title: Dormancy-breaking and germination requirements for seeds of Symphoricarpos orbiculatus (Caprifoliaceae).
abstract: Fruits (drupes) of Symphoricarpos orbiculatus ripen in autumn and are dispersed from autumn to spring. Seeds (true seed plus fibrous endocarp) are dormant at maturity, and they have a small, linear embryo that is underdeveloped. In contrast to previous reports, the endocarp and seed coat of S. orbiculatus are permeable to water; thus, seeds do not have physical dormancy. No fresh seeds germinated during 2 wk of incubation over a 15°/6°-35°/20°C range of thermoperiods in light (14-h photoperiod); gibberellic acid and warm or cold stratification alone did not overcome dormancy. One hundred percent of the seeds incubated in a simulated summer → autumn → winter → spring sequence of temperature regimes germinated, whereas none of those subjected to a winter → spring sequence did so. That is, cold stratification is effective in breaking dormancy only after seeds first are exposed to a period of warm temperatures. Likewise, embryos grew at cold temperatures only after seeds were exposed to warm temperatures. Thus, the seeds of S. orbiculatus have nondeep complex morphophysiological dormancy. As a result of dispersal phenology and dormancy-breaking requirements, in nature most seeds that germinate do so the second spring following maturity; a low to moderate percentage of the seeds may germinate the third spring. Seeds can germinate to high percentages under Quercus leaf litter and while buried in soil; they have little or no potential to form a long-lived soil seed bank.
authors.affiliation: School of Biological Sciences, University of Kentucky, Lexington, Kentucky 40506-0225 USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Hidayati
authors.forename: J M
authors.initials: JM
authors.lastname: Baskin
authors.forename: C C
authors.initials: CC
authors.lastname: Baskin