Physical dormancy in seeds of Dodonaea viscosa (Sapindales, Sapindaceae) from Hawaii

Abstract

Dormancy in seeds ofDodonaea viscosais due to a water-impermeable seed coat (physical dormancy, PY). Thus, mechanically scarified seeds imbibed water (c.95% increase in mass) and germinated to high percentages over a wide range of temperature regimes in both white light and darkness, whereas non-scarified seeds did not take up water. Dry heat at 80–160°C and dipping in boiling water for 1–60 s also broke dormancy in a high percentage of the seeds, and continuous far-red light was not inhibitory to germination. However, dry storage in the laboratory for >1 year did not overcome dormancy. Seeds made water-permeable by boiling imbibed water, and thus germinated, at a much slower rate than those made water-permeable by mechanical scarification. We suggest that boiling opened the ‘water gap’ in the seed coat (not yet described inSapindaceaebut present in other taxa with PY) and that water entered the seed only through this small opening, thereby accounting for the slow rate of imbibition and subsequent germination. Physical dormancy has now been shown to occur in seeds of this polymorphic, worldwide species from Australia, Brazil, Hawaii, Mexico and New Zealand. The low level of dormancy reported for seed lots ofD. viscosain China, India and Pakistan is probably due to collection of seeds before they dried to the critical moisture content for development of water-impermeability of the seed coat. Germination of non-dormant seeds over a wide range of temperatures and in white light, far-red (leaf-canopy shade) light and darkness are part of the germination strategy ofD. viscosaand of other taxa whose seeds have PY at maturity.

Overcoming the Physical Seed Dormancy in Bambara Groundnut (Vigna subterranea L.) by Scarification: A Seed Quality Study

“…4). These findings were congruent with these researches where mechanical method of breaking seed dormancy was also found most successful [19,25,26]. Mechanically scarified seeds reached 98.22% germination, which was within the range of 96%-100% seed germination reported by Baskin et al [25].…”

“…Mechanical scarification physically creates scars on the surface of the seed [21][22][23], while chemical (acid) scarification employs chemicals that soften and melt hard seed coat [24]. Mechanical scarification was presented as the most successful method in alleviating legume seed dormancy, achieving 96%-100% seed germination [25]. Uzun and Aydin [26] and Ibiang et al [19] agreed with these findings using sand paper.…”

Relationship between seed moisture content and acquisition of impermeability in Nelumbo nucifera (Nelumbonaceae)

“…1). There are numerous explanations for the insufficient drying of seeds in the field including (1) maternal environment having higher relative humidity during seed development (D'hondt et al 2010;Hudson et al 2015); (2) position of seeds in inflorescence possibly under leaf cover preventing direct exposure to sunlight resulting in inadequate drying (Taylor & Palmer 1979;Hay et al 2010); (3) age of mother-plant (Baskin & Baskin 2014) and (4) maturation stage at which the seeds were collected (Egley 1979;Baskin et al 2004;. Whatever the case, our results unequivocally illustrate that seeds of N. nucifera become impermeable only when moisture content drops to 10 %.…”

Requerimientos germinativos de enredaderas características del Chaco Serrano de Córdoba, Argentina

“…Por otro lado, aquellas especies a las cuales se les realizó una escarificación mecánica, por poseer cubiertas duras e impermeables al agua (dormición física sensu; Baskin & Baskin 1998), como I. purpurea, I. rubriflora, I. cairica, I. hieronymi, Centrosema virginianum, C. broussonetii y R. edulis, germinaron en un rango amplio de condiciones. Esto coincide con lo expresado por Baskin & Baskin (1998) y Baskin et al (2000, 2004 en relación a que las semillas que poseen dormición física germinan en amplias condiciones de luz y temperatura una vez que son escarificadas natural o artificialmente.…”