Graduate Thesis Or Dissertation
 

Factors influencing dormancy and persistence in buried seed of five grass species

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/qz20sv859

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  • Field and growth chamber studies were conducted to ascertain the effects of some environmental factors on the persistence of viable buried seed of Agrostis tenuis, Avena fatua, Lolium multiflorum, Lolium perenne, and Poa annua. Through the use of a population model, specific effects of environment on parameters of viability and nonviability were studied. The parameters of viability included seed quiescence and terminal dormancy. In situ germination and nonviability among ungerminated seed plus their composite, total nonviability, comprised the parameters of nonviability. Of the five species studied, only buried seed of L. perenne was found to be nonpersistent. Variation in the degree of persistence was found among different seed lots of L. multiflorum. Quiescence among buried seed of the persistent species was greater at deeper burial depths. Nonviability among buried seed was found to be less extensive at deeper burial depths. Seed samples of persistent species recovered from burial under perennial ryegrass plant cover displayed higher levels of terminal dormancy than similar samples recovered from indigenous weed, wheat and alfalfa plots. Low soil temperature and high soil moisture, characteristic of winter conditions in western Oregon, were effective in maintaining viability of buried seed. These conditions were also found to be conducive to the induction of secondary seed dormancy. The depletion of viable, buried seeds through in situ germination occurred at intermediate soil temperatures and soil moisture. Such conditions prevail in western Oregon during autumn and spring periods. High temperature and soil moisture percentage was found to increase non-viability among ungerminated seed. Seed quiescence played an important role in persistence during the early stages of seed burial. With the progression of time, terminal dormancy played an increasingly important role as a mode of buried seed persistence. In situ germination was the principle mode of buried viable seed depletion in A. fatua, L. multiflorum, L. perenne, and P. annua. Nonviability among ungerminated seed was found to be the principle mode of viable seed depletion in A. tenuis.
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