Electronic Theses and Dissertations





Document Type


Degree Name

Doctor of Philosophy



Committee Chair

S. Reza Pezeshki

Committee Member

Duane McKenna

Committee Member

T. Nakazato

Committee Member

James Moore


Baud, Donald Reon. PhD. University of Memphis. December 2012. Leaf and Root Responses of Three Wetland Tree Species to Anthropogenic-generated Stressors. Major Professor: S. Reza Pezeshki.Published research to date has shown that anthropogenic-generated stressors, such as increased ultraviolet-B exposure, higher temperatures and the concomitant increase in herbivorous insect populations, as well as increased copper and ethanol contamination, are having a negative impact on plant growth and survival. However, there is a lack of data on the morphological and physiological responses woody wetland species. This series of independent, but related, experiments will focus on Salix nigra, Acer negundo, and Quercus phellos, important members of southeastern U.S. bottomland hardwood forests, and elucidate the impacts on these species due to anthropogenic-generated stressors. S. nigra responded to elevated ultraviolet-B exposure with a decrease in total biomass and by increasing aerenchyma tissue development, an anatomical change known to be associated with stress. S. nigra had a similar response to copper, with aerenchyma tissue increasing, while total biomass decreased. Copper exposure also shifted resource allocation to the shoot system, at least partially as a result of increased foliage production. No interaction was found between UV-B and copper exposure. S. nigra responded to increased soil temperature by increasing aerenchyma tissue development while net photosynthesis, transpiration rate, and stomatal conductance decreased. The response of Q. phellos to higher soil temperatures was similar except foliage production increased. Q. phellos responded to an increase in herbivory with a decrease in net photosynthesis and increased foliage production. A concomitant shift in resource allocation resulted in an overall decrease in shoot biomass. An interactive effect was found for temperature and herbivory indicating higher soil temperature with a concomitant increase in herbivory has a greater negative impact on wetland tree seedling survival than either stressor along. The response of Q. phellos and A. negundo to root-zone ethanol was a decrease in both net photosynthesis and transpiration rate. Q. phellos, A. negundo, and S. nigra shifted resource allocation to the roots in response to root-zone ethanol, however, aerenchyma development increased only in S. nigra and A. negundo. Scanning electron microscopy of S. nigra adventitious root tips determined aerenchyma development is expansigenous for this wetland tree. Enhanced growth and survival were the results of soaking S. nigra and A. negundo cuttings in dilute sucrose solutions prior to planting, indicating this is a useful tool in wetland remediation projects involving the reintroduction of these two wetland tree species.


Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.