http://hdl.handle.net/10214/1995 Wed, 16 May 2012 11:16:44 GMT 2012-05-16T11:16:44Z http://hdl.handle.net/10214/3370 A meta-analytical review of the effects of elevated CO2 on plant–arthropod interactions highlights the importance of interacting environmental and biological variables Robinson, Emily A.; Ryan, Geraldine D.; Newman, Jonathan A. We conducted the most extensive meta-analysis of plant and animal responses to elevated CO2 to date. We analysed > 5000 data points extracted from 270 papers published between 1979 and 2009. We examined the changes in 19 animal response variables to the main effect of elevated CO2. We found strong evidence for significant variation among arthropod orders and feeding guilds, including interactions in the direction of response. We also examined the main effects of elevated CO2 on: six plant growth and allocation responses, seven primary metabolite responses, eight secondary metabolite responses, and four physical defence responses. We examined these response variable changes under two-way and three-way interactions between CO2 and: soil nitrogen, ambient temperature, drought, light availability, photosynthetic pathway, reproductive system, plant growth rate, plant growth form, tissue type, and nitrogen fixation. In general we found smaller effect sizes for many response variables than have been previously reported. We also found that many of the oft-reported main effects of CO2 obscure the presence of significant two- and three-way interactions, which may help better explain the relationships between the response variables and elevated CO2. Fri, 02 Mar 2012 05:00:00 GMT http://hdl.handle.net/10214/3370 2012-03-02T05:00:00Z http://hdl.handle.net/10214/3328 Climate change and tropic interactions Ryan, GD; Rasmussen, S; Newman, JA Increasing atmospheric CO2 is hypothesized to alter plant physiology and metabolism, which may have important implications for species interactions. In this chapter, we review published studies on the effects of elevated atmospheric CO2 on plant-derived allelochemicals and the possible effects of CO2-mediated changes on higher trophic levels such as herbivores, parasitoids, and predators. We provide a critical assessment of conventional ecological theories used to predict phytochemical responses to CO2 and we make some suggestions as to how this field may be expanded and improved. Fri, 01 Jan 2010 05:00:00 GMT http://hdl.handle.net/10214/3328 2010-01-01T05:00:00Z http://hdl.handle.net/10214/3322 Metabolic profiles of Lolium perenne are differentially affected by nitrogen supply, carbohydrate content, and fungal endophyte infection Rasmussen, S; Parsons, AJ; Xue, H; Newman, JA; Fraser, K Lolium perenne cultivars differing in their capacity to accumulate water soluble carbohydrates (WSCs) were infected with three strains of fungal Neotyphodium lolii endophytes or left uninfected. The endophyte strains differed in their alkaloid profiles. Plants were grown at two different levels of nitrogen (N) supply in a controlled environment. Metabolic profiles of blades were analyzed using a variety of analytical methods. A total of 66 response variables were subjected to a principle components analysis and factor rotation. The first three rotated factors (46% of the total variance) were subsequently analyzed by analysis of variance. At high N supply nitrogenous compounds, organic acids and lipids were increased; WSCs, chlorogenic acid (CGA), and fibers were decreased. The high-sugar cultivar ‘AberDove’ had reduced levels of nitrate, most minor amino acids, sulfur, and fibers compared to the control cultivar ‘Fennema’, whereas WSCs, CGA, and methionine were increased. In plants infected with endophytes, nitrate, several amino acids, and, magnesium were decreased; WSCs, lipids, some organic acids, and CGA were increased. Regrowth of blades was stimulated at high N, and there was a significant endophyte x cultivar interaction on regrowth. Mannitol, a fungal specific sugar alcohol, was significantly correlated with fungal biomass. Our findings suggest that effects of endophytes on metabolic profiles of L. perenne can be considerable, depending on host plant characteristics and nutrient supply, and we propose that a shift in carbon/N ratios and in secondary metabolite production as seen in our study is likely to have impacts on herbivore responses. Tue, 01 Jan 2008 05:00:00 GMT http://hdl.handle.net/10214/3322 2008-01-01T05:00:00Z http://hdl.handle.net/10214/3320 Even after death the endophytic fungus of Schedonorus phoenix reduces the arbuscular mycorrhizas of other plants Antunes, P; Miller, J; Carvalho, L; Klironomos, J; Newman, JA * 1 Plants can host microbial communities whose integrated functions are often responsible for their success. Understanding mechanisms regulating such functions is thus a major goal in ecology. * 2 Fungal endophytes of grasses, particularly of the genus Neotyphodium, have been reported to reduce colonization of their host plant by arbuscular mycorrhizal (AM) fungi. However, it is unclear which mechanism(s) may explain the effects produced by the endophyte and whether these effects are present in nature. * 3 We used Schedonorus phoenix (syn. Lolium arundinaceum) plants that were endophyte-free or infected with one of two strains of Neotyphodium coenophialum known to produce different putative allelochemicals to test the hypotheses that (i) allelopathic effects of the endophyte reduce AM fungal spore germination; and (ii) the allelochemical compound(s) are leached into the soil even after the death of S. phoenix, where they reduce AM fungal colonization of other plants. * 4 In a first experiment, aqueous extracts from the shoots of S. phoenix were applied onto spores of the AM fungus Glomus intraradices to test germination effects. Both endophyte strains reduced spore germination by approximately 10% relative to endophyte-free controls. * 5 In a second experiment, we placed dried shoot material (‘thatch’) on the soil surface of pots containing Bromus inermis, which were either inoculated with G. intraradices or not. We watered the plants through the thatch, relying upon leaching to translocate potential allelochemicals to the soil. AM fungal colonization of B. inermis was significantly reduced when thatch was infected with the common strain, but not with AR542, compared to the endophyte-free thatch. Furthermore, the arbuscule : vesicle ratio was 11-fold smaller when thatch was infected with the common strain compared to endophyte-free thatch, suggesting that G. intraradices was stressed by the presence of common strain-leachate. * 6 We observed situations whereby two ecologically widespread plant-microbe symbioses interact. Potential mechanisms may include allelopathic effects, although other factors are also possible, and leaching is a mode of entry of putative endophyte-induced AM fungal inhibitors in soil. Understanding these processes is important as they affect AM fungal communities which contribute to plant success and, consequentially, grassland ecosystem dynamics. Wed, 01 Oct 2008 04:00:00 GMT http://hdl.handle.net/10214/3320 2008-10-01T04:00:00Z