Population genetic structure of diploid sexual and polyploid apomictic hawthorns (Crataegus; Rosaceae) in the Pacific Northwest

Polyploidy and gametophytic apomixis are two important and associated processes in plants. Many hawthorn species are polyploids and can reproduce both sexually and apomictically. However, the population genetic structure of these species is poorly understood. Crataegus douglasii is represented exclusively by self-compatible tetraploid pseudogamous apomicts across North America, whereas Crataegus suksdorfii found in the Pacific Northwest is known to include self-incompatible diploid sexuals as well as polyploid apomicts. We compare population structure and genetic variability in these two closely related taxa using microsatellite and chloroplast sequence markers. Using 13 microsatellite loci located on four linkage groups, 251 alleles were detected in 239 individuals sampled from 15 localities. Within-population multilocus genotypic variation and molecular diversity are greatest in diploid sexuals and lowest in triploid apomicts. Apart from the isolation of eastern North American populations of C. douglasii , there is little evidence of isolation by distance in this taxon. Genetic diversity in western populations of C. douglasii suggests that gene flow is frequent, and that colonization and establishment are often successful. In contrast, local populations of C. suksdorfii are more markedly differentiated. Gene flow appears to be limited primarily by distance in diploids and by apomixis and self-compatibility in polyploids. We infer that apomixis and reproductive barriers between cytotypes are factors that reduce the frequency of gene flow among populations, and may ultimately lead to allopatric speciation in C. suksdorfii . Our findings shed light on evolution in woody plants that show heterogeneous ploidy levels and reproductive systems.     

Patterns, sources and ecological implications of clonal diversity in apomictic Ranunculus carpaticola (Ranunculus auricomus complex, Ranunculaceae)

Sources and implications of genetic diversity in agamic complexes are still under debate. Population studies (amplified fragment length polymorphisms, microsatellites) and karyological methods (Feulgen DNA image densitometry and flow cytometry) were employed for characterization of genetic diversity and ploidy levels of 10 populations of Ranunculus carpaticola in central Slovakia. Whereas two diploid populations showed high levels of genetic diversity, as expected for sexual reproduction, eight populations are hexaploid and harbour lower degrees of genotypic variation, but maintain high levels of heterozygosity at many loci, as is typical for apomicts. Polyploid populations consist either of a single AFLP genotype or of one dominant and a few deviating genotypes. genotype/genodive and character incompatibility analyses suggest that genotypic variation within apomictic populations is caused by mutations, but in one population probably also by recombination. This local facultative sexuality may have a great impact on regional genotypic diversity. Two microsatellite loci discriminated genotypes separated by the accumulation of few mutations ('clone mates') within each AFLP clone. Genetic diversity is partitioned mainly among apomictic populations and is not geographically structured, which may be due to facultative sexuality and/or multiple colonizations of sites by different clones. Habitat differentiation and a tendency to inhabit artificial meadows is more pronounced in apomictic than in sexual populations. We hypothesize that maintenance of genetic diversity and superior colonizing abilities of apomicts in temporally and spatially heterogeneous environments are important for their distributional success.     

Reticulate evolution in North American black-fruited hawthorns (Crataegus section Douglasia; Rosaceae): evidence from nuclear ITS2 and plastid sequences

Background and Aims

The taxonomic complexity of Crataegus (hawthorn; Rosaceae, Maleae), especially in North America, has been attributed by some to hybridization in combination with gametophytic apomixis and polyploidization, whereas others have considered the roles of hybridization and apomixis to be minimal. Study of the chemical composition and therapeutic value of hawthorn extracts requires reproducible differentiation of entities that may be difficult to distinguish by morphology alone. This study sought to address this by using the nuclear ribosomal spacer region ITS2 as a supplementary DNA barcode; however, a lack of success prompted an investigation to discover why this locus gave unsatisfactory results.

Methods

ITS2 was extensively cloned so as to document inter- and intraindividual variation in this locus, using hawthorns of western North America where the genus Crataegus is represented by only two widely divergent groups, the red-fruited section Coccineae and the black-fruited section Douglasia. Additional sequence data from selected loci on the plastid genome were obtained to enhance further the interpretation of the ITS2 results.

