太白红杉顶芽动态及其对分枝格局的影响

应用计盒维数方法比较研究了与太白红杉顶芽动态相关的不同分枝格局对空间占据能力的差异.结果表明,Ⅰ型分枝有利于对所拥有的空间进行有效填充和利用,Ⅱ型分枝有利于扩展枝条所占的面积,Ⅲ型分枝既扩展了面积,又实现了对所拥有空间的有效填充和利用.总的来讲,顶芽的死亡使分枝对空间的占据能力和对光能利用的效率有所提高,同时对植株冠型的调整也有重要作用.太白红杉枝条顶芽的死亡是外界严酷环境条件的被迫"产物".     

太白红杉分枝格局的可塑性研究

研究了不同竞争类型和地形因子对太白红杉分枝格局的影响。结果发现：(1)处于不同竞争地位的太白红杉分枝格局有较大差异,主要是分枝率、枝长和枝间距变化明显;(2)太白红杉南、北方向的分枝格局有明显差异,主要是分枝率、枝长和末级枝的分枝角度的差异;而东、西方向上无明显差异;(3)由于受到地形的影响,太白红杉个体中存在明显的侧枝上转现象。研究结果表明：处于不同竞争地位的太白红杉植株在分枝格局上表现出明显的差异,太白红杉不同方位的分枝也具有较大的差异,说明太白红杉植冠构型具有较强的形态可塑性和适应性。     

不同生境栓皮栎天然更新幼苗植冠构型分析

栓皮栎存在于秦岭南坡的多种林分中,生活在不同生境中的个体往往形成不同的树冠形态和构型特征。为了说明不同生境条件下栓皮栎幼苗的植冠构型变化,采用典型抽样法,对秦岭南坡3种生境中(林冠下、林隙、林缘)的栓皮栎天然更新幼苗的侧枝、叶片特征及其空间分布进行了调查分析,结果表明:3种不同生境中栓皮栎幼苗植冠形态发生了明显的可塑性变化,(1)林冠下的幼苗明显为开阔型树冠,林隙和林缘处的幼苗树冠相对紧密;(2)幼苗的1级侧枝密度与分枝角度在3种生境下均差异显著(P0.05);从Ⅰ到Ⅳ层,林冠下幼苗的分枝角度在冠层内变化幅度不到5°,而林缘处幼苗的分枝角度变化高达40°;发生5个以上1级侧枝的概率以林冠下最大,为0.6;(3)从林缘、林隙到林冠下,幼苗的叶长、叶宽、单叶面积、叶面积指数逐渐降低,数量叶密度和比叶面积则逐渐增大,与其它两种生境相比,林冠下幼苗的叶片逐渐向树冠上层集中,且以更高序的侧枝为主要着生枝条;(4)林隙中栓皮栎幼苗的树高、地径明显优于林缘和林冠下,缩短了苗木进入主林层的时间,林隙对栓皮栎种群更新有利。在今后栓皮栎林的经营中,可以通过适当间伐来增加林隙数量,为森林更新和结构的优化的提供有利条件。     

太白红杉种内和种间竞争研究

采用逐步扩大范围的方法确定影响对象木 (Objectivetree) 的最佳竞争范围, 利用单木竞争指数的改进模型对太白红杉 (Larixchinensis) 种内和种间竞争强度进行了定量分析, 并讨论了不同竞争强度下太白红杉的形态变化。结果表明 :随对象木胸径的增大, 由于太白红杉种群自然稀疏过程中密度调节作用, 植株距离增加, 种内竞争强度降低 ;太白红杉主要分布于亚高山地段, 群落内其它物种较少, 个体普遍较小, 结果种间竞争相对较弱, 种内与种间竞争关系顺序为 :太白红杉 太白红杉 >巴山冷杉 (Abiesfargesii) 太白红杉 >牛皮桦 (Betulaplatyphylla) 太白红杉 >其它树种 太白红杉 ;竞争强度和对象木胸径的关系服从幂函数关系 (CI =AD-B), 当太白红杉胸径达到 35cm以上时, 竞争强度几乎没有变化, 所得的预测模型能很好地预测太白红杉种内和种间的竞争强度 ;不同竞争强度下, 太白红杉主茎各层的分枝角度、总分枝数、当年生枝条长、平均枝长和活枝数均表现出显著的差异。表明采用逐步扩大范围的方法能有效地确定竞争木范围, 较好地反应太白红杉种内和种间的竞争关系。同时, 太白红杉通过自身形态变化, 提高了对光的截获能力和对不同竞争强度的适应能力。     

