Factors That Affect Seed Germination and Changes in Endogenous Gibberellins and Abscisic acid Concentrations in Mukdenia rossii (Oliv.) Koidz

Abstract

The present study was conducted to establish storage conditions that accelerate germination and maintain the germination rate of Mukdenia rossii (Oliv.) Koidz. seeds. Fresh seeds of M. rossii exhibited an excellent germination rate of over 95.5%, and cotyledon development was confirmed by the presence of a sufficiently developed embryo. Therefore, the seeds of M. rossii were classified as nondormant type. Seeds with weak germination potential due to long-term storage were used for the experiment to determine the temperature and light condition and improve germination rate. To evaluate how changes in storage conditions affect the relationship between germination characteristics and hormone content, fresh seeds were stored at different temperatures for 2, 4, and 6 months and germinated at 20°C in the presence of light. Treatment with 100 mg·L-1 gibberellic acid (GA) improved the germination rate of M. rossii seeds by 94.8% whose germination rate had decreased due to long-term storage. Seeds stored at different temperatures and for different periods of time exhibited high germination rates between 88.8%-99.5% under all storage conditions; however, storage period had negative effects on mean germination time, germination energy, and time taken for the germination rate to reach 50% that were statistically significant (p < 0.001). Endogenous GA content in seeds that had been stored for 6 months at 25°C changed marginally, therefore, it can be predicted that the relative proportion of ABA in the seed is increased. On the other hand, the relative concentration of abscisic acid (ABA) increased significantly. In contrast, the M. rossii seeds stored at -20°C had a decrease in activated GA (GA4) levels and increased levels of precursor GAs, such as GA24 and GA9. Furthermore, endogenous ABA content decreased significantly, which increased the relative GA concentration in seeds. Therefore, -20°C is an effective storage temperature for the propagation of M. rossii seeds.