Background/Question/Methods Parasitic plants in the genus Cuscuta (dodders) are completely dependent on host plants for nutrition: dodder vines lack roots and leaves and contain little or no chlorophyll. This dependence makes it critical for dodder seedlings to quickly locate and attach to suitable hosts before exhausting their limited energy reserves. Previous work from my advisor's lab showed that seedlings of C. pentagona accomplish this in part by exploiting odor cues from host plants. Moreover, seedlings preferentially responded to the odors of plant species that are high quality hosts (tomato) as compared to poor quality hosts (wheat). Less is known about the foraging tactics employed by mature dodder vines when making secondary attachments to new hosts. Because established vines presumably face less intense pressure that seedlings to quickly locate and assess potential hosts, it is plausible that they rely less, or not at all, on odor cues—especially if maintaining the ability to perceive and respond to such cues is energetically expensive. On the other hand, previous research suggests that established dodder vines can be selective in making secondary attachments (e.g., making more attachments to high-quality host species in heterogeneous plant communities) and the mechanisms responsible for this selectivity are unknown.

Results/Conclusions

This project examines the growth responses of mature C. pentagona vines to odor cues from potential host plants, using vine-growth assays conducted in two-arm olfactometers (designed to present host odors while minimizing light cues). My initial results indicate selective growth away from potential host plants suffering nutritive or water stress. Ongoing work will confirm this result by testing responses to extracted plant volatiles presented in the absence of any other potential cues. Additional assays will explore whether mature vines, like seedlings, also use odor cues to distinguish among plant species differing in host quality. In addition to providing insight into the ecology of a significant agricultural pest, this research will further our emerging understanding of the role volatile cues in mediating interactions among plant species.