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Copyright of EPPO Bulletin is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Jordan Journal of Pharmaceutical Sciences is the property of University of Jordan and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Currently, many attempts have been made worldwide to isolate compounds from plants that could prevent transmission of HIV and offer new treatments. In this study, the methanolic extract of Onopordum illyricum aerial parts was evaluated for the inhibition of the HIV-1 reverse transcriptase (RT) ribonuclease H (RNase H), an attractive target for the identification of new antiretroviral inhibitors. Using an HIV-1 reverse transcriptase (RT)-associated RNase H inhibition assay, the bio-guided fractionation of the extract led to the isolation of seven compounds (luteolin, apigenin, hispidulin, arctiin, 1,5-dicaffeoylquinic acid, and two germacranes, 8α-(5-hydroxy)-angeloylsalonitenolide and onopordopicrin). Among them, luteolin was the most effective on RNase H RT-associated function (IC50 of 12.8 μM), followed by 1,5-dicaffeoylquinic acid and apigenin with IC50 values of 16.9 and 59.6 μM, respectively. Pure compounds were then assayed for their effects also on HIV-1 integrase (IN). 1,5-Dicaffeoylquinic acid, arctiin, onopordopicrin, and luteolin exhibited the most potent inhibition with IC50 values ranging from 0.50 to 22.5 μM. 1,5-Dicaffeoylquinic acid was also able to inhibit the early stages of HIV-1 replication in cell-based assays. [ABSTRACT FROM AUTHOR]

Onopordum is one of the extremely armed genus of the family of Asteraceae which is native to the Mediterranean and Irano-Turanian regions. This genus comprises 7 species that are distributed in most parts of the country. In spite of 12% of Onopordum species are found in Iran, but few taxonomic studies have been carried out and it seems that there are still unknown species of this genus. For taxonomic study of the genus Onopordum, extensive collection of distribution areas of genus was conducted in Iran. Plant specimens were collected by conventional methods and identified based on reliable sources. As a observations, O. cinereum is reported as a new record from the flora of Iran. It is easily distinguished form the other species of genus in Iran by having densely tomentose-arachnoidwhitish indumentum in throughout the plant especially in the capitula. Finally, a key identification to all species of the genus Onopordum in Iran is presented. [ABSTRACT FROM AUTHOR]

Copyright of Trakya University Journal of Natural Sciences is the property of Trakya University Journal of Natural Sciences (TUJNS) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two taxon names in the genus Onopordum are lectotypified: O. heteracanthum var. carmanicum Bornm. and O. myriacanthum Boiss. Images of the type specimens are provided. [ABSTRACT FROM AUTHOR]

In this study Onopordum carduiforme (Asteraceae) is recorded for the first time from South Anatolia region (Hatay) of Turkey. The diagnostic characters of Onopordum carduiforme are given. Besides to description of the new record, photograph of the general habitus in nature is provided. Geographical distribution is mapped, and also IUCN threat category of the species at the regional scale is proposed as VU. [ABSTRACT FROM AUTHOR]

The carbohydrate composition (inulin and sugars) and antioxidant potential of 95% ethanol and subsequent water extracts from flower heads of Carduus acanthoides L. and Onopordum tauricum Willd. grown in Bulgaria were investigated. The total fructans content in both thistle species was analyzed by ketose-specific assay, while individual inulin and sugars content was defined by HPLC-RID method. The total phenolic content and the antioxidant capacity of the studied extracts were also examined as the antioxidant potential was determined by four in vitro assays (DPPH, ABTS, FRAP and CUPRAC). O. tauricum Willd. flower heads were evaluated for the first time as a rich source of prebiotics and total phenols. Higher fructans content was found in the water extracts, while the ethanol extracts possessed better antioxidant activity. [ABSTRACT FROM AUTHOR]

