Date of Award

8-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Dirk Vanderklein

Committee Member

Karina V. R. Schäfer

Committee Member

Jennifer Adams Krumins

Committee Member

Paul Bologna

Abstract

In order to cope with a variety of environmental stresses, trees use starch storage as a buffering system to compensate for energy needs. Starch allocation into different tissues throughout the year can determine the health of deciduous trees. Natural environmental stresses including seasonal changes, water and nitrogen availability and defoliation are known to have direct effects on starch storage. Anthropogenic stresses such as heavy metal and other toxic contaminants in soils have not been investigated as factors that alter the normal starch trends in the different tissues of trees. This study assesses how starch storage in different tissues in B. populifolia and Populus spp. roots, twigs and leaves may have been altered by heavy metal contamination in trees growing in an urban brownfield over the course of a year. A heavy metal polluted site was used where varying levels of toxic metals including Zn, Pb, As, Cu and Cr were previously identified. Starch concentrations between the two species was significantly different (p=0.03) with Populus spp. having almost twice as high a starch concentration as B. populifolia when all tissue data for the year are considered. The level of metal contamination in the soil had some significant interaction effects on starch concentration in all of the tissues sampled between the two investigated species. Root and twig tissues of Populus spp. showed an increase in starch content with increasing metal load while B. populifolia showed no significant change in starch concentration at the different metal load sites. The difference in starch between the two species across the metal load sites indicates different responses to metal stress of the two species, which may in turn account for variations in species dominance where there is more or less metal pollution in the soil.

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