Date of Award

Summer 8-15-2017

Author's School

Graduate School of Arts and Sciences

Author's Department

Earth & Planetary Sciences

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

The hydrogen isotopic composition (δ2H) of precipitation records fluxes of water in the hydrological cycle, and can reflect climatic variables such as temperature and humidity. Leaf wax n-alkanes can record δ2H of precipitation; consequently, n-alkanes extracted from sedimentary archives are commonly used as proxies for paleoenvironmental reconstruction. However, the utility of the leaf wax paleoclimate proxy is modulated by uncertainty about how physiological processes affect hydrogen isotopic compositions during alkane biosynthesis. This work aims to improve our understanding of the leaf wax paleoclimate proxy by examining biological and environmental sources of variability on cuticular leaf waxes. We used Solanum (tomato) species as a model organism complex to study leaf wax variability and found significant biological effects on leaf wax δ2H values and leaf wax structural traits.

Using a set of introgression lines (ILs) between Solanum pennellii and Solanum lycopersicum cv M82, we observed up to 60‰ variability among genetically similar plants grown in the same environmental conditions and found that biological variance accounted for up to 24% of the observed variance in leaf wax δ2H values. Our results imply that the majority of the leaf wax δ2H signal is determined by environmental variance, but suggest that changes in δ2H values from sedimentary alkanes also reflect variability induced by biological differences. Additionally, we found that n-alkane chain-length distributions (ACLs) are under a moderate degree of genetic control and are conserved among Solanum plants. These findings suggest that ACLs of sedimentary alkanes may record environmental change due to changes in plant communities rather than physiological changes induced by shifts in environmental conditions.

We found that leaf wax δ2H values were more variable among juvenile plants than mature plants. Additionally, we found that leaf wax δ2H values were enriched along a base-to-tip gradient within a single leaf, likely reflecting 2H-enrichment due to leaf water evapotranspiration. We observed species-specific differences in biosynthetic fractionation among Solanum plants.

Language

English (en)

Chair and Committee

Alexander S. Bradley

Committee Members

Daniel H. Chitwood, David A. Fike, Jeffrey G. Catalano, Scott A. Mangan,

Comments

Permanent URL: https://doi.org/10.7936/K7WQ036G

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