Cynarin is a derivative of hydroxycinnamic acid and it has biologically active functional groups constituent of some plants and food. We elucidated the antioxidant activity of cynarin by using differentin vitrocondition bioanalytical antioxidant assays like DMPD•+, ABTS•+,, DPPH•and H2O2scavenging effects, the total antioxidant influence, reducing capabilities, Fe2+chelating and anticholinergic activities. Cynarin demonstrated 87.72% inhibition of linoleic acid lipid peroxidation at 30 µg/mL concentration. Conversely, some standard antioxidants like trolox, α-tocopherol, butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA) exhibited inhibitions of 90.32, 75.26, 97.61, 87.30%, and opponent peroxidation of linoleic acid emulsion at the identical concentration, seriatim. Also, cynarin exhibited effective DMPD•+, ABTS•+,, DPPH•, and H2O2scavenging effects, reducing capabilities and Fe2+chelating effects. On the contrary, IC50andKiparameters of cynarin for acetylcholinesterase enzyme inhibition were determined as 243.67 nM (r2: 0.9444) and 39.34 ± 13.88 nM, respectively. This study clearly showed that cynarin had marked antioxidant, anticholinergic, reducing ability, radical-scavenging, and metal-binding activities. [ABSTRACT FROM AUTHOR]

Hybridization is known to have a creative role in plant evolution. However, it can also have negative effects on parental species. Onopordum is a large genus whose species frequently hybridize. In the Southwest Iberian Peninsula, the rare O. hinojense co-occurs with the widely distributed O. nervosum, and hybrids between these two taxa have been described as O. × onubense., In this study we determine the extinction risk in a hybrid zone, both for hybrids and parentals, using analyses of morphological and cytogenetic traits as well as genetic markers and demographic models. To investigate the introgression process we used amplified fragment length polymorphism ( AFLP) markers, Bayesian analyses and genome scan methods., Morphology, genome size and molecular markers confirmed homoploid hybridization and also indicated unidirectional backcrossing of F1 hybrids with O. nervosum, which is likely to swamp O. hinojense, the parental with lower pollen size and a very low fruit set (8%). Genome scan methods revealed several loci significantly deviating from neutrality. Finally, our demographic modeling indicated that the higher fitness of O. nervosum threats the survival of O. hinojense by demographic swamping., Our study provides strong new evidence for a scenario of rapid extinction by unidirectional introgression and demographic swamping. The multifaceted approach used here sheds new light on the role of introgression in plant extinctions. [ABSTRACT FROM AUTHOR]

Pollen grains are complex three-dimensional structures, and are identified using specific distinctive morphological characteristics. An efficient automatic system for the accurate and rapid identification of pollen grains would significantly enhance the consistency, objectivity, speed and perhaps accuracy of pollen analysis. This study describes the development and testing of an expert system for the identification of pollen grains based on their respective morphologies. The extreme learning machine (ELM) is a type of artificial neural network, and has been used for automatic pollen identification. To test the equipment and the method, pollen grains from 10 species ofOnopordum(a thistle genus) from Turkey were used. In total, 30 different images were acquired for each of the 10 species studied. The images were then used to measure 11 morphological parameters; these were the colpus length, the colpus width, the equatorial axis (E), the polar axis (P), the P/E ratio, the columellae length, the echinae length, and the thicknesses of the exine, intine, nexine and tectum. Pollen recognition was performed using the ELM for the 50–50%, 70–30% and 80–20% training-test partitions of the overall dataset. The classification accuracies of these three training-test partitions of were 84.67%, 91.11% and 95.00%, respectively. Therefore, the ELM exhibited a very high success rate for identifying the pollen types considered here. The use of computer-based systems for pollen recognition has great potential in all areas of palynology for the accurate and rapid accumulation of data. [ABSTRACT FROM AUTHOR]

