Encouraging of embryo development and seed germination in actaea racemosa l. By gibberellic acid

Abstract

Actaea racemosa L. (syn. Cimicifuga racemosa (L.) Nuttal) or black cohosh is a perennial plant of the buttercup family (Ranunculaceae) growing wild in deciduous forests of North America. Because mature seeds of A. racemosa have a rudimentary embryo and exhibit deep simple epicotyl morphophysiologi- cal dormancy, germination is a long-lasting process requiring warm-cold stratification. The study has been conducted in 2015-2016 and aimed to develop an efficient germination protocol. For imbibition, graded seeds (1.22-2.5 mm in length) were incubated in tap water or aqueous gibberellic acid solution for 12 hours. The imbibed seeds were kept in darkness at 23°C for 4 weeks (warm phase) followed by 4 weeks of incubation at 14°C or 7°C (cold phase) in darkness or light. Most embryos in mature seeds were developed to the heart stage. They reached after 4 weeks of warm phase the torpedo stage. During the following cold phase, the embryo development was more pronounced in seeds imbibed in gibberellic acid. This promoting effect of gibberellic acid showed a dose-effect response. Application of 2 g L-1 gibberellic acid resulted in germination of around 60% seeds after 4 weeks of cold phase while 1 g L-1 gibberellic acid caused germination of up to 20% seeds. Due to the application of 2 g L-1 gibberellic acid to the imbibition solution the germination of most seeds was possible after 8 weeks warm-cold stratification. The observation of the embryo development proved the promoting effect of gibberellic acid, especially during the cold phase.