Abstract
Cheatgrass (Bromus tectorum L., Poaceae), an introduced winter annual, has invaded a variety of habitats in western North America. This study examines variation in cheatgrass germination response and after-ripening patterns that are related to differences in habitat and to yearly differences in weather conditions during seed maturation. Seeds collected from five contrasting populations in 1992 and 1993 were subjected to controlled dry storage and then incubated across a range of temperatures. Recently harvested seeds were dormant and germinated slowly, while fully after-ripened seeds were nondormant and germinated rapidly. The optimal incubation temperature for mean germination time shifted from 5:15 to 20:30 °C as a result of after-ripening. Between-population differences in germination response appear to be related to the potential risk of precocious summer germination. The results from this 2-year study suggest that the more extreme yet predictable environments select for seed germination and after-ripening patterns that are genetically fixed, while populations from more favorable environments tended to show more between-year variations, suggesting more phenotypic plasticity. Germination percentage showed greater between-year variation than mean germination time. Between-year differences could not be explained simply by differences in maximum temperature or total precipitation during maturation. Adaptive germination responses in cheatgrass populations from contrasting habitats may have both genetic and environmental components, thus explaining why this species can become established in such a variety of habitats. Keywords: after-ripening, invading species, dormancy, mean germination time, cheatgrass, downy brome.
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Claims 8
Claim · model-written summary
Recently harvested seeds were dormant and slow to germinate.
- Taxon
- Bromus tectorum L.
Bromus tectorume0 - Organ / stage
- seedse1
- Outcome
- dormant and germinated slowlye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“Recently harvested seeds were dormant and germinated slowly”
Claim · model-written summary
Fully after-ripened seeds were nondormant and germinated rapidly.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Organ / stage
- seedse1
- Outcome
- nondormant and germinated rapidlye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“fully after-ripened seeds were nondormant and germinated rapidly”
Claim · model-written summary
After-ripening shifted optimal incubation temperature from 5:15 to 20:30 °C.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Treatment
- after-ripeninge1
- Outcome
- optimal incubation temperature for mean germination timee1
- Direction
- shiftede1
- Value
- 20:30 °Ce1
- Comparator
- 5:15e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“The optimal incubation temperature for mean germination time shifted from 5:15 to 20:30 °C as a result of after-ripening”
Claim · model-written summary
Between-population germination differences appeared related to risk of premature summer germination.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Outcome
- germination responsee1
- Qualifier
- appear to be relatede1
- Setting
- summere1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“Between-population differences in germination response appear to be related to the potential risk of precocious summer germination”
Claim · model-written summary
Populations in extreme predictable environments appeared to have genetically fixed germination patterns.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Outcome
- seed germination and after-ripening patterns that are genetically fixede1
- Setting
- more extreme yet predictable environmentse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“the more extreme yet predictable environments select for seed germination and after-ripening patterns that are genetically fixed”
Claim · model-written summary
Populations in more favorable environments tended toward greater between-year variation.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Outcome
- between-year variationse1
- Direction
- moree1
- Setting
- more favorable environmentse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“populations from more favorable environments tended to show more between-year variations”
Claim · model-written summary
Germination percentage varied more between years than mean germination time.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Outcome
- Germination percentagee1
- Direction
- greatere1
- Comparator
- mean germination timee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“Germination percentage showed greater between-year variation than mean germination time”
Claim · model-written summary
Maximum temperature and precipitation did not simply explain between-year differences.
- Taxon
- Bromus tectorum L.Bromus tectorume0
- Outcome
- Between-year differencese1
- Setting
- maximum temperature or total precipitation during maturatione1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cheatgrass (Bromus tectorum L., Poaceae)”
e1“Between-year differences could not be explained simply by differences in maximum temperature or total precipitation during maturation”