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

Atmospheric drought and low light impede mycorrhizal effects on leaf photosynthesis—a glasshouse study on tomato under naturally fluctuating environmental conditions

“…The present study indicates that it may be worth also paying attention to water relations in the future when nutrient exchange budgets are investigated in mycorrhizal systems, because soil and atmospheric drought will affect symbiotic C-N-P trade-offs. We agree with other scientists working on carbon flows in AMF symbioses (Řezáčová et al 2018) that integrative, plant-based and process-oriented approaches need to be used that account for environmental variability, to better understand mycorrhizal growth responses.…”

“…Under low light, photosynthetic rates are dominantly sensitive to light (Ögren and Evans 1993), which is the reason why similar photosynthetic rates were found in canopies of mycorrhizal and NM plants under low irradiance. This frequent scenario may constitute a carbon costly scenario for mycorrhizal plants because an equally efficient photosynthetic canopy may not compensate additional carbon sinks such as AMF (Řezáčová et al 2018). This is a feasible assumption for plants of similar size if AMF do not reduce other plant carbon sinks, but also for larger mycorrhizal plants when carbon demands of AMF scale with fungal biomass, which in turn scales with plant size.…”

“…Both direct and indirect contributions to nutrient and water extractability from soils require that hyphae proliferate beyond the ambit of roots which are developed with sustenance by plant C fixed in photosynthesis (Smith and Read 2008). Hence, mycorrhizal plants possess an additional and significant C sink (as reviewed in: Řezáčová et al 2017, 2018), which can be compensated by photosynthesis, provided that AMF do not only substitute other plant C sinks in the symbiotic interaction (Kaschuk et al 2009; Řezáčová et al 2018). Indeed, rates of photosynthesis of mycorrhizal plants are commonly altered in comparative studies with non-mycorrhizal (NM) counterparts (Augé 2001; Augé et al 2014, 2016; Boldt et al 2011).…”

Little Cross-Feeding of the Mycorrhizal Networks Shared Between C3-Panicum bisulcatum and C4-Panicum maximum Under Different Temperature Regimes

“…Mycorrhizal inoculation strongly increased P content of the plants (nearly two-fold at low t and even more so under high t, Figure 2B ), which confirmed that the symbiosis was fully functional under both temperature regimes in terms of P uptake improvement of the plants. Bit surprisingly though (but see also Řezáčová et al, 2017b , 2018 ), establishment of mycorrhizal symbiosis did not increase biomass production of our experimental plants (actually it did decrease it by about 10–15%, Figure 2A ), most likely because of C limitation, due to temperature stress (of which the latter was, however, not measured directly, e.g., by assessing molecular stress markers or efficiency of photosynthetic C fixation) or other constraints (see also Johnson et al, 2015 for further discussion). N limitation of growth of the M+ plants due to competition for N between the plants and the AMF and/or their associated bacteria (such as described, e.g., by Saia et al, 2014 or Püschel et al, 2016 ) is not a likely explanation of the observed growth reduction because the N content of the plants was actually not affected at all by mycorrhiza formation ( Figure 2C ).…”

“…Particular attention should also be dedicated in the future to better description of the rates of organic N decomposition at different temperatures and how these (directly or interactively with other factors) affect the mycorrhizal N uptake pathway and nutrient-for-C trades at the symbiotic interface (sensu Fellbaum et al, 2014 ). Last but not least, more C 3 –C 4 congeneric pairs should be employed as model hosts in similarly designed experiments as ours to allow generalizations of the results to a broader range of plant taxa (see Řezáčová et al, 2018 for further discussion).…”