Germinação de sementes de Ipomoea cynanchifolia após armazenamento em diferentes temperaturas e escarificação.

Germination of Ipomoea cynanchifolia seeds after storage at different temperatures and scarification. Abstract ? Ipomoea cynanchifolia Meisn., Convolvulaceae, is a wild relative of Ipomoea batatas (L.) Lam. (sweet potato). In this study, seeds with 7.8% water content were stored in a germinator (25 °C), a freezer (-18 °C) and in liquid nitrogen (-196 °C) for seven days. After storage, seeds underwent a decontamination treatment for 15 min, followed by three rinses with sterile distilled water, and after that seeds were scarified, by means of a cut in the opposite pole to the hilum made with nail pliers. Non-scarified (control, ESC-) and scarified (ESC +) seeds were sown in Petri dishes between filter paper discs soaked with water equivalent to three times the mass of the discs, and taken to a growth room at 25 ± 2 °C, with a 12h photoperiod. Observations occurred daily and counts occurred at 3, 7, 15 and 30 days after sowing using botanic (radicle protrusion) or technological (formation of a normal seedling with a green hypocotyl, cotyledons and root) criteria. Regardless of the storage temperature, germination percentages of ESC- seeds were low, with highest percentage of germination (15%) for seeds stored at -196 °C. In contrast, germination percentages for ESC+ seeds were high, ranging from 97% to 100%. These results show the occurrence of dormancy in I. cynanchifolia seeds, the need for scarification to promote seed germination and seed tolerance to storage at temperatures below freezing.