EFFECTS OF SEED TREATMENT ON VIABILITY OF AGED CRYPTOMERIA JAPONICA SEEDS AFTER STORAGE

Seeds of Japanese cedar, Cryptomeria japonica, stored for 4 years at -20°C, were primed with osmotic solutions at -0.4 and -1.2 MPa for 4 d in darkness at 15°C using polyethylene glycol 8000 or KNO₃. Primed seeds showed 1.8 times higher germination percentage than non-primed ones. Addition of 1 mM gibberellic acid (GA₃) or ethephon during priming had little or no promotional effect on seed germination. Pre-chilling treatments at 4°C for 10 d with or without the addition of 1 mM ethephon significantly increased germination percentage, whereas pre-chilling treatment for 5 d alone reduced germination percentage as compared to the control. Exogenous applications of 1-3 mM of GA₃ or ethephon resulted in significant reduction in germination percentage. Considering the significant decreases in seed viability of aged seeds after a long-term storage of Japanese cedar, osmotic priming could be effectively used in seeds of Japanese cedar and possibly other forest trees as one of the efficient methods that could effectively compensate reduced viability of aged seeds for ex situ conservation of forest genetic resources.