Ecological factors that influence host acquisition by the parasitic plant Cuscuta campestris
Open Access
- Author:
- Johnson, Beth Irwin
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 20, 2013
- Committee Members:
- Mark C Mescher, Dissertation Advisor/Co-Advisor
Consuelo M De Moraes, Dissertation Advisor/Co-Advisor
John Frazier Tooker, Committee Member
David A Mortensen, Committee Member - Keywords:
- Cuscuta spp.
dodder
environmental factors
light spectral quality
parasitic plants
temperature - Abstract:
- Parasitic plants steal resources from host plants through vascular connections called haustoria, which directly reduces host biomass and can impact the structure and dynamics of ecosystems. When agricultural crops are parasitized, the economic losses are devastating. Yet despite the ecological and economic significance of parasitic plants, we know relatively little about how ecological factors influence their growth prior to host acquisition. In this work we explore the effects of two important environmental cues—temperature and light spectral quality—on host acquisition by obligate parasites in the genus Cuscuta (dodders). The majority of dodder research has focused on their ecology as a mature parasite, but much less is known about their ecology as a seedling in search of a host. We conducted a series of experiments to better understand how temperature and light spectral quality influence the host acquisition process of dodder seedlings. First we explored how changes in temperature impact dodder parasitism. Temperature significantly affected seedling circumnutation: seedlings rotated fastest in warm temperatures; however, it did not affect dodder foraging success, as the majority of seedlings located their hosts in conditions from 28°C to 45°C. The ability of dodder seedlings to successfully parasitize tomato hosts was also affected by temperature: parasitism was significantly reduced above 37°C. Next we examined how temperature and light spectral quality (the ratio of red to far-red light, R:FR) impact the constitutive release of tomato volatiles. Temperature did not influence the overall total emission of volatiles but it did affect the release of several individual compounds. The ratio of R:FR light had a slight effect on total volatile emissions and a significant effect on the release of several individual compounds, with reduced emissions occurring in high R:FR environments. Last we investigated the effect of R:FR on host acquisition using two light manipulation approaches. We found dodders had significantly reduced foraging and parasitism success in high R:FR environments. The effect of brief exposure to high R:FR on the short- and long-term growth of host plants was negligible. We conclude dodder host acquisition is significantly impacted by environmental factors such as temperature and light spectral quality. Moving forward, we recommend expanding this work to develop novel forms of control against this economically destructive pest.