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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/26/2017 Publication Date: 7/11/2017 Citation: Hardegree, S.P., Moffet, C., Walters, C.T., Sheley, R.L., Flerchinger, G.N. 2017. Hydrothermal germination models: Improving experimental efficiency by limiting data collection to the relevant hydrothermal range. Crop Science. 57(5):2753-2760. doi:10.2135/cropsci2017.02.0133. DOI: https://doi.org/10.2135/cropsci2017.02.0133 Interpretive Summary: Hydrothermal germination models are an important tool in predicting cumulative germination response under the highly variable conditions of weather and microclimate in the field. A major difficulty in development of predictive hydrothermal germination models, however, is the high cost of laboratory experimentation in order to obtain data for model parameterization. We hypothesized that these costs could be greatly reduced if the range of treatment conditions measured in the laboratory could be limited to only the range of conditions likely to be experienced in the field. We simulated a long-term series of field temperature and water availability, and determined that laboratory costs for model parameterization could be reduced by 80-90% by limiting treatment conditions to only the relevant range of field conditions. This cost savings now makes it possible to screen large numbers of seedlots for potential field germination response. This could lead to standardized methodology for improving the way in which we interpret seedlot viability in the seed collections contained in national and international germplasm repositories. Technical Abstract: Hydrothermal models used to predict germination response in the field are usually parameterized with data from laboratory experiments that examine the full range of germination response to temperature and water potential. Inclusion of low water potential and high and low-temperature treatments, however, may not be necessary if their contribution to germination rate in the field is negligible. In this study, we simulated cumulative germination response of 13 range grass seedlots to a typical seasonal planting scenario used for rangeland restoration in the Great Basin region of the western U.S. Given realistic estimates of actual time spent within the full hydrothermal range of these seedlots, over 95% of germination response in the field could be predicted by models that only considered germination at water potentials less negative than 0.5 MPa and temperatures below 25 ºC. Limiting laboratory treatments to a restricted hydrothermal range could greatly increase the efficiency of parameterizing hydrothermal models for predicting field response. Laboratory expenditures in this example could be reduced by 80-90% with only a relatively small reduction in the potential accuracy of field predictions. |
