Submitted to: Southern Pasture and Forage Crop Improvement Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 1, 2001
Publication Date: April 1, 2001
Interpretive Summary: Eastern gamagrass is recognized as one of the most productive native grasses in North America; however, its potential has not been reached due to difficulty in establishment from seed. We investigated the seed germination and dormancy in 'Iuka' and 'Pete' eastern gamagrass. Seed germination was affected only by caryopsis weight. Seed dormancy of the two cultivars studied was attributed to the fruit case. Under natural conditions, a caryopsis must first overcome the integrity of the cupulate fruit case to germinate. Light, alternating temperatures, freezing and thawing, fire, rodents, and soil microorganisms to name a few, may be involved in the decay of the fruit case. Given that the force required to open the cupulate fruit case did not significantly change after a 4-wk moist prechill at 0 to 5 oC, late winter plantings would be adequate if soil temperatures and moisture were favorable. Planting prechill- conditioned seed in early spring would be an alternative if soil temperatures and moisture were unfavorable in late winter.
Technical Abstract: Stand establishment of eastern gamagrass is slow and can take three years before a full stand is attained. Early research focused on determining a pure seed unit in hopes to improve seed quality. Identification of the pure seed unit, i.e., a pure seed unit or intact spikelet is a caryopsis within a cupulate fruitcase, is impossible to do visually. Air and floatation separation have been used to successfully improve seed quality. Research continued with studies on the germination of the intact spikelet with hopes to improve germination. Several chemical agents have been used unsuccessfully to stimulate germination. Several studies have shown that removal of the caryopsis from the cupulate fruitcase significantly improves its germination, however, specialized equipment needed to commercially hull eastern gamagrass without significantly damaging the caryopsis has not yet been developed. Our studies have shown for 'Pete' and 'Iuka' eastern gamagrass that caryopsis weight affects germination, the cupulate fruitcas acts as a barrier to germination (mechanical dormancy), and the force required to open the fruit case does not change significantly after 4-wk of moist prechill. Given the last fact, the effects of prechill may largely involve predisposing the cupule to subsequent deterioration from other factors, such as light, alternating temperatures, freezing and thawing, fire, rodents, and/or soil microorganisms. Thus, late winter seedings would be adequate if soil temperatures and moisture are favorable or seeding prechill-conditioned seed in early spring would be an alternative if soil temperatures and moisture are unfavorable in late winter.