川鄂山茱萸染色体研究

本文对川鄂山茱萸染色体的数目和核型进行了研究,结果为染色体数目2n=18,与山茱萸相同;核型为K(2n)=18=12 m+6 sm。与山茱萸的核型进行比较,认为川鄂山茱萸核型比山茱萸的进化,同时山茱萸属染色体数目与其他相近的几个属进行比较,认为川鄂山茱萸与山茱萸应为同一独立的属,即山茱萸属。     

菊科紫菀属3种植物的核型分析

菊科紫菀属密毛系(Aster Series Vestiti Ling)含3个物种:密毛紫菀(A.vestitus Franch.)、灰枝紫菀(A.poliothamnus Diels)和西固紫菀(A.sikuensis W.W.Smith et Farr.),新近的分子系统学研究对密毛系是否单系提出质疑。该文采用常规根尖压片法,对紫菀属密毛系3种植物4个居群的核型进行观察分析。结果显示:3种植物的核型公式均为2n=2x=18=14m+4sm(2SAT);密毛紫菀居群2个的核型属于1A型,灰枝紫菀和西固紫菀为2A型。密毛紫菀和西固紫菀的核型资料为首次报道。灰枝紫菀的染色体数目、基数和不对称性等核型资料与先前唯一的相关报道结果(体细胞染色体数目为32,核型公式2n=2x=32=26sm+6st,属4A型,染色体中未发现随体)迥然不同。3种植物的核型结果不支持保留密毛系,而核型不对称性类型支持该实验室先前提出的亚属划分。3种植物随体的大小属于紫菀亚族型,这支持欧亚紫菀属与北美紫菀类没有密切亲缘关系的观点。     

高茎紫菀(菊科)形态描述补充及细胞学和分子系统学研究北大核心CSCD

结合在模式产地采集的高茎紫菀(Aster procerus Hemsley)以及查阅文献资料,发现原始文献对其形态描述不充分且缺乏细胞学和分子系统学方面的报道。本研究对高茎紫菀的形态特征进行了补充描述以及核型特征和系统位置分析,为紫菀属的修订提供资料。结果表明:(1)依据观察结果,补充了高茎紫菀新的形态特征:基生叶羽状分裂,成熟的基生叶较大,长可达26 cm,宽可达8 cm;花序托圆锥状。(2)高茎紫菀的染色体数目为2n=18;核型公式为2n=2x=16 m+2 M,核型属于1 A。(3)基于ITS和ETS标记的分子系统发育树分析表明,高茎紫菀不同居群的2个个体在同一进化支上(LP=100,PP=1.00),且位于核心紫菀属(LP=100,PP=1.00),与女菀[Turczaninovia fastigiata(Fischer)Candolle]构成姐妹类群(LP=52,PP=0.99)。研究认为,高茎紫菀基生叶和花序托的特征可为紫菀属的分类提供新的证据,支持高茎紫菀位于紫菀属(Aster L.)内,建议将女菀并入紫菀属。     

小花三脉紫菀和狭叶三脉紫菀的区别:形态学和细胞学证据

产自湖北神农架的狭叶三脉紫菀Aster ageratoides var. gerlachii (Hance) Chang一直被各种文献和有关标本馆误定为小花三脉紫菀A. ageratoides var. micranthus Ling。我们对二者进行了野外采集和形态学、细胞学的比较研究,分析了导致错误鉴定的原因,重新确定了二者的界限。小花三脉紫菀无横走地下茎,这一性状具有重要的分类学价值。核型研究发现,小花三脉紫菀为二倍体,2n=2x=18=18m,核型属1A型;狭叶三脉紫菀则是四倍体,2n=4x=36=32m+4sm (2SAT),核型属2A型。二变种的染色体数目、核型均为首次报道。狭叶三脉紫菀在湖北为新分布记录。     

菊科紫菀属横斜系的核型研究

菊科紫菀属横斜系（Asterseries Hersileoides Ling）特产于中国,含横斜紫菀（Aster hersileoides Schneid.）和亮叶紫菀（A.nitidus Chang）2个狭域分布种。细胞学研究表明,横斜紫菀和亮叶紫菀均为二倍体,染色体较小,长度在1.64～2.8μm之间,核型公式为2n=2x=18=16m＋2sm,属1A类型。横斜紫菀和亮叶紫菀的染色体数目和核型为首次报道。     

