spotted knapweed Dotaz Zobrazit nápovědu
BACKGROUND AND AIMS: Spotted knapweed (Centaurea stoebe s.l., Asteraceae) is native to Europe, where it occurs as a diploid (2xEU) and tetraploid cytotype (4xEU), but so far only the tetraploid has been reported in the introduced range in North America (4xNA). In previous studies, significant range shifts have been found towards drier climates in 4xEU compared with 2xEU, and in 4xNA when compared with the native range. In addition, 4x plants showed thicker leaves and reduced specific leaf area compared with 2x plants, suggesting higher drought tolerance in 4x plants. It is thus hypothesized that the 4x cytotype might be better pre-adapted to drought than the 2x, and the 4xNA better adapted than the 4xEU due to post-introduction selection. METHODS: Plants of the three geocytotypes (2xEU, 4xEU and 4xNA ), each represented by six populations, were subjected to three water treatments over 6 weeks in a greenhouse experiment. Plasticity and reaction norms of above- and below-ground biomasses and their ratio, survival rate, stomatal conductance and carbon isotope discrimination were analysed using linear and generalized linear mixed effect models. KEY RESULTS AND CONCLUSIONS: Above-ground and total biomasses of European tetraploids were slightly less affected by drought than those of European diploids, and 4xEU plants maintained higher levels of stomatal conductance under moderate drought than 4xNA plants, thus supporting the pre-adaptation but not the post-introduction evolution hypothesis. Plasticity indexes for most of the traits were generally higher in 2xEU and 4xNA than in 4xEU plants, but these differences were not or were only marginally significant. Interestingly, the effect of population origin and its interaction with treatment was more important than the effects of geocytotype and range. Population means for the control treatment showed several significant associations either with latitude or some aspect of climatic data, suggesting evolution of local adaptations, especially within the 2xEU and 4xEU geocytotypes.
Million of acres of U.S. wildlands are sprayed with herbicides to control invasive species, but relatively little is known about non-target effects of herbicide use. We combined greenhouse, field, and laboratory experiments involving the invasive forb spotted knapweed (Centaurea stoebe) and native bunchgrasses to assess direct and indirect effects of the forb-specific herbicide picloram on arbuscular mycorrhizal fungi (AMF), which are beneficial soil fungi that colonize most plants. Picloram had no effect on bunchgrass viability and their associated AMF in the greenhouse, but killed spotted knapweed and reduced AMF colonization of a subsequent host grown. Results were similar in the field where AMF abundance in bunchgrass-dominated plots was unaffected by herbicides one year after spraying based on 16:1ω5 phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) concentrations. In spotted-knapweed-dominated plots, however, picloram application shifted dominance from spotted knapweed, a good AMF host, to bulbous bluegrass (Poa bulbosa), a poor AMF host. This coincided with a 63% reduction in soil 16:1ω5 NLFA concentrations but no reduction of 16:1ω5 PLFA. Because 16:1ω5 NLFA quantifies AMF storage lipids and 16:1ω5 PLFA occurs in AMF membrane lipids, we speculate that the herbicide-mediated reduction in host quality reduced fungal carbon storage, but not necessarily fungal abundance after one year in the field. Overall, in greenhouse and field experiments, AMF were only affected when picloram altered host quantity and quality. This apparent lack of direct effect was supported by our in-vitro trial where picloram applied to AMF mycelia did not reduce fungal biomass and viability. We show that the herbicide picloram can have profound, indirect effects on AMF within one year. Depending on herbicide-mediated shifts in host quality, rapid interventions may be necessary post herbicide applications to prevent loss of AMF abundance. Future research should assess consequences of these potential shifts for the restoration of native plants that differ in mycorrhizal dependency.
- MeSH
- Centaurea účinky léků mikrobiologie MeSH
- herbicidy škodlivé účinky MeSH
- lipnicovité účinky léků mikrobiologie MeSH
- mykorhiza účinky léků MeSH
- pikloram škodlivé účinky MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Montana MeSH
Práce prezentuje výsledky studie mastných kyselin (FA) ve květech a nati volně rostoucí a pěstované chrpy (Centaurea cyanus (L.)). Analýza byla provedena metodou plynové chromatografie (GC) s vnitřní normalizací. V nati obou typů chrpy bylo identifikováno 13 mastných kyselin. V květech a nati pěstovaných chrp, stejně jako v květech volně rostoucích, převládaly nenasycené mastné kyseliny, zejména kyselina linolová, linolenová a olejová. Kyselina palmitová představovala nejhojněji se vyskytující nasycenou FA.
The presented study shows the composition of fatty acids (FA) in fl owers and herb of wild and cultivated cornfl ower (Centaurea cyanus (L.)). The analysis was performed by gas chromatography (GC) with a method using internal normalization. Together 13 fatty acids were identifi ed in both types of cornfl ower herb. Unsaturated fatty acids, particularly, linoleic, linolenic, and oleic acids, were prevailing in cultivated cornfl ower fl owers and herb, as well as in wild cornfl ower fl owers. Palmitic acid was the most abundant saturated FA.
