Submitted to: Crop Science Society Of America
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2000
Publication Date: September 1, 2001
Technical Abstract: Eastern gamagrass [Tripsacum dactyloides (L.) L.] is an important native rangeland species and improved pasture grass. Pasture establishment is slow, however, and can take three years before a full stand is attained. The objectives of this study were to determine the caryopsis size distributions, the germination of sized caryopses, the role of the cupulate fruit case in seed dormancy, and the force required to open the cupulate fruit case. Caryopses of 'Iuka' and 'Pete' gamagrass were extracted from the cupulate fruit case by hand, individually weighed and separated into five size classes and germinated. Differences in percentage 7- and 14-day actual germination and total potential germination were attributed only to caryopsis size. To test the role of the cupulate fruit case, an artificial fruit case (banded) was fashioned from an extruded plastic hexagonal tube and a caryopsis placed inside. Unbanded caryopses averaged 44% germination compared to 6% for the banded caryopses. For these cultivars, seed dormancy is likely mechanical in nature. Given that the force required to open the fruit case does not change significantly after 4-wks of moist prechill, other factors, such as light, alternating temperatures, freezing and thawing, fire, rodents, and soil microorganisms may be involved in the slow decay of the fruit case.