A Study on the effect of moist-chilling and GA3 application on evening primrose (Oenothera biennis L.) seed germination

Evening primrose (Oenothera biennis L.) is native to North America, belongs to Onagraceae family, and is a biennial plant. This experiment was performed as factorial based on a completely randomized design in three replications. The main purpose of the study was to evaluate the effect of moist-chilling and GA3 on seed germination and flower induction of evening primrose. The seeds were soaked in distilled water for 30 min, and treated with seven levels of moist-chilling period (0,10, 20, 30, 40, 50, and 60 days) and were kept in 2-4 °C in refrigerator conditions. At the end of day 60 half of the seeds were treated with 500 ppm GA3 solution for 24 hours. After that, both groups were planted in pots with three replications to see the plant reproductive responses. Simultaneously, the same seeds were planted in Petri dishes with three replications for seed germination. Germination was controlled every three days and seed germination test was done for 15 days. Seedling characteristics were measured at the end of germination test. Results showed that moist-chilling and GA3 significantly influenced the seed germination percentage. The highest germination percentage was observed in a combination of 20 days moist-chilling conditions and 500 ppm GA3. Rootlet length increased while moist-chilling was increased from 10 to 30 days. By increasing moist-chilling to 40 - 60 days, rootlet length decreased unexpectedly. Combination of moist-chilling and GA3 did not influence flower stem production and seed yield significantly. On the other hand, the earliest flower stem production was observed in seeds treated with moist chilling for 40 and 60 days. To guaranty flower stem production of spring sowing evening primrose in the areas with warm winter, seeds are strongly recommended to be treated with moist chilling for 40 days at 4 °C.