Osmotic conditioning and shading on the germination and on the initial growth of <italic>Myracrodruon urundeuva</italic> Allem&#227;o seedlings

<p id="para1">The present work aimed to evaluate the osmotic conditioning and shading on the germination and on the initial growth of aroeira seedlings. The seeds were pre-imbibed in solutions with different concentrations of PEG (polyethylene glycol) and KNO₃ and incubated at 10&#176;C and 20&#176;C temperatures, during 0 (control), 12 and 24 hours. After these periods, the seeds were dried until they reached the initial levels of humidity. After that, they were put for germinating in BOD (Biochemical Oxygen Demand) chambers, at alternated 20-30&#176;C. The control treatment and the pre-conditionings that presented the best results in BOD germination were selected, PEG (-1.0 MPa) + KNO₃ (-1.0 MPa) and KNO₃ (-1.0 MPa), with pre-imbibition for 12 h and incubated in BOD at 20&#176;C. The seeds were sowed on trays and then they were transplanted, keeping under a net covered with 50% and 70% of shading and at sunlight. The osmotic conditioning did not change the seeds germination in BOD, but the highest aerial part size was observed in PEG -1.0 MPa + KNO₃-1.0 MPa treatment. The shading levels at 50% and 70% and the osmotic conditioning with PEG -1.0 MPa + KNO₃-1.0 MPa offered a higher emergence in a greenhouse condition; however, at sunlight the seeds presented a better index of quality on the 145^th day.</p><br><p id="para2">O presente trabalho objetivou avaliar o condicionamento osm&#243;tico e o sombreamento na germina&#231;&#227;o e no crescimento inicial de mudas de aroeira. As sementes foram pr&#233;-embebidas em solu&#231;&#245;es de diferentes concentra&#231;&#245;es de PEG (Polietilenoglicol) e KNO₃ e incubadas em temperatura de 10&#176;C e 20&#176;C durante 0 (controle), 12 e 24 horas. Ap&#243;s estes per&#237;odos as sementes foram secas at&#233; atingirem os n&#237;veis iniciais de umidade. Posteriormente elas foram colocadas para germinar em BOD (Demanda Bioqu&#237;mica de Oxig&#234;nio) na temperatura de 20-30&#176;C. O tratamento controle e os pr&#233;-condicionamentos que apresentaram os melhores resultados de germina&#231;&#227;o em BOD foram selecionados, sendo PEG (-1,0 MPa) + KNO₃ (-1,0 MPa) e KNO₃ (-1,0 MPa), com pr&#233;-embebi&#231;&#227;o por 12 horas e incubados em BOD a 20&#176;C. As sementes foram semeadas em bandejas e posteriormente transplantadas, permanecendo sob telado coberto com sombrite de 50% e 70% de sombreamento e a pleno sol. O condicionamento osm&#243;tico n&#227;o alterou a germina&#231;&#227;o das sementes em BOD, por&#233;m o maior tamanho de parte a&#233;rea foi observado no tratamento PEG-1,0 MPa+KNO₃ -1,0 MPa. Os n&#237;veis de sombreamento de 50 e 70% e o condicionamento osm&#243;tico com PEG-1,0 MPa+KNO₃-1,0 MPa proporcionaram maior emerg&#234;ncia em casa de vegeta&#231;&#227;o, entretanto a pleno sol as mudas apresentaram melhor &#237;ndice de qualidade aos 145 dias.</p