏荒漠草原土壤种子库中共出现14种植物,分属6科14属,除牛枝子(Lespedeza potanimii)为半灌木外其余均为草本植物。多年生植物占土壤种子库植物总数的65.3%,一年生植物占土壤种子库植物总数的35.7%;多年生植物种子数量随封育年限增加而表现为下降趋势,封育1a和未封育草地最多;2)不同管理方式下土壤种子库和地上植被的共有物种数为2—6种,封育时间延长导致土壤种子库物种与地上植被相似性下降,土壤种子库和地上植被共有物种数有减少趋势,自由放牧降低了土壤种子库和地上植被的共有物种数,补播恢复的草地土壤种子库中未出现补播物种;3)种子库物种多样性与管理方式无明显的相关性;种子库物种多样性指数4区轮牧草地最高,封育7a草地最低,物种丰富度指数封育1a草地最高,均匀度指数自由放牧草地最高,补播草地最低。若荒漠草原仅依靠土壤种子库恢复自然植被,则不建议封育时间过久,需间以适当的干扰(放牧);补播外来种未对荒漠草原土壤种子库产生贡献,反而对乡土种产生了一定限制。     

科尔沁沙质草地放牧和围封条件下的土壤种子库

该文研究了科尔沁沙质草地在放牧和围封条件下土壤种子库密度、组成及其与地上植被的关系。结果表明:1)放牧草地植物种数22种,围封草地植物种数30种,围封使土壤种子库植物种数增加了36%;2)放牧草地土壤种子库密度为16 149±1 900有效种子数·m^-2, 围封草地土壤种子库密度为20 657±3 342有效种子数·m^-2,比放牧草地增加了28%。放牧和围封草地种子库组成密度均以一年生植物为主(分别占99%和98%的比例),多年生植物所占的比例很小;3)放牧草地种子库的Shannon-Wiener指数和丰富度指数分别为0.836 3和4.954 9,明显小于围封草地的0.968 2和7.226 0,表明自由放牧导致物种多样性下降;4)放牧和围封草地土壤种子库密度与地上植被密度均存在显著的相关性(p<0.001)。表明了随着土壤种子库密度的增加, 地上植被密度随之增加,放牧草地地上植被密度78%的变异可归结为土壤种子库密度的变异, 而围封草地地上植被密度58%的变异可由土壤种子库密度的变异来解释。     

铜尾矿废弃地与相邻生境土壤种子库特征的比较

土壤种子库是植被群落的重要组成部分,其特征决定了群落的演替方向。对铜陵杨山冲尾矿库6个植被群落及相邻两处生境的土壤种子库进行了研究。结果表明,尾矿内各植被群落种子库的种子密度间存在较大差异,变化范围为57—593粒/m2,平均种子密度为370粒/m2,尾矿坝体和周围山体种子库种子密度分别为999和121粒/m2,各样地土壤中种子均主要集中在0—5 cm范围内。尾矿种子库与坝体种子库间的相似性指数大于其与周围山体种子库的相似性指数,但尾矿内各植被群落种子库间的相似性较差,相似性指数的变化范围为0.308—0.636。可见,群落微生境对土壤种子库的种子密度和物种组成产生了较大的影响。尾矿种子库种类与地上植被的平均相似指数为0.355,低于坝体种子库种类与地上植被相似性系数。3处样地土壤种子库的物种多样性、丰富度和均匀度指数均表现为坝体>尾矿>山体。尾矿种子库在农田土壤中萌发并正常生长的幼苗为16科44属53种,而在尾矿基质中仅为9科36属45种,均以禾本科、菊科和豆科植物萌发和生长状况较好,这3科构成了尾矿地上植被的主要类型。尾矿种子库在尾矿基质中萌发成活率为62.2%—91.2%,约为坝体和山体土壤种子库在尾矿基质中萌发成活率的2倍。说明,组成尾矿种子库的种子大部分已经适应了尾矿的极端恶劣环境或者其本身就是耐性极强的植物类型。     

青藏高原东缘封育和退化高寒草甸种子库差异

采用幼苗萌发法研究了青藏高原东部高寒草甸封育和退化地区土壤种子库的差异.结果表明:(1)两个样地总共有10161株幼苗萌发,分属55个物种,23个科.封育样地多年生植物比例高于退化样地,禾草和单子叶植物比例在两个样地间差异不大.(2)退化样地土壤种子库种子密度((6105±1530) m-2)显著高于封育样地((3883±798) m-2),而物种丰富度差异不显著.所研究区域拥有较为丰富的种子库资源,退化地区资源更丰富,说明恢复不存在种子限制问题,土壤种子库可以成为植被恢复的潜在资源.(3)种子密度和物种丰富度在垂直分层上差异显著,且随着深度的增加而显著减小.(4)用Srensen coefficient指数计算出土壤种子库和地上植被之间的相似性在整体上较低,封育样地(45.3%)略高于退化样地(40.4%),两个样地地上植被之间的相似性为50%,而种子库之间相似性高达84.6%,说明种子库起到一个"缓冲器"的作用.(5)Shannon-Wiener多样性指数分析显示,无论在地上植被或种子库中,物种多样性都是封育样地显著高于退化样地.过度放牧不仅导致地上植被的生物多样性丧失,而且使种子库中的物种多样性降低,而封育管理可以维持地上植被和种子库中的物种多样性.     