Onopordum hasankeyfense Pınar & Behçet (Asteraceae: Cardueae) from south-eastern Anatolia, Turkey, is described. This species grows on the rocky slopes beneath the Hasankeyf castle in the Hasankeyf District (C8, Batman province). Morphologically, the new species is related to Onopordum anatolicum (Boiss.) Boiss. & Heldr. ex Eig, a species endemic to central and western Anatolia, and O. acanthium L. This new species differs from the others in its indumentum, capitulum shape, phyllary colour and shape, unequal corolla lobes, and pappus. The ecology and phenology of the new species, as well as its etymology and diagnostic features, are presented and discussed. Images of the new species are provided and compared with O. anatolicum and O. acanthium. In addition, the pollen characteristics and achene features of the species were examined using both light and scanning electron microscopy. The conservation status of O. hasankeyfense was assessed according to IUCN criteria. A distribution map of O. hasankeyfense and related species is also presented. [ABSTRACT FROM AUTHOR]

Campanula aktascii Aytaç & H.Duman (Campanulaceae) has been described as a new species. The diagnostic characters of C. aktascii were compared and discussed with its resembling species and the ecology and phenology of the new species were presented. Onopordum rhodense Boiss. ex Rech.f. (Asteraceae) and Daucus conchitae W.Greuter (Apiaceae) have been reported as a new records from Antalya (South Anatolia) for Turkey. The distribution map and Red List categories of these taxa according to the IUCN were also given. [ABSTRACT FROM AUTHOR]

Copyright of Research in Complementary Medicine / Forschende Komplementärmedizin is the property of Karger AG and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The highly oligophagous tephritid Chaetostomella cylindrica infests the flower heads of six genera and ten species of thistles in Lebanon. It predominantly utilizes two hosts occurring in sympatry, Notobasis syriaca and Onopordum illyricum. Previous work showed that adult flies emerging from N. syriaca fit more closely the description of the species, particularly with respect to the colour and pattern on the mesonotum; furthermore, significant differences were observed between the aculeus shape and length. This study investigates the biology of the immatures and compares adults from the two host races behaviourally and genetically. Larvae of both races fed in a similar way, with each larva destroying 3-10 achenes; however, the oviposition behaviour of females differed. Females of the Onopordumassociated flies laid an average of three eggs per head, and deposited the eggs glued to each others in a cluster, while females of the Notobasis-associated flies deposited their eggs unattached, usually with one egg per head. Subtle differences were also observed in the post-mating behaviour of adult males. DNA sequencing of an amplified fragment of the mitochondrial NADH-dehydrogenase subunit 1 gene revealed 44 single nucleotide polymorphisms in 622 base pairs. A PCR-RFLP method was developed to distinguish the two host-associated populations. Together with previously published morphometric studies, our data show that C. cylindrica consists of distinct host races, which seem to be reproductively isolated as two separate genetic lineages were observed. [ABSTRACT FROM AUTHOR]

The limits of the genera that compose the Onopordumgroup of the Cardueae–Carduinae are difficult to establish. There are two main life forms; one is exemplified in the genus Onopordum, which includes only biennial colonisers in the Mediterranean region and temperate Eurasia; the second life form is exemplified in the group of perennial herbs of the genera Alfredia, Ancathia, Lamyropappus, Olgaea, Synurus, Syreitschikoviaand Xanthopappus, all of them growing in the mountains of central Asia. We explored relationships among the genera of the complex by using Bayesian and parsimony analyses of a combined dataset of nuclear and plastid DNA sequences. Our results confirmed that the group is natural and the two life forms correspond to well defined entities. Generic limits within the eight central Asian genera are, however, very difficult to establish. Our results suggested that the present genus circumscription is artificial, especially for the largest genus, Olgaea, which appears paraphyletic. Some solutions are suggested. The most preferable might be lumping all small genera together in a broadly redefined genus Alfredia, and assigning sectional rank to the natural groups that result from correlating morphology with our molecular results. However, none of the possible solutions is free of problems because morphological characters and molecular phylogeny are not fully congruent. Some considerations on the origin and peculiar adaptations for becoming a successful coloniser shown by Onopordumare also offered, finding parallels to these adaptations in other examples of biennial colonisers within subtribe Carduinae. [ABSTRACT FROM AUTHOR]

