Effects of seed structures, sucrose and gibberellic acid on the germination of Butia capitata (Arecaceae)

The effects of seed structures, sucrose and gibberellic acid (GA(3)) on seedling germination and development of Butia capitata were assessed. The cultivation of whole seeds, seeds without opercula, transversely and longitudinally sectioned seeds, and isolated embryos was tested in vitro using MS salts supplemented with organic substances, and with the addition or absence of sucrose. The effects of different GA(3) concentrations (0, 50, 100, 500, 1000 and 2000 mg L-1) on the germination of seeds with or without opercula were tested under in vitro conditions. Isolated embryos taken from seeds subjected to the same doses of GA(3) were cultured in vitro. Sucrose promoted seed germination and seedling development, although the excised embryos contained sufficient reserves to germinate when isolated. The pronounced effect of the operculum on germination was found to be mechanical and not solely related to gas diffusion restriction. GA(3) did not affect the germination of seeds without opercula and had only modest effects on the germination of seeds with opercula and on isolated embryos. The inability of the embryo to overcome the mechanical restriction of adjacent tissues and the effectiveness of GