The Black Box of Plant Demography: Seed Germination and Pathogens
| dc.contributor.author | Mackin, Hunter Castle | |
| dc.date.accessioned | 2019-11-07T16:13:20Z | |
| dc.date.available | 2019-11-07T16:13:20Z | |
| dc.date.issued | 2019 | |
| dc.description | 50 pages | |
| dc.description.abstract | Most demography studies tend to overlook germination, in favor of seedling survival. However, germination itself is limited by many factors, and remains an essential part of the fitness equation. This study examines seeds of the two native perennial grasses Festuca roemeri and Danthonia californica, assessing germination rates and seed pathogen richness across both species as well as seed type for D. californica, which produces both open-pollinated (chasmogamous) and obligately self-pollinated (cleistogamous) seeds. Germination was found to be significantly lower for cleistogamous seeds, possibly a consequence of a decrease in outcrossing. Germination varied considerably between populations, and we asked whether the environment the seeds developed in, that of the seed mother, influenced these rates. The maximum spring temperature and total spring precipitation each significantly predicted for decreases in germination as they increased, indicating the importance of the growth environment through maternal effects. Further, both soil nitrogen and plant density significantly increased germination rates, likely due to increases in nutrient provision to developing seeds, increased pollen deposition and outcrossing. Pathogen species richness was also assessed for every seed. There were substantial decreases in attack rates for cleistogamous seeds, a plausible benefit of being housed and insulated within their mother’s stalks. Pathogen richness depended on the region where the seeds had been collected, and was apparently limited by increases in spring precipitation, a counterintuitive finding that may have been the result of correlation with a variable left unmeasured. There were more pathogens per seed when plant densities were higher. This is a negative consequence of larger population size, as with these increases in pathogen species richness came decreased germination. These findings suggest that maternal environment plays a large role both in germination and pathogen attack rates, which has implications for present and future climate change. Further, cleistogamous seeds had lower germination rates, but decreased rates of pathogen attack rates, which may serve to counterbalance each other, as the increases in germination for higher populations of higher density may be kept in check by pathogens. | en_US |
| dc.identifier.uri | https://hdl.handle.net/1794/25042 | |
| dc.language.iso | en_US | |
| dc.publisher | University of Oregon | |
| dc.rights | Creative Commons BY-NC-ND 4.0-US | |
| dc.subject | Economics | en_US |
| dc.subject | Germination | en_US |
| dc.subject | Pathogens | en_US |
| dc.subject | Maternal Effects | en_US |
| dc.subject | Climate | en_US |
| dc.subject | Plant Density | en_US |
| dc.title | The Black Box of Plant Demography: Seed Germination and Pathogens | |
| dc.type | Thesis/Dissertation |
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