Deep Simple Morphophysiological Dormancy in Seeds of Adonis amurensis Regel & Radde Native to Korea

The Ranunculaceae is a family reported to have morphological dormancy (MD) or morphophysiological dormancy (MPD), with underdeveloped embryos. There are few reports on seed dormancy and germination in Adonis amurensis. This research was performed to determine the type of dormancy for A. amurensis seeds and its dormancy-breaking requirements. Phenology in field conditions, temperature requirements, and GA₃ treatment for embryo growth and germination were evaluated. Seeds had underdeveloped embryos that were about 8% of the length of fully matured seed. In phenological study, the embryos grew very little from June until September, while rapid growth was observed from October until November. Embryo growth was completed from late November until early December. Seeds sown on the field soil started to germinate from 24 February and 50% of them germinated by 17 March. In laboratory experiments, embryo growth occurred only in two sequences of simulated thermoperiods (25/15 °C→5 °C and 25/15 °C→15 °C), whereas embryos in constant temperatures (25 °C and 5 °C) grew very little. Therefore, it seems that a warm followed by a cold temperature sequence is essential for embryo growth. The GA₃ increased embryo growth in the seeds, but only 1% to 6% of them germinated at 5 °C or 25/15 °C with 100 mg·L^-1. To test low temperature requirements for germination after embryo maturation, the seeds in the field were transferred monthly to a growth chamber from 18 November to 14 February. In seeds transferred on 18 November, GA₃ was treated to determine whether it could substitute for cold requirements. When transferred to laboratory on 18 November, the seeds germinated 20% and 83% without and with GA₃, respectively. However, ≥ 82% of them germinated without GA₃ when the seeds were transferred from 5 January. Based on these results, seed dormancy of  A. amurensis can be broken through warm followed by cold temperature sequence and classified as having deep simple morphophysiological dormancy (MPD).