AN ABSTRACT OF THE THESIS OF M. Melinda Trask for the degree of Master of Science in Department of Rangeland Resources presented on July 12, 1996. Title: Breaking Seed Dormancy in Three Western Oregon Grasses. Redacted for Privacy Abstract approved: David A. Pyke Germination characteristics of three native grass species (Danthonia californica, Festuca viridula, and Achnatherum lemmonii) were investigated. These species were known to exhibit low germination rates and it was believed that seed dormancy was the reason. Germination and viability of each of four seed lots (i.e., collections from geographically distinct populations) per species were characterized by conducting standard germination and viability tests, and initial dormancy. The resulting average standard germination of most of the seed lots was quite low (< 21% for most seed lots). Germination enhancement treatments were conducted on each seed lot using a factorial arrangement of various treatments, such as seed coat scarification or applications of different concentrations of gibberellic acid. Each of these native grasses and even some of the individual populations had unique dormancy enforcing and germination promoting characteristics. In each species investigated, effect of treatments on mean cumulative germination was significantly different among the four seed lots. However, there usually was at least one treatment that consistently produced higher germination than others in each of the lots within a species. In D. californica, scarification enhanced cumulative germination (usually > 20%) and decreased median germination rates by 7 d. Addition of GA3 further increased germination in D. californica, resulting in over 80% cumulative germination and breaking as much as 90 to 100% of the dormancy in most lots. In F. viridula, treatment with GA3 substantially enhanced cumulative germination(usually > 40%), while addition of 4-wk stratification to GA3 producedover 60% germination among the lots, breaking 70 to 100% of the dormancy and reaching median germination rate an average of 12 d less than similar treatments not stratified. Seed scarificationand 2-wk stratification always increased cumulative germination in A. lemmonii,resulting in 17% germination for the scarification factor and 6% germination for the stratification factor. None of the treatments used in this study werevery effective at breaking dormancy in A. lemmonii. Breaking Seed Dormancy in Three Western Oregon Grasses by M. Melinda Trask A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented July 12, 1996 Commencement June 1997 Master of Science thesis of M. Melinda Trask presented on July 12, 1996 APPROVED: Redacted for Privacy Major Professor, representing Department of angeland Resources Redacted for Privacy Head of Department of Rangeland sources Redacted for Privacy Dean of Graduate Sc I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis toany reader upon request. Redacted for Privacy " M. Melinda Trask, Author ACKNOWLEDGMENTS My first and foremost acknowledgments go to my major advisor andmentor, Dr. David A. Pyke and to the National Biological Service, United States Departmentof the Interior, Forest and Rangeland Ecosystem Science Center. Dr. Pyke, for havingthe confidence in me and my "radical" ideas about studying the production of native plant seeds. While many scientists agree that it is important touse native seeds in ecological restoration, few realize the importance of the role of research in providing plantmaterials for such projects. The National Biological Service, Vegetation Diversity Projectis responsible for most of the financial support for this project. I would also liketo acknowledge Jerry White and Forbes Seed and Grain, Inc., for providingme with an internship that inspired my interest in native plant materials research. Jerry White assisted in the initiation this study. Financial support for this projectwas also provided by the U. S. Forest Service, Rogue River National Forest, and by the Medford District, Bureau of Land Management. Cooperative support was provided by Forbes Seed and Grain, Inc. and the Department of Rangeland Resources at Oregon State University. Additional thanks to the following: Lisa Ganio, Oregon State University, for statistical consulting; Wayne Rolle (Botanist, Rogue River National Forest) and his seed collecting volunteers for providing seeds for the study; Oregon State University SeedLab for conducting viability tests; Priscilla Schmidt for assisting in the laboratory; Larry Erickson, NASA, for mathematical consulting; Chris Scalley and George Taylor, Oregon Climate Service at Oregon State University for climate data searches and feedbackon my