Ethan Fenner

Date of Award

2016

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Clore, Amy

Area of Concentration

Biology

Abstract

The mint family Lamiaceae is typified by plants with strong smells and tastes due to small organic molecules called terpenoids which collect on epidermal outgrowths called trichomes. In addition to being used in culinary, cosmetic, and medicinal industries, relative concentrations of mint terpenoids have been used by taxonomists as the basis for specific and generic delineations. However, chemotaxonomic comparison between mint species is often complicated by environmental differences including season, nutrient quality, and herbivore pressures. Using the case genus Dicerandra, plant tissue culture was explored as a possible method of more standardized chemotaxonomic comparison. Individual plants representing several parent populations of Dicerandra subg. Kralia species were collected across their seasonal life cycle in an effort to more accurately gauge the extent of chemotypic variability within the genus. Attempts at establishing callus culture were partially successful but met with widespread contamination. Callus, a de-differentiated tissue type useful as an intermediate in plant regeneration, formed from stem and leaf explants of D. christmanii, D. frutescens, D. immaculata var. immaculata, D. imm. var. savannarum, and D. thinicola, and from leaf explants of D. modesta. No callus was obtained from D. cornutissima explants. Callus growth was slow, first observed on average 15 days after culturing, and reaching a maximum diameter of about 5.0 mm 50 days after first emergence. Browning of the medium, a deleterious accumulation of oxidized phenolics sometimes reported in plant tissue culture, was not observed in callus cultures; however, transplanted callus did not produce differentiated tissue in the period of study. Attempts to identify relative concentrations of oil components by GC-MS were largely unsuccessful. While sample extracts revealed the likely presence of early-eluting oil components such as pinene and limonene in small amounts, prepared standards of pulegone showed no chromatogram peaks, and peak sizes were inconsistent between duplicate samples. These initial studies suggest this source of error may be a product of mechanical error, samples that were too dilute, or both. Further studies are necessary in order to determine the relevance of plant tissue culture to mint chemotaxonomy and to understand the genus‟ chemical variability over season.

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