Effects of Priming Treatment and Cryopreservation on Seed Germination of the Bulgarian Endemic Papaver degenii

The study evaluated the effects of seed priming and short-term cryopreservation on the germination of Papaver degenii, a vulnerable Bulgarian endemic from the Pirin Mountains. Seeds (17–22 seeds per dish, two independent biological replicates per treatment) were primed with melatonin (MT), proline (Pro), or chitosan (CHT), cryopreserved either by direct immersion in liquid nitrogen or following vitrification procedures with Plant Vitrification Solution 2 (PVS2) or Plant Vitrification Solution 3 (PVS3), and assessed using germination parameters, binomial generalized linear models, time-to-event analysis, and Kaplan–Meier curves. Untreated seeds, as well as MT- and Pro-primed seeds, exhibited high germination percentages (>90%), whereas CHT reduced germination and delayed the germination process. MT exhibited a concentration-related pattern, with low concentrations promoting faster germination and higher concentrations delaying germination. Untreated seeds retained post-thaw germination capacity, with comparatively high germination observed following PVS2 and PVS3 procedures. Seeds primed with 0.5 and 1 μM MT also retained high germination after cryopreservation, whereas Pro- and CHT-primed seeds showed lower post-cryopreservation germination under the tested conditions. These findings provide preliminary evidence that P. degenii seeds retain germination capacity after short-term exposure to liquid nitrogen. Longer cryostorage periods, additional biological replication, appropriate procedural controls, and evaluation of subsequent seedling development are required to determine whether observed post-thaw germination can support long-term ex situ conservation.