Physical Stress, Not Biotic Interactions, Preclude an Invasive Grass from Establishing in Forb-Dominated Salt Marshes

Biological invasions have become the focus of considerable concern and ecological research, yet the relative importance of abiotic and biotic factors in controlling the invasibility of habitats to exotic species is not well understood. Spartina species are highly invasive plants in coastal wetlands; however, studies on the factors that control the success or failure of Spartina invasions across multiple habitat types are rare and inconclusive.We examined the roles of physical stress and plant interactions in mediating the establishment of the smooth cordgrass, Spartina alterniflora, in a variety of coastal habitats in northern China. Field transplant experiments showed that cordgrass can invade mudflats and low estuarine marshes with low salinity and frequent flooding, but cannot survive in salt marshes and high estuarine marshes with hypersaline soils and infrequent flooding. The dominant native plant Suaeda salsa had neither competitive nor facilitative effects on cordgrass. A common garden experiment revealed that cordgrass performed significantly better when flooded every other day than when flooded weekly. These results suggest that physical stress rather than plant interactions limits cordgrass invasions in northern China.We conclude that Spartina invasions are likely to be constrained to tidal flats and low estuarine marshes in the Yellow River Delta. Due to harsh physical conditions, salt marshes and high estuarine marshes are unlikely to be invaded. These findings have implications for understanding Spartina invasions in northern China and on other coasts with similar biotic and abiotic environments

FoxO and Stress Responses in the Cnidarian Hydra vulgaris

Background: In the face of changing environmental conditions, the mechanisms underlying stress responses in diverse organisms are of increasing interest. In vertebrates, Drosophila, and Caenorhabditis elegans, FoxO transcription factors mediate cellular responses to stress, including oxidative stress and dietary restriction. Although FoxO genes have been identified in early-arising animal lineages including sponges and cnidarians, little is known about their roles in these organisms. Methods/Principal Findings: We have examined the regulation of FoxO activity in members of the well-studied cnidarian genus Hydra. We find that Hydra FoxO is expressed at high levels in cells of the interstitial lineage, a cell lineage that includes multipotent stem cells that give rise to neurons, stinging cells, secretory cells and gametes. Using transgenic Hydra that express a FoxO-GFP fusion protein in cells of the interstitial lineage, we have determined that heat shock causes localization of the fusion protein to the nucleus. Our results also provide evidence that, as in bilaterian animals, Hydra FoxO activity is regulated by both Akt and JNK kinases. Conclusions: These findings imply that basic mechanisms of FoxO regulation arose before the evolution of bilaterians an

Extesa in scrittura non anchora finita della relazione, che io feci in Voce per più di quatr’hore continue nell’Eccelentissimo Consiglio de Pregadi alli 12 del Marzo 1596 della mia ambascieria di Constantinopoli a Sultan Mehemet Gran Sinior de’Turchi l’an

Pagination: 263-321Text Genre:Pros

Tragédies ... Texte établi

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Sénèque. Les seize premières lettres à Lucilius. Texte latin en regard de la traduction française.

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Dialogues ...

French and Latin on opposite pages, numbered in duplicate.At head of title:... Sénèque.I. De ira; texte établi et traduit par A. Bourgery. 1922.--II. De la vie heureuse. De la brièveté de la vie; texte établi et traduit par A. Bourgery. 1923.--III. Consolations; texte établi et traduit par René Waltz. 1923.--IV. De la providence. De la coǹstance du sage. De la tranqulliité de l'âme. De l'oisivité; texte établi et traduit par René Waltz. 1927.Mode of access: Internet

Théatre complet des Latins, comprenant Plaute, Térence et Sénèque le tragique,

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