Untersuchungen zur Genexpression in Wurzeln der reblausresistenten Unterlagsrebsorte ’Börner’

Die reblausresistente Unterlagsrebsorte ’Börner’ reagiert auf einen Reblausbefall mit einer Hypersensitivitätsreaktion (HR), die sich in Form von Nekrosen an Blättern und Wurzeln zeigt. Im Rahmen dieser Dissertation wurde der Resistenzmechanismus mittels differenzieller Genexpressionsanalysen untersucht. Unter Anwendung der suppressiven subtraktiven Hybridisierung, der DNA-Microarraytechnik sowie der GeneFishingTM-Methode erfolgte ein Vergleich zwischen der Genexpression in hypersensitivem Wurzelgewebe und Normalgewebe der Unterlagsrebe ’Börner’. Neben der Reblaus induzierten HR wurde insbesondere auf die experimentelle Induktion durch das Pflanzenhormon Indol-3-Essigsäure (IES) zurückgegriffen. Damit sollten Kenntnisse über die Rolle der IES als auslösender Faktor der Resistenzreaktion gewonnen werden. Die Ergebnisse bestätigen die Annahme, dass die IES Pathogenabwehrreaktionen in ’Börner’ induziert. So konnten Hinweise auf die transkriptionelle Aktivierung Resistenz und HR assoziierter Proteine gefunden werden, wie z.B. Phytoalexine und pathogen-related (PR)-Proteine sowie Vertreter aus der hypersensitive-induced response-Familie. Es konnten weiterhin wertvolle Informationen im Hinblick auf die Transduktion des IES-Signals im Zusammenhang mit der Aktivierung von Resistenzreaktionen gewonnen werden. So wurden Hinweise auf die Beteiligung der Signalsubstanzen Ethylen, Salicylsäure, Jasmonsäure, Calcium sowie reaktiver Sauerstoffspezies gefunden. Es konnten zudem Anhaltspunkte für die Aktivierung des Auxin induzierten Ubiquitin/26S-Proteolyseweges und weiterer Signalkomponenten, wie z.B. Kinasen und Transkriptionsfaktoren, ermittelt werden. Auch auf die Beteiligung von Auxinrezeptoren konnte aufgrund der Resultate geschlossen werden. Damit war es im Rahmen der Dissertation möglich, potenzielle Signaltransduktionswege zu erarbeiten, die für weiterführende Untersuchungen des Reblausresistenzmechanismus von entscheidender Bedeutung sind.

La ville comme labyrinthe: réécritures d'un mythe entre les années 1950 et 1980

Entre les années 1950 et 1980, émerge une nouvelle forme de labyrinthe chez des romanciers européens comme Michel Butor, Alain Robbe-Grillet, Italo Calvino, Patrick Modiano et Alasdair Gray : un labyrinthe insaisissable et non cartographiable. Pour en rendre compte nous avons recours au modèle du rhizome, issu de la philosophie de Gilles Deleuze et de Félix Guattari, aussi bien qu'au concept d'hétérotopie de Michel Foucault. La spatialité de nos romans nous pousse à prendre en compte également les réécritures ironiques du mythe de Thésée, Ariane, le Minotaure, Dédale. Les citations et les allusions au mythe nous font remarquer la distance d'avec le modèle traditionnel et les effets de ce qu'on peut considérer comme un « bricolage mythique », dans le cadre d'un regard ironique, parodique ou satirique. La représentation romanesque du labyrinthe accentue d'un côté l'absence d'un centre, et de l'autre côté l'ouverture extrême de cet espace qu'est la ville contemporaine. En même temps, la présence de nombreux « espaces autres », les hétérotopies de Foucault, définit l'égarement des protagonistes des romans. Au fur et à mesure que les écrivains acquièrent conscience des caractéristiques « labyrinthiques » de ces espaces, celles-ci commencent à informer l'œuvre romanesque, créant ainsi un espace métafictionnel. Entre les années Cinquante et le début des années Soixante-dix, les Nouveaux romanciers français accentuent ainsi l'idée de pouvoir jouer avec les instruments de la fiction, pour exaspérer l'absence d'un sens dans la ville comme dans la pratique de l'écriture. Calvino reformule cette conception du roman, remarquant l'importance d'un sens, même s'il est caché et difficile à saisir. Pour cette raison, à la fin de l'époque que nous analysons, des auteurs comme Modiano et Gray absorbent les techniques d'écriture de ces prédécesseurs, en les faisant jouer avec la responsabilité éthique de l'auteur.

