Butenolide from plant-derived smoke functions as a strigolactone analogue: Evidence from parasitic weed seed germination

AbstractThe main germination active compound in smoke, 3-methyl-2H-furo[2,3-c]pyran-2-one (butenolide), has structural similarities with strigolactones that function as germination stimulants for root parasitic plants such as Orobanche spp. and Striga spp. (Scrophulariaceae). Consequently, we tested whether butenolide also functions as a germination stimulant for parasitic weeds. Butenolide stimulated germination of both Orobanche minor and Striga hermonthica to similar levels as the synthetic strigol analogue GR24 and was effective at similar concentrations (10−5 to 10−11 M). Both butenolide and GR24 were more effective than the synthetic strigol analogue Nijmegan-1. Across eight further Orobanche spp., and for species from the root parasitic genera Cistanche, Conopholis and Lathraea, butenolide also had a similar level of activity to GR24. These results suggest that the germination stimulatory activity of butenolide may result from analogy with strigolactones

Canary in the coal mine: Lessons from the Jarrah Forest suggest long-term negative effects of phosphorus fertilizer on biodiverse restoration after surface mining

Despite nutrient enrichment having widely reported negative impacts on biodiversity, fertilizer is routinely applied in post mining restoration to enhance plant growth and establishment. Focusing on surface mine restoration (predominately bauxite and mineral sands), we outline the long-term negative impacts of fertilizer, particularly phosphorus fertilizer, on plant community composition, species richness, fire fuel loads, and belowground impacts on nutrient-cycling. We draw from extensive research in south-western Australia and further afield, noting the geographical coincidence of surface mining, phosphorus impoverished soil and high plant biodiversity. We highlight the trade-offs between rapid plant-growth under fertilisation and the longer-term effects on plant communities and diversity. We note that the initial growth benefits of fertilisation may not persist in water-limited environments: growth of unfertilised forests can eventually match that of fertilised forest, throwing doubt on the premise that fertilisation is necessary at all

Phosphorus supply affects seedling growth of mycorrhizal but not cluster-root forming jarrah-forest species

Aims Fertiliser is often used to kick-start ecological restoration despite growing evidence of the potentially negative impacts on plant diversity. Jarrah (Eucalyptus marginata) forest species growing on nutrient (especially phosphorus) impoverished soils in southwestern Australia have a suite of adaptations for phosphorus (P) acquisition, including the formation of cluster roots, and associations with mycorrhizal fungi. Here we investigated how escalating P supply, along with a stoichiometric adjustment of nitrogen (N) supply, impacted the growth and nutrition of a wide range of jarrah forest seedlings. Methods In a pot experiment, we measured seedling biomass and nutritional responses of 12 jarrah forest species to a gradient of P supply in relation to N supply, and for the mycorrhizal species, inoculation with arbuscular mycorrhizal fungi. Results Three cluster-root forming species did not respond to increasing P, probably because they were reliant on seed P. Generally, mycorrhizal species showed a positive biomass response to increasing P when N was available. Mycorrhizas benefited seedling growth at low P (9 mg P added per kg of jarrah forest soil) when N was also available, and were parasitic to seedling growth at high P (243 mg P/ kg soil) without additional N. Conclusions These results highlight importance of P and N supply in determining the nature of the symbiosis between plants and mycorrhizal fungi. Since P supply has the potential to reduce plant growth, for a range of species, our results suggest careful consideration of fertiliser amounts for ecological restoration of ecosystems adapted to nutrient poor soils