Aboveground herbivory does not affect mycorrhiza-dependent nitrogen acquisition from soil but inhibits mycorrhizal network-mediated nitrogen interplant transfer in maize

Arbuscular mycorrhizal fungi (AMF) are considered biofertilizers for sustainable agriculture due to their ability to facilitate plant uptake of important mineral elements, such as nitrogen (N). However, plant mycorrhiza-dependent N uptake and interplant transfer may be highly context-dependent, and whether it is affected by aboveground herbivory remains largely unknown. Here, we used N-15 labeling and tracking to examine the effect of aboveground insect herbivory by Spodoptera frugiperda on mycorrhiza-dependent N uptake in maize (Zea mays L.). To minimize consumption differences and N-15 loss due to insect chewing, insect herbivory was simulated by mechanical wounding and oral secretion of S. frugiperda larvae. Inoculation with Rhizophagus irregularis (Rir) significantly improved maize growth, and N/P uptake. The N-15 labeling experiment showed that maize plants absorbed N from soils via the extraradical mycelium of mycorrhizal fungi and from neighboring plants transferred by common mycorrhizal networks (CMNs). Simulated aboveground leaf herbivory did not affect mycorrhiza-mediated N acquisition from soil. However, CMN-mediated N transfer from neighboring plants was blocked by leaf simulated herbivory. Our findings suggest that aboveground herbivory inhibits CMN-mediated N transfer between plants but does not affect N acquisition from soil solutions via extraradical mycorrhizal mycelium.

Automated summary

This study examined the effect of aboveground herbivory on mycorrhiza-dependent nitrogen uptake in maize. The results showed that aboveground leaf herbivory did not affect nitrogen acquisition from soil via extraradical mycorrhizal mycelium, but it blocked nitrogen transfer from neighboring plants through common mycorrhizal networks (CMNs).