Term of Award

Fall 2015

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Biology

Committee Chair

Checo Colon-Gaud

Committee Member 1

Doug Aubrey

Committee Member 2

Subhrajit Saha

Abstract

Nonstructural carbohydrates (NSC) can supply substrate during periods when current photosynthate is unavailable or inadequate to meet metabolic demands. I hypothesized that natural selection has favored higher nonstructural carbohydrate concentrations ([NSC]) in species that have an evolutionary history of frequent disturbance and tested this using three southern pine species that have evolved under a continuum of disturbance frequencies (evolutionary history of fire ~ longleaf > slash > loblolly). Stem and root samples were collected from 12 similar-sized individual trees of each species during time periods that reflect the annual minimum and maximum [NSC]. A modified colorimetric method was performed on the samples to determine [NSC]. Both [sugar] and [starch] differed among species, between organs, and exhibited seasonal patterns; however, these individual effects were not always independent of each other. Longleaf roots exhibited higher [sugar] than loblolly and slash; however, [sugar] in the stems were similar among species. Both [sugar] and [starch] of roots were higher than stems in March. Roots exhibited seasonal changes in [sugar] and [starch] (higher in October for sugar and higher in March for starch). The results suggest that evolutionary history of disturbance partly explains patterns of [NSC] observed in southern pines as longleaf—the species with an evolutionary history of frequent fire—exhibited the highest [NSC] in roots; however, similarities between slash and loblolly indicate that other factors must also be considered. The results are likely explained by the different life histories exhibited in the juvenile stages of these pines; specifically, patterns of allocation to above- and belowground tissues. I suggest that the increased belowground storage observed in adult longleaf pine may simply be a relic of selective pressures imposed at the juvenile stage.

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