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
MAIN CONCLUSION: The key step in the mode of action of strigolactones is the enzymatic detachment of the D-ring. The thus formed hydroxy butenolide induces conformational changes of the receptor pocket which trigger a cascade of reactions in the signal transduction. Strigolactones (SLs) constitute a new class of plant hormones which are of increasing importance in plant science. For the last 60 years, they have been known as germination stimulants for parasitic plants. Recently, several new bio-properties of SLs have been discovered such as the branching factor for arbuscular mycorrhizal fungi, regulation of plant architecture (inhibition of bud outgrowth and of shoot branching) and the response to abiotic factors, etc. To broaden horizons and encourage new ideas for identifying and synthesising new and structurally simple SLs, this review is focused on molecular aspects of this new class of plant hormones. Special attention has been given to structural features, the mode of action of these phytohormones in various biological actions, the design of SL analogs and their applications.
Arbuscular mycorrhizal fungi (AMF) are expected to be one of the key drivers determining the diversity of natural plant communities, especially in nutrient-poor and dry habitats. Several previous studies have explored the importance of AMF for the composition of plant communities in various types of habitats. Surprisingly, studies of the role of AMF in nutrient-poor dry grassland communities dominated by less mycotrophic plant species are still relatively rare. We present the results of a 3-year study in which a plant community in a species-rich dry grassland was subjected to the fungicide carbendazim to suppress AMF colonization. We tested the effect of the fungicide on the following parameters: the plant species composition; the number of plant species; the cover of the rare, highly mycorrhiza-dependent species Aster amellus; the cover of the dominant, less mycorrhiza-dependent species Brachypodium pinnatum; and the cover of graminoids and perennial forbs. In addition, we examined the mycorrhizal inoculation potential of the soil. We found that the suppression of AMF with fungicide resulted in substantial changes in plant species composition and significant decrease in species richness, the cover of A. amellus and the cover of perennial forbs. In contrast the species increasing their cover after fungicide application were graminoids--the C3 grasses B. pinnatum and Bromus erectus and the sedge Carex flacca. These species appear to be less mycorrhiza dependent. Moreover, due to their clonal growth and efficient nutrient usage, they are, most likely, better competitors than perennial forbs under fungicide application. Our results thus suggest that AMF are an essential part of the soil communities supporting a high diversity of plant species in species-rich dry grasslands in nutrient-poor habitats. The AMF are especially important for the maintenance of the populations of perennial forbs, many of which are rare and endangered in the area.
- MeSH
- biodiverzita MeSH
- ekosystém MeSH
- fungicidy průmyslové farmakologie MeSH
- fyziologie rostlin * MeSH
- houby účinky léků fyziologie MeSH
- lipnicovité MeSH
- mykorhiza účinky léků fyziologie MeSH
- období sucha * MeSH
- půda * chemie MeSH
- rostliny účinky léků mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Significant effects of humic acid-like material (HALM) extracted from sewage sludge on dry matter production of cultures of ectomycorrhizal basidiomycetes were found in vitro. Mycelial growth of the majority of isolates tended to increase in the presence of the HALM and this effect was significant for 6 isolates. Strongest stimulation was observed in the case of Amanita muscaria, Leccinum aurantiacum and Lactarius deterrimus. The results suggest that the HALM can be used as an additive to media for cultivation of ectomycorrhizal basidiomycetes.
- MeSH
- Amanita růst a vývoj účinky léků MeSH
- financování organizované využití MeSH
- houby růst a vývoj účinky léků MeSH
- huminové látky parazitologie MeSH
- interpretace statistických dat MeSH
- kokultivační techniky metody statistika a číselné údaje využití MeSH
- mycelium růst a vývoj účinky léků MeSH
- mykorhiza růst a vývoj účinky léků MeSH