An existing method to induce systemic rust infections in creeping thistles (Cirsium arvense) using an insect vector, the weevil Ceratapion onopordi, was successfully applied in the field. Urediniospores of Puccinia punctiformis were experimentally transmitted to naturally grown thistles, to our knowledge for the first time resulting in systemically infected shoots in an established thistle population. [ABSTRACT FROM AUTHOR]

Because weevils are used as biocontrol agents against thistles, it is important to document and understand host shifts and the evolution of host-specificity in these insects. Furthermore, such host shifts are of fundamental interest to mechanisms of speciation. The mediterranean weevil Larinus cynarae normally parasitizes either one of two thistle genera, Onopordum and Cynara, being locally monophagous. In Sardinia, however, both host genera are used. We used three types of data to help understand this complex host use: (i) weevil attack rates on the two host genera among 53 different populations in Sardinia and nearby Corsica, (ii) host preference in a lab setting, and (iii) genetic (allozyme) differentiation among weevil populations exploiting the same or different hosts. Using a subset of populations from northern Sardinia, we attempted to relate interpopulation differences in host preference to gene flow among populations by comparing pairwise differences in oviposition preference ( Qst) and in allozyme frequencies ( Fst). Overall, Qst and Fst were positively correlated. Fst was positively correlated with geographic distance among pairs of populations using the same host, but not among different-host population pairs. As mating occurs on the hosts, this result suggests reinforcement. Genetic evidence indicates Cynara as the ancestral host of the weevils from both islands and our current studies suggest repeated attempts to colonize Onopordum, with a successful shift in Corsica and a partial shift in Sardinia. This scenario would explain why in Sardinia the level of attack was higher on Cynara than on Onopordum and why, when given a choice in the laboratory, Sardinian weevils preferred Cynara even when sampled from Onopordum. The lability of host shifts in L. cynarae supports caution in using these or related weevils as biocontrol agents of exotic thistles. [ABSTRACT FROM AUTHOR]

Chaetostomella cylindrica is a highly oligophagous tephritid infesting the flower heads of six genera and 10 species of thistles in Lebanon, and is predominant on two hosts in sympatry, Notobasis syriaca and Onopordum illyricum. Adult flies emerging from N. syriaca fit more closely the description of the species with respect to the colour and pattern on the mesonotum. This study compares morphometrically and morphologically the host races associated with N. syriaca and O. illyricum. Immatures of both races were similar, but all stages of the Onopordum-associated race were significantly larger. Morphometric studies, based on two head and five wing measurements, using canonical discriminant analysis, allowed for the differentiation of the host races with more than 70% accuracy. The aculeus shape and length differed significantly between females of both races. The holotype of Trypeta lurida Loew 1844 was examined and appeared closer to the Onopordum host race. Chaetostomella cylindrica appears to be a complex of cryptic and reproductively isolated species. [ABSTRACT FROM AUTHOR]

Between 1992 and 2000, seven insect agents were released in Australia for the biological control of Onopordum spp. thistles. This paper describes the protocol used for the selection of these agents, starting with the development of a preliminary strategy, based on the ecology and population dynamics of the target weed. The strategy informed the surveys for natural enemies in the native range of Onopordum, targeting insects that attacked key transitional stages of the weed’s life cycle. Ongoing studies of Onopordum populations in both Australia and Europe, plus experimental studies on the ecology, potential impact and preliminary host specificity of the agents, led to the refinement of the strategy and the selection and prioritisation of the agents. It is argued that development of an explicit strategy prior to release should be encouraged, as it forces researchers to revisit the rationale for and aims of particular biological control projects, ensuring that the process of agent selection remains focused. It also provides a tool to improve the process of agent selection, as subsequent results can be measured against the strategy and agent success or failure evaluated against the a priori expectations. [ABSTRACT FROM AUTHOR]