深山含笑分枝成花规律及其系统演化证据

以10年生深山含笑(Michelia maudiae Dunn)为材料,研究其年生长发育节律、芽的种类、混合芽分化、分枝类型和成花规律。结果显示:(1)深山含笑芽可为分未分化芽和分化芽,其中分化芽包括营养芽、混合芽和花芽。(2)年生长周期依次划分为营养芽生长期、混合芽分化期、混合芽快速膨大期、混合芽/花芽发育滞缓期、开花启动期和开花期。(3)分枝类型为同生-预生分枝混合型;同生分枝的枝条当年形成混合芽,发育形成短枝并在枝顶成花,而预生分枝的枝条当年不分化形成混合芽。(4)不同分枝类型的枝条成花率具有显著性差异。同生分枝的枝条顶芽抽枝成花概率最高,预生分枝的枝条侧芽抽枝成花率最低。研究结果表明,深山含笑不同分化状态的芽发育形成不同的分枝类型,并且同生-预生分枝特征及成花规律具有观赏性状培育的参考价值与系统演化意义。     

秦岭太白红杉种群空间分布格局动态及分形特征研究

采用相邻格子样方法采集数据,应用计盒维数和信息维数研究了太白红杉种群空间格局的分形特征,结果表明,太白红杉种群有较高的计盒维数(1.8087)和信息维数(1.7931),表明其对空间占据程度较高.用分布系数法和Morisita格局指数法检验格局类型,发现不同年龄组太白红杉种群均呈聚集分布.运用Greig-Smith的方法研究格局规模,发现太白红杉种群在128m²和512m²处聚集,不同年龄组在不同规模尺度聚集.以区组分布格局强度(PI)检测聚集强度,发现太白红杉种群格局强度随尺度变化程度较高,个体分布不均匀,随着年龄的增大,其聚集强度呈下降趋势.太白红杉种群的空间分布格局特征是其对严酷生境长期适应的结果.     

两种亚热带榕属乔木植冠损伤后的位置依赖性枝发生

三峡库区需要大量植株用于三峡工程所涉及的诸多建设(如铁路、公路、建筑)之后的植被恢复和绿化.由于具有优美树冠和耐瘠薄土壤的能力,榕(Ficus microcarpa L.)和黄桷树(Fvirens Ait.var.sublanceolata(Miq.)Cornor) 在三峡库区作为绿化和行道树木大量栽植.在三峡库区,这两种树种苗木的培育主要通过切枝扦插的方式进行.大量切枝损伤植株植冠并且使叶组织数量减少,对植株生长有很大影响.植株生长与植株的枝发生格局有很大关系,为明确植冠损伤对植株生长的可能影响,对榕和黄桷树植冠损伤后的枝发生进行了研究.实验发现,切枝造成的植冠损伤对榕和黄桷树植株侧枝上的枝发生没有影响,不同损伤强度之间和不同损伤发生时间之间都不存在明显的差异.但是,植冠损伤后,榕和黄桷树植株主茎上的枝发生是位置依赖性的.植冠损伤不影响榕和黄桷树植株损伤处理后新生主茎段和具侧枝主茎段上的枝发生,却促进了损伤处理后裸露主茎段上的枝发生,并且裸露主茎段上枝发生的数量和密度随植冠损伤强度的升高而增大.此外,实验结果表明,秋季植冠损伤植株裸露主茎段上的枝发生要高于春季植冠损伤植株裸露主茎段上的枝发生;在榕和黄桷树的枝发生中,仅有裸露主茎段上增强的枝发生会促进植冠损伤植株对叶组织的生物量投资并有利于受损植株的恢复和生长.     

