Introduction: Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst, P. glandulosa
Torr., Vachellia schaffneri (S. Watson) Seigler & Eibinger, V. pennatula (S. Watson)
Seigler & Eibinger and V. farnesiana (L.) Wight & Arn. are characteristic species of
semi-arid areas. Their seeds show physical dormancy and are naturally scarified by
chewing, trampling, digestive tract of fauna, fire, or washing away during rains.
Objective: To describe the morphology of the seed coat of three species of Vachellia
and two of Prosopis, and to assess the chemical, mechanical and thermal scarification
Materials and methods: Chemical (HCl for 30, 120, 150 and 180 min), thermal (80,
100, 120 and 140 °C for 3 min) and mechanical (sanding) scarification were applied.
Resistance to breaking by compression was measured. The experimental design was
randomized complete blocks per species.
Results and discussion: Seeds showed a layer of lignified and impermeable
macrosclereids, but the aleurone layer could not be detected. Sanding allowed
germination from 81.2 to 100 %. Chemical and thermal treatments showed no
differences, only in the case of P. laevigata, chemical scarification for 180 min caused
higher germination (72.5 %) compared to the control. Vachellia schaffneri seeds were
more resistant to compression (669 N) and had more intense dormancy (0.83), while P.
glandulosa had the lowest dormancy (0.42).
Conclusions: Mechanical scarification was the best method to eliminate dormancy in
Vachellia and Prosopis seeds.