Matrix projection models occupy a central role in population and conservation biology. Matrix models divide a population into discrete classes, even if the structuring trait exhibits continuous variation (e.g., body size). The integral projection model (IPM) avoids discrete classes and potential artifacts from arbitrary class divisions, facilitates parsimonious modeling based on smooth relationships between individual state and demographic performance, and can be implemented with standard matrix software. Here, we extend the IPM to species with complex demographic attributes, including dormant and active life stages, cross-classification by several attributes (e.g., size, age, and condition), and changes between discrete and continuous structure over the life cycle. We present a general model encompassing these cases, numerical methods, and theoretical results, including stable population growth and sensitivity/ elasticity analysis for density-independent models, local stability analysis in density-dependent models, and optimal/evolutionarily stable strategy life-history analysis. Our presentation centers on an IPM for the thistle Onopordum illyricum based on a 6-year field study. Flowering and death probabilities are size and age dependent, and individuals also vary in a latent attribute affecting survival, but a predictively accurate IPM is completely parameterized by fitting a few regression equations. The online edition of the American Naturalist includes a zip archive of R scripts illustrating our suggested methods. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Taraxasteryl acetate was isolated for the first time from Scotch thistle Onopordum acanthium. Its crystal and molecular structure was found using x-ray structure analysis. [ABSTRACT FROM AUTHOR]

Cypsela dormancy in Scotch thistle (Onopordum acanthium) may be affected by the presence of chemical inhibitors. To investigate this phenomenon, a leachate from O. acanthiurn cypselas was tested for its ability to inhibit germination of the cypselas from which it was derived (i.e., autoinhibition). Leachates varied in their degree of autoinhibition, depending on the cypsela population from which they were prepared. Overall, removal of leachate from a group of O. acanthium cypselas increased their germinability. Using lettuce (Lactuca sativa) cypselas as an indicator species, bioactivity-guided fractionation was used to isolate a water-soluble, parasubstituted benzamide from O. acanthiutn cypselas, which caused germination inhibition. Various chromatographic, spectroscopic, and spectrometric techniques were applied to the characterization of the bioactive compound. [ABSTRACT FROM AUTHOR]

Cypselas (fruits) of four local populations of Scotch thistle, Onopordum acanthium L., were stored for 3 months, heated gradually from room temperature to 50, 75, or 100 Celsius and then gradually cooled to determine effects on germination. Populations responded similarly to this treatment. The lowest germination percentages and slowest rates followed the 100 Celsius treatment, while the fastest germination rates followed 75 Celsius. In a direct-heating experiment, cypselas (from central and peripheral positions in the capitulum) of one population were stored for 4 1/2 months and then exposed directly to 50, 75, or 100 Celsius for 0.5, 1, or 2 min. This treatment at 75 and 100 Celsius increased germination percentages, with higher percentages for the central cypselas. The 2 min treatment at 100 Celsius yielded the highest percentage and fastest germination rate. Central cypselas were heavier but were similar to peripheral ones in imbibition and in the ratio between cypsela coat and embryo weights. In subsidiary experiments, wax-removed cypselas had smoother surfaces, heated cypselas had visible surface cracks, and germinated cypselas had thinner pericarps. Increases in the percentage and rate of germination in response to dry heat suggest that seedlings of O. acanthium may emerge sooner and in greater numbers following a fire event on disturbed or agricultural lands. [ABSTRACT FROM AUTHOR]

Summary 1. Several European thistle species of the genus Onopordum have become naturalized in Australia and are considered serious pasture weeds, leading to a project aimed at their biological control. 2. The population structure of a potential control agent, the crown weevil Trichosirocalus briesei , a newly described member of the Trichosirocalus horridus species group, was studied under natural conditions on its Onopordum spp. host-plants in northern Spain. 3. Trichosirocalus briesei was found to be the most abundant of three species of crown-feeding insect utilizing these plants. Adults of this univoltine weevil began to lay eggs in mid-autumn and larval population sizes increased over winter until pupation in early spring. 4. The spatial distribution of the immobile larvae was not random, indicating that females were selective in their oviposition behaviour. Field data suggested that plants in dense patches were attacked less frequently, and larger rosettes were preferred for egg-laying. 5. A preliminary cage experiment indicated that feeding by T . briesei could damage Onopordum spp. thistles. A second experiment using plants in individual cages showed a clear relationship between the density of the weevils and the reduction in several growth parameters and seed production. At the highest densities, larval feeding could kill Onopordum rosettes before they produced flowering stems. 6. These results indicated that T . briesei has the potential to contribute to the biological control of Onopordum spp. thistles in Australia. Following host-specificity testing, the weevil was released in 1997. [ABSTRACT FROM AUTHOR]

