中生代银杏类植物系统发育、分类和演化趋向

长期以来银杏类植物化石分类都依据营养叶形态为基础。由于叶形态的多型性和异源性,导致分类和系统发育解释的紊乱。根据对保存完好的繁殖器官(胚珠器官)系统发育分析结果所作的银杏目分类表明中生代除了银杏和银杏科以外,至少还存在着3．5个已灭绝的科级单元。此方案把已知其繁殖器官的成员和仅仅根据营养器官建立起来的分类位置不明的属严格地区分开来,并注明各科的限定性特征和已知成员的地质地理分布。银杏目植物自古生代起源,至早中生代以后朝着不同的方向辐射,呈现出丰富的多样性并经历了错综复杂的演化过程,其总的演化趋向是退缩：叶片扁化、蹊化和融合;胚珠器官简化,胚珠增大、数目减少,珠柄趋于消失。     

胚珠的类型

胚珠(ouvle)是种子植物的大孢子囊,种子的前身。裸予植物的胚珠裸露,被子植物的胚殊被包在子房内,子房内胚珠的数目随植物种类而不同。被子植物的胚珠由珠被(一般分内珠被和外珠被两层)和珠心两部分组成,珠心的中央是胚囊,珠被包在珠心的外面。珠被在珠心顶端的小孔叫珠孔,珠心的基部与珠被相连的部位叫合点。胚珠通过珠柄着生在胎坐上。由于胚珠各部分生长速度不同,可把胚珠区分为四大类。如果胚珠各部分的生长速度均匀一致,所生成的胚珠,珠孔、合点和珠柄三者在一条直线上,珠孔在珠柄的相对一端,这类     

荧光素钠在香子兰生活胚珠中的运输

在香子兰（Vanilla planifolia Andr.)未受精的胚珠中,外珠被只包到胚珠的下半部,荧光素钠自珠柄进入胚珠,先在胚珠含点区形成一个荧光中心,然后沿内珠被向珠孔端运输,在内珠被的珠孔端形成第二个荧光中心,不久卵器中显现荧光,受精以后,胚珠的外珠被向上延伸,与内珠被共同形成珠孔,荧光素钠经珠柄进入后向几个方向扩展;1．运至珠孔口处的外珠被中。2．沿珠柄一侧的外珠被向下至合点区;3．由合点区分别向内部和向远离珠柄一侧的外珠被扩展,香子兰胚珠中不具维管束,不过荧光素钠在内珠被中运输时,明显可见紧贴胚囊的内层细胞是其主要运输通道,胚囊成熟时,珠孔端一半在内珠被与胚囊之间有角质层相隔,胚囊合点端的一半与球心细胞间无角质层,营养物质无疑可由合点端进入胚囊,但是卵器是在内珠被珠孔端荧光中心形成后才出现荧光的,不能排除营养物质自珠孔端进入胚囊的可能性。     

荧光素钠在香子兰生活胚珠中的运输

在香子兰（Vanilla planifolia Andr.)未受精的胚珠中,外珠被只包到胚珠的下半部,荧光素钠自珠柄进入胚珠,先在胚珠含点区形成一个荧光中心,然后沿内珠被向珠孔端运输,在内珠被的珠孔端形成第二个荧光中心,不久卵器中显现荧光,受精以后,胚珠的外珠被向上延伸,与内珠被共同形成珠孔,荧光素钠经珠柄进入后向几个方向扩展;1．运至珠孔口处的外珠被中。2．沿珠柄一侧的外珠被向下至合点区;3．由合点区分别向内部和向远离珠柄一侧的外珠被扩展,香子兰胚珠中不具维管束,不过荧光素钠在内珠被中运输时,明显可见紧贴胚囊的内层细胞是其主要运输通道,胚囊成熟时,珠孔端一半在内珠被与胚囊之间有角质层相隔,胚囊合点端的一半与球心细胞间无角质层,营养物质无疑可由合点端进入胚囊,但是卵器是在内珠被珠孔端荧光中心形成后才出现荧光的,不能排除营养物质自珠孔端进入胚囊的可能性。     

无核荔枝假种皮发育过程的研究

无核荔枝是荔枝中较为珍贵的品系 ,种子多退化 ,故为无核品系。其胚珠在发育过程中由于胚囊败育而萎缩 ,假种皮发生于珠脊外侧及外珠被外侧 ,由于胚珠中部的表皮及表层下的几层细胞先后脱分化形成分生组织 ,而在以后的发育中经历一个由“中层”假种皮发育到“平台”假种皮的过程 ,当“平台”假种皮形成以后 ,在其外侧边缘形成一个明显的“上翘”假种皮 ;继而 ,把发育缓慢的胚珠和珠柄包埋 ,而形成“无核”。此外 ,在其发育过程中 ,外界温度对其影响较为明显 :扬花期的高温会产生大核、焦核 ,低温则产生无核 ,因此 ,无核荔枝可能是低温敏感型。     

侧柏雌球果及其胚珠的发育

观察了侧柏（Ｐｌａｔｙｃｌａｄｕｓ ｏｒｉｅｎｔａｌｉｓ（Ｌ．）Ｆｒａｎｃｅ）胚珠的发育过程及后期球果苞片的结构变化。在北京,雌球果原基７月分化。通常一个球果有４对苞片,中部两对可育,靠球果顶端一对各产生一枚胚珠,其下一对各两枚。胚珠的发育顺序是向顶的,下部可育苞片腑部的两枚胚珠源于同一原基。胚珠原基分化成珠心和珠被,在发育过程中,珠被逐渐包围珠心,最后形成２烧瓶状的胚珠。１１月至次年１月,球果处     

籽银桂雌雄配子体的发育研究

利用石蜡切片和扫描电子显微镜技术。研究了南京地区银桂品种群的‘籽银桂’雌雄配子体的发育过程。雄蕊的孢原细胞在8月中旬出现。花药壁的发育为基本型,分泌型绒毡层。小孢子母细胞减数分裂为同时型。形成的4个小孢子四分体呈典型的四面体型。成熟花粉粒即雄配子体为二核花粉粒。籽银桂为倒生胚珠。单珠被,薄珠心。珠被内层细胞特化为珠被绒毡层。在胚珠合点端。有承珠盘结构。在9月中旬,雌蕊的孢原细胞开始分化出来。孢原细胞直接发育成大孢子母细胞,然后大孢子母细胞减数分裂形成大孢子。‘籽银桂’的胚囊发育类型为蓼型。成熟胚囊即雌配子体由2个助细胞、1个卵细胞、1个中央细胞(2个核)和3个反足细胞组成。     

五唇兰雌配子体发育和胚胎发生的研究

五唇兰的胚珠倒生型,具薄珠心,两层珠被。胚囊发育为双孢子葱型,成熟胚囊８核。从传粉到受精约５０ｄ,正常双受精。胚具５－６细胞的胚柄,种子成熟时胚柄及胚乳核消失,成熟种子只具单层细胞的种皮和一个未分化的珠珠形胚。     

白桦胚珠发育及胚、胚乳发育关系的研究

以30年生白桦(Betula platyphylla)的雌花序为材料,研究了白桦有性生殖期间胚珠和胚乳的发育过程,以及胚和胚乳发育之间的关系。观察结果表明:白桦为合生心皮雌蕊,花柱2,子房室2,每室1~2个胚珠或无,中轴胎座,倒生胚珠,单层珠被,厚珠心发育;胚柄短小,由三个细胞构成;在历时4个月之久的雌配子体形成、胚胎发育直至成熟期间,胚珠经历了形态结构的变化和适应;在胚的发育过程中,胚乳起主要营养作用,胚乳发育类型为核型胚乳。最后对胚、胚乳发育的解剖结构及其相互关系以及影响种子质量的各环节进行了研究和讨论。     

银杏雌性生殖器官的形态学本质及其系统学意义

关于古老裸子植物银杏Ginkgo biloba L.雌性生殖器官形态学本质的问题争论 很多,因此这一类群的分类位置尚存争议。本文进一步发展了Florin提出的“种鳞复合 体(Seed-scale complex)”概念,提出解释裸子植物生殖器官形态演化的“苞鳞一种鳞复 合体(Bract-scale and seed-scale complex)概念和演化理论,并试图用以解释银杏的生 殖器官形态学本质和裸子植物系统发育的有关问题。由银杏着生胚珠的结构(Ovuliferous structure)生于可育短枝上鳞状叶叶腋的事实,赞同该结构为次级轴性(枝性)性质,提 出该次级轴性结构及连同下部的鳞状叶相当于裸子植物大部分类群所具有的苞鳞—种 鳞复合体(Bract-scale and seed-scale complex),并保留了较多的原始古老性质,可能 代表着苞鳞—种鳞复合体较原始的形态式样。该结构的鳞状叶与可育短枝上正常的营 养叶均为不育苞片的性质,鳞状叶叶腋生出的长柄则是次级轴性结构的次生性伸长,长 柄上部二分叉的着生胚珠结构相当于该次级轴性器官仅存的极度退化的二枚可育叶性器 官,而整个可育短枝相当于一个分化程度很低的复合大孢子叶球。银杏生殖器官中的某 些性状与苏铁十分相似,但由于苞鳞一种鳞复合体的出现,标志着这一类群已远较苏铁特 化,并应与所有具苞鳞—种鳞复合体的类群在同一条演化线上,即苞鳞—种鳞复合体 演化线(Bract-scale and seed-scale complex evolutionary line,BS-line),而不具苞鳞 —种鳞复合体的苏铁类(Cycas)则构成裸子植物中的苏铁演化线(Cycas evolutionary line,C-line)。银杏大孢子叶球的式样,可能代表着裸子植物一种早期的原始大苞子叶 球式样,为古裸子植物不甚分化的可育枝条向高度压缩和变态的可育枝条(苞鳞一种鳞复合体及典型的球果)演化的一种中间过渡式样。     

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.     

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     

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.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

Identification and Characterization of the First Equine Parainfluenza Virus 5

正Dear Editor,Parainfluenza virus 5 (PIV5), known as canine parainfluenza virus in the veterinary field, is a negative-sense,nonsegmented, single-stranded RNA virus belonging to the Paramyxoviridae family (Chen 2018). The virus was first reported in primary monkey kidney cells in 1954 (Hsiung1972), then it has been frequently discovered in various     

Pathogenic Characterization and Full Length Genome Sequence of a Reassortant Infectious Bursal Disease Virus Newly Isolated in Pakistan

<正>Dear Editor,Infectious bursal disease (IBD) is one of the most important diseases of the poultry. The IBD virus (IBDV), a nonenveloped virus belonging to the Birnaviridae family with a genome consisting of two segments of double-stranded RNA (segments A and B), targets B lymphocytes of bursa of Fabricious leading to immunosuppression. In Pakistan,poultry farming is the second biggest industry and IBD is the second biggest disease threating the poultry sector.However, there is limited genome information of IBDV