Date of Award
Doctor of Philosophy
William R. Graves
Trees native to seasonally flooded wetlands can be valuable in managed landscapes where wide fluctuations in soil moisture occur regularly. Nyssa aquatica L. (water tupelo) is a large, deciduous tree native to continuously and periodically flooded wetlands of the southeastern United States. I investigated the potential for using this tree in horticulture based on its tolerance to extreme fluctuations in soil moisture, water deficit, and its capability to be propagated asexually via stem cuttings. I also examined the genetic structure of the species across its native range by using inter-simple sequence repeats (ISSRs). Seedlings of N. aquatica were more tolerant to water deficit than seedlings of Nyssa ogeche Bartram ex. Marsh. (Ogeechee tupelo), another native North American species indigenous to wetland soils. Up to 40% mortality was observed for N. ogeche when subjected to repeated cycles of soil drying, whereas a maximum of 20% mortality was observed for N. aquaticasubjected to the same treatment. Seedlings of N. aquatica were tolerant to wide fluctuations in soil moisture but were sensitive to long-term water deficit when growth potential was high during spring and early summer. Plants exposed to moderate soil moisture before water deficit exhibited reduced photosynthetic rates and predawn water potentials, whereas plants subjected to flooding before water deficit had photosynthetic rates and predawn water potentials similar to those of well-watered controls and had greater aesthetic appeal than those pretreated with moderate soil moisture. Slower growth rates and reduced leaf area resulted when plants were treated with water deficit or flooding, which led to reduced transpirational demand and probably contributed to increased tolerance to future water deficit compared with plants pretreated with moderate soil moisture. Softwood cuttings of juvenile stems rooted at high frequency (up to 93% success). Rooting was best among cuttings from terminal positions on stock plants treated with a solution containing 1-naphthalenacetic acid (NAA). Genetic analyses of 24 populations of N. aquatica revealed moderate differentiation among populations and minimal regional structure.
Nickolee Zollinger Boyer
Boyer, Nickolee Zollinger, "Horticultural potential and population genetics of Nyssa aquatica L. (water tupelo)" (2009). Graduate Theses and Dissertations. 11102.