Greenhouse and laboratory studies on the ecological life cycle of Dalea foliosa (Fabaceae), a federal endangered species

Jerry M. Baskin, Carol C. Baskin

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19 Scopus citations


Certain aspects of the seed and flowering stages of the ecological life cycle of the endangered species Dalea foliosa (Gray) Barneby were investigated under greenhouse and laboratory conditions. Seed dormancy in this species is due to a water-impermeable ('hard') seed coat that can be broken completely by mechanical scarification. Nondormant seeds germinated over a wide range of temperatures in both light and darkness. Soaking in concentrated sulfuric acid for 5 min, dry-heating at 80-100 °C for 25-80 min, and dipping in boiling water for 1 min broke dormancy in 52%, 50-77%, and 29%, respectively, of the seeds. Fire caused breakdown of the hard seed coat of seeds on the soil surface, but killed the seeds. Dormancy was not broken by freezing and thawing, soaking in absolute ethanol, or exposing seeds to simulated-summer followed by winter-stratifying temperatures. Seeds sown in a nonheated greenhouse and those in soil samples collected at a population site germinated over a several-year period, mostly in March and April. Thus, the species can form a persistent seed bank. No plants of D. foliosa flowered under a 10-h daily photoperiod (short day), whereas 100% of those given an 8-h photoperiod plus a 2-h night interruption (long day) flowered. One-hundred percent of the plants kept in a heated greenhouse all winter and 100% of those exposed to winter cold in a nonheated greenhouse flowered. Thus, D. foliosa is an obligate long-day plant that does not require exposure to low temperatures for bud break, shoot growth, or flowering. Management implications of this study are discussed.

Original languageEnglish
Pages (from-to)54-62
Number of pages9
JournalNatural Areas Journal
Issue number1
StatePublished - 1998


  • Dalea
  • Endangered plant species
  • Fabaceae
  • Hard seed-coat dormancy
  • Long-day plant

ASJC Scopus subject areas

  • Ecology
  • Nature and Landscape Conservation


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