Water absorption and dormancy-breaking requirements of physically dormant seeds of Schizolobium parahyba (Fabaceae - Caesalpinioideae)

Physical dormancy refers to seeds that are water impermeable. Within the Fabaceae, the structure associated with the breaking of dormancy is usually the lens. This study verified the role of the lens in physical dormancy of seeds of Schizolobium parahyba a gap species of Fabaceae from the Atlantic Forest of Brazil. The lens in S. parahyba seeds appeared as a subtle depression near the hilum and opposite the micropyle. After treatment of the seeds with hot water, the lens detached from the coat. Blocking water from contacting the lens inhibited water absorption in hot-water-treated seeds. High constant (30 degrees C) and alternating (20/30 degrees C) temperatures promoted the breaking of physical dormancy and germination in non-scarified seeds. Maximum percentage of germination occurred earlier for seeds incubated at 20/30 degrees C than for those incubated at 30 degrees C. Seeds with a blocked lens did not germinate at alternating or high temperatures. This study suggests that alternating temperatures are probably the cause of physical dormancy break of seeds of S. parahyba in gaps in the forest.