Dormancy induction in dried seeds of Scorzonera reverchonii (Compositae) stored at low temperature

Abstract

We analyzed the processes of both dormancy break and induction in Scorzonera reverchonii (Compositae) seeds when desiccated to 5 % of humidity and stored at low temperature (5 ºC). At dispersal time, seeds were dormant and only 1 % germinated when incubated at 20/7 ºC in light/darkness during 30 days. Seeds permanently stored at 5 ºC kept dormant. However, this became viable after two years, since 88-93 % seeds germinated if afterwards they were treated with gibberellic acid. When seeds were stored at room-laboratory conditions (i.e., temperature = 22 ºC, relative humidity = 50-60 %), they gradually surpassed dormancy, and after one year germination reached 85 %. Thus, S. reverchonii seeds have non-deep physiological dormancy. When seeds stored one year in the room-laboratory (non-dormant seeds) were transferred to 5 ºC in dryness, a gradual induction of secondary dormancy was triggered, reducing germination in 21-29 % after one year in comparison with seeds permanently stored in room-laboratory conditions. After one year at 5 ºC, seeds transferred again to room-laboratory germinated progressively, showing germination percentages as high as those in seeds permanently stored in room-laboratory conditions 10 months later.