岳麓紫菀（菊科）的分布及其形态学与核型研究

岳麓紫菀（Aster sinianus Hand. Mazz.,菊科紫菀族）为多年生草本,特产于中国湘赣毗邻地区。在对其整个分布区进行野外采集和生境观察时,发现了2个新的分布地点,同时确认其已在模式产地湖南省长沙市岳麓山灭绝。该研究将岳麓紫菀从浏阳市沙市镇回迁至岳麓山,以期恢复模式产地的居群。形态学研究表明,现有文献对该种的描述多处不准确,如对基生叶、株高、茎下部叶、托片和海拔等的记载。基于形态性状,讨论了岳麓紫菀的系统学地位,并首次报道了该种的核型特征：岳麓紫菀为二倍体,核型为2n=2x=16m+2m(SAT),属于1A型。该研究结果为岳麓紫菀的分类地位的修订和物种保护提供了重要的资料。     

百合属4种植物的核型研究

采用常规压片法对4种百合属植物野百合(L.brow n ii F.E.B row n ex M ie llez.)、兰州百合(L.d av id iiDuchartre var.un icolor(Hoog.)Co Hon.)、川百合(L.d av id ii Duchartre)、湖北百合(L.henry i B aker)进行了核型研究.结果表明,4种百合的染色体数目均为2n=24,核型除川百合为3A外,其余3种均为3B型.核型公式分别为:野百合2n(2x)=24=4m(2SAT) 2sm(2SAT) 4st 14t,兰州百合2n(2x)=24=2m(2SAT) 2sm 10st(2SAT) 8t 2T,川百合2n(2x)=24=2m(2SAT) 2sm 12st(3SAT) 8t,湖北百合2n(2x)=24=4m 18st 2t,其中湖北百合染色体核型为首次报道.通过比较发现,兰州百合与川百合的核型最为相似,亲缘关系相近;核型不对称性为兰州百合>川百合>野百合>湖北百合,以湖北百合的核型较为原始.     

微糙三脉紫菀的细胞地理学研究

三脉紫菀多倍体复合体一直被认为是一个困难的类群．但是,作为该复合体主产地的中国,其分类学研究和细胞学资料十分缺乏．因此,对微糙三脉紫菀9个居群进行了细胞学研究、结果显示,微糙三脉紫菀为四倍体(2n=4x=36),关于微糙三脉紫菀有六倍体的报道应属鉴定错误．微糙三脉紫菀6个居群的核型资料表明,其核型的不对称性具有经度地带性变异的趋势．据此认为,微糙三脉紫菀起源于浙皖山丘西部,然后向西扩散,抵达云贵高原和四川．这一假设得到横走地下茎演化证据的支持．     

迷果芹(\%Sphallerocarpus gracilis)和红三叶

对迷果芹(Sphallerocarpusgracilis(Bess.)K-Pol.)和红三叶(TrifoliumpratenseL.)进行了染色体计数及核型分析.迷果芹的染色体数目为2n=20,核型公式为K(2n)=2x=20=14m+4sm+2st(SAT);核型类型为2A,为较对称核型,该种植物的染色体数目及核型均为首次报道.红三叶的染色体数目有2n=14、16、28、32等类型,本研究首次报道了2n=14的核型公式为K(2n)=2x=14=2M+12m,核型类型为1B,为较原始的对称核型.     

川滇冷杉的核型分析兼论冷杉属的进化地位

本文分析了我国特产树种川滇冷杉Abies forrestii的核型,K(2n)=24=14 m+8 sin+2 st,属2B类型,染色体相对长度组成为2n=24=2 L+10 M_2+10 M_1+2 S。冷杉属植物(除川滇冷杉)的核型全由中部和近中着丝粒染色体组成,属2A类型(表2)。根据松科各属核型的比较,作者讨论了冷杉属的亲缘关系和进化地位,并得到形态学、解剖学、生化学、古植物学等的支持。     

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.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.