Primary physiological dormancy is a basic concept for courses that emphasize general plant propagation or specific courses in seed biology or technology. Primary seed dormancy is a condition where seeds will not germinate even when the environmental conditions (water, temperature, light, and aeration) are permissive for germination (Hartmann et al., 2011). Not only does seed dormancy prevent immediate germination, it also regulates the time, conditions, and location where germination will occur. In nature, different kinds of dormancy have evolved to aid the survival of a species by programming germination for particularly favorable times in the annual seasonal cycles. The major type of seed dormancy seen in temperate plant species is classified as primary, endogenous, physiological dormancy (Baskin and Baskin, 1998). Therefore, the purpose of this manuscript is to describe an easily performed laboratory experiment suitable for undergraduate courses (both on campus and for distance learning), which demonstrates the mechanism for dormancy release in seeds with endogenous, physiological dormancy.
Eastern redbud (Cercis canadensis) is a good model system to illustrate dormancy maintenance and release in seeds with physiological dormancy because there is available published research concerning eastern redbud dormancy to support student laboratory reports (Geneve, 1991; Jones and Geneve, 1995) and the seeds are widely available commercially or from local collections. Additionally, eastern redbud seed is fairly large and easy for students to manipulate during laboratory.
The learning outcomes for this laboratory exercise are that a student will understand the role seed coverings play in maintaining seed dormancy, be able to explain the concept of embryo growth potential and the contribution of growth potential to seed dormancy release, be able to describe the possible roles plant hormones play in seed dormancy maintenance and release, be able to recognize different tissue types in a seed, and have an appreciation for the interaction of these tissues related to seed dormancy.
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Baskin, C.C. & Baskin, J.M. 1998 Seeds, ecology, biogeography, and evolution of dormancy and germination. Academic Press, New York, NY
Finch-Savage, W.E. & Leubner-Metzger, G. 2006 Seed dormancy and the control of germination New Phytol. 171 501 526
Hartmann, H.T., Kester, D.E., Davies, F.T. Jr & Geneve, R.L. 2011 Hartmann and Kester’s plant propagation: Principles and practices. 8th ed. Prentice-Hall, Englewood Cliffs, NJ
Jones, R.O. & Geneve, R.L. 1995 Seedcoat structure related to germination in eastern redbud (Cercis canadensis L.) J. Amer. Soc. Hort. Sci. 120 123 127
Kucera, B., Cohn, M.A. & Leubner-Metzger, G. 2005 Plant hormone interactions during seed dormancy release and germination Seed Sci. Res. 15 281 307