Monitoring CO2 emissions to gain a dynamic view of carbon allocation to arbuscular mycorrhizal fungi

• Published in: Mycorrhiza 2017, Vol.27 (1), p.35-51
• Main Authors: Slavíková, Renata, Püschel, David, Janoušková, Martina, Hujslová, Martina, Konvalinková, Tereza, Gryndlerová, Hana, Gryndler, Milan, Weiser, Martin, Jansa, Jan
• Format: Article
• Language: English
• Subjects: Agriculture; Alfalfa; Biomedical and Life Sciences; Carbon dioxide emissions; Ecology; Environmental conditions; Forestry; Life Sciences; Microbiology; Original Article; Plant Sciences
• ISSN: 0940-6360; 1432-1890
• DOI: 10.1007/s00572-016-0731-2

Quantification of carbon (C) fluxes in mycorrhizal plants is one of the important yet little explored tasks of mycorrhizal physiology and ecology. 13 CO 2 pulse-chase labelling experiments are increasingly being used to track the fate of C in these plant–microbial symbioses. Nevertheless, continuous monitoring of both the below- and aboveground CO 2 emissions remains a challenge, although it is necessary to establish the full C budget of mycorrhizal plants. Here, a novel CO 2 collection system is presented which allows assessment of gaseous CO 2 emissions (including isotopic composition of their C) from both belowground and shoot compartments. This system then is used to quantify the allocation of recently fixed C in mycorrhizal versus nonmycorrhizal Medicago truncatula plants with comparable biomass and mineral nutrition. Using this system, we confirmed substantially greater belowground C drain in mycorrhizal versus nonmycorrhizal plants, with the belowground CO 2 emissions showing large variation because of fluctuating environmental conditions in the glasshouse. Based on the assembled 13 C budget, the C allocation to the mycorrhizal fungus was between 2.3% (increased 13 C allocation to mycorrhizal substrate) and 2.9% (reduction of 13 C allocation to mycorrhizal shoots) of the plant gross photosynthetic production. Although the C allocation to shoot respiration (measured during one night only) did not differ between the mycorrhizal and nonmycorrhizal plants under our experimental conditions, it presented a substantial part (∼10%) of the plant C budget, comparable to the amount of CO 2 released belowground. These results advocate quantification of both above- and belowground CO 2 emissions in future studies.