Date of Award

6-30-2016

Document Type

Open Access Dissertation

Department

Biological Sciences

First Advisor

David E Lincoln

Abstract

Plants as sessile organisms encounter myriad biotic and abiotic challenges in their habitats. Pathogen and herbivore attack are among the prominent biotic challenges that plants face in their environment. Plants respond to these attacks by using chemical compounds including monoterpenes that are constitutively and inductively produced in some plants, and stored inside glands on their leaves. Among the abiotic factors that influence the production of defense compounds, especially monoterpenes are light intensity and nutrient availability.

The objectives of this dissertation are to 1) comprehend the defensive role of monoterpenes, specifically investigating the associational defense of a non-odorous species (Ilex vomitoria) co-occurring with other odorous species (Morella cerifera and Iva frutescens), along the marsh edge at Goat Island, Belle Baruch Hobcow Barony in Georgetown, South Carolina, 2) to evaluate the effects of Morella cerifera-Frankia symbiotic association on leaf monoterpene production, and the relationship between nitrogen availability and rate of nitrogen fixation by Frankia, 3) to determine the combined effect of light intensity and nutrient availability on monoterpene production in Morella cerifera. . Results indicated that leaf damage was significantly higher in both monocultures of I. vomitoria and M. cerifera. However, predation was significantly lower in the mixed species culture. The lowest level of predation was observed in the three species combination of I. vomitoria, M. cerifera, and I. frutescens. Although the nitrogen fixation rate within the 1/4 strength Hoagland inoculated treatment group was higher than full strength Hoagland inoculated, and the un-inoculated groups, the observed difference was not statistically significant F (3, 16) = 1.447, p = .266. Analysis of average monoterpene concentration revealed a statistically significant difference for the four treatment groups, (F (3, 12) = 34.11, p < .001). There was a positive significant correlation between nitrogen fixation rate and monoterpene production in the full strength Hoagland inoculated (FS H) treatment group (r = 0.81, p < 0.01). Additionally, a statistically significant difference in monoterpene concentration was observed between the plants in the native marsh edge and forest interior, F1,8 = 200.45, p < 0.000005. The fertilized and unfertilized treatments within the forest interior were also significantly different. Monoterpene production was highest among the plants growing under high intensity and high nitrogen soil concentration, therefore highlighting the sygergistic influence of light and nutrient availability on plant defense mechanism.

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Biology Commons

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