Condicionamento fisiológico e níveis de sombreamento em sementes de barbatim?o (Stryphnodendron polyphyllum (Mart.) e S. adstringens (Mart.) Coville)

摘要

The technical difficulty to obtain seedlings due to seed dormancy is an obstacle in the production of native species in the recovery of Brazilian Savannah degraded areas programs. Thus, the objective of the present study was to evaluate the effect of physiological conditioning and shading on seed quality of two species of barbatim?o (Stryphnodendron polyphyllum and Strypnhodendron adstringens). Seeds were soaked in seven conditions: 1) PEG -1.0 MPA; 2) PEG -1.0 MPA+ KNO3 -1.0 MPA; 3) PEG -0.5 MPA; 4) PEG -0.5 MPA + KNO3 -0.5 MPA; 5) KNO3 -1.0 MPA; 6) distillate water and 7) without soaking (control). During the treatments, the seeds remained incubated in BOD 20/30 oC for 24 h, then they were sown in cell trays containing Plantmax?, and maintained under four shading levels (full sun, 30%, 50% and 70%) with four repetitions of 20 seeds. After the evaluation of the emergency percentage, the seedlings were transplanted and kept under the same shade levels. The physiological conditioning on water of both species seeds, followed by sowing under 50 to 70% shade, are effective for faster and high emergency, greater height and dry mass of seedlings. S. polyphyllum seeds can be conditioned with PEG -1.0 MPa and PEG - 0.5 MPa if sown under 30% shade. However, seeds from S. polyphyllum and S. adstringens species should not be sown at full sun.