Overcoming dormancy in Helianthus annuus achenes and Echinacea purpurea seed
Smith, Crystal Lea
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In this study, seed quality factors of Helianthus annuus L. and E. purpurea were investigated as well as the effects of carotenoid inhibiting herbicides on their germination ability. The intent was to find a method of overcoming seed dormancy without compromising shelf life. Viability testing for H. annuus resulted in a germination percent of 57% and a germination percent of 63% for E. purpurea. Seed quality testing focused on size, density, Hull:Embryo (H:E) and age. Carotenoid inhibitors were applied to the seed as a soak for varying lengths of time and at differing concentrations to determine their effectiveness on overcoming seed dormancy. Volume of E. purpurea seeds and H. annuus achenes increased with increasing density. H:E of H. annuus increased with increasing achene density. The surface area of a H. annuus achene hull can be used to predict the surface area of an embryo. For H. annuus, between H:E, surface area and density, density appears to be the best predictor of germinability. Age had more of an impact on germinability of E. purpurea seed than density. Carotenoid inhibitor treatments alone were not sufficient in overcoming dormancy in H. annuus. Discoloration of treated seedlings that germinated showed signs of herbicide damage indicating that the herbicide is able to penetrate the seed coat. Further study is needed. Germination rate and percent were improved for E. purpurea seed treated with fluridone and norflurazon at concentrations between 0.005 g/L and 0.020 g/L at soak times between 4 to 8 hours.