Focuses on the series of host-specificity tests carried out for the biological control of Onopordum in Australia. Evolution of host-plant lineages; Use of molecular data to determine plant taxonomic relationships; Interpretation of formal quarantine testing.

A strategy is described for the biological control of exotic Onopordum spp. thistles in Australia. This strategy is based on identification of critical transitional stages in the life-cycle of the weed and targeting a complementary group of insect herbivores against these stages. The strategy has both long- and short-term aims and is focussed on the long-lived soil seed bank of these thistles. In the longer term it is considered essential to reduce soil seed reserves to levels at which emergent plant densities are not economically damaging, and in the shorter term it aims to minimize the impact of those plants that do emerge during the period of seed bank decline. From more than 120 insect species found to feed on Onopordum spp. in their native European range, six were selected to form a complementary herbivore guild, targeting the small rosette ⇒ large rosette, stem elongation ⇒ flowering and seed production ⇒ soil seed reserves transitions of their host plant. Descriptions are given of these agents and the role that they are expected to play. The importance of determining the order of agent release from the host-plant interactions is also discussed. [ABSTRACT FROM AUTHOR]

1. The impact of the oligophagous capitulum weevil Larinus tatus on seed production by its host Onopordum species was studied in its native range in order to assess its potential as a biological control agent of these thistles in Australia. 2. Field surveys in Greece during 1988–89 showed a strong positive relationship between attack levels of L. tatus and seed destruction in Onopordum species Differences in attack levels were found between populations of different species, with heavier attack on those having larger capitula. 3. In the case of O. bracteatum, attack levels attained 100% with total seed destruction. More detailed studies at one location over a full season in 1991 confirmed that L. tatus is the dominant capitulum insect, being responsible for the loss of 37% of seed, compared with 8% for the lepidopteran Homeosoma nebutetta and 2% for the tephritid fly Tephritis postica. 4. A regression surface was produced that estimated seed loss in terms of capitulum size and number of developing L. latus larvae. This provides a tool for measuring overall population seed loss from easily measurable parameters. 5. While able to reduce seed production by Onopordum thistles severely in a single season, the longer-term impact of these weevils on their host-plant population dynamics may not be as great. Onopordum species have long-lived seed banks and thus escape in time will dampen the effects of high seed loss in any one year. Moreover, populations of L. latus are themselves subject to density-dependent regulatory processes that would further buffer the system. 6. This weevil was released in Australia in 1992 for the control of Onopordum thistles, and these findings suggest that L. tatus would be most effective as part of a complementary guild of biological control agents. [ABSTRACT FROM AUTHOR]

Focuses on a study that explored the evolution of delayed, size-dependent reproduction in the monocarpic perennial Onopordum illyricum, using mathematical models. Connection of plant's age and size at maturity on its fitness; Biology of Onopordum illyricum; Data collection and analysis.

