毛冠菊属的系统学研究

　　毛冠菊属是菊科21个“有问题”属中的一个，主要分布于青藏高原地区。按照林镕、陈艺林的概念，它包含了Nannoglottis、．Stereosanthus、Vierhapperia、Senecio和Doronicum5个属的成员。它曾先后被放入旋覆花族、千里光族和紫菀族，在上述三族中的亚族位置也不确定。它的许多重要性状，如舌片颜色、染色体数目等等，人们所知甚少。由于缺乏野外工作以及看不到大多数名字的模式，林镕、陈艺林对该属的修订有待深入的研究。本文研究了该属的外部形态学、微形态学、解剖学、孢粉学、细胞学、生态学以及ITS序列，确定了毛冠菊属的分类位置，并建立了一个新的属下分类系统。 1．外部形态 在检查大量标本（包括大多数模式）和野外居群考察的基础上，分析了主要外部形态学性状的变异式样及其对划定物种范围的价值。共确认以下9个种：青海毛冠菊、厚毛毛冠菊、狭舌毛冠菊、虎克毛冠菊、宽苞毛冠菊、大果毛冠菊、毛冠菊、玉龙毛冠菊和云南毛冠菊。川西毛冠菊被处理成狭舌毛冠菊的异名。 2．微形态学 在光镜下检查了毛冠菊属9种和紫菀族2个代表属的花柱的形状、花药顶端不育附属物、花药基部、花药基部、花盘、花丝领、药室内壁细胞等微形态性状。除了花柱基外，其他的微形态学在属内一致。管状花的花柱形态支持将毛冠菊属放在紫菀族，但其药室内壁细胞两极加厚式样表明它和广义的旋覆花有某些联系。 3．叶表皮研究 在光镜和电镜下检查了毛冠菊属8个种的叶表皮特征。．所有种的气孔器都为不规则型。青海毛冠菊表皮细胞的为多边形，而其他种都为不规则型。青海毛冠菊表皮角质层的加厚方式也与其他种明显不同。 4．扫描电镜下的舌片和花柱分枝特征 在扫描电镜下观察毛冠菊属8种和紫菀族7个代表种的舌片近轴面表皮细胞。发现毛冠菊属的舌片近轴面表皮细胞都为板状，并且沿细胞中央特征性加厚，这与紫菀族类型的表皮细胞一致，但毛冠菊属表皮细胞的角质层主要是纵向条纹或皱纹，而紫菀族总是横向的条纹或皱纹，明显不同。 在扫描电镜下又检查了毛冠菊属8种和紫菀族8个代表种的管状花花柱分枝近轴面的结构，结果在毛冠菊属管状花花柱分枝的近轴面都发现了柱头毛状的突起，而在紫菀族8种中没有发现。从突起的形状和位置判断，它可能是残存的、未充分发育的柱头毛。这表明雌性不育管状花可能刚刚从两性管状花演化而来。 也在扫描电镜下观察了毛冠菊属6种和紫菀族8个代表种的舌状花和丝状花的花柱分枝的远轴面，结果在毛冠菊属4种中发现了类似扫集毛状的突起。从这种突起的位置和形状判断，它可能是残余的扫集毛。这种突起在除雏菊以外的其他紫菀族代表种中缺失。 5．细胞学 检查了毛冠菊属8种的细胞学性状。结果发现毛冠菊属所有种的染色体基数都为x -9。染色体长度大约4um-lOum。核型公式：毛冠菊、厚毛毛冠菊、狭舌毛冠菊、宽苞毛冠菊和云南毛冠菊都为2n=14m+2sm+2st;玉龙毛冠菊、大果毛冠菊和青海毛冠菊都为2n=12m+4sm+2st。A1、A2值在属内没有明显差异。所有种的核型都是2A型。这表明在物种形成的过程中没有多倍化参与，毛冠菊属宜放在紫菀族而不是千里光族。细胞学证据支持毛冠菊属为一单系类群。 6．分子生物学 测定了毛冠菊属7种的ITS序列，并从基因库里下载了46个ITS序列，涵盖紫菀族14个亚属和旋覆花族、春黄菊族、金盏菊族。以旋覆花族、春黄菊族、金盏菊族为外类群。简约性分析显示，毛冠菊属在紫菀族中，并有较高的bootstrap值，在紫菀族中处于基部位置。Olearia和Chiliotrichum两个Hinterhuberinae亚族的代表属与毛冠菊属密切相关。在属下系统发育分析中，Olearia和Chiliotrichum被选做外类群。652个性状中，共有7】个信息位点（31个在ITSI，33个在ITS2，7个在5.8S）。简约性分析时只获得一棵最简约树。树上有两个明显的进化支，一支仅有青海毛冠菊一种，另一支包含其他种类。这种分支方式也得到形态学和生态学证据的支持。 7．毛冠菊属的系统学 从上述结果可以看出，毛冠菊属宜放入紫菀族中，在紫菀族中处于基部位置，与Hinterhuberinae亚族关系密切。综合上述研究结果，提出一个新的属下 分类系统： 毛冠菊属的新系统 组I单头组Sect. Monocephala T.G.Gao et YL.Chen Sect nov. 青海毛冠菊Nannoglottis ravida (C.Winkl.)Y.L.Chen 组II毛冠菊组Sect. Nannoglottis 系1．长舌系Ser. Delavayanae Ling et YL.Chen 厚毛毛冠菊Nannoglottis delavayi(Franch.)Ling et Y.L.Chen 狭舌毛冠菊Nannoglottis gynura(C.Winkl.) Ling et YL.Chen 虎克毛冠菊Nannoglottis hookeri (C.B.Clarke ex Hook.f.)Kitam. 宽苞毛冠菊Nannoglottis latisquama Ling et Y.L.Chen 大果毛冠菊Nannoglottis macrocarpa Ling et YL.Chen 系2．短舌系Ser. Nannoglottis 毛冠菊Nannoglottis carpesioides Maxim. 玉龙毛冠菊Nannoglottis hieraciphylla (Hand.-Mzt.)Ling et YL.Chen 云南毛冠菊Nannoglottis yuennanensis (Hand.-Mzt.) Hand.-Mzt.

