Superação da dormência em sementes de Brachiaria humidicola cv. BRS Tupi pelo uso de ácido giberélico

This study aimed to evaluate the effects of gibberellic acid in different concentrations and periods of immersion acting as promoters of dormancy overcoming of Brachiaria humidicola cv. BRS Tupi of different lots and storage times before treatments. The experiments, in number of four, were carried out with different seed lots, in a factorial scheme in different post-harvest storage periods (6, 7, 8 and 9 months), in which the treatments consisted of immersion of the seeds in solutions with (0, 50, 150, 300 and 600 mg L-1) for three exposure periods (12, 24 and 48 h), compared to a control (without treatment) in a completely randomized design. The evaluations were: imbibition curve, germination, germination speed index, first germination count and viability by tetrazolium test. The seeds responded positively to all treatments after eight months of storage, while the controls remained dormant. None of the treatments provided a viability loss and they demonstrated the storage possibility. For periods above 24 h of imbibition there is a risk of root protrusion, which may lead to the death of the seed.