PARENT SESSION
Wednesday, August 9, 1:30-5:00 pm
COS 68 - Ecophysiology III: thermoregulation, nutrition, and photoreception
L-3, Lobby Level, Cook Convention Center
Presiders: U Rascher

The effects of ultra-violet radiation (UV-B) on the foliar concentration and emission of mono- and sesquiterpenes in lemon verbena (Aloysia citriodora).

Chapman, Rebekah^*,1, Affolter, James¹, Kays, Stanley ¹, ¹ University of Georgia, Athens, GA

ABSTRACT- We are currently investigating the effects of UV-B on the accumulation and emission of mono- and sesquiterpenes of lemon verbena (Aloysia citriodora) which is native to the semi-arid, mountainous regions of Argentina, Chile and Peru. Mono- and sesquiterpenes are the primary components of the volatile essences of flowers, leaves and resins. Ecologically they act as feeding deterrents, antimicrobial agents, pollination attractants, and allelopathic chemicals. The response of known photoprotective compounds such as flavanoids and anthocyanins to UV-B have been intensively studied in the past decade; however, very little is known about how UV-B radiation affects the synthesis of other carbon-based secondary metabolites. The objective of our study is to elucidate the effect of UV-B on terpene synthesis, foliar concentration, and emission in A. citriodora. Preliminary results demonstrate that the foliar concentration of monoterpenes (e.g., -pinene and citral) are significantly affected by UV-B radiation. The foliar concentration of citral, the dominant mono-terpene found in the leaves of A. citriodora, was significantly higher in plants for which UV-B radiation was blocked (p<.005). The emission of lower molecular weight mono-terpenes was higher under UV-B radiation, while the opposite trend was observed for the higher molecular weight sesquiterpenes. Furthermore, these changes in carbon allocation happened in the absence of any permanent damage to photosystem II. Given that terpenes and other secondary metabolites play critical roles in ecological interactions at multiple trophic levels, the importance of light-induced (e.g., UV-B) alteration in their synthesis and accumulation should be factored into developing theoretical models of plant defense and carbon allocation.

Key words: plant secondary metabolites photoprotection, semi-arid plant communities, plant chemistry