Investigations on seed dormancy breaking mechanisms in wild medicinal plant species

Abstract:

A paradox runs through wild medicinal plant conservation: the very seed dormancy mechanisms that ensure species survival in unpredictable habitats become the main barrier when these plants need to be cultivated or propagated for research and restoration. This research tested five dormancy-breaking treatments—cold stratification (4°C, 30 days), gibberellic acid (GA₃, 500 ppm), acid scarification (conc. H₂SO₄, 10 min), smoke water (10% v/v), and potassium nitrate (KNO₃, 0.2%)—on six wild medicinal species collected from montane habitats in central Japan: Withania somnifera, Rauvolfia serpentina, Picrorhiza kurroa, Nardostachys jatamansi, Podophyllum hexandrum, and Gloriosa superba. Trials were conducted at the Kanto Institute of Agricultural Sciences, Tsukuba, from April to December 2023 using a factorial completely randomized design. The most effective treatment varied sharply among species: GA₃ gave the highest germination in R. serpentina (84.3%) and G. superba (67.1%); cold stratification was best for P. kurroa (81.7%) and N. jatamansi (74.3%); acid scarification was uniquely effective for P. hexandrum (88.7%); and smoke water performed best on W. somnifera (54.7%). These species-specific responses reflect fundamentally different dormancy classes—physical, physiological, and morphophysiological—that require matched treatments. The results provide a practical germination protocol for each species and advance understanding of dormancy ecology in Himalayan medicinal flora.