Cyclic Seed Dormancy in the Short-Lived Perennial Penstemon Palmeri

Abstract

Penstemon palmeri is a short-lived perennial herb that occupies early-successional habitats at mid altitude in the semi-arid south-western United States. Laboratory germination experiments with seeds from nine populations showed that most seeds were non-dormant at autumn temperatures (15°C), but a majority required light for germination. Moist chilling at winter temperatures (1°C) for 4 weeks induced secondary dormancy in about half the seedsn whilst moist incubation at superoptimal summer temperatures (30°C) for 2 weeks removed most primary and chilling-induced secondary dormancy, prevented the induction of dormancy by chilling, and reduced the proportion of light-requiring seeds (...)