Strati, piano, rizoma. John Cage e la filosofia di Gilles Deleuze e Félix Guattari

In base ad una recensione esaustiva dei riferimenti alla musica e al sonoro nella produzione filosofica di Gilles Deleuze e Félix Guattari, la presente ricerca s’incentra sulla posizione che il pensiero musicale di John Cage occupa in alcuni testi deleuziani. Il primo capitolo tratta del periodo creativo di Cage fra il 1939 e il 1952, focalizzandosi su due aspetti principali: la struttura micro-macrocosmica che contraddistingue i suoi primi lavori, e i quattro elementi che in questo momento sintetizzano per Cage la composizione musicale. Questi ultimi sono considerati in riferimento alla teoria della doppia articolazione che Deleuze e Guattari riprendono da Hjelmslev; entrambi gli aspetti rimandano al sistema degli strati e della stratificazione esposta su Mille piani. Il secondo capitolo analizza la musica dei decenni centrali della produzione cagiana alla luce del luogo in Mille piani dove Cage è messo in rapporto al concetto di “piano fisso sonoro”. Un’attenzione particolare è posta al modo in cui Cage concepisce il rapporto fra durata e materiali sonori, e al grado variabile in cui sono presenti il caso e l’indeterminazione. Le composizioni del periodo in questione sono inoltre viste in riferimento al concetto deleuzo-guattariano di cartografia, e nelle loro implicazioni per il tempo musicale. L’ultimo quindicennio della produzione di Cage è considerata attraverso il concetto di rizoma inteso come teoria delle molteplicità. In primo luogo è esaminata la partitura di Sylvano Bussotti che figura all’inizio di Mille piani; in seguito, i lavori testuali e musicali di Cage sono considerati secondo le procedure compositive cagiane del mesostico, delle parentesi di tempo che concorrono a formare una struttura variabile, e dell’armonia anarchica dell’ultimo Cage.

The role of olfactory cues in the sequential radiation of a gall-boring beetle, Mordellistena convicta

1. Herbivorous insects often have close associations with specific host plants, and their preferences for mating and ovipositing on a specific host-plant species can reproductively isolate populations, facilitating ecological speciation. Volatile emissions from host plants can play a major role in assisting herbivores to locate their natal host plants and thus facilitate assortative mating and host-specific oviposition. 2. The present study investigated the role of host-plant volatiles in host fidelity and oviposition preference of the gall-boring, inquiline beetle, Mordellistena convicta LeConte (Coleoptera: Mordellidae), using Y-tube olfactometers. Previous studies suggest that the gall-boring beetle is undergoing sequential host-associated divergence by utilising the resources that are created by the diverging populations of the gall fly, Eurosta solidaginis Fitch (Diptera: Tephritidae), which induces galls on the stems of goldenrods including Solidago altissima L. (Asteraceae) and Solidago gigantea Ait. 3. Our results show that M. convicta adults are attracted to galls on their natal host plant, avoid the alternate host galls, and do not respond to volatile emissions from their host-plant stems. 4. These findings suggest that the gall-boring beetles can orient to the volatile chemicals from host galls, and that beetles can use them to identify suitable sites for mating and/or oviposition. Host-associated mating and oviposition likely play a role in the sequential radiation of the gall-boring beetle.

The Role of Olfactory Cues in the Sequential Radiation of a Gall-boring Beetle, Mordellistena convicta

1. Herbivorous insects often have close associations with specific host plants, and their preferences for mating and ovipositing on a specific host-plant species can reproductively isolate populations, facilitating ecological speciation. Volatile emissions from host plants can play a major role in assisting herbivores to locate their natal host plants and thus facilitate assortative mating and host-specific oviposition. 2. The present study investigated the role of host-plant volatiles in host fidelity and oviposition preference of the gall-boring, inquiline beetle, Mordellistena convicta LeConte (Coleoptera: Mordellidae), using Y-tube olfactometers. Previous studies suggest that the gall-boring beetle is undergoing sequential host-associated divergence by utilising the resources that are created by the diverging populations of the gall fly, Eurosta solidaginis Fitch (Diptera: Tephritidae), which induces galls on the stems of goldenrods including Solidago altissima L. (Asteraceae) and Solidago gigantea Ait. 3. Our results show that M. convicta adults are attracted to galls on their natal host plant, avoid the alternate host galls, and do not respond to volatile emissions from their host-plant stems. 4. These findings suggest that the gall-boring beetles can orient to the volatile chemicals from host galls, and that beetles can use them to identify suitable sites for mating and/or oviposition. Host-associated mating and oviposition likely play a role in the sequential radiation of the gall-boring beetle.