Stability Of Adhesion Clusters And Cell Reorientation Under Lateral Cyclic Tension

This work is motivated by experimental observations that cells on stretched substrate exhibit different responses to static and dynamic loads. A model of focal adhesion that can consider the mechanics of stress fiber, adhesion bonds, and substrate was developed at the molecular level by treating the focal adhesion as an adhesion cluster. The stability of the cluster under dynamic load was studied by applying cyclic external strain on the substrate. We show that a threshold value of external strain amplitude exists beyond which the adhesion cluster disrupts quickly. In addition, our results show that the adhesion cluster is prone to losing stability under high-frequency loading, because the receptors and ligands cannot get enough contact time to form bonds due to the high-speed deformation of the substrate. At the same time, the viscoelastic stress fiber becomes rigid at high frequency, which leads to significant deformation of the bonds. Furthermore, we find that the stiffness and relaxation time of stress fibers play important roles in the stability of the adhesion cluster. The essence of this work is to connect the dynamics of the adhesion bonds (molecular level) with the cell's behavior during reorientation (cell level) through the mechanics of stress fiber. The predictions of the cluster model are consistent with experimental observations.

Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation

Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals ((OH)-O-.) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that (OH)-O-. photoproduction increased from 1.80 to 2.74 muM by increasing the HA concentration from 10 to 40 mg L-1 at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of (OH)-O-. in the HA solution with Fe(111) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of (OH)-O-. in HA solution with algae with or without Fe(111) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of (OH)-O-. in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest (OH)-O-. photoproduction at pH 4.0.

Copolymerization of CO2 and propylene oxide under rare earth ternary catalyst: design of ligand in yttrium complex

Copolymerization of carbon dioxide and propylene oxide was carried out employing (RC6H4COO)(3)Y/glycerin/ZnEt2 (R = -H, -CH3, NO2, -OH) ternary catalyst systems. The feature of yttrium carboxylates (ligand, substituent and its position on the aromatic ring) is of great importance in the final copolymerization. Appropriate design of substituent and position of the ligand in benzoate-based yttrium complex can adjust the microstructure of aliphatic polycarbonate in a moderate degree, where the head-to-tail linkage in the copolymer is adjustable from 68.4 to 75.4%. The steric factor of the ligand in the yttrium complex is crucial for the molecular weight distribution of the copolymer, probably due to the fact that the substituent at 2 and 4-position would disturb the coordination or insertion of the monomer, lead the copolymer with broad molecular distribution. Based on the study of ultraviolet-visible spectra of the ternary catalyst in various solvents, it seems that the absorption band at 240-255 nm be closely related to the active species of the rare earth ternary catalysts.

Ion-molecule reactions of cis- and trans-cyclopropane derivatives with methane, acetone and vinyl acetate under chemical ionization conditions

Ion-molecule reactions of four isomeric cyclopropane derivatives were investigated under chemical ionization(CI) conditions, using methane, acetone and vinyl acetate as reagent gases, The methane positive-ion CI mass spectra of each of two isomer pairs 1,2 and 3,4 are identical, and so are the collision-induced dissociation (CTD) spectra of the protonated molecules of each of the two isomer pairs, The protonation reactions for the isomer pairs 1,2 and 3,4 occurred on the sites of the carboxyl groups and the R groups, respectively, Differences between isomers 1 and 2 are observed in their acetone (A) positive-ion CI mass spectra and in the CID spectra of their adduct ions ([M+H+A](+)), The adduct ions of compounds 2, 3 and 4 with protonated acetone and with protonated acetone dimer are observed in their CI mass spectra, However, only the adduct ions of compound 1 with protonated acetone appear in its CI mass spectrum, The protonated dimers of each of the four compounds are found in their vinyl acetate positive-ion CI mass spectra, and the CID spectra of these dimers for isomers 1 and 2 can also reflect their stereostructural difference. (C) 1998 John Wiley & Sons, Ltd.

Phylogenetic analyses of Fringillidae (Aves : Passeriformes) using mitochondrial tRNA gene sequences and secondary structure

Fringillidae is a large and diverse family of Passeriformes. So far, however, Fringillidae relationships deduced from morphological features and by a number of molecular approaches have remained unproven. Recently, much attention has been attracted to mitochondrial tRNA genes, whose sequence and secondary structural characteristics have shown to be useful for Acrodont Lizards and deep-branch phylogenetic studies. In order to identify useful phylogenetic markers and test Fringillidae relationships, we have sequenced three major clusters of mitochondrial tRNA genes from 15 Fringillidae, taxa. A coincident tree, with coturnix as outgroup, was obtained through Maximum-likelihood method using combined dataset of 11 mitochondrial tRNA gene sequences. The result was similar to that through Neighbor-joining but different from Maximum-parsimony methods. Phylogenetic trees constructed with stem-region sequences of 11 genes had many different topologies and lower confidence than with total sequences. On the other hand, some secondary structural characteristics may provide phylogenetic information on relatively short internal branches at under-genus level. In summary, our data indicate that mitochondrial tRNA genes can achieve high confidence on Fringillidae phylogeny at subfamily level, and stem-region sequences may be suitable only at above-family level. Secondary structural characteristics may also be useful to resolve phylogenetic relationship between different genera of Fringillidae with good performance.