S05 - Session P4 - Germination characteristics and cryopreservation of Paeonia emodi Wall. ex Royle seed

Authors: Wan Yingling *, Min Zhang, Hao Zhou, Yan Liu

Paeonia emodi Wall. ex Royle has a very narrow distribution and only exists on both sides of the Himalayas. It is of vital ornamental and breeding value because of the excellent characteristics of up to 150 cm stem height and 3 n 4 numbers of terminal or axillary white flowers. However, it has not been developed and utilized to date, due to the limited existing numbers, difficulties in ex situ cultivation and seed germination, which needs long time to germinate. To preserve and utilize the resources, in this study, we aimed to explore seed dormancy breaking method of P. emodi , analyze physiological response to cold during long period in epicotyl dormancy breaking, and explore seed cryopreservation technology procedure. The results are as follows. (1) Seed viability of the naturally harvested P. emodi was directly proportional to the water content, and seed vitality decline along with water content decrease was mainly caused by cell membrane lipid peroxidation happening. (2) The epicotyl dormancy of P. emodi seeds can be broken by cold stratification at 4°C for 110 days, and the emergence rate of seedlings was 67.50%. If soaking the seeds in 300 n 500 mg/L GA 3 solution for 24 hours at room temperature after cold stratification for 90 days, the start time of seedling emergence can be advanced by 16 n 19 days. Importantly, we have obtained P. emodi seedlings in Beijing by this way. (3) Sugars and proteins were main energy basis of P. emodi seeds during epicotyl dormancy breaking, and cold temperature can promote their transformation by improving the activity of corresponding metabolic enzymes. Crude fat was not the main energy supply in this process. Endogenous ABA and GA 3 played a vital role in the dormancy release of P. emodi seeds, and their balance indicated the key stage of dormancy breaking. (4) Cryopreservation procedure of P. emodi seeds was established. First, decreased water content of P. emodi seed to 8.77%, then cryopreserved seeds by the way of throwing into liquid nitrogen directly or slowly in freezing tubes, and thawing method was thawing in tap water or water bath after liquid nitrogen storage. After 90 days of cryopreservation, the seed viability was 96.67%, which was not significantly different from that of naturally harvested seeds. This study provides a technical and theoretical basis for the conservation and utilization of P. emodi resources, and is of great significance to clarify the underlying mechanism of Paeonia seed dormancy breaking at cold temperature.