蔡家河湿地土壤种子库特征及其与地上植被和土壤因子的关系

为明确蔡家河湿地土壤种子库特征及其与地上植被和土壤因子的关系, 采用野外调查取样和室内萌发实验相结合的方法, 对芦苇群落, 野艾蒿群落和林下杂草群落3种不同植被类型的土壤种子库密度, 物种组成, 地上植被以及土壤理化性质进行了调查研究。结果表明: 蔡家河湿地3种植被类型的土壤种子库密度分别为(7725±1286) 粒•m-2, (2535±556) 粒•m-2和(5085±984) 粒•m-2; 物种数量分别为36种, 28种和39种。3种植被类型土壤种子库的物种丰富度以及多样性均高于地上植被, 并且3种植被类型间土壤种子库物种组成的相似性高于地上植被, 说明土壤种子库比地上植被具有更高的稳定性。芦苇群落的种子库密度, 物种多样性指数以及土壤种子库和地上植被物种组成的相似性均高于野艾蒿群落和林下杂草群落。土壤含水量与土壤有机质是影响土壤种子库物种组成的主要土壤因子, 在土壤水分以及有机质含量高的芦苇群落中含有大量湿生植物种子, 但在水分和有机质含量低的野艾蒿和林下杂草群落未发现柳叶菜(Epilobium hirsutum)、马先蒿(Pedicularis resupinata)、问荆(Equisetum arvense)等湿生植物的种子。因此, 蔡家河湿地土壤种子库已出现一定程度的退化, 芦苇群落土壤种子库可用作退化湿地植被恢复的种源, 在植被恢复时要满足种子萌发对土壤水分和有机质的需求。     

三峡库区消落带回水区水淹初期土壤种子库特征

将三峡库区消落带回水区次生灌丛和弃耕地分成水淹区段、未水淹区段和对照样带,通过萌发法对其土壤种子库进行研究.结果表明:两种植被类型的土壤种子库储量存在极显著差异,次生灌丛种子密度为(6991±954)粒·m^-2、弃耕地种子密度为(26193±6928)粒·m^-2.3种生境中,水淹区段的种子密度最低,未水淹区段最高.随着土层加深,种子库密度逐渐下降.土壤种子库萌发试验出现的物种分属45科97属118种,以一年生和多年生草本植物为主,其中菊科、禾本科、玄参科和十字花科为优势科;个体数量占土壤种子库总储量小于0.01%的物种有34种,占28.8%.两种植被类型的土壤种子库中物种数较接近,物种多样性指数和均匀度较高,但优势物种组成差异很大,生态优势度较低.3种生境中,未水淹区段的生物多样性最高,水淹区段的生态优势度最高;而水淹区段和未水淹区段相似性指数最大.     

城市绿地种子库的初步研究

对城市绿地土壤种子库的组成、种群数量、空间分布和物种多样性进行了初步研究,结果表明：城市绿地土壤种子库存中共出现植物42种,其中在第一层中共出现植物1 477株,多样性指数为2.05,均匀度是0.58,最大的物种多样性指数是3.56,第二层的物种多样性指数,均匀度和最大物种多样性指数均比第一层要低,分别为1.94、0.56和3.47,植物种类也要少一些。城市绿地土壤种子库中种的丰富度、种子苗量、多样性指数均不如远郊区山地天然次生林。城市绿地土壤种子库中蕴藏着一些潜在种群,有些植物种可以用于城市绿化建设。     

黔中石漠化地区不同土地利用类型土壤种子库特征

在贵州省普定县喀斯特石漠化地区通过种子萌发试验,对封山育林、退耕还林2a、农耕地等3种不同土地利用类型的土壤种子库进行分析.结果表明,不同利用类型土壤中种子数量差异显著,封山育林土壤中平均种子密度为1664粒/m2,退耕还林2 a土壤中平均种子密度为8060粒/m2,农耕地土壤中平均种子密度为6239粒/m2.土壤中的种子集中分布在表层0～5cm范围内,随土层深度变化,土壤中所含种子数量和物种数呈减少的趋势.不同利用类型土壤种子库物种相似指数较低,物种数、多样性指数、均匀度及生态优势度指数以退耕还林地最大,农耕地高于封山育林地.土壤种子库所含物种数较接近,物种组成以草本植物为主,菊科、禾本科占优势.封山育林地、退耕还林地属于进展演替,封山育林地处于较高演替阶段,农耕地属于逆行演替.应引进适宜物种以促进植被恢复.     

河水漫溢对塔里木河下游荒漠河岸林地表植被与土壤种子库的影响

采用种子萌发法,研究了河水漫溢对塔里木河下游荒漠河岸林地表植被与土壤种子库的影响.结果表明：塔里木河下游漫溢区地表植被分属8科13属14种,非漫溢区为10科21属26种植物;与非漫溢区相比,漫溢区地表植被中出现了一些浅根系和喜湿的草本植物;漫溢区单位面积物种数、植被盖度、植株密度、物种多样性指数和丰富度指数均比非漫溢区有明显增加.漫溢区土壤种子库中有物种19种,比非漫溢区增加了5种;漫溢区土壤种子库总密度比非漫溢区增加了3.94倍;与非漫溢区相比,漫溢区1年生草本植物种子的比例增加了23.07%,而灌木植物种子比例减少了20.99%;多年生草本的变化则不明显;河水漫溢提高了土壤种子库的生物多样性.漫溢区和非漫溢区土壤种子库与地表植被的共有物种分别为18和9种,土壤种子库与地表植被的相似性系数分别为0.842和 0.667.     

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).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.