Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Way, Danielle A.

Affiliation

Research School of Biology, Australian National University

2nd Supervisor

McNeil, Jeremy, N.

Abstract

Climate change is a significant threat to plant survival and reproduction. Warmer temperatures could affect floral traits that are important for attracting pollinators and for regulating flower temperature. I grew Cucumis sativus at ambient or ambient +4 °C temperatures to determine if warming affects plant development (date of anthesis, floral display size, biomass), UV-floral traits, and the composition and concentration of floral flavonoids. Warming accelerated the date of anthesis and increased floral display size but did not affect plant biomass. Although warming decreased floral area, it increased the UV-absorbing proportion of flower area, so UV-absorbing area was not significantly affected by warming. Warming did not affect the composition of floral flavonoids but did increase their concentration. In conclusion, warming accelerated plant phenology and increased floral flavonoid concentrations but further research is required as the observed changes in UV traits could influence both pollinator attraction and temperature regulation.

Summary for Lay Audience

Humans have increased the amount of carbon dioxide in the air and contributed to global warming. These warmer temperatures have affected habitat conditions and the survival and reproduction of plants. Studying how warming affects plants is important because plants provide food to humans. Warming can affect flowers, which are important for plant reproduction, by influencing flower traits that attract pollinators and affect flower temperature. The ultraviolet (UV) bullseye is a pattern on flowers that is visible to and attracts pollinators looking for food. How warming affects the chemicals responsible for UV bullseye patterns has not been studied and it could be a trait that affects flower temperature. I determined how flower traits that are important for pollinator attraction and controlling flower temperature changed when cucumber plants were grown at ambient or +4 °C warmed temperatures. To study these effects I measured plant development, UV flower traits, and the identity and concentration of chemicals that absorb UV in flower petals. I found that flowers opened ~14 days earlier and the total number of flowers was 44% greater when plants were grown at warmer temperatures, but warming did not affect plant weight. The UV bullseye size of the flower was not affected by warming, because warming decreased the total area of the flower but increased the proportion of the flower that absorbed UV light. Finally, four UV-absorbing chemicals were found in cucumber flowers and their concentrations increased with warming. My results suggest that flower characteristics that attract pollinators have different responses to warming. Plants may keep a constant UV-absorbing area to maintain pollinator attraction. Further research is needed to determine how the changes I observed could influence pollinator visitation and how plants manage flower temperature.

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