Seed Germination Timing Patterns in Intermountain Penstemon (Scrophulariaceae)

Abstract

Regulation of seed germination timing is an important component of population persistence, especially for short-lived plants in seasonal environments with unpredictable year-to-year weather variation. Seed germination patterns were examined in the laboratory for seeds from 135 populations belonging to 38 species and 13 sections of the genus Pensternon (Scrophulariaceae), from habitats ranging from warm desert to alpine tundra. Seeds of most species were dormant at dispersal and required a period of moist chilling to become germinable. Response to chilling was related to probable chilling duration at the collection site. Populations from habitats with severe winters produced seeds with long chilling requirements, while those from habitats with mild winters produced seeds with short chilling requirements. Populations from midelevation habitats produced seeds with intermediate chilling requirements but with a sizeable fraction whose dormancy was not broken by chilling of any length. Another pattern observed mostly in warm desert populations was little primary dormancy at autumn temperatures combined with induction of a fraction into secondary dormancy by short chilling. Species with a wide habitat range included populations with contrasting germination patterns. Parallel habitat-correlated patterns were observed in different sections. Most species showed germination patterns that combined predictive mechanisms with potential for carryover of a persistent seed bank. Results of common garden experiments suggested that germination differences had a strong genetic basis both among populations and among plants in a population. Adaptive radiation in the genus Penstemon has thus included the evolution of habitat-specific germination timing strategies in multiple lineages within the genus.

Differential performance of reciprocal hybrids in multiple environments

“…Infestations of fungus gnats and snails also contributed to mortality for all types of seedlings, with the number of seedlings that died during this period similar regardless of mother, father or the interaction ( P > 0.10 for all tests). Most species of Penstemon do have prolonged dormancy that is fairly difficult to break, even with cold stratification and gibberellic acid (Baskin & Baskin 1998), and alpine Penstemon can require longer periods of cold stratification than Penstemon from lower elevations (Meyer et al . 1995).…”

Assessing Potential Seed Transfer Zones for Five Forb Species from the Great Basin Floristic Region, USA

“…The remaining 10 dishes were placed in winter germination conditions for eight weeks, at which point two petri dishes were moved every two weeks from winter to spring conditions to create each winter length treatment. All replicates were monitored three times per week, with any germinants (radicle emergence >1 mm) recorded and discarded following Meyer et al (1995). Filter paper was kept moist throughout the study with regular application of deionized water.…”

Using hydrothermal time concepts to model seed germination response to temperature, dormancy loss, and priming effects in Elymus elymoides

“…The plotted regression lines have a common slope derived from analysis of covariance (ANCOVA) but have significantly different y-intercepts (see Table 2 for details). The T b value of 0ЊC was characteristic of many species of Intermountain North America, where germination under snow cover in winter is a principal mode of seedling establishment (Meyer et al, 1989;Meyer and Monsen, 1991;Meyer et al, 1995). Horizontal dotted lines represent Y b (50) values for fully after-ripened seeds.…”