Research Accomplishment Reports 2007

The Role of Ethylene and Polyamine Interaction in the Time to Radicle Protrusion during Seed Germination

R.L. Geneve
Department of Horticulture

 

Project Description

Eastern gamagrass (Tripsacum dactyloides L.) is a warm-season perennial grass recommended for forage, wildlife, and conservation purposes in Kentucky and across its native range. However, widespread adoption of this species has been limited by poor germination and stand establishment. Less than adequate field stands have been attributed to a combination of seed dormancy and low seed quality. Stratification and fall planting has been recommended to promote natural release of dormancy, but dormancy may not be completely released.

The objectives were to investigate the interaction between germination temperature, stratification, ethylene and hydrogen peroxide on dormancy release in Eastern gamagrass. Stratification between 2 and 8 weeks as well as hydrogen peroxide application enhanced germination speed, total germination and reduced dormancy compared to untreated seeds. Stratification was more effective than hydrogen peroxide for dormancy release, but the impact on germination speed was similar. Germination temperature had a significant impact on germination percentage in both stratified and hydrogen peroxide treated seeds. The mechanism for hydrogen peroxide stimulated germination is not fully understood and it is not clear if hydrogen peroxide production plays a significant role during natural dormancy release. Germin (calcium oxalate oxidase) is an enzyme that converts calcium oxalate to calcium and hydrogen peroxide. It has been shown to be upregulated specifically in a number of grass species following dormancy release.

The putative gene for germin has been isolated from gamagrass and shows 95% homology to maize germin. In preliminary experiments, gamagrass germin mRNA was induced during germination suggesting that the hydrogen peroxide produced via germin action could have physiological importance for gamagrass germination. The seed lots used for this study demonstrate typical performance of commercially available Eastern gamagrass seed lots with a germination potential between 60-70% based on pre-treatment TZ viability assessment. Lab germination in untreated seeds was approximately 15%. These data suggest that germination temperature contributes to poor stands observed for stratified seeds sown under field conditions. Additional work will determine if there is a benefit for combining stratification and hydrogen peroxide treatments to decrease seed sensitivity to germination temperature and possibly improve stand establishment.

Impact

This research demonstrates the importance of seed bed temperature on germination and potential stand in Eastern gamagrass. Optimal germination occurred at 15/25, 15/35 or 20/30 C, where germination averaged approximately 64% for seeds stratified at 10 C for 6 weeks. In contrast, seeds germinated at constant 15 or 20 C germinated at less than 12% for stratified seeds. Growers could expect better stands waiting to sow stratified seeds later in the spring. This study also shows the potential for substituting hydrogen peroxide for stratification. The advantage to the grower is that hydrogen peroxide treatment takes less than 24 hours while stratification typically requires at least 4 weeks. This would allow more flexibility for the seed producer to supply seeds on short notice.

Publications

Geneve, R.L. (2008). Vigor testing for small-seeded horticultural crops. Acta Horticulturae 782:77-82.

Klein, J.D., Wood, L.A., and Geneve, R.L. (2008). Hydrogen peroxide induced germination in gama grass (Tripsacum dactyloides). Acta Horticulturae 782:93-98.

Geneve, R.L., Kester, S.T. and Pomper, K.W. (2007). Autonomous shoot production in pawpaw [Asimina triloba (L.) Dunal] on plant growth regulator free media. Propagation of Ornamental Plants 7:51-56.

Jayasuriya, K.M.G., Baskin, J.M., Geneve, R.L., and Baskin,C.C. (2007). Seed development in Ipomoea lacunosa (Convolvulaceae), with particular reference to anatomy of the water gap. Annals of Botany 100:459 - 470.

Jayasuriya, K.M.G., Baskin, J.M., Geneve, R.L., and Baskin,C.C. (2007). Morphology and anatomy of physical dormancy in Ipomoea lacunosa: Identification of the water gap in Convolvulaceae (Solanales). Annals of Botany 100:13-22.

Dutt, M. and Geneve, R.L. (2007). Time to radicle protrusion does not correlate with early seedling growth in individual seeds of impatiens and petunia. Journal of the American Society for Horticultural Science 132:423-428.

Geneve, R.L., Kester, S.T. and Pomper, K.W. (2007). Cytokinin habituation for autonomous shoot initiation in pawpaw (Asimina triloba). Acta Horticulturae 738:371-374.

Jayasuriya, K.M.G., J.M. Baskin, R.L. Geneve, and C.C. Baskin. 2007. Morphology, anatomy and ontogeny of the water gap in seeds of Ipomoea lacunosa (Convolvulaceae). Seed Ecology II, 2007. The 2nd International Society for Seed Science meeting on Seeds and the Environment. Perth, Australia.

Wood, L.A. and R.L. Geneve. 2007. Germination of Echinacea species is enhanced by ethylene. AOSA/SCST annual meeting. Cody, WY.

Geneve, R.L. 2007. Seed labs for plant propagation. HortScience 42:840-841.

Fulcher, A., R.L. Geneve, and J. Norikane. 2007. Photosynthetic characterization and water use efficiency in Hibiscus rosa-sinensis. HortScience 42:940.

Geneve, R.L. 2007. Using sequential digital imaging to study seed germination. Fifth International Conference on the Propagation of Ornamental Plants. Sofia, Bulgaria.

Stolz, S., Beale, J., Dougherty, L., Long, S., Fulcher, A., and Geneve R. (2007). Biofungicide and conventional control of Rhizoctonia solani in a container production system. Proceedings of Southern Nursery Association Research Conference.