Elevated CO₂ and ozone reduce nitrogen acquisition by Pinus halepensis from its mycorrhizal symbiont

Abstract

The effects of 700 µmol mol-1 CO2 and 200 nmol mol-1 ozone on photosynthesis in Pinus halepensis seedlings and on N translocation from its mycorrhizal symbiont, Paxillus involutus, were studied under nutrient-poor conditions. After 79 days of exposure, ozone reduced and elevated CO2 increased net assimilation rate. However, the effect was dependent on daily accumulated exposure. No statistically significant differences in total plant mass accumulation were observed, although ozone-treated plants tended to be smaller. Changes in atmospheric gas concentrations induced changes in allocation of resources: under elevated ozone, shoots showed high priority over roots and had significantly elevated N concentrations. As a result of different shoot N concentration and net carbon assimilation rates, photosynthetic N use efficiency was significantly increased under elevated CO2 and decreased under ozone. The differences in photosynthesis were mirrored in the growth of the fungus in symbiosis with the pine seedlings. However, exposure to CO2 and ozone both reduced the symbiosis-mediated N uptake. The results suggest an increased carbon cost of symbiosis-mediated N uptake under elevated CO2, while under ozone, plant N acquisition is preferentially shifted towards increased root uptake.

Plant carbon limitation does not reduce nitrogen transfer from arbuscular mycorrhizal fungi to Plantago lanceolata

“…The fact that both low CO 2 in our experiment and shading in Hodge and Fitter (2010) did not reduce plant nutrient uptake in a whole-plant system highlights the influence of shoots as strong nutrient sinks (Stonor et al 2014). In addition, increasing carbohydate availibility under elevated CO 2 reduced N acquisition in Pinus halepensis via its ectomycorrhizal fungi, paxillus involutus (Kytöviita et al 2001), but increased AMF-mediated plant 15 N uptake for three arbuscular mycorrhizal fungi, Gigaspora margarita, Glomus clarum and Acaulospora morrowiae (Cheng et al 2012). These results suggest that C availibity does not always control AMF-mediated N transfer and that the overall effect may depend on mycorrhizal types.…”

Mutualism effectiveness of a fungal endophyte in an annual grass is impaired by ozone

“…). Ozone, in particular, is recognized as a tropospheric pollutant that causes oxidative stress in organisms, and it is known to affect plant‐to‐plant communication (Blande, Holopainen & Li ) and the interaction of plants with herbivores and microorganisms (Kytöviita, Le Thiec & Dizengremel ). Alternatively, ozone can be an elicitor of plant hormonal pathways such that it can induce defences against herbivores and pathogens (Kangasjärvi et al .…”

“…One aspect focuses on understanding the impact of factors causing oxidative stress such as UVb and ozone, on the plant interactions with other species in the same or different trophic level (Booker et al 2009;Kiers et al 2010;Lindroth 2010;Men endez et al 2010;Ballar e et al 2012;Landesmann et al 2013;Pineda et al 2013). Ozone, in particular, is recognized as a tropospheric pollutant that causes oxidative stress in organisms, and it is known to affect plant-to-plant communication (Blande, Holopainen & Li 2010) and the interaction of plants with herbivores and microorganisms (Kyt€ oviita, Le Thiec & Dizengremel 2001). Alternatively, ozone can be an elicitor of plant hormonal pathways such that it can induce defences against herbivores and pathogens (Kangasj€ arvi et al 1994;Sandermann et al 1998;Kangasj€ arvi, Jaspers & Kollist 2005).…”

A 3-year exposure to CO2 and O3 induced minor changes in soil N cycling in a meadow ecosystem

“…The previous studies have mainly concentrated on the effects of these gases on mycorrhiza (Kasurinen et al 1999(Kasurinen et al , 2005Kytö viita et al 2001;Pé rez-Soba et al 1995), microbial biomass C and soil organic C quantity (Islam et al 1999(Islam et al , 2000, C allocation (Kytö viita et al 1999), soil C formation (Karberg et al 2005King et al 2001;Loya et al 2003), microbial community composition (Kasurinen et al 2005;Phillips et al 2002), decomposition (Booker et al 2005Karnosky et al 2003 and references within) (Islam et al 2000;Kytö viita et al 1999Kytö viita et al , 2001Phillips et al 2002). Given that there are so few experiments with both gases, any absolute impacts are hard to address, since the effects are highly dependent on the measured variables and plant species.…”