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Mycorrhizal symbiosis induces plant carbon reallocation differently in C3 and C4 Panicum grasses

Řezáčová, Veronika, Slavíková, Renata, Zemková, Lenka, Konvalinková, Tereza, Procházková, Věra, Šťovíček, Václav, Hršelová, Hana, Beskid, Olena, Hujslová, Martina, Gryndlerová, Hana, Gryndler, Milan, Püschel, David, Jansa, Jan
Plant and soil 2018 v.425 no.1-2 pp. 441-456
C3 photosynthesis, C3 plants, C4 photosynthesis, C4 plants, Panicum, carbon, carbon dioxide, fertilizer application, fungi, grasses, harvesting, isotope labeling, phosphorus, phosphorus fertilizers, vesicular arbuscular mycorrhizae
AIMS: Although arbuscular mycorrhizal symbiosis is common in many plants with either C₃ or C₄ photosynthesis, it remains poorly understood whether photosynthesis type has any significant impact on carbon (C) fluxes in mycorrhizal plants. Thus, we compared mycorrhizal and non-mycorrhizal (NM) plants belonging to Panicum bisulcatum (C₃) to its congeneric P. maximum (C₄). METHODS: Plants were or were not exposed to arbuscular mycorrhiza (AM) fungal inoculation and/or phosphorus (P) fertilization. Plants’ C budgets were assembled based on ¹³CO₂ pulse-chase labelling and sequential harvesting. RESULTS: Mycorrhizal plants allocated on average 3.9% more recently fixed C belowground than did their NM counterparts. At low P, mycorrhizal C₃-Panicum plants allocated less C to aboveground respiration as compared to their respective NM controls. In contrast, mycorrhizal C₄-Panicum increased the rates of photosynthesis and allocated more C to aboveground respiration than the respective NM controls. At high P, the differences were less prominent. CONCLUSIONS: We demonstrated consistent differences in aboveground C allocation due to AM symbiosis formation in congeneric C₃ and C₄ grasses. Both grasses benefited from AM symbiosis in terms of improved P uptake (at least at low P). These results advocate a holistic (whole-plant) perspective in studying C fluxes in mycorrhizal plants.