Ecophysiology of seed dormancy and germination in the alpine-subalpine medicinal plant species Sinopodophyllum hexandrum (Royle) T. S. Ying

We investigated the dormancy and germination characteristics of seeds of Sinopodophyllum hexandrum, an endangered medicinal plant of the high altitude Himalaya-Hengduan Mountains in China. The embryo is underdeveloped and germination is cryptogeal. Fresh seeds germinated well (> 70 %) at 20, 25, and 25/15 degrees C in light but not at <= 15 degrees C and to higher percentages in light than in dark. With two exceptions after-ripening did not significantly improve germination in light but did so in darkness. GA3 increased germination percentage of fresh seeds at 15/5 degrees C, and cold stratification increased final germination percentage, germination rate (speed), and widened the temperature range for germination from high to low. Thus, after dormancy release seeds germinated over a wide range of constant and alternating temperatures, regardless of light conditions. A portion of the fresh seeds germinated at high temperatures without treatment, but after cold stratification seeds also germinated at low temperatures. These dormancy/germination characteristics prevent seeds from germinating after dispersal in autumn when temperatures are low but allow them to germinate after snowmelt in spring. We conclude that the seeds of S. hexandrum have cryptogeal morphophysiological dormancy with a dormancy formula of C1aBpa. Application of our results to ex situ propagation of plants from seeds of this endangered medicinal species is discussed.