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Quantifying the effects of temperature on dormancy change and germination in orchardgrass (Dactylis glomerata L.) and western wheatgrass (Pascopyrum smithii [Rydb.] L.)

dc.contributor.advisorBai, Yuguangen_US
dc.contributor.committeeMemberTanino, Karenen_US
dc.contributor.committeeMemberRomo, James T.en_US
dc.contributor.committeeMemberJefferson, P.en_US
dc.contributor.committeeMemberHughes, Geoffrey R.en_US
dc.contributor.committeeMemberCoulman, Bruce E.en_US
dc.creatorQiu, Jieen_US
dc.date.accessioned2005-06-13T15:13:55Zen_US
dc.date.accessioned2013-01-04T04:38:20Z
dc.date.available2005-06-14T08:00:00Zen_US
dc.date.available2013-01-04T04:38:20Z
dc.date.created2005-05en_US
dc.date.issued2005-05-30en_US
dc.date.submittedMay 2005en_US
dc.description.abstractOrchardgrass (Dactylis glomerata L.) and western wheatgrass (Pascopyrum smithii (Rydb.) L.) seeds have different degrees of dormancy that result in non-uniform seedling emergence in the field. Seed dormancy of the two species, in part, causes disagreement between germination tests in the laboratory and seedling emergence in the field. Experiments were conducted over two years in the laboratory and in the field to determine the effects of alternating temperatures on changes in seed dormancy and germination of orchardgrass and western wheatgrass. The two western wheatgrass cultivars (‘Walsh’ and ‘LC9078a’) had deeper dormancy than the two orchardgrass cultivars (‘Arctic and Lineta’). Dormancy of both species was broken by temperatures with 10oC amplitude; this temperature variation was similar to that which occurred at a 1 cm depth in the soil. Optimal temperatures for germination of orchardgrass (10-25oC) were broader than those for western wheatgrass (15-20oC). Seedling emergence of orchardgrass was less sensitive to seeding date in the spring than western wheatgrass; seedling emergence of western wheatgrass increased as seeding date was delayed from early to late May if soil water was not limiting. The rate of seedling emergence increased with increasing temperature in both species, therefore, faster and more uniform seedling emergence can be expected from late spring seeding dates. Seeds were often exposed to light during germination tests in the laboratory while planting seeds in the soil usually prevented exposure of seeds to light. Seedling emergence of orchardgrass in the field was usually less than the germination percentage obtained in the laboratory because of light exposure during germination tests could break dormancy in orchardgrass seeds and the small seeds of orchardgrass had limited energy reserves for pre-emergence seedling growth. On the other hand, germination of western wheatgrass seeds was reduced by exposure to light during germination and seeds were larger than those of orchardgrass. Therefore, seedling emergence of western wheatgrass in the field was usually greater than germination tests would predict. The use of thermal time models to study seed dormancy changes and germination revealed the dual effects of temperature on these processes. The modified thermal time model takes the difference between germination and seedling emergence into account and can accurately predict seedling emergence in the field (R2=0.88 to 0.99). Thermal time models for predicting seedling emergence in the field can also be developed for other forages, however, cultivar- and species-specific parameters must be developed for the models.en_US
dc.identifier.urihttp://hdl.handle.net/10388/etd-06132005-151355en_US
dc.language.isoen_USen_US
dc.subjectbase temperatureen_US
dc.subjectgermination rateen_US
dc.subjectdormancyen_US
dc.subjectseed germinationen_US
dc.subjectalternating temperatureen_US
dc.subjectthermal time modelen_US
dc.titleQuantifying the effects of temperature on dormancy change and germination in orchardgrass (Dactylis glomerata L.) and western wheatgrass (Pascopyrum smithii [Rydb.] L.)en_US
dc.type.genreThesisen_US
dc.type.materialtexten_US
thesis.degree.departmentPlant Sciencesen_US
thesis.degree.disciplinePlant Sciencesen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M.Sc.)en_US

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