Ginger phenylpropanoids inhibit IL-1beta and prostanoid secretion and disrupt arachidonate-phospholipid remodeling by targeting phospholipases A2

The rhizome of ginger (Zingiber officinale) is employed in Asian traditional medicine to treat mild forms of rheumatoid arthritis and fever. We have profiled ginger constituents for robust effects on proinflammatory signaling and cytokine expression in a validated assay using human whole blood. Independent of the stimulus used (LPS, PMA, anti-CD28 Ab, anti-CD3 Ab, and thapsigargin), ginger constituents potently and specifically inhibited IL-1β expression in monocytes/macrophages. Both the calcium-independent phospholipase A(2) (iPLA(2))-triggered maturation and the cytosolic phospholipase A(2) (cPLA(2))-dependent secretion of IL-1β from isolated human monocytes were inhibited. In a fluorescence-coupled PLA(2) assay, most major ginger phenylpropanoids directly inhibited i/cPLA(2) from U937 macrophages, but not hog pancreas secretory phospholipase A(2). The effects of the ginger constituents were additive and the potency comparable to the mechanism-based inhibitor bromoenol lactone for iPLA(2) and methyl arachidonyl fluorophosphonate for cPLA(2), with 10-gingerol/-shogaol being most effective. Furthermore, a ginger extract (2 μg/ml) and 10-shogaol (2 μM) potently inhibited the release of PGE(2) and thromboxane B2 (>50%) and partially also leukotriene B(4) in LPS-stimulated macrophages. Intriguingly, the total cellular arachidonic acid was increased 2- to 3-fold in U937 cells under all experimental conditions. Our data show that the concurrent inhibition of iPLA(2) and prostanoid production causes an accumulation of free intracellular arachidonic acid by disrupting the phospholipid deacylation-reacylation cycle. The inhibition of i/cPLA(2), the resulting attenuation of IL-1β secretion, and the simultaneous inhibition of prostanoid production by common ginger phenylpropanoids uncover a new anti-inflammatory molecular mechanism of dietary ginger that may be exploited therapeutically.

The role of olfactory cues in the sequential radiation of a gall-boring beetle

Species diversity itself may cause additional species diversity. According to recent findings, some species modify their environment in such a way that they facilitate the creation of new niches for other species to evolve to fill. Given the vast speciesdiversity of insects, the occurrence of such sequential radiation of species is likely common among herbivorous insects and the species that depend on them, many of them being insects as well. Herbivorous insects often have close associations with specific host plants and their preferences for mating and ovipositing on a specific host-plant species can reproductively isolate host-specific populations, facilitating speciation. Previous research by our laboratory has established that there are two distinct populations of thegall fly, Eurosta solidaginis (Tephritidae), which attack different species of goldenrods, Solidago altissima (Asteraceae) and S. gigantea. The gall fly’s host-associated differentiation is facilitating the divergence and potential speciation of twosubpopulations of the gall-boring beetle Mordellistena convicta (Mordellidae) by providing new resources (galls on stems of the galdenrods) for the gall-boring beetles. These beetles exist as two host-plant associated populations of inquilines that inhabit the galls induced by the gall fly. While our previous research has provided genetic and behavioral evidence for host-race formation, little is known about the role of their host plants in assortative mating and oviposition-site selection of the gall-boring beetles’ hostassociated populations. Volatile emissions from host plants can play a major role in assisting herbivores to locate their natal host plants and thus facilitate assortative mating and host-specific oviposition. The present study investigated the role of host-plant volatiles in host fidelity (mating on the host plant) and oviposition preference of M. convicta by measuring its behavioral responses to the host-plant volatile emissions using Y-tube olfactometers. In total, we tested behavioral responses of 615 beetles. Our resultsshow that M. convicta adults are attracted to their natal host galls (67% of S. altissima-emerging beetles and 70% of S. gigantea-emerging beetles) and avoid the alternate host galls (75% of S. altissima-emerging beetles and 66% of S. gigantea-emerging beetles),while showing no preference for, or avoidance of, ungalled plants from either species. This suggests that the gall beetles can orient to the volatile chemicals emitted by the galls and can potentially use them to identify suitable sites for mating and/or oviposition. Thus, host-associated mating and oviposition may play a role in the sequential speciation of the gall-boring beetle.

