Abstract
Elevated carbon dioxide (eCO2), a much-discussed topic in global warming, influences development and functions of mycorrhizal fungi and plants. However, due to the inconsistent results reported in various publications, the response patterns of symbionts associated with the arbuscular mycorrhizal (AM) or with ectomycorrhizal (ECM) fungi to eCO2 remains still unclear. Therefore, we performed a meta-analysis to identify how eCO2 affected mycorrhizal fungi and if there is a significant different response between AM and ECM symbionts. Our results demonstrated that eCO2 increased mycorrhizal plants biomass (+26.20%), nutrient contents [+2.45% in nitrogen (N), and +10.66% in phosphorus (P)] and mycorrhizal fungal growth (+22.87% in extraradical hyphal length and +21.77% in mycorrhizal fungal biomass), whereas plant nutrient concentrations decreased (−11.86% in N and −12.01% in P) because the increase in plant biomass was greater than that in nutrient content. The AM plants exhibited larger increases in their biomass (+33.90%) and in their N (+21.99%) and P contents (+19.48%) than did the ECM plants (+20.57% in biomass, −4.28% in N content and −13.35% in P content). However, ECM fungi demonstrated increased responses of mycorrhizal fungal biomass (+29.98%) under eCO2 compared with AM fungi (+6.61%). These data indicate different patterns in the growth of AM and ECM symbionts under eCO2: AM symbionts contributed more to plant growth, while ECM symbionts were more favorable to mycorrhizal fungal growth. In addition, the responses of plant biomass to eCO2 showed no significant difference between short-term and long-term groups, whereas a significant difference in the responses of mycorrhizal fungal growth was found between the two groups. The addition of N increased plant growth but decreased mycorrhizal fungal abundance, and P addition increased total plant biomass and extraradical hyphal length, but shoot biomass largely increased in low P conditions. Mixtures of mycorrhizal fungi affected the total plant and root biomasses more than a single mycorrhizal fungus. Clarifying the different patterns in AM and ECM symbionts under eCO2 would contribute to a better understanding of the interactions between mycorrhizal fungi and plant symbionts under the conditions of global climate change as well as of the coevolution of flora with Earth's environment.
Highlights
The rising level of carbon dioxide (CO2) in the atmosphere is a major concern worldwide and could cause many changes in plant physiology and metabolism (Leakey et al, 2009; McGrath and Lobell, 2013)
The significantly different responses of mycorrhizal fungi to elevated CO2 (eCO2) in the short-term and long-term groups in our study indicate that the progressive nitrogen limitation (PNL) has little effect on mycorrhizal fungi
Plants in nutrient-rich or well-fertilized soils tend to be less frequently colonized by arbuscular mycorrhizal (AM) fungi (Staddon et al, 2004), and our study showed that changes in mycorrhizal fungal colonization depend heavily on N sufficiency rather than P sufficiency
Summary
The rising level of carbon dioxide (CO2) in the atmosphere is a major concern worldwide and could cause many changes in plant physiology and metabolism (Leakey et al, 2009; McGrath and Lobell, 2013). Individual studies have been conducted to assess the effects of elevated CO2 (eCO2) levels on plant growth, including nutrient absorption (Feng et al, 2015), the net assimilation rate, stomatal conductance (Augé et al, 2015), transpiration, water-use efficiency and sugar accumulation in leaves (Drake et al, 1997). Extensive interactions exist between mycorrhizal fungi and plant symbionts: mycorrhizal fungi transfer N and P to plants, while plants supply organic carbon (C) to mycorrhizal fungi (Smith and Smith, 2012). This phenomenon improves plant growth, nutrient absorption, and water-use efficiency (Smith and Smith, 2012). Discussing the responses of plants to eCO2, their interactions with mycorrhizal fungi must be considered (Grover et al, 2015; Simonin et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
