PHYSIOLOGICAL CHANGES DURING HYDRATION OF Dalbergia nigra ((Vell.) Fr. All. ex Benth.) SEEDS

During germination, a series of sequential events occur in seeds in response to endogenous and / or exogenous factors. The objective of this study was to investigate the physiological changes resulting from the controlled hydration in water and temperature in seeds of jacaranda-da-bahia ( Dalbergia nigra ). To this end, two lots of seeds separated as high and low vigor were used in the tests. Seeds belonging to the two lots, after desinfect, were hydrated in water, with the method of humid atmosphere (relative humidity95-99%) to reach four hydration levels: 10, 15, 20 and 25% moisture content in seeds, in temperatures (exogenous factor) of 15 and 25 \ub0 C. After hydration and temperature treatments, were analyzed the following variables: curve soaking, germination percentage, germination speed index (GSI) and electrical conductivity. The results showed no significant difference in seeds physiological response between the temperatures. On the other hand, for hydration was found that up to 15% moisture content increased the seeds physiological quality of both lots, which showed higher germination values , IVG and smaller amounts of leached compounds. From 15% moisture content were found a reduction in the quality of seeds classified as high vigor, while those of low vigor continued to show positive responses in 20 and 25% humidity. Given this, it is concluded that the technique of controlled hydration in water favors the germination of Dalbergia nigra seeds, independent of the vigor. Hydration moisture content of 15% is more appropriate to increase the seeds quality. The hydration in values below or above resulted in a decrease in the stimulus.Durante a germina\ue7\ue3o, uma s\ue9rie de eventos sequenciais ocorre nas sementes em resposta a fatores end\uf3genos e/ou ex\uf3genos \ue0s mesmas. O objetivo deste trabalho foi investigar as altera\ue7\uf5es fisiol\uf3gicas decorrentes da hidrata\ue7\ue3o controlada em \ue1gua e da temperatura (fatores ex\uf3genos) em sementes de Dalbergia nigra (jacarand\ue1-da-bahia). Para tanto, dois lotes de sementes, um de alto e um de baixo vigor foram utilizados nos ensaios. As sementes pertencentes aos dois lotes, ap\uf3s desinfestadas com Captan 0,5%, foram ent\ue3o hidratadas em \ue1gua, pelo m\ue9todo da atmosfera \ufamida (umidade relativa de 95-99%), at\ue9 atingirem quatro n\uedveis de hidrata\ue7\ue3o: 10, 15, 20 ou 25% de teor de \ue1gua nas sementes, nas temperaturas de 15 e 25\ubaC. Ap\uf3s os tratamentos foram analisadas as seguintes vari\ue1veis: curva de embebi\ue7\ue3o, percentagem de germina\ue7\ue3o, \uedndice de velocidade (IVG) e condutividade el\ue9trica. Os resultados mostraram que n\ue3o houve diferen\ue7a significativa na resposta fisiol\uf3gica das sementes entre as temperaturas. Por outro lado, para a hidrata\ue7\ue3o verificou-se que at\ue9 15% do teor de \ue1gua aumentou a qualidade fisiol\uf3gica das sementes de ambos os lotes, que apresentaram maiores valores de germina\ue7\ue3o, IVG e menores quantidades de compostos lixiviados. A partir de 15% de teor de \ue1gua verificou-se redu\ue7\ue3o na qualidade das sementes classificadas como de alto vigor, enquanto aquelas de baixo vigor continuaram apresentando respostas positivas em 20 e 25% de teor de \ue1gua. Diante disto, conclui-se que a t\ue9cnica de hidrata\ue7\ue3o controlada em \ue1gua favorece a germina\ue7\ue3o de sementes de Dalbergia nigra, independentemente do vigor das mesmas. A hidrata\ue7\ue3o no teor de \ue1gua de 15% \ue9 a mais indicada para incrementar a qualidade das sementes. A hidrata\ue7\ue3o nos valores abaixo ou acima resultaram em redu\ue7\ue3o no est\uedmulo