ent-Labdane glycosides from the aquatic plant Potamogeton lucens and analytical evaluation of the lipophilic extract constituents of various Potamogeton species

Two new ent-labdane glycosides, one known furano-ent-labdane and a new hydroxylated fatty acid were isolated from the dichloromethane extract of the freshwater aquatic plant Potamogeton lucens. The new compounds were assigned the structures of beta-d-glucopyranosyl-8(17),13-ent-labdadien-16,15-olid-18-oate, 18-beta-d-glucopyranosyloxy-8(17),13-ent-labdadien-16,15-olide and 13(R)-hydroxy-octadeca-(9Z,11E,15Z)-trien-oic acid by spectroscopic means. The algicidal activity of these compounds was tested against Raphidocelis subcapitata. Based on our previous study of Potamogeton pectinatus, other constituents were identified in P. lucens by LC-UV-MS, LC-NMR and GC-MS. The lipophilic extract profiles of both species are presented. Two other species, Potamogeton perfoliatus and P. crispus, were also investigated by analytical comparison of their non-polar extracts. The distribution of ent-labdanes characterized in Potamogeton is summarized.     

鄂西南香蒲科、黑三棱科、眼子菜科和茨藻科植物区系特征

本文在采集标本基础上,结合分析大量有关资料,讨论了鄂西南香蒲科等四科植物区系特征。结果表明:1.区系组成包括5属20种2变种1杂种。其中有1新种1新变种和3个湖北分布新记录。2.区系种类丰富,起源古老,对湖北同类区系具有代表性。3.有一定比例的特有成分(8.70%)。4.区系地理成分复杂多样,但主要具有东亚亚热带一温带分布(26.09%)和世界性分布(26.09%)的性质。5.本区四科植物区系主要与处于我国地貌第三级阶梯上的省区发生密切联系。其区系分区,在亚区的划分上与陆生种子植物相同。     

Euploid and aneuploid evolution in Potamogeton (Potamogetonaceae): a factual basis for interpretation

In a review of chromosome numbers in the genus Potamogeton, we highlight numerous errors that have crept into the literature. These have resulted chiefly from reliance on abstracts in chromosome number indices and compilations, rather than on the original publications, but partly also because of misleading summaries even in the primary literature. We present a list of counts that we believe are original and genuine, and a list of those that were never made but which nevertheless appear in the literature. Scrutiny of the list of accepted counts indicates that aneuploidy is widespread in the genus and that transition between the two common chromosome numbers (2n=26 and 2n=28) has occurred several times. Currently available data are insufficient to resolve the question of the ancestral base number. We also present details of the first chromosome counts from English populations of five taxa: P. polygonifolius Pourr. (2n=28), P. pectinatus L. (2n=ca. 78), P. perfoliatus L. (2n=ca. 52), P.×nitens Weber (P. gramineus×P. perfoliatus) (2n=ca. 52) and P.×salicifolius Wolfg. (P. lucens×P. perfoliatus) (2n=ca. 52).     

湖北省泽泻科、水鳖科、眼子菜科及茨藻科植物花粉形态研究

本文利用光镜及扫描电镜对湖北省泽泻科、水鳖科、眼子菜科及茨藻科11属29种1变种1变型植物(另加采于湛江的软骨草)的花粉形态进行了研究,发现泽泻科植物花粉具多个圆形萌发孔,外壁表面为小刺状纹饰;茨藻科植物花粉具远极单槽,表面为绉波状纹饰;眼子菜科及本文研究的水鳖科植物花粉均无萌发孔,分别具网状和小刺状饰纹饰。1.茨藻科植物花粉最原始,泽泻科花粉较进化,眼子菜科花粉较水鳖科花粉进化;2.泽泻属与泽苔草属花粉较慈姑属花粉原始;3.鞘叶眼子菜亚屈花粉较眼子菜亚属的花粉处于更高演化阶段;4.多孔茨藻花粉在该科中最原始。本文工作尚对易变形水生植物花粉形态研究方法进行了尝试。     

Phylogenetic relationships and hybrid origin of Potamogeton species (Potamogetonaceae) distributed in China: insights from the nuclear ribosomal internal transcribed spacer sequence (ITS)

