Eastern gamagrass would be an excellent pasture grass, but producers have difficulty establishing a stand. Various techniques for solving the dormancy problems in eastern gamagrass were investigated and analyzed

Gibson, Lance R.

Knapp, Allen D.

Eastern gamagrass would be an excellent pasture grass, but producers have difficulty establishing a stand. Various techniques for solving the dormancy problems in eastern gamagrass were investigated and analyzed.</p

Gibson, Lance

Knapp, Allen

Digital Repository @ Iowa State University (ISU)

Competitive Grant Report 01-19 Development of dormancy breaking mechanisms in eastern gamagrass Abstract: Eastern gamagrass would be an excellent pasture grass, but producers have difficulty establishing a stand. Various techniques for solving the dormancy problems in eastern gamagrass were investigated and analyzed. Question & Answer Q: What can be done to affect dormancy in eastern gamagrass? A: If gibberellic acid (GA3) is added to stratification procedures for eastern gamagrass, it would reduce the amount of time needed to completely break dormancy to as little as three weeks from the six weeks that are currently needed. The seed resulting from these procedures would germinate more rapidly providing the potential for quicker stand establishment.  Seed stratification with GA3 would be important for spring planting because stratified seed is required and eastern gamagrass is sensitive to soil drying that frequently occurs in late spring. This research has demonstrated through other studies that full eastern gamagrass stands are best achieved with fall planting. Stratification is not required for fall planting because winter conditions easily break eastern gamagrass seed dormancy in Iowa. Background Eastern gamagrass is a highly productive and palatable native, warm-season, perennial grass with great potential for use in forage systems and soil and water conservation efforts.  It is indigenous to the eastern, southern, and central United States and was almost eliminated from range sites because of livestock preference for its foliage and heavy grazing pressures. There is renewed interest in the potential value of gamagrass as a forage crop, a possible silage replacement for corn on marginal land, in grass hedges for control of soil erosion, and wildlife habitat. Unfortunately, it is difficult to establish a stand of gamagrass because of extensive seed dormancy. The viable gamagrass seed will not germinate even under suitable moisture, temperature, and oxygen conditions. Under normal conditions, dormancy can positively impact species survival and is controlled by complex interaction of environmental factors. However, the dormancy is detrimental during the establishment year for domestic gamagrass production. Commercial gamagrass producers chill the wet seed for six weeks, a process called stratification. The procedure Eastern gamagrass plants. Principal Investigator: Co-Investigator: Budget: Lance R. Gibson Allen D. Knapp $19,510 for year one Agronomy $20,199 for year two Iowa State University $21,500 for year three Volume 13 (2004) • Leopold Center Progress Report • page 16 results in highly variable germination and is less than ideal. Then one wishing to plant the seed receives wet seed that must be refrigerated until planted and deterio-rates rapidly. Improvements in the dormancy-breaking process would aid gamagrass management and production. The goal of this project was to develop a priming protocol for eastern gamagrass that practically breaks seed dormancy, increases germination rate and speeds seedling development. The improved seed would germi-nate rapidly upon planting and quickly establish a fast growing, uniform stand. Approach and methods Gibberellic acid (GA3), a plant growth hormone known to break seed dormancy and speed germination, was assessed for its ability to enhance germination in eastern gamagrass seed in combination with two priming tech-niques—solid matrix priming and stratification. Solid matrix priming—A standard germination test with three replicates was done on both cold, moist stratified and stratified seed in 2000 and 2001. Germination was counted at seven, 14, 21, and 28 days. Conditioning systems were developed for three solid carrier materials (Agro-Lig, Micro Cel E, and Vermiculite #5) stored in airtight containers. Water was added to the carriers and 12 different carrier/water mixtures were created. Seeds were added to the various carrier mixtures and condi-tioned for varying intervals.  