Key Results

In the ITS2 gene tree, ribotypes from western North American hawthorns are found in two clades. Ribotypes from diploid members of section Douglasia occur in one clade (with representatives of the east-Asian section Sanguineae). The other clade comprises those from diploid and polyploid members of section Coccineae. Both clades contribute ribotypes to polyploid Douglasia. Data from four plastid-derived intergenic spacers demonstrate the maternal parentage of these allopolyploids.

Conclusions

Repeated hybridization between species of section Douglasia and western North American members of section Coccineae involving the fertilization of unreduced female gametes explains the observed distribution of ribotypes and accounts for the phenetic intermediacy of many members of section Douglasia.     

Atypical foliar anatomy related to Kranz syndrome in Paspalum inaequivalve and Paspalum microstachyum (Poaceae: Panicoideae: Paniceae)

Paspalum L. is a large and complex genus, enclosing more than 300 species, whose boundaries and infrageneric classification are still being studied. Recent phylogenetic analyses suggest that Paspalum inaequivalve Raddi and Paspalum microstachyum J. Presl, from the Inaequivalvia informal group, should be excluded from Paspalum. Focused on the unclear taxonomic position of P. inaequivalve and P. microstachyum, their leaf anatomy was studied, and some atypical features related to C₄ photosynthesis were found. This atypical Kranz syndrome is the aim of this research. Transverse leaf blade sections from fresh and herbarium material of P. inaequivalve were studied by light, fluorescence, and transmission microscopy. Additionally, sheaths and culms of P. inaequivalve and leaf blades of P. microstachyum were observed by light microscopy. δ¹³C isotope discrimination was determinated for P. inaequivalve. We compared our results with available anatomical data from related taxa. As well as typical mesophyll cells (PCA) and mestome sheath cells (PCR), a third type of cells, here called ‘globose parenchymatous cells’, was observed in leaf blades of P. inaequivalve and P. microstachyum. These cells are placed externally to the mestome sheaths of the first and second vascular bundles, they have thin walls, with no developed suberine lamella, few chloroplasts with 1–2 starch grains, thylakoids not organized in grana, and a large central vacuole. The globose parenchymatous cells represent a novel trait in P. inaequivalve and P. microstachyum, further supporting the close relation between both species and their exclusion from the genus Paspalum. This atypical Kranz syndrome has not been described in Paspalum before, but the globose parenchymatous cells here described resemble the distinct cells considered as remnants of the outer parenchymatous sheath described for Anthaenantiopsis, some sections of Panicum L., and Chaetium Nees, providing possible taxonomic significance.     

百喜草及其在南方果园生草栽培和草被体系中的应用

果园立地条件差、土壤肥力不足是影响我国果树产量和果实品质的重要因素。百喜草是优良的果园生草栽培和草被体系草种。在我国南方果产区推广应用百喜草,对于防止水土流失、改善果园生态环境、培肥果园土壤、提高果实产量和品质具有重要意义。     

Ecological factors influencing tetraploid establishment in snow buttercups (Ranunculus adoneus , Ranunculaceae): minority cytotype exclusion and barriers to triploid formation

Polyploid speciation is an ongoing, important source of angiosperm diversity. However, the barriers to polyploid speciation and mechanisms of establishment remain poorly understood for all but a few species. Several factors likely to have influenced tetraploid establishment, including barriers to triploid formation, consequences of mixed-ploidy pollen loads, and the reproductive success of the minority cytotype, were examined in snow buttercups (Ranunculus adoneus) through a series of pollination and transplant experiments. Tetraploid snow buttercups do not have stigmatic barriers to pollen from diploid plants, nor does pollen from tetraploid plants have an advantage over pollen from diploids when on tetraploid stigmas. Tetraploid plants transplanted into a diploid population produced 50% fewer seeds than tetraploid plants in a tetraploid population. Intrinsic barriers to triploid formation were relatively weak, but few triploid seeds formed when mixed-ploidy pollen was present. Fecundity of triploid plants was very low, and no tetraploid offspring resulted. These results indicate that in snow buttercups, a triploid plant will contribute 0.8% of the tetraploid seeds of a minority tetraploid plant making it a minor contributor to the demographics of tetraploid establishment. The reproductive costs facing minority cytotype plants may explain the previously observed spatial segregation in snow buttercups.     