Hybridization and polyploidization are important evolutionary processes in higher plants and have greatly enriched the diversity of the genus Potamogeton (Potamogetonaceae). To study the phylogenetic relationships and hybrid origin of Potamogeton species, 35 accessions representing 20 species, including diploids, tetraploids and hexaploids, and three hybrids were collected in China and their ribosomal internal transcribed spacers (ITS) were cloned, sequenced and statistically analyzed. The data showed that ITS sequences were informative to analyze the phylogeny of Potamogeton, and the phylogenetic tree revealed that Potamogeton species examined could be mainly divided into two groups (Group I and II), corresponding to subgenus Potamogeton and subgenus Coleogeton, respectively. Then, the evolutionary mechanism on the polyploidy of Potamogeton species was discussed. P. natans probably was an allotetraploid and one of its parent might result from aneuploidy change of species with 2n=28. P. hubeiensis might be derived from the hybridization between P. octandrus and P. cristatus. We suggested that both P. lucens and P. maackianus probably were allotetraploids, and P. obtusifolius might be a diploid hybrid between P. compressus and P. pusillus. Moreover, P. malainoides might have undergone biased concerted evolution toward one of its parent P. wrightii, and P. intortusifolius might be a synonymy of P. × anguillanus.     

Identification of the polar constituents of Potamogeton species by HPLC-UV with post-column derivatization, HPLC-MSn and HPLC-NMR, and isolation of a new ent-labdane diglycoside

The polar extracts of Potamogeton pectinatus, P. lucens, P. perfoliatus and P. crispus (Potamogetonaceae) were analyzed by HPLC-UV-MS and their chromatographic profiles were very similar. The polar constituents of P. pectinatus were more exhaustively investigated by HPLC-UV with post-column derivatization, HPLC-MS(n) and HPLC-NMR, which allowed the on-line identification of various known flavones (dereplication). One of these compounds, luteolin 3'-O-glucoside, has never been characterized in the Potamogeton genus. The HPLC-UV-MS and HPLC-NMR analyses revealed also the presence of ent-labdane diterpene glycosides in the polar extracts of P. pectinatus and P. lucens and led to the isolation of a new ent-labdane diglycoside from P. pectinatus, beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-15,16-epoxy-12-oxo-8(17),13(16),14-ent-labdatrien-19-oate.     

Testing four barcoding markers for species identification of Potamogetonaceae

The pondweeds (Potamogetonaceae) are among the most important plant groups in the aquatic environment. Owing to their high morphological and ecological diversity, species identification of this aquatic family remains problematic. DNA barcoding involves sequencing a standard DNA region and has been shown to be a powerful tool for species identification. In the present study, we tested four barcoding markers (rbcL, matK, internal transcribed spacer (ITS), and trnH-psbA) in 15 Potamogeton species and two Stuckenia species, representing most species of the Potamogetonaceae in China. The results show that all four regions can distinguish and support the newly proposed genera of Stuckenia from Potamogeton. Using ITS and trnH-psbA, significant interspecific genetic variability was shown. However, intraspecific genetic variability of trnH-psbA is high and so it is not suitable for barcoding in Potamogetonaceae. The ITS and matK regions showed good discrimination. However, matK was not easy to sequence using universal primers. The best performing single locus was ITS, making it a potentially useful DNA barcode in Potamogetonaceae.     

Morphology of Maundia supports its isolated phylogenetic position in the early‐divergent monocot order Alismatales

According to recent molecular phylogenetic data, the rare Australian endemic Maundia triglochinoides does not form a clade with taxa traditionally classified as members of Juncaginaceae. Therefore, views on the morphological evolution and taxonomy of Alismatales require re‐assessment. As the morphology of Maundia is poorly known and some key features have been controversially described in the literature, the flowers, fruits, inflorescence axes and peduncles were studied using light and scanning electron microscopy. Inflorescences are bractless spikes with flowers arranged in trimerous whorls. Except in the inflorescence tip (where the flower groundplan is variable), flowers possess two tepals in transversal‐abaxial positions, six stamens in two trimerous whorls and four carpels in median and transversal positions. Fruits are indehiscent. The shared possession of orthotropous ovules supports the molecular phylogenetic placement of Maundia as sister to a large clade including Potamogetonaceae and related families. Maundia and Aponogeton spp. share the same highly unusual floral groundplan, a homoplastic similarity that can be explained by spatial constraints in developing inflorescences. The nucellar coenocyte of Maundia appears to be unique among monocots. As Maundia exhibits a mosaic of features characteristic of other families of tepaloid core Alismatales, its segregation as a separate family is plausible. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 12–45.     

Diterpenoid hydrocarbons in the sea grass Amphibolis antartica

The leaves of Amphibolis antartica from Shark Bay, Western Australia contain a previously unreported cleistanthene hydrocarbon. Other collections of the sea grass near Perth also contained sandaracopimaradiene and isopimaradiene. Concentrations of the diterpenes increase with leaf age, while n-hydrocarbon content decreases with leaf age.