An efficient method of propagation of Podophyllum hexandrum: an endangered medicinal plant of the Western Himalayas under ex situ conditions

Abstract

This study shows an effective but simple method of conserving characterized populations and elite clones through vegetative propagation and genetic diversity through seeds in Podophyllum hexandrum (family Berberidaceae). Seed dormancy has been considered to be a major constraint in these seeds and most of the earlier reports recommended dormancy-breaking pretreatments such as chilling, gibberellic acid (GA₃), etc. However, seeds of the 14 accessions that we tested exhibited no dormancy and hence did not require any pretreatments. Besides accession, collection of seeds with high moisture content could be one of the reasons for lack of dormancy. Thus, we propose germination of seeds (while they still retained moisture) in sand at 25°C for high and reproducible results within a shorter period of time compared with earlier reports. Hypocotyl dormancy is known to considerably delay plant establishment and hence en masse propagation by preventing the emergence of functional leaves for up to 11–12 months. Manual removal of cotyledonary leaves, being labor and time intensive, is not a feasible method for large-scale seedling establishment. However, in this study, we showed that GA₃ at 200 ppm can alleviate hypocotyl dormancy besides reducing the time taken for true or functional leaf emergence. Treatment of cotyledonary leaves of 1 week-old-seedlings with 200 ppm GA₃ resulted in true or functional leaf emergence within 7 days, and the resultant plants were also more vigorous than the ones obtained from manual removal of cotyledonary leaves. The study helped advance the establishment of seedlings by one growing season (almost 1 year).