INTEGRATED MANAGEMENT OF THE INVASIVE SPECIES CIRSIUM ARVENSE, CANADA THISTLE, AND PHRAGMITES AUSTRALIS, COMMON REED: USING ECOLOGICALLY BASED CONTROL MEASURES AT EACH STAGE OF THE INVASION PROCESS

Invasive plant species threaten natural areas by reducing biodiversity and altering ecosystem functions. They also impact agriculture by reducing crop and livestock productivity. Millions of dollars are spent on invasive species control each year, and traditionally, herbicides are used to manage invasive species. Herbicides have human and environmental health risks associated with them; therefore, it is essential that land managers and stakeholders attempt to reduce these risks by utilizing the principles of integrated weed management. Integrated weed management is a practice that incorporates a variety of measures and focuses on the ecology of the invasive plant to manage it. Roadways are high risk areas that have high incidence of invasive species. Roadways act as conduits for invasive species spread and are ideal harborages for population growth; therefore, roadways should be a primary target for invasive species control. There are four stages in the invasion process which an invasive species must overcome: transport, establishment, spread, and impact. The aim of this dissertation was to focus on these four stages and examine the mechanisms underlying the progression from one stage to the next, while also developing integrated weed management strategies. The target species were Phragmites australis, common reed, and Cisrium arvense, Canada thistle. The transport and establishment risks of P. australis can be reduced by removing rhizome fragments from soil when roadside maintenance is performed. The establishment and spread of C. arvense can be reduced by planting particular resistant species, e.g. Heterotheca villosa, especially those that can reduce light transmittance to the soil. Finally, the spread and impact of C. arvense can be mitigated on roadsides through the use of the herbicide aminopyralid. The risks associated with herbicide drift produced by application equipment can be reduced by using the Wet-Blade herbicide application system.

Characterization of the Agrobacterium tumefaciens VirB2 pilin of the VirB/D4 Type IV Secretion System

The Agrobacterium tumefaciens VirB/D4 type IV secretion system (T4SS) delivers oncogenic T-DNA and effector proteins to susceptible plant cells. This leads to the formation of tumors termed Crown Galls. The VirB/D4 T4SS is comprised of 12 subunits (VirB1 to VirB11 and VirD4), which assemble to form two structures, a secretion channel spanning the cell envelope and a T-pilus extending from the cell surface. In A. tumefaciens, the VirB2 pilin subunit is required for assembly of the secretion channel and is the main subunit of the T-pilus. The focus of this thesis is to define key reactions associated with the T4SS biogenesis pathway involving the VirB2 pilin. Topology studies demonstrated that VirB2 integrates into the inner membrane with two transmembrane regions, a small cytoplasmic loop, and a long periplasmic loop comprised of covalently linked N and C termini. VirB2 was shown by the substituted cysteine accessibility method (SCAM) to adopt distinct structural states when integrated into the inner membrane and when assembled as a component of the secretion channel and the T-pilus. The VirB4 and VirB11 ATPases were shown by SCAM to modulate the structural state of membrane-integrated VirB2 pilin, and evidence was also obtained that VirB4 mediates extraction of pilin from the membrane. A model that VirB4 functions as a pilin dislocase by an energy-dependent mechanism was further supported by coimmunoprecipitation and osmotic shock studies. Mutational studies identified two regions of VirB10, an N-terminal transmembrane domain and an outer membrane-associated domain termed the antennae projection, that contribute selectively to T-pilus biogenesis. Lastly, characterization of a VirB10 mutant that confers a ‘leaky’ channel phenotype further highlighted the role of VirB10 in gating substrate translocation across the outer membrane as well as T-pilus biogenesis. Results of my studies support a working model in which the VirB4 ATPase catalyzes dislocation of membrane-integrated pilin, and distinct domains of VirB10 coordinate pilin incorporation into the secretion channel and the extracellular T-pilus.

