Improving seed germination: effect of stratification and dormancy-release priming in Lonicera insularis Nakai

<i>Lonicera insularis</i> Nakai is endemic plant predominantly distributed along the coastlines of Ulleung-do and Dok-do in South Korea, and is significant for medicinal and ornamental uses. However, previous studies reported that <i>L. insularis</i> seeds exhibit morphological dormancy (MD), causing them to germinate only at specific temperatures. Therefore, this study aimed to classify the dormancy type of <i>L. insularis</i> seeds, expand the germination temperature range, and confirm the industrial applicability through dormancy-release (DR) priming. The seeds of <i>L. insularis</i> exhibited no inhibition of water absorption by the seed coat, with 85.0% germination observed at 15°C, similar to the viability (84.0%). Initially, the initial seeds of <i>L. insularis</i> exhibited an embryo-to-seed (E:S) ratio of 0.24 during dispersal, which increased to 0.81 by day 18 at 15°C, indicating that the seeds exhibit MD with underdeveloped embryos. Treatments with GA₃ and GA_{4 + 7} to overcome MD and expand the germination temperature range did not significantly enhance germination. However, seeds that grew embryos through stratification for 2 weeks at 15°C effectively expanded the germination temperature range. Additionally, DR-primed seeds maintained the expanded germination temperature range even after redrying, confirming the commercial potential of DR-primed seeds. Therefore, this study represents the first application of a novel approach to alleviate dormancy in <i>L. insularis</i> seeds through the integration of stratification and priming techniques, termed dormancy-release priming. This approach resulted in a significant increase in germination and expanded the effective temperature range for seed germination. These findings suggest that dormancy-release priming could be a valuable method for producing non-dormant seeds, enhancing the potential for <i>L. insularis</i> distribution and industrial applications.