Does field dodder (Cuscuta campestris) allow nutrient flow among parasitized host plants?

Background/Question/Methods

An increasing body of evidence now indicates that parasitic species can have ecosystem-level impacts on species diversity patterns, trophic energy flow, and food web stability. Plant parasitic dodders (Cuscuta spp.) are globally distributed holoparasites that form a direct physical connection to host vascular tissue. As a hypergeneralist plant parasite, field dodder (Cuscuta campestris) can connect the phloem and xylem of widely divergent species simultaneously. Using C. campestris as a live bridge between plants, this study investigated the movement of nutrients between dodder-parasitized tomato plants (Lycopersicon lycopersicum). In particular, the study sought to address two questions: (1) If two hosts are connected by dodder, does nutrient supplementation for one “donor” host plant lead to an increased growth rate in an unmanipulated “receiver” host plant? and (2) Does shading of the donor plant lead to a reduced growth rate in a receiver host plant? 

Results/Conclusions

While nutrient addition did lead to significantly increased growth in the donor plants, the unmanipulated receiver plants to which they were connected by dodder showed no significant differences in any of the response variables measured, regardless of treatment. In addition, there were no significant differences in growth response variables between donor and receiver plants in the shading treatment. These results suggest that little (if any) nutrients pass through dodder from the donor to the receiver host plant.