WATER GAP COMPLEXES IN PHYSICALLY DORMANT SEEDS
Geneve, R.L.1, Baskin, C.C.2, 3, Baskin, J.M.3, Jayasuriya, K.M.G.G.4 and Gama-Arachchige, N.S.4
1Department of Horticulture, University of Kentucky, Lexington, Kentucky USA 2Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky USA
3Department of Biology, University of Kentucky, Lexington, Kentucky USA
4Department of Botany, University of Peradeniya, Peradeniya, Sri Lanka
Contact: Robert Geneve, email@example.com
Physical dormancy occurs in at least 16 angiosperm plant families and is caused by water-impermeable palisade cells in seed coats or fruit coverings. The breaking of physical dormancy involves disruption or dislodgement of water-gap structures causing the seeds/fruits to become water permeable. The water-gap region is a morphologically distinct area of the seed or fruit coat forming a water gap complex. The location, anatomy, morphology and origin of water gaps can differ between and even within families. Water-gap structures sense environmental conditions to allow seeds with physical dormancy to become permeable just prior to the commencement of conditions favorable for germination and plant establishment. There are three basic water gap morphologies characterized by the way the water gap opens. These can be organized as Type I, II, and III water gaps. In Type I water gaps, specific cells pull apart to form a surface opening, while in Type-II water gaps a portion of the surface structure is pulled back from adjacent cells to open the water gap. Type-III water gaps are the least common type and have a circular, plug-like structure that is dislodged to permit water entry. In addition, seeds may have water gap complexes that are either simple or compound depending the whether there is only a single primary water gap structure involved in dormancy release or whether there is an additional secondary water gap structure that opens permitting water entry.