盐适应过程中香根草内源游离态、结合态、束缚态多胺含量的变化

研究了不同浓度NaCl胁迫下,香根草（Vetiteria zizanioides）根、叶中的游离态、结合态、束缚态多胺（PAs）[包括腐胺（Put）,尸胺（Cad）,亚精胺（Sod）和精胺（Spm）]含量的变化。在中度盐胁迫（100,200mmol L^-1NaCl）9天时,香根草基本能够正常生长,但在重度盐胁迫（300mmol L^-1NaCl）下,其生长受到严重抑制。在上述3个不同浓度的NaCl胁迫下,香根草根、叶中游离态Put,Cad,spd,Stma和总的游离态PAs含量明显下降,在高盐浓度下下降幅更大;结合态Put,Cad,Sod,Spm和总的结合态PAs含量显著上升,但在重度盐胁迫下升幅较小或与对照相当;束缚态Put,Cad和总的束缚态PAs含量均减少,而束缚态Spd和Spm含量在叶中是下降的,在根中则增加,且在中度盐胁迫下更明显。对根和叶片而言,除游离态（Spd＋Spm）,Put比值在重度盐胁迫下较对照显著下降外,其它游离态、结合态、束缚态和总的（Spd＋Spm）／Put比值在不同盐胁迫下均上升,在中度盐胁迫下更明显。这表明,维持多胺总量的稳态和较高的（Spd＋Spm）／Put比值是香根草适应中度盐胁迫的一个重要机制。     

百喜草及其在南方果园生草栽培和草被体系中的应用

果园立地条件差、土壤肥力不足是影响我国果树产量和果实品质的重要因素。百喜草是优良的果园生草栽培和草被体系草种。在我国南方果产区推广应用百喜草,对于防止水土流失、改善果园生态环境、培肥果园土壤、提高果实产量和品质具有重要意义。     

Mercury(II)-methylene blue interactions: Complexation and metallate formation

Reactions of HgX₂ (X = Cl, Br, I) with methylene blue (MB) chloride dihydrate and the reaction of HgCl₂ with MB nitrate dihydrate have been undertaken in an attempt to prepare metal derivatives of MB. The products were characterized by elemental analysis, UV-Vis, IR, ¹H NMR spectroscopy and X-ray crystallography. The reaction of HgCl₂ with MB chloride dihydrate and subsequent crystallization in a DMF/H₂O mixture yielded the products (1 and 2) with different crystal morphologies. The structure of complex 1 represents the first structural report of a complex of MB with any metal ion. The efficacy of MB to act as a ligand in spite of its cationic nature is thus demonstrated. The structure of 1 comprises a distorted tetrahedral geometry around Hg(II); the coordination valencies being provided by three chloride ions and a MB cation. The structure of 2 is a salt consisting of an anion and two MB cations. The reaction of HgI₂ and HgBr₂ with MB chloride dihydrate yielded salts 3 and 4 with (X = Br or I) anions and MB cations. A mixed salt 5, whose anions comprise mercury(II), chloride and nitrate species resulted from the reaction between HgCl₂ with MB nitrate dihydrate. The reaction of Hg₂F₂ with MB chloride dihydrate and the crystallization of the resulting product 6 in aqueous DMF yielded crystals of (MB)₂HgCl₄ · H₂O.     

