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Tall Plants (tall + plant)
Selected AbstractsInvasive species of Heracleum in Europe: an insight into genetic relationships and invasion historyDIVERSITY AND DISTRIBUTIONS, Issue 1 2007árka Jahodová ABSTRACT Several species of the genus Heracleum (Umbelliferae) were introduced into Europe from south-west Asia in the 19th century and are now widespread in many countries. At least three invasive taxa with unresolved relationships to one another are thought to occur in Europe: Heracleum mantegazzianum Sommier & Levier, H. sosnowskyi Manden, and H. persicum Desf. ex Fischer. They are tall plants forming extensive stands with a high cover. To elucidate genetic relationships between the species, and gain insight into their invasion history, samples were collected from native ranges in Asia and invaded ranges of the three species in Europe and analysed using amplified fragment length polymorphism. Five other Heracleum species were also studied and in total, 189 samples from 72 populations were analysed. The results confirmed that there are three distinct tall Heracleum species invading in Europe. Within each of the three species, plants collected in the invaded range are genetically close to those from their native ranges. A close genetic relationship between the three invasive Heracleum species in Europe was also found. A high overall genetic variability detected in the invaded range suggests that the majority of invading populations were not affected by a genetic bottleneck and that rapid evolution, drift, or hybridization played a role in genetic structuring of invading populations. For H. mantegazzianum, genetic distance of populations in the native range significantly decreased with geographical distance, but not in the invaded range. It is likely that the current pattern of genetic diversity in Europe resulted from multiple introductions of all three species. [source] Herbivore and neighbour effects on tundra plants depend on species identity, nutrient availability and local environmental conditionsJOURNAL OF ECOLOGY, Issue 1 2008Anu Eskelinen Summary 1I performed a factorial transplant experiment to test the roles of plant,plant interactions, herbivory by mammal grazers and resource availability for plant performance in two contrasting habitat types in a mountain tundra environment. 2Three perennial dicot herbs, Solidago virgaurea, Erigeron uniflorus and Saussurea alpina, were used as target plants to study the effects of neighbour removal and grazer exclusion, and nutrient enrichment and liming on plant growth, survival and reproductive success. These treatments were replicated in two contrasting habitat types, infertile acidic and fertile non-acidic tundra heaths. 3The effects of plant,plant interactions on Saussurea varied from facilitation in infertile acidic habitats to competition in fertile non-acidic habitats and in nutrient-enriched conditions, while the overall performance of Saussurea was strongly negatively influenced by the presence of grazers, the effects being greater when plants were fertilized and in fertile non-acidic heaths. Erigeron performed better under nutrient-enriched conditions than in unfertilized plots, when neighbours had been removed. Solidago was negatively affected by grazing and this impact was greater in nutrient-enriched plots and in non-acidic heaths than in acidic heaths and for unfertilized controls. There were no interactions between neighbour removal and herbivory in any of the three species, indicating that these processes operated independently. 4Grazer-preferred tall plants are strongly limited by consumption by mammal herbivores in nutrient-enriched conditions and in inherently fertile habitats. By contrast, arctic,alpine specialists and species of low stature experience increased competition with neighbouring vegetation in fertile habitats and in enriched nutrient conditions. 5Synthesis. Overall, the results suggest that the strength and directions of plant,plant and plant,herbivore interactions depend on plant species identity and are modified by soil edaphic factors to govern vegetation processes in tundra plant communities. These findings have important implications for understanding the forces structuring vegetation in barren tundra ecosystems under a changing environment. [source] Plant-mediated nitrous oxide emissions from beech (Fagus sylvatica) leavesNEW PHYTOLOGIST, Issue 1 2005Mari Pihlatie Summary ,,Nitrous oxide (N2O) emission estimates from forest ecosystems are based currently on emission measurements using soil enclosures. Such enclosures exclude emissions via tall plants and trees and may therefore underestimate the whole-ecosystem N2O emissions. ,,Here, we measured plant-mediated N2O emissions from the leaves of potted beech (Fagus sylvatica) seedlings after fertilizing the soil with 15N-labelled ammonium nitrate (15NH415NO3), and after exposing the roots to elevated concentrations of N2O. ,,Ammonium nitrate fertilization induced N2O + 15N2O emissions from beech leaves. Likewise, the foliage emitted N2O after beech roots were exposed to elevated concentrations of N2O. The average N2O emissions from the fertilization and the root exposure experiments were 0.4 and 2.0 µg N m,2 leaf area h,1, respectively. Higher than ambient atmospheric concentrations of N2O in the leaves of the forest trees indicate a potential for canopy N2O emissions in the forest. ,,Our experiments demonstrate the existence of a previously overlooked pathway of N2O to the atmosphere in forest ecosystems, and bring about a need to investigate the magnitude of this phenomenon at larger scales. [source] Effectiveness of resistance genes to the large raspberry aphid, Amphorophora idaei Börner, in different raspberry (Rubus idaeus L.) genotypes and under different environmental conditionsANNALS OF APPLIED BIOLOGY, Issue 2 2000A T JONES Summary The introduction into commerce of raspberry cultivars with major gene resistance to the large raspberry aphid, Amphorophora idaei, an important pest and virus vector on red raspberry in Europe, has been very effective both in decreasing pest numbers and greatly restricting infection with the viruses it transmits. However, biotypes of the aphid able to overcome these genes have developed in the field in recent years. Additionally, in field and laboratory tests, the response to aphid biotypes and recognised aphid strains of certain raspberry cultivars, such as Glen Prosen and Delight, differ markedly despite the fact that they are reputed to contain the same A. idaei -resistance gene, A1. In attempts to understand the reasons for this difference in response, analysis was made of the segregation of progeny seedlings from crosses between A. idaei -resistant and -susceptible cultivars to two recognised strains of the aphid. These studies showed that, as expected, cv. Autumn Bliss contained the A. idaei -resistance gene, A10, and cvs Delight and Glen Prosen each contained the A. idaei -resistance gene, A1. When progeny seedlings were assayed in a heated glasshouse as young plants and in an unheated Tygan house as 1 m tall plants, the segregation ratios for resistance and susceptibility to A. idaei were largely unchanged. However, when the resistance of individual progeny plants was assessed, c. 37% of the putative gene A1 -containing progeny and 9,23% of the putative gene A10 -containing progeny, behaved differently in these two environments. Experiments involving an A. idaei -resistant and -susceptible parent cultivar showed that shading plants increased their susceptibility to A. idaei colonisation. Whilst this shading effect has implications for experimentally detecting A. idaei -resistant progeny in segregating raspberry seedlings, it does not explain the difference in field resistance to A. idaei of cvs Delight and Glen Prosen. Such differences in the field seem best explained by the presence in these cultivars of ,minor' genes for A. idaei resistance and/or susceptibility that influences the effectiveness of gene A1. [source] | ||||||||||