Prolonged dormancy is a stage in which mature plants fail to resprout during the growing season and instead remain alive belowground. Though it is relatively common, the causes and consequences of this intriguing stage have remained elusive. In this dissertation, I investigate the causes and consequences of prolonged dormancy in a long lived perennial herb, Astragalus scaphoides.
First, I use a combination of demography and ecophysiology to study the proximate mechanisms associated with prolonged dormancy. Analysis of a long-term demographic dataset indicates that both endogenous factors (e.g. age, condition, and history) and exogenous factors (e.g. climate and spatial variation) are associated with dormancy. I then investigate the association between stored resources and dormancy. My results indicate that individual plants with low levels of stored available carbon are more likely to enter prolonged dormancy. Surprisingly, individuals increased their mobile carbon concentrations while dormant, presumably by remobilizing structural carbon into mobile forms. Since stored resources integrate past conditions and performance with current state, these results can explain why some individuals remain belowground while others emerge to grow and reproduce.
I used matrix models to examine the ultimate causes and consequences of prolonged dormancy. I found evidence that prolonged dormancy acts as a conservative strategy that allows plants to avoid the risk of a variable environment. Further, my results demonstrate that intermediate levels of dormancy result in the highest fitness advantage. Finally, I measured the trade-offs associated with emerging during times of environmental stress. Although plants showed remarkable physiological tolerance to stress, stress led to demographic costs. Therefore, prolonged dormancy is shown to be a beneficial strategy in a variable environment.
Together, my research identifies both the proximate causes of prolonged dormancy, as well as the ultimate consequences of remaining belowground during the growing season. Therefore, my research not only identifies why some plants go dormant while others emerge, but also explains the prevalence of this intriguing life stage in the life histories of so many perennial plants.
|Advisor:||Sala, Anna, Crone, Elizabeth E.|
|Commitee:||Callaway, Ragan, Deluca, Thomas H., Fishman, Lila|
|School:||University of Montana|
|Department:||Organismal Biology & Ecology|
|School Location:||United States -- Montana|
|Source:||DAI-B 72/03, Dissertation Abstracts International|
|Subjects:||Plant biology, Ecology|
|Keywords:||Astragalus scaphoides, Life history, Nonstructural carbohydrates, Prolonged dormancy, Vegetative dormancy|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be