Ethylene as a possible cue for seed germination of Schoenoplectus hallii (Cyperaceae), a rare summer annual of occasionally flooded sites

Abstract

The purpose of our research was to determine why seeds of Schoenoplectus hallii germinate only in some wet years. Seeds mature in autumn, at which time they are dormant. Seeds come out of dormancy during winter, if buried in nonflooded, moist soil, but they remain dormant if buried in flooded soil. Nondormant seeds require flooding, light, and exposure to ethylene to germinate. One piece of apple in water (1/12 of an apple in 125 mL of water in a glass jar for a depth of 5 cm) or a 1-mol/L solution of ethephon elicited very similar (high) germination percentages and vigor of seedlings. Apple, which was shown to produce ethylene in the air space of the jar, was used in a series of experiments to better understand germination. Seeds germinated to 72% if apple was removed from the water after 1 d of incubation, and they germinated to 97% if seeds were washed and placed in fresh water after 3 d of exposure to apple. No seeds germinated in control with no apple. Seeds incubated in apple leachate for 5 d and then transferred to filter paper moistened with distilled water germinated to 90%. Minimum depth of flooding in apple leachate (no soil in jars) for optimum germination was Ն3 cm. Buried seeds of S. hallii exhibited an annual conditional dormancy/nondormancy cycle. Regardless of the month in which seeds were exhumed, they germinated to 59-100% in light in water with apple at daily alternating temperature regimes of 25Њ/15Њ, 30Њ/15Њ, and 35Њ/20ЊC, but germination at 20Њ/10ЊC (and to some extent at 15Њ/6ЊC) tended to peak in autumn to spring. Thus, seeds can germinate throughout the summer if flooded (ethylene production) and exposed to light. An ethylene cue for germination serves as a ''flood-detecting'' mechanism and may serve as an indirect signal that water is available for completion of the life cycle and competing species are absent.

Nitric oxide, hydrogen cyanide and ethylene are required in the control of germination and undisturbed development of young apple seedlings

“…Such a response suggests that ethylene at the applied concentration is necessary for cotyledon and hypocotyl growth, while the same concentration of ethylene is too high to remove the block of radicle growth. A similar result was also reported in Schenoplectus hallii (Baskin et al 2003). Seedlings developed from seeds treated with low concentrations of ethephone had normal leaves and roots, while higher concentration of ethephone resulted in development of ''seedlings'' with normal leaves but stunted or no roots (Baskin et al 2003).…”

“…A similar result was also reported in Schenoplectus hallii (Baskin et al 2003). Seedlings developed from seeds treated with low concentrations of ethephone had normal leaves and roots, while higher concentration of ethephone resulted in development of ''seedlings'' with normal leaves but stunted or no roots (Baskin et al 2003). Promotion of seedling shoot growth by ethylene was also reported for barley (Locke et al 2000).…”

Schoenoplectus hallii, S. saximontanus, and the Putative S. hallii X S. saximontanus Hybrid: Observations from the Wichita Mountains Wildlife Refuge and the Fort Sill Military Reservation 2002 - 2010

“…We observed culms of S. saximontanus, S. hallii, and the putative hybrid flowering and producing viable fruit from July through mid-October, indicating that they are able to do so anytime during the growing season when conditions for germination and growth are favorable (Baskin et al 2003). At all four sites where S. hallii and S. saximontanus occur in mixed populations, the putative hybrid was present (Medicine Tank, Quanah Parker Lake, Zania Pond, and Pottawatomie Pond) (see Table), suggesting that hybridization is a definite possibility in any mixed population.…”

Sand verbenas (Abronia spp., Nyctaginaceae) germinate in response to ethylene

“…The amplitude of the difference between the two temperatures is relatively small, probably less than that experienced in the surface layers of a sandy soil, and less than the amplitude used in most alternating temperature treatments (e.g., 15 1C; Baskin et al, 2003). Furthermore, the minimum and maximum temperatures were less extreme than those temperatures implicated in ethylene-mediated germination responses (Van Assche and Van Nerum, 1997; Whitehead and Sutcliffe, 1995).…”

“…Any achenes not germinated after 1.5 months were subjected to a tetrazolium test for viability according to standard procedures (International Seed Testing Association, 1985). Once ethephon was shown to promote germination, the effect of placing slices of ripe golden delicious apples, each approximating 1/12 of an apple, in the Petri dishes as a source of ethylene was tested (Baskin et al, 2003). Germination percentages were arcsine transformed prior to statistical analysis with the STATGRAPHICS Centurion XV statistical package (StatPoint Inc., VA, USA).…”