1. Seed input, changes in the seed bank and seedling recruitment of Onopordum were monitored over 1 year at three contrasting sites (pasture, oat crop and hillside) within an 80-hectare paddock at Galong, New South Wales, about 100 km NW of Canberra. Each site was c. 2000m². Time constraints precluded a longer study and repetition of the sampling procedures at similar sites in other areas. 2. In the pasture there were few Onopordum plants but a seed bank of c. 5000 seeds m[sup -2]. During the year the seed bank decreased by more than half, but the most dormant component remained constant at c. 800 seeds m[sup -2]. 3. In an oat crop nearby there were no flowering Onopordum plants and there was no direct seed input. Nevertheless, the seed bank of c. 700 seeds m[sup -2] did not decrease. 4. At the third site, a grazed hillside, Onopordum density was high (19 plants m[sup -2]). The seed input of 1788 seeds m[sup -2] caused a temporary small increase in the seed bank in summer but there was no change over the 1-year period either in the total seed bank (c. 3000 seeds m[sup -2]) or in its most dormant component (c. 750 seeds m[sup -2]). 5. Seedlings appeared in all seasons, invariably after rain. More than 95% of seedlings appeared in late summer or autumn, but different management practices changed the pattern of winter establishment. 6. For ecological studies of weeds, the population dynamics of the seeds in the soil and of the plants above ground are equally significant. This study shows that the existence of a small pool of labile seeds (c. 15% minimum) in the seed bank that can be recruited opportunistically, together with a large, strongly persistent. [ABSTRACT FROM AUTHOR]

Achenes of seven species of Carduus, Cirsium and Onopordum were collected in August—September and mixed with the top 2·5 cm of soil which was then periodically disturbed during 3 or more years. Between 0 and 40% of the achenes produced seedlings in the autumn of sowing. There was wide variation between sowings of the same species in different years, as well as between species. Subsequent seedling emergence was mainly in March—April (Cirsium eriophorum, C. palustre, C. vulgare), April (Carduus acanthoides, C. nutans) or April—May (Cirsium arvense). Onopordum acanthium showed a contrasting pattern; most seedlings appeared in July—September, with small numbers in other months. More than 90% of all seedlings of Cirsium and Carduus spp. that emerged did so within a year after sowing. There were few or none after the second year and very few dormant achenes remained after 5 years. Only about half the achenes of O. acanthium mixed with 7·5 cm of soil produced seedlings in the first 16 months. Seedlings continued to appear subsequently and up to 8% of the achenes sown were still dormant and viable after 5 years. [ABSTRACT FROM AUTHOR]

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

(1) Seedlings of six species of thistle (Carduus nutans, C. 'pycnocephalus', Carthamus lanatus, Cirsium vulgare, Onopordum aff. illyricum and Silybum marinum) common in mixed pastures of south-eastern Australia, were grown in pots of sand to each of which one of twelve concentrations of nutrient solution was applied regularly for 14 weeks. The species were grown either as monocultures or in mixtures. (2) The total yield of all species increased in monocultures and in mixtures with increasing total nutrients. Analyses of variance confirmed that nutrients, species and nutrient × species interactions were significant for both monocultures and mixtures. (3) Polynomial regressions were fitted to the responses of indivudual species to the nutrient-concentration gradient. High degree (quartic) functions were necessary to describe some responses. For individual species, the response curves in monoculture and mixture were different. (4) Non-linear smoothing with running medians was used to provide a more appropriate functional relationship. Complex response curves to nutrient concentration were obtained. Curves of shoot/root quotient (S/R) were also complex, although S/R quotients were generally higher in mixtures than in monocultures, especially for some taxa at the higher end of the nutrient gradient. (5) When species performance in monoculture was expressed on a relative basis (relative physiological performance, R[SUBij]), most showed a characteristic response; only Onopordum aff. illyricum and silybum marianum were similar. Carthamus lanatus achieved maximum yield at low, Carduus 'pycnocephalus' at intermediate and Cirsium vulgare at high nutrient concentrations. (6) There were differences between species in terms of their normalized ecological performances (E[SUBij]) in mixtures -- Carthamus lanatus was dominant at low, Carduus 'pycnocephalus' at intermediate and Silybum marianum at high nutrient concentrations. (7) Prediction of thistle performance in... [ABSTRACT FROM AUTHOR]

The name Onopordum arabicum Podlech is illegitimate because there exists an earlier homonym. A new name, O. podlechii Negaresh, is proposed for O. arabicum Podlech. [ABSTRACT FROM AUTHOR]