Type of Document Dissertation Author Shen, Zhengxing Author's Email Address firstname.lastname@example.org URN etd-8297-134015 Title Studies on the Plasticity of Dormancy and on Aging in Switchgrass Seeds Degree PhD Department Crop and Soil Environmental Sciences Advisory Committee
Advisor Name Title Parrish, David J. Committee Chair Abaye, Azenegashe Ozzie Committee Member Orcutt, David M. Committee Member Welbaum, Gregory E. Committee Member Wolf, Dale D. Committee Member Keywords
- panicum virgatum
Date of Defense 1997-07-02 Availability restricted AbstractThe dormancy of switchgrass (Panicum virgatum L.) seeds may be broken by a
variety of treatments, including after-ripening and stratification.
This study was conducted to investigate and characterize more systematically
factors affecting both after-ripening and stratification effectiveness, and
the aging that can occur concomitantly with after-ripening. More than one
year of after-ripening at ambient temperature and humidity was necessary
for germination of newly harvested seeds to increase from as low as 5% to
around 80%. After-ripening was not accelerated at temperatures above ambient
for seeds stored in paper bags, which permitted the loss of seed moisture at
the increased temperatures. Both after-ripening and aging accelerated with
increases in temperature (5 to 60°C) and seed moisture content (50 to 130
g kg-1), except that there was evidence of a moisture optimum for after-ripening that shifted downward as temperature increased. For many seedlots, storage at 60 60°C and 50 g kg-1 seed moisture content for about 1 mo broke most of the dormancy and resulted in acceptably low numbers of abnormal (aged) seedlings. Decreases in germinability caused by post-stratification drying of switchgrass seeds (described herein as "reversion", in which the reverted seeds could be made germinable again by further stratification) increased as the desiccation increased. Revertibility decreased as stratification or after-ripening time increased. Stratification and after-ripening worked additively to release switchgrass seeds from dormancy. Reversion (germination with stratification minus germination after stratification followed by drying) may reveal seedlot differences and changes over time and moisture content that can not be seen otherwise. Imbibed, dormant seeds placed at 21 or 30 °C were induced into deeper dormancy, as indicated by length of stratification needed to break the dormancy. Dormancy deepened more as storage temperature and time increased for imbibed seeds. There are transitional temperature and seed moisture ranges where opposing processes (aging vs. after-ripening, stratification vs. dormancy deepening) appeared to overlap or surpass one another. Switchgrass seeds, either on a single seed level, or on the population level, responded continuously to changing temperature and moisture conditions. Less aging was observed for switchgrass seeds stored in N2. After-ripening of switchgrass seemed not to be influenced by N2 or air. In sum, switchgrass is revealed to be remarkably plastic in its ability to move toward both greater germinability and greater dormancy.
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