Degree Type

Dissertation

Date of Award

2005

Degree Name

Doctor of Philosophy

Department

Forestry

First Advisor

Richard B. Hall

Second Advisor

Allen D. Knapp

Abstract

Sensitivity to desiccation of recalcitrant seeds of the Leucobalanus subgenus of Quercus poses limitations to successful storage and regeneration efforts. My three studies evaluated different aspects of these problems. The first study investigated the effect of parent tree and seed size on seedling performance and morphology over the first three months of growth for Quercus alba and Quercus macrocarpa. The second study evaluated the effect of nitrous oxide (N2O) on seed storage as measured by seed, seedling, and starch thermal variables. Seeds from both species were placed in containers with one of three treatments: air, 80/20% and 98/2% N2O/O 2. The third study investigated the effect of parent tree, seed size, and desiccation time on seed, seedling, and starch thermal variables for Quercus macrocarpa. Two parent trees, and two seed sizes (19.5 and 20.5mm) for each parent were selected, and desiccated under ambient room conditions. We found an effect of both parent tree and seed size on the majority of seed-related and seedling performance variables, with larger seeds performing better. Storage time under N2O had an effect for most of the seed related variables. Seedling performance declined with storage time for Quercus alba, while it improved for Quercus macrocarpa. In both species, seedling performance following N2O treatments was poorer. Seed desiccation showed an effect of parent tree and seed size for almost all seed-related variables. Parent tree also affected seedling performance. Desiccation time negatively affected most of the studied variables. For the storage and the desiccation objectives, starch thermal analysis indicated alterations during the treatment periods. Our results suggest that regeneration success could be enhanced by proper parent tree and seed size selection, since those variables could provide more vigorous seedlings and delay the deleterious effects of desiccation. N2O is effective in reducing seed metabolism, but more work is needed to find optimal storage conditions. Starch thermal values proved to be sensitive indicators of metabolic alterations when seeds were exposed to desiccation and storage environments.

DOI

https://doi.org/10.31274/rtd-180813-11848

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Valasia Iakovoglou

Language

en

Proquest ID

AAI3184622

File Format

application/pdf

File Size

158 pages

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