In some instances, GA3 solutions were added to conditioning systems using the two water potentials in each material category that provided the greatest seed water content without causing seed germination in the first seven days of priming. The moisture content of the seed and the water potential of the carrier system were tested at the conclusion of a week’s conditioning period. The percent germination, abnormal seedlings, dead seeds, and dormant seeds were calculated after adjusting for the failed seeds in each treatment. Stratification with gibberellic acid—Two seed lots used for this study were stored with blotter paper saturated with GA3 or de-ionized water. Then seeds were placed in cold temperatures for a one- to seven-week stratification period. A box for each imbibition treatment was removed from the cold room at weekly intervals to test the effect of stratification period length on germination. Fifty dry (unimbibed) seeds from the original lot were randomly sampled for germination testing as well. Results and discussion Solid matrix priming—Seed moisture content varied with water potential and duration of conditioning in Micro Cel E and in Vermiculite #5. Full seed hydration took longer in Micro Cel E than in Vermiculite #5 at similar water poten-tials and final seed water contents. The hydrophobic nature of the Agro-Lig mixture resulted in inconsistent hydration of the material and the seed. The conditioning systems were continued for 28 days to determine if seed germination occurred in any of the various water potential systems. No germination occurred in Agro-Lig during this period or in Micro Cel E and Vermiculite #5 until 14 days after conditioning began. Since eastern gamagrass reaches its maximum moisture content at seven days with no visible germination, this amount of time appeared to be sufficient for conditioning seeds within the range of water potentials used in this study. Solid matrix priming with gibberellic acid—Actual water potentials attained were close to the intended water potentials for all three carriers. The results suggested that Agro-Lig was not as suitable a carrier for use in solid matrix priming systems for eastern gamagrass as Micro Cel E and Vermiculite #5. The seeds primed in Agro-Lig had lower levels of germination and higher levels of dead seed than were found in the other two carriers. When averaged for all three carriers, GA3 promoted seed germi-nation and resulted in greater numbers of normal and abnormal seedlings. Priming eastern gamagrass seed in water did not increase seed germination levels above those of unprimed and unstratified seed in this lot. The interaction of germination time and priming solution effects removed. Gamagrass seed from fully intact cupule to cupule Volume 13 (2004) • Leopold Center Progress Report • page 17 on the amount of seed germination was not significant for any of the carrier materials, indicating that addition of GA3 did not accelerate the rate of seed germination. Stratification with gibberellic acid—Seed treatment, seed lot, and stratification duration influenced the amount of seed germination at the conclusion of the 28-day germina-tion period. Germination of both GA3 and water-treated seeds peaked at four weeks of stratification exposure and was maintained at these levels through the remaining four weeks of stratification. Field studies are required to determine if combinations of GA  and stratification could3increase field establishment success. Conclusions The project was partially successful in generating a practical method of breaking seed dormance and enhanc-ing seed quality in eastern gamagrass. Of the methods tested, the addition of GA3 to stratification was the most practical option for producing seed that germinates more rapidly. Stratification with GA3 has the potential to reduce the stratification time needed to break most seed dor-mancy in eastern gamagrass to as little as three weeks. It is unlikely that solid matrix priming with GA3 would be adopted as a practice for improving eastern gamagrass seed because it only slightly increased seed germination. Solid matrix priming was effective for controlling seed hydration in eastern gamagrass and should be investi-gated in combination with other known seed dormancy breaking practices. For more information, contactLance Gibson, 1126 Agronomy, Iowa State University, Ames,Iowa  50011; (515) 294-2143, e-mail lgibson@iastate.eduEastern gamagrass plants June 2002. Impact of results The addition of GA3 to stratification proved to be the most practical option for hastening seed germination. As a next step, solid matrix priming, GA3, and stratification should be tested in combination for their ability to more rapidly break seed dormancy than stratification alone. Additional study also should focus on combining solid matrix priming with other seed breaking mechanisms such as hydrogen peroxide. Ease of handling, storage, transportation, and use will require that eastern gamagrass be dried after it has been primed. Methods for drying the seed after stratification and solid matrix priming while retaining the seed’s ability to germinate will need to be developed. Education and outreach Three journal articles and a thesis resulted from this project. Presentations on seed dormancy of eastern gamagrass were given at the Native Seed Quality Workshop (2003) and the 2002 Crop Science Society of America meeting. Volume 13 (2004) • Leopold Center Progress Report • page 18 

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Development of dormancy breaking mechanisms in eastern gamagrass

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Development of dormancy breaking mechanisms in eastern gamagrass

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