Print PageAllelopathic interactions between plants have been repeatedly demonstrated in the lab, but are often difficult to show in more natural field settings. This may relate to the complexity of the soil matrix that allelochemicals must traverse from supplier to target plants. Diffusion through the soil is likely slow, and often further impeded by sorption of allelochemicals to organic matter in soil. Degradation by soil microbes will also serve to limit the amount of allelochemicals reaching any distance from the donor plant. All of these factors combine to decrease the likelihood that allelochemicals reach target plants in the field in bioactive doses, but we suggest a mechanism providing more direct delivery of allelochemicals from supplier to target plants. Common mycorrhizal networks (CMNs) form belowground networks that interconnect multiple plant species; yet these networks are typically ignored in studies of allelopathy. We tested the hypothesis that CMNs facilitate transport of allelochemicals from supplier to target plants, thereby affecting allelopathic interactions. We analyzed accumulation and bioactivity of the herbicide imazamox and two allelopathic thiophenes released from Tagetes tenuifolia roots, through bulk soil and CMNs.
Results/Conclusions
All compounds accumulated to greater levels in target sites with CMNs as opposed to sites without CMNs. The increased accumulation led to reduced growth of target plants in soils with CMNs. Our results show that CMNs support transfer of allelochemicals from supplier to target plants and thus lead to allelochemical accumulation at levels that could not be reached through bulk soil diffusion alone. We conclude that CMNs expand the bioactive zones of allelochemicals in natural environments, with significant implications for interspecies chemical interactions in plant communities.