temperature model. The 1995 germination enhancement pilot project provided in Appendix 1 was originally published in Grasslands, Volume VI, No. 1, March 1996. Thanks to the "bean" gang, who reminded me that science is not everything! Finally, a special note of appreciation to my mother, Shirley,my stabilizing force, without whom I may not have survived and championed the difficult times. TABLE OF CONTENTS INTRODUCTION 1 Problem Definition 1 Statement of Purpose 3 MATERIALS AND METHODS 5 Plant Materials 5 Literature Review 6 Germination and Dormancy Testing 7 Germination Enhancement Testing 11 Pilot Projects 11 Laboratory Experiments 12 Greenhouse Experiments 15 Seed Size Analysis 16 Data Analysis 17 RESULTS 22 Literature Review 22 Germination and Dormancy Testing 27 Germination Enhancement Testing 28 Germination Rate Analysis 28 Effects of Treatments on Danthonia californica 29 Effects of Treatments on Festuca viridula 33 Effects of Treatments on Achnatherum lemmonii 37 Greenhouse Experiments 39 Seed Size Analysis 41 DISCUSSION 42 Summary and Recommendations 51 LITERATURE CITED 53 LIST OF FIGURES Figure Page 1. Mean monthly temperature and precipitation data. 23 2. Comparison of observed versus Logistic and Gompertz functions for germination rate modeling. 30 3. Mean cumulative germination of the significant lot by scarification by KNO3 by GA3 interaction in D. californica 32 4. Mean germination rates for F. viridula. 34 5. Mean cumulative germination of the significant interactions in F. viridula. 36 6. Mean cumulative germination of the stratification factor in A. lemmonii. 38 7. Mean cumulative germination of the significant interactions in A. lemmonii. 38 8. Seedling survival from greenhouse experiments and average germination from laboratory experiments. 40 LIST OF TABLES Table Page 1. Population names, locations, and habitat information for each seed lot used in this study 6 2. Summary of germination enhancement factors and levels (in parentheses) applied to each species. 14 3. Summary of greenhouse treatments 16 4.Characteristics of untreated seeds based on the germination, viability, and purity tests. 28 5. Goodness of fit analysis of the Gompertz and Logistic functions for germination rate of D. californica. 29 6. T50 values for each lot and treatment on D. californica 31 7. Potential correlation between seed size and germination for D. californica and A. lemmonii. 41 LIST OF APPENDICES Appendix Page 1. 1995 Germination enhancement trials pilot project 58 2. Other pilot projects 62 Breaking Seed Dormancy in Three Western Oregon Grasses INTRODUCTION Problem Definition Many land management agencies have begun using native species in plant community restoration and rehabilitation projects. However, revegetationwith native plants is both complex and expensive, and has exhibited limitedsuccess. A common limitation of successful revegetation is the inability of most native speciesto germinate readily and compete with other species. Many native species have lowgermination that is often due to seed dormancy. When dormant seedswere sown, they are often so slow to germinate that the site becomes occupied by plants that outcompetetarget species. For native plant species to compete effectively, they must germinate readilyto establish at a rate that is competitive. Seed dormancy is an adaptive characteristic to promote seedling establishmentunder only optimal environmental conditions. Dormant seedmay undergo biochemical changes called afterripening, when the seed embryo is gradually maturing (Young andYoung, 1986). However, even when the seed may be physiologically "mature", certain environmental cues, such as changes in temperature, may be required to break dormancy. There were two main categories of seed dormancy, coat-imposed dormancy and embryo dormancy. Seeds with coat-imposed dormancy require physical alterationof the seed coat for germination, whereas the mechanisms for germinating seeds with embryo dormancy were usually biochemical and were not related to the seed coat (Webster,1995; 2 Copeland and McDonald, 1985). Termination of embryo dormancy is poorly understood, although a variety of stimuli have been identifiedas dormancy-breaking agents, including light, plant hormones, low temperature, and alternating temperatures (Bewley and Black, 1985; Karssen et al., 1989; Simpson, 1990; Young, Emmerich, and Patten, 1990). Most research on seed physiology, germination, and dormancy has been conducted on herbaceous species, annual grasses, and commercial grasses (Simpson, 1990). The Association of Seed Analysts (AOSA) has developed rules and testing proceduresto aid in crop production (AOSA, 1993). These guidelineswere directed