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2020 Projects

Extraction and Analysis of Volatiles from Flowers of the Orchid Genus Pleurothallis

Isobel Hensley ’22
Major: Chemistry

Isobel Hensley ’22

Major: Chemistry

Faculty Collaborators: Murphy Brasuel, Chemistry & Biochemistry; Mark Wilson, Organismal Biology & Ecology

Previous research conducted on the micromorphology of Pleurothallis in the family Orchidaceae suggests that some Pleurothallis species may be pollinated by pseudocopulation. These species’ labellar structure is similar to that of another orchid genus pollinated by pseudocopulation, Ophrys. We hypothesize that flowers of these species produce floral volatiles similar to insect pheromones to attract the pollinator. The aim of our study was to utilize pre-determined optimized sample preparation and GC-MS analysis parameters for analyzing floral volatiles (March 2020), to analyze unknown volatile samples from Pleurothallis flowers. Samples stored at -80°C were prepared with anhydrous salt for water removal and left to sit in a 2 mL screw-cap vial for 48 hours at room temperature to allow the salt to settle before being run in the GC-MS. The GC-MS was programmed from 60°C (2-minute hold) to 290°C at a rate of 10°C/min with a 3.5-minute solvent delay. The injection volume was set at 5 μL in splitless mode, and washes of 3 μL acetone (Solvent A) and 3 μL methanol (Solvent B) were also programmed. Chromatograph data was inputted to MiniTab and used to generate dendrograms of different species based on their volatile composition. Most notably, hypothesized deceptive species grouped separately from hypothesized rewarding species, and samples from different plants of the same species grouped together. An analysis of chromatograph peaks was also done to identify possible allomones. Promising volatiles that are known insect attractants were discovered and confirmed. These volatiles were: (Z)-9-Tricosene, 4-hydroxy-4-methyl-2-pentanone, Hexadecanoic acid ethyl ester, and (Z)-7-Pentacosene.

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