The role of cytochromes P450 and peroxidases in the detoxification of sulphonated anthraquinones by rhubarb and common sorrel plants cultivated under hydroponic conditions

Sulphonated anthraquinones are precursors of many synthetic dyes and pigments, recalcitrant to biodegradation and thus not eliminated by classical wastewater treatments. In the development of a phytotreatment to remove sulphonated aromatic compounds from dye and textile industrial effluents, it has been shown that rhubarb (Rheum rabarbarum) and common sorrel (Rumex acetosa) are the most efficient plants. Both species, producing natural anthraquinones, not only accumulate, but also transform these xenobiotic chemicals. Even if the precise biochemical mechanisms involved in the detoxification of sulphonated anthraquinones are not yet understood, they probably have cross talks with secondary metabolism, redox processes and plant energy metabolism. The aim of the present study was to investigate the possible roles of cytochrome P450 monooxygenases and peroxidases in the detoxification of several sulphonated anthraquinones. Both plant species were cultivated in a greenhouse under hydroponic conditions, with or without sulphonated anthraquinones. Plants were harvested at different times and either microsomal or cytosolic fractions were prepared. The monooxygenase activity of cytochromes P450 toward several sulphonated anthraquinones was tested using a new method based on the fluorimetric detection of oxygen consumed during cytochromes P450-catalysed reactions. The activity of cytosolic peroxidases was measured by spectrophotometry, using guaiacol as a substrate. A significant activity of cytochromes P450 was detected in rhubarb leaves, while no (rhizome) or low (petioles and roots) activity was found in other parts of the plants. An induction of this enzyme was observed at the beginning of the exposition to sulphonated anthraquinones. The results also indicated that cytochromes P450 were able to accept as substrate the five sulphonated anthraquinones, with a higher activity toward AQ-2,6-SS (0.706 nkat/mg protein) and AQ-2-S (0.720 nkat/mg protein). An activity of the cytochromes P450 was also found in the leaves of common sorrel (1.212 nkat/mg protein (AQ-2,6-SS)), but no induction of the activity occurred after the exposition to the pollutant. The activity of peroxidases increased when rhubarb was cultivated in the presence of the five sulphonated anthraquinones (0.857 nkat/mg protein). Peroxidase activity was also detected in the leaves of the common sorrel (0.055 nkat/mg protein), but in this plant, no significant difference was found between plants cultivated with and without sulphonated anthraquinones. Results indicated that the activity of cytochromes P450 and peroxidases increased in rhubarb in the presence of sulphonated anthraquinones and were involved in their detoxification mechanisms. These results suggest the existence in rhubarb and common sorrel of specific mechanisms involved in the metabolism of sulphonated anthraquinones. Further investigation should be performed to find the next steps of this detoxification pathway. Besides these promising results for the phytotreatment of sulphonated anthraquinones, it will be of high interest to develop and test, at small scale, an experimental wastewater treatment system to determine its efficiency. On the other hand, these results reinforce the idea that natural biodiversity should be better studied to use the most appropriate species for the phytotreatment of a specific pollutant.

Gynaikothrips uzeli (Zimmermann) y Androthrips ramachandrai Karny (Thysanoptera, Phlaeothripidae), primeras citas para la Argentina

Se cita por primera vez para la Argentina Gynaikotrhrips uzeli y Androthrips ramachandrai en agallas sobre hojas de Ficus benjamina en la Provincia de Misiones. La primera de estas especies es fitófago inductor de agallas y la segunda presumiblemente predadora. Se brinda una descripción breve y se ilustran ambas especies.

Gamma irradiation on Alstroemeria aurea G. in vitro rhizomes: : an approach to the appropriate dosage for breeding purposes

Gamma irradiation has been widely used as a breeding technique to obtain new cultivars in ornamental species such as Alstroemeria, where several cultivars have been obtained through rhizome radiation. The optimum dosage for an appropriate induction of mutation must be considered for breeding purposes and it depends mainly on plant susceptibility. Thus in this study in vitro cultured rhizomes of Alstroemeria aurea were irradiated with a gamma source using different dosages to evaluate the direct effect produced. Damage and number of rhizome sprouting were observed and recorded during 61 days after irradiation. At the end of this period, rhizomes were weighted and mortality was evaluated. Both mortality and weight increased depending on dosage. All irradiated rhizomes showed early sprouting in comparison with control (0 Gy) and no significant difference in final number of shoots after 61 days among irradiated treatments was observed. Bleaching and necrosis was observed in all irradiated rhizomes and was more evident at higher doses. LD50 was established at about 40 Gy and the optimum dosage to induce mutation was suggested between 2.5 and 5 Gy, when the growth was reduced in 50%, and probably this dosage could be used for breeding purposes.

