Effect of thermal storage on seed coat dormancy and germination of Ipomoea purpurea (L.) roth (Convolvulaceae) seeds

The impermeability of the Ipomoea purpurea (L.) Roth (Convolvulaceae) seed coat may change if the seeds are exposed to different temperatures during the six months of the dry season, i.e. from dispersal to the beginning of the rainy season. The effects on seed coat dormancy of three constant storage temperatures (15 °C, 25 °C and 35 °C), over a six month period were evaluated. 96% of the impermeable newly collected seeds were not affected by storage at 15 °C: 97% of these remained hard and only 3% germinated; while seeds stored at 25 °C and 35 °C had broken seed coat dormancy in nonscarified seeds, increasing germination up to 80% and 95%, respectively. Results show that: a) under the three thermal conditions, seeds maintained their viability during six months, b) seed coat impermeability was preserved at low storage temperature with the potential formation of a seed bank, and c) seed coat dormancy was broken by the high storage temperatures of 25 °C and 35 °C, and the resulting permeable seeds could germinate in the favorable conditions of the rainy season.