Duthieeae,a new tribe of grasses (Poaceae) identified among the early diverging lineages of subfamily Pooideae: molecular phylogenetics,morphological delineation,cytogenetics and biogeography

The phylogeny of Pooideae, one of the largest subfamilies of grasses, has been intensively studied during the past years. To investigate the early evolutionary splits in Pooideae we used a broad sample of genera with uncertain placement, some of which have not been studied in molecular phylogenetics before, complemented by representatives from other lineages of this subfamily. Morphological, cytogenetic and biogeographical analyses were added to the molecular sequence work on chloroplast matK–3’trnK and nuclear ITS. According to chloroplast DNA data, a new and well-supported lineage was identified among the early branches. It consisted of Phaenosperma and a larger group of genera encompassing Anisopogon, Danthoniastrum, Duthiea, Metcalfia, Pseudodanthonia (inclusion resting on ITS and morphology), Sinochasea and Stephanachne. Based on structural characters we suggest to keep Phaenosperma under the monotypic tribe Phaenospermateae and to accommodate the other genera under a new tribe Duthieeae, which is morphologically well-defined by synapomorphic spikelet features. Megalachne and Podophorus were not part of the early diverging Pooideae lineages but belong to the Aveneae/Poeae complex. Morphological characteristics of Duthieeae are discussed with respect especially to Stipeae and reveal consistent differences between both tribes. The genera of Duthieeae and the major lineages of Stipeae are keyed. A cytogenetic survey of exemplary taxa corroborates high chromosome base numbers as prevailing within the early diverging lineages of Pooideae, but chromosome sizes are more highly varied than previously reported. Ecogeographical analyses point to warm and humid conditions as the ancestral bioclimatic niche of Phaenosperma and Duthieeae, whereas adaptation to cold and drought occurred only in a part of Duthieeae but was obviously less successful than in the widespread and much more species-rich tribe Stipeae. The distribution of Duthieeae with species-poor or monotypic genera in mountains of the northern hemisphere and Anisopogon as an outlier in Australia suggests relict character.     

Waterlogging tolerance in the tribe Triticeae: the adventitious roots of Critesion marinum have a relatively high porosity and a barrier to radial oxygen loss

Nine species from the tribe Triticeae – three crop, three pasture and three ‘wild’ wetland species – were evaluated for tolerance to growth in stagnant deoxygenated nutrient solution and also for traits that enhance longitudinal O₂ movement within the roots. Critesion marinum (syn. Hordeum marinum) was the only species evaluated that had a strong barrier to radial O₂ loss (ROL) in the basal regions of its adventitious roots. Barriers to ROL have previously been documented in roots of several wetland species, although not in any close relatives of dryland crop species. Moreover, the porosity in adventitious roots of C. marinum was relatively high: 14% and 25% in plants grown in aerated and stagnant solutions, respectively. The porosity of C. marinum roots in the aerated solution was 1·8–5·4‐fold greater, and in the stagnant solution 1·2–2·8‐fold greater, than in the eight other species when grown under the same conditions. These traits presumably contributed to C. marinum having a 1·4–3 times greater adventitious root length than the other species when grown in deoxygenated stagnant nutrient solution or in waterlogged soil. The length of the adventitious roots and ROL profiles of C. marinum grown in waterlogged soil were comparable to those of the extremely waterlogging‐tolerant species Echinochloa crus‐galli L. (P. Beauv.). The superior tolerance of C. marinum, as compared to Hordeum vulgare (the closest cultivated relative), was confirmed in pots of soil waterlogged for 21 d; H. vulgare suffered severe reductions in shoot and adventitious root dry mass (81% and 67%, respectively), whereas C. marinum shoot mass was only reduced by 38% and adventitious root mass was not affected.     

Concentration-dependent palladium(II)-indole bond formation in complexes with a 2N-donor ligand containing an indole moiety: Synthesis, characterization, and reaction analysis