Effects of Galleria mellonella cadavers infected with Heterorhabditis bacteriophora and Steinernema rarum, their macerates and dead infective juveniles on Meloidogyne javanica suppression

Nematodes of the Meloidogyne genus affect to most of crops of an economic importance in Argentina. Researches related to new control strategies are needed to reduce the damage produced by these organisms. The objective of this work was to compare the effects of Galleria mellonella cadavers infected with the Argentine isolates Heterorhabditis bacteriophora Rama Caída and Steinernema rarum NOE, cadaver macerates and dead infective juveniles (IJs) on M. javanica suppression. Experiments were performed using 24-well plates and pepper plants grown in a growth chamber. The entomopathogenic nematodes-infected G. mellonella cadavers, their cadaver macerates and dead IJs were effective in suppressing M. javanica second-stage juveniles under laboratory conditions. The use of H. bacteriophora-infected cadavers caused a significant decrease in the number of galls and egg masses on pepper plants parasitized by M. javanica, in a growth-chamber.

Radiocarbon dating of peat soil in Schüttsiel, Schleswig-Holstein

Bei Schüttsiel (Nordfriesland) konnten die ersten Auswirkungen der postglazialen Meerestransgression durch eine Reihe von 14C-Bestimmungen datiert werden. Für den Beginn der Vermoorung (~ 485 cm unter NN) ergab sich ein Alter von 5630 ± 70 Jahren. Der Torf/Klei-Kontakt (~ 470-473 cm unter NN) konnte auf ein Alter von 5460 ± I30 Jahren oberhalb und 5520 ± 130 Jahren unterhalb des Kontaktes eingeengt werden. Auf Altersverfälschungen durch tiefwurzelnde Phragmites-Rhizome wird aufmerksam gemacht. An entsprechendem Probenmaterial durchgeführte l4C-Datierungen bekräftigen den Verdacht auf eine mögliche Datenverschiebung. Zwei tonreiche Schichten aus dem oberen Torfhorizont ('Upper Peat') wurden auf 1850 ± 50 Jahre (A: ~300 cm unter NN) und 1980 ± 50 Jahre V. Chr. (B: ~ 315 cm unter NN) datiert.

(Table 1) Biomass and total standing crop of major wet sedge tundra species at five sites at Alexandra Fiord in 1981 and 2005

The global climate is changing rapidly and Arctic regions are showing responses to recent warming. Responses of tundra ecosystems to climate change have been examined primarily through short-term experimental manipulations, with few studies of long-term ambient change. We investigated changes in above- and belowground biomass of wet sedge tundra to the warming climate of the Canadian High Arctic over the past 25 years. Aboveground standing crop was harvested from five sedge meadow sites and belowground biomass was sampled from one of the sites in the early 1980s and in 2005 using the same methods. Aboveground biomass was on average 158% greater in 2005 than in the early 1980s. The belowground biomass was also much greater in 2005: root biomass increased by 67% and rhizome biomass by 139% since the early 1980s. Dominant species from each functional group (graminoids, shrubs and forbs) showed significant increases in aboveground biomass. Responsive species included the dominant sedge species Carex aquatilis stans, C. membranacea, and Eriophorum angustifolium, as well as the dwarf shrub Salix arctica and the forb Polygonum viviparum. However, diversity measures were not different between the sample years. The greater biomass correlated strongly with increased annual and summer temperatures over the same time period, and was significantly greater than the annual variation in biomass measured in 1980-1983. Increased decomposition and mineralization rates, stimulated by warmer soils, were likely a major cause of the elevated productivity, as no differences in the mass of litter were found between sample periods. Our results are corroborated by published short-term experimental studies, conducted in other wet sedge tundra communities which link warming and fertilization with elevated decomposition, mineralization and tundra productivity. We believe that this is the first study to show responses in High Arctic wet sedge tundra to recent climate change.