Methods for overcoming dormancy of Parkinsonia aculeata L. seeds

The Parkinsonia aculeata L seeds have tegumentary dormancy, which makes them last for a long period in the seed bank of the earth so that their germination occurs in favorable conditions. Our aim was to evaluate the influence of pregermination treatments for overcoming the dormancy of P. aculeata seeds. The seeds were submitted to the following treatments: sample – intact seeds (T1); mechanical scarification with water sandpaper no. 80, followed by room temperature water soaking for 12 and 24 hours (T3 e T4, respectively); immersion in sulfuric acid for 5, 10, 15 and 20 minutes (T5, T6, T7 e T8, respectively); immersion in water in 60ºC, 70ºC, 80ºC and 90ºC for one minute (T9, T10, T11 e T12, respectively). The characteristics evaluated were: percentage of emergence, emergence first count, emergence speed index, height and dry weight of seedlings. In the treatments that involved immersion in water in 60ºC, 70ºC, 80ºC and 90ºC, a low percentage of emergence was obtained. The P. aculeate seeds tegumentary dormancy is overcome with maximum efficiency by the mechanical scarification with sandpaper, suggesting that, in natural environment the movement of contraction and expansion of the soil results in a mechanical scarification of the tegument of the seeds, thus, allowing a high percentage of germination with distribution as time passes