The Pd(II) complexes of a 2N-donor ligand containing a pendent indole, 3-(2-pyridylmethylamino)ethylindole (L), were synthesized and characterized. Reaction of the ligand with [PdCl₂(CH₃CN)₂] at room temperature gave [Pd(L)Cl₂] (1) as pale yellow crystals. The X-ray crystal structure analysis and ¹H NMR spectrum of 1 revealed that the complex has a 2N2Cl-donor set in a square-planar geometry and that the pendent indole ring has no characteristic intramolecular interaction with the Pd(II) ion and the coordinated pyridine moiety. Refluxing a solution of 1 in CH₂Cl₂/DMF for a few hours under basic conditions gave yellow crystals, which were shown to be an indole-C2 binding complex [Pd(L)Cl] (2) by X-ray analysis. Conversion of complex 1 to 2 in DMSO was observed upon dilution of the solution of complex 1. From solution equilibrium and kinetic studies the initial step of the conversion by dilution has been assigned to the replacement of a coordinated Cl⁻ ion with the DMSO molecule. The ligand replacement easily occurred at low concentrations of 1. The complex with a coordinated solvent molecule exhibited a high reactivity and formed a stable Pd-C bond with the indole ring located close to the Pd(II) center. We discussed the concentration dependent formation of the indole-C2 binding complex 2 and its detailed mechanism.     

Thallium(III) chloride in organic solvents: Synthesis, solutions and solvates. The crystal structures of trichlorobis(dimethylsulfoxide)thallium(III) and tribromobis(dimethylsulfoxide)thallium(III)

The synthesis of thallium(III) chloride and bromide was performed in solution by chlorination and bromination, respectively, of the suspensions of the corresponding thallium(I) halides in acetonitrile. Crystalline compounds TlX₃(CH₃CN)₂ (X = Cl⁻, Br⁻) were prepared from the acetonitrile solutions. Thallium(III) chloride and bromide in dimethylsulfoxide solution were obtained by dissolving the corresponding solid compounds TlX₃(CH₃CN)₂ (Cl⁻, Br⁻) in DMSO. Both acetonitrile and dimethylsulfoxide solutions of thallium(III) chloride were studied by UV-Vis and ²⁰⁵Tl NMR spectroscopy. The UV-Vis study of the TlCl₃-CH₃CN system showed presence of at least two thallium(III) chloride species. Only one signal arising from the thallium(III) species was, however, detected by the ²⁰⁵Tl NMR in the solution because of the fast chemical exchange. The ²⁰⁵Tl NMR study of thallium(III) chloride in dimethylsulfoxide showed three separate signals assigned to the solvated , TlCl₃ and species. The crystalline compounds of trichlorobis(dimethylsulfoxide)thallium(III) and tribromobis(dimethylsulfoxide)thallium(III) were prepared and their crystal structures were solved by single-crystal X-ray analysis. The thallium atom in the complexes has a trigonal bipyramidal environment built by three halide ions occupying equatorial positions of the polyhedron and two oxygen atoms of the DMSO molecules in the apical positions.     

Ethylene production,cluster root formation,and localization of iron(III) reducing capacity in Fe deficient squash roots

Dicots and non-graminaceous monocots have the ability to increase root iron(III) reducing capacity in response to iron (Fe) deficiency stress. In squash (Cucurbita pepo L.) seedlings, Fe(III) reducing capacity was quantified during early vegetative growth. When plants were grown in Fe-free solution, the Fe(III) reducing capacity was greatly elevated, reached peak activity on day 4, then declined through day 6. Root ethylene production exhibited a temporal pattern that closely matched that of Fe(III) reducing capacity through day 6. On the 7th day of Fe deficiency, cluster root morphology developed, which coincided with a sharp increase in the root Fe(III) reducing capacity, although ethylene production decreased. Localization of Fe(III) reducing capacity activity was observed during the onset of Fe deficiency and through the development of the root clusters. It was noted that localization shifted from an initial pattern which occurred along the main and primary lateral root axes, excluding the apex, to a final localization pattern in which the reductase appeared only on secondary laterals and cluster rootlets. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phylogenetic relationships in Elymus (Poaceae: Triticeae) based on the nuclear ribosomal internal transcribed spacer and chloroplast trnL-F sequences

