Methods for enhancing seed germination of eastern gamagrass
Eastern gamagrass (Tripsacum dactyloides, L.) is a perennial grass species that is highly productive, has sufficient forage quality, and can be used to reduce soil erosion from croplands, but is grown on a limited land area in the U.S. Problems with stand establishment have been a major restraint to its adoption. These establishment problems in eastern gamagrass result, at least partially, from a very strong seed dormancy. The seed dormancy mechanisms of this species are not yet fully understood. A better understanding of the inhibitors to gamagrass seed germination and development of methods for breaking the seed dormancy could lead to management strategies that result in more widespread use of this promising warm-season grass. This thesis reports methods tested for breaking seed dormancy in eastern gamagrass and new insight into the dormancy mechanisms in this species. In one study, eastern gamagrass seed germination after treatment with a combination of two known germination promoters - moist, pre-chilling and gibberellic acid (GA) - was compared to germination after moist, pre-chilling alone and no pre-chilling. GA3 provided an increase in rate of germination but not overall germination and was able to reduce dormant seed in these lots from 73% to 3%. In a second study, solid matrix priming methods for eastern gamagrass seed were developed for three solid materials. Water uptake into eastern gamagrass seeds was determined at various water potentials in each material. Solid matrix priming systems were then designed to hydrate eastern gamagrass seed to levels that would stimulate the early phases of germination while restricting advancement into later stages of germination. Germination of eastern gamagrass seed was observed after 7 d of conditioning in each of the three solid materials hydrated at either high or low water potentials with water, buffered GA3 solution, unbuffered GA3 solution, or buffer solution alone to determine if any of these systems could break dormancy. GA3 was able to significantly increase the germination of eastern gamagrass compared to water treated seed, but only to levels of 20% of all live seed.