Double Dormancy in a Threatened Western Himalayan Population of Polygonatum cirrhifolium (Maha-Meda): Response to Ambient Storage and Pre-treatments

Polygonatum cirrhifolium (Wall.) Royle (Asparagaceae), commonly known as Maha-meda, belongs to Astavarga, a distinct group of medicinal herbs, used in specific formulations in Ayurveda, highly prized for its aphrodisiac, rejuvenating and tonic effects. The species has an endangered population status; thus, propagation/conservation efforts are required. However, the seeds of a population from Kullu (Himachal Pradesh) in Western Himalaya exhibited ‘double dormancy’ characterized by a delayed radicle emergence (started after 40 days) followed by epicotyl dormancy (no epicotyl emergence until 92 days). The latter imposes an added hindrance for seed-based propagation of the species. Therefore, current investigation was undertaken with an aim to achieve better germination and seedling growth using various seed pre-treatments. GA 3 and cold stratification significantly stimulated the germination albeit the epicotyl and radicle emergence were affected differentially; the former being more responsive than the latter. During a 24-month period of ambient storage, seed viability and vigour were maintained as such until 12 months but declined steadily thereafter. The seed longevity was found to be more than 24 months. Although the seeds remained dormant during the storage period, the requirement of warm stratification for dormancy alleviation was significantly reduced possibly as a metabolic consequence of the after-ripening processes. The status of epicotyl dormancy and its response to the stated pre-treatments were not considerably altered due to seed storage. In spite of double dormancy, the seed viability, longevity, response to pre-treatments and seedling survival observed were reasonably high and hold the potential for successful seed-based propagation of species.