The reason for different descriptions of the germination behavior of Idesia polycarpa seeds and their secondary dormancy

The seeds of iigiri (Idesia polycarpa Maxim.) have been described both as dormant and responsive to chilling and as having the ability to germinate without any pretreatment. Both descriptions are correct. When collected at the end of October, Idesia seeds fail to germinate without previous exposure to chilling, whereas most Idesia seeds collected at the end of December are non-dormant. However, if the collection time is further delayed, Idesia seeds again lose their germinability by entering a secondary dormant state. The occurrence of secondary dormancy in Idesia seeds may be caused by a decrease of O₂ tension within the fruit during early winter and the secondary dormancy is relieved by exposure to chilling under aerobic and wet conditions. All Idesia seeds are easily capable of germinating when subjected to a combination of GA and BA under a condition of enriched oxygen tension regardless of their time of collection.