To estimate the phylogenetic relationship of polyploid Elymus in Triticeae, nuclear ribosomal internal transcribed spacer (ITS) and chloroplast trnL-F sequences of 45 Elymus accessions containing various genomes were analysed with those of five Pseudoroegneria (St), two Hordeum (H), three Agropyron (P) and two Australopyrum (W) accessions. The ITS sequences revealed a close phylogenetic relationship between the polyploid Elymus and species from the other genera. The ITS and trnL-F trees indicated considerable differentiation of the StY genome species. The trnL-F sequences revealed an especially close relationship of Pseudoroegneria to all Elymus species included. Both the ITS and trnL-F trees suggested multiple origins and recurrent hybridization of Elymus species. The results suggested that: the St, H, P, and W genomes in polyploid Elymus were donated by Pseudoroegneria, Hordeum, Agropyron and Australopyrum, respectively, and the St and Y genomes may have originated from the same ancestor; Pseudoroegneria was the maternal donor of the polyploid Elymus; and some Elymus species showed multiple origin and experienced recurrent hybridization.     

Copper(II) complexes as superoxide dismutase mimics: Synthesis, characterization, crystal structure and bioactivity of copper(II) complexes

Two new copper(II) complexes of the type [Cu(L)X₂), where L = (E)-N-phenyl-2-[phenyl (pyridine-2-yl)methylene]hydrazinecarboxamide X = Cl/Br have been synthesized and characterized by elemental analyses, FAB (fast atomic bombardment) magnetic measurements, electronic absorption, conductivity measurements cyclic voltammetry (CV) and Electron paramagnetic resonance (epr) spectroscopy. The structures of these complexes determined by single crystal X-ray crystallography show a distorted square based pyramidal (DSBP) geometry around copper(II) metal center. The distorted CuN₂OX (X = Cl/Br) basal plane in them is comprised of two nitrogen and one oxygen atoms of the meridionally coordinated ligand and a chloride or bromide ion and axial position is occupied by other halide ion. The epr spectra of these complexes in frozen solutions of DMSO showed a signal at g ca. 2. The trend in g-value (g_|| > g_⊥ > 2.00) suggest that the unpaired electron on copper(II) has d_x²-y² character. Biological activities in terms of superoxide dismutase (SOD) and antimicrobial properties of copper(II) complexes have also been measured. The superoxide dismutase activity reveals that these two complexes catalyze the fast disproportionation of superoxide in DMSO solution.     

Floral development in the tribe Cedreleae (Meliaceae, sub-family Swietenioideae): Cedrela and Toona

BACKGROUND AND AIMS: Floral development of Cedrela and Toona, the genera comprising the basal tribe Cedreleae of the sub-family Swietenioideae of Meliaceae, is described. The focus was on three endangered, ecologically and economically important species: Cedrela fissilis, Cedrela odorata and Toona ciliata. The aims of the study were to characterize the patterns of floral development in the tribe and to establish apomorphic and plesiomorphic floral characters in relation to other taxa within the family based on the current molecular phylogeny of Meliaceae. METHODS: A detailed floral structural and developmental study was completed using both scanning electron microscopy and visualization of microtome sections with a light microscope. KEY RESULTS: Twelve floral developmental stages were identified. The initial development of the pentamerous flowers of both Toona and Cedrela is strikingly similar. The morphological differences observed between them are due to differential patterns of organ elongation and adnation/connation occurring late in development. Additionally, the formation of functionally male and female flowers was found to occur at specific positions within the inflorescence. CONCLUSIONS: Due to the basal position of the tribe Cedreleae in the phylogeny of Meliaceae, functionally either male or female pentamerous flowers and the presence of (at least partially) free stamens may be considered plesiomorphic traits within the family. In contrast, sympetaly and the absence of nectaries in Cedrela species are synapomorphies.     

Seasonal colour changes, sexual maturation and oviposition in Psylla peregrina (Homoptera: Psylloidea)

ABSTRACT.

• 1 Colour change is shown to be related to the timing of sexual maturation of P.peregrina Förster. Males become sexually mature and attain their autumnal coloration about 3 weeks before females.
• 2 Upon maturation males migrate down branches into the inner crowns of hawthorn trees. Females show a similar movement as they mature later in the season.
• 3 Seasonal colour changes may serve cryptic functions and are appropriate to the different environments in which adults are found during the season.
• 4 The distribution of overwintering eggs reflects the post maturation distribution of adult psyllids, with eggs being concentrated on old wood towards the base of hawthorn branches.