When working on basic biology of the endangered American Chaffseed (Schwalbea americana), we noticed that the limited literature suggested no need for cold moist stratification (despite the natural range of the species up through NJ). We are working on populations in South Carolina and we found that germination rates are about 10% without after ripening, but 75-95% with about a month of cold moist stratification (4C). That is when one of the undergraduate researchers asked how fewer cold days in the winter would effect germination rates. Has anyone else started look into shifts in winter stratification conditions as a factor affecting population persistence?
Dear Dr. Danny,
I believe that the quantitiy of information about temperature stratification of the Schwalbea american is not enough for a literature review, but the four degree reported by your under-graduated researcher is close to to five degree Celsius which is the most effective temperature for overcoming the physiological seed germination of a serie of seeds of temperate plants (Popinigis, 1977 -- this book is free to download and the species are reported by their scientific name). Otherwise, we have the hours of stratification in the current case: there is only one way to know the response -- it envolves the design of an experiment with treatments evaluating the percentage at week intervals for at least one month, maybe more. You can have the time to first germination and the daily percentages. In research, the work do be done is not so much. The most interesting in your question is the percentage that is ranging from 75 to 95%, which is a characteristic of physiological seed dormancy. In this case, the subject was converted into an experiment because the most interesting is that the current response requires an evaluation much more important that is the variability in these data. This variability can be show easily by EDA (Exploratory data analysis) from where the statistical distribution describing the phenomenon can be inferred from the data. Next I believe that is easy for you to have an stratification analysis of these data (here, stratification is Statistics). Finally, a good thesis which I am sure about.
I hope these observations can help you.
Yours Sincerely,
José Walter
Thank you for the response Jose,
My post was basically pointing out that sometimes our undergraduates ask good scientific (basic) questions that us researchers can over look. We are designing a series of experiments with crosses (local, local*more southern, local*more northern) to generate the F1 crosses and we will see if there is a difference in the cold - moist stratification performance. Thinking quantitative genetic control of physiological dormancy (plant nerd) and how to convey this important aspect of plant biology to the natural resource managers who manage the populations of these endangered species. Are you aware of any primary literature looking at quant. genetics of seed physiological dormancy? I will start my literature search this summer, but it never hurts to ask an international community of experts at the beginning. Cheers, Danny
Dear Dr. Danny,
I understood your point, but under field conditions I believe that the temperature, soil moisture at each conditions, and the sowing depth have to monitored. I do not have experience in quantitative genetics but I believe that time to first germination, and the percentage of germination have to be the variables to evaluate the level of physiological dormancy. Specifique literature about this subject as those to be used in references, I do not believe that will be easy to find, but the application of the theory, in my opinion, is available on the usual books. If available, I would like to read the responses.
Best regards,
José Walter
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