两种亚热带榕属乔木植冠损伤后的位置依赖性枝发生

三峡库区需要大量植株用于三峡工程所涉及的诸多建设(如铁路、公路、建筑)之后的植被恢复和绿化。由于具有优美树冠和耐瘠薄土壤的能力,榕(Ficus microcarpa L.)和黄桷树(F. virens Ait. var. sublanceolata (Miq.) Cornor)在三峡库区作为绿化和行道树木大量栽植。在三峡库区,这两种树种苗木的培育主要通过切枝扦插的方式进行。大量切枝损伤植株植冠并且使叶组织数量减少,对植株生长有很大影响。植株生长与植株的枝发生格局有很大关系,为明确植冠损伤对植株生长的可能影响,对榕和黄桷树植冠损伤后的枝发生进行了研究。实验发现,切枝造成的植冠损伤对榕和黄桷树植株侧枝上的枝发生没有影响,不同损伤强度之间和不同损伤发生时间之间都不存在明显的差异。但是,植冠损伤后,榕和黄桷树植株主茎上的枝发生是位置依赖性的。植冠损伤不影响榕和黄桷树植株损伤处理后新生主茎段和具侧枝主茎段上的枝发生,却促进了损伤处理后裸露主茎段上的枝发生,并且裸露主茎段上枝发生的数量和密度随植冠损伤强度的升高而增大。此外,实验结果表明, 秋季植冠损伤植株裸露主茎段上的枝发生要高于春季植冠损伤植株裸露主茎段上的枝发生; 在榕和黄桷树的枝发生中,仅有裸露主茎段上增强的枝发生会促进植冠损伤植株对叶组织的生物量投     

银杏枝、花、种子在树冠上的分布格局及其相互关系研究

采用分层调查的方法研究了１４年生银杏嫁接植株树冠上枝、花、种子的分布格局及其相互关系。结果表明,长枝、短枝、短果枝和花主要分布在树冠中部,且分布比较均匀,树冠上从上到下,长枝平均年龄逐渐增大,分枝角度逐渐升高,种子主要集中分布在距地面１８０－３２０ｃｍ的体积冠层中,这一冠层中的种子数占植株种子总数的５１．３％,不同冠层中枝、花、种子数量之间密切相关     

不同光环境下桂花幼苗的构型差异

通过对不同光照条件下桂花幼苗的冠形、分枝率、叶片在树冠中的空间分布等特征进行研究,结果表明桂花幼苗构型发生了明显的可塑性适应:其树冠对光照条件的变化有显著的可塑性响应。在林隙中的幼苗受光的间歇性影响,总体分枝率明显小于全光、林冠下的幼苗分枝率。全光的幼苗叶片集中于二级枝,叶片长度和叶片面积相对较小,对光照利用充分;而林隙中的幼苗叶片集中于一级枝,避免处于植冠内侧受到遮蔽,表现出较大的叶片长度和叶面积;林冠下的叶片较均匀分布在一、二级枝上,叶片总数量较少,枝条高生长较全光下明显。幼苗在总体分枝格局中表现出独自的特点,即强光环境下产生短枝和高分枝率,在适度庇荫条件下产生长枝及低分枝率,在强度庇荫条件下以较长枝和较高分枝率来同时满足高生长和横向生长的需求。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

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.     

Synthesis and antimicrobial studies of hydrazone derivatives of 4-[3-(2,4-difluorophenyl)-4-formyl-1H-pyrazol-1-yl]benzoic acid and 4-[3-(3,4-difluorophenyl)-4-formyl-1H-pyrazol-1-yl]benzoic acid

Microbial resistance to antibiotics is an unresolved global concern, which needs urgent and coordinated action. One of the guidelines of the Centers for Disease Control and Preventions (CDC) to combat antibiotic resistance is the development of new antibiotics to treat drug-resistant bacteria. In our effort to find new antibiotics, we report the synthesis and antimicrobial studies of 30 new pyrazole derivatives. These novel molecules have been synthesized by using readily available starting materials and benign reaction conditions. Some of these molecules have shown activity with MIC values as low as 0.78?µg/mL against four bacterial strains; Staphylococcus aureus, methicillin-resistant S. aureus, Bacillus subtilis, and Acinetobacter baumannii. Furthermore, active molecules are non-toxic to mammalian cell line.

     

Novel compounds with potent CDK9 inhibitory activity for the treatment of myeloma

Cyclin-dependent kinases (CDKs) and Polo-like kinases (PLKs) play key role in the regulation of the cell cycle. The aim of our study was originally the further development of our recently discovered polo-like kinase 1 (PLK1) inhibitors. A series of new 2,4-disubstituted pyrimidine derivatives were synthesized around the original hit, but their PLK1 inhibitory activity was very poor. However the novel compounds showed nanomolar CDK9 inhibitory activity and very good antiproliferative effect on multiple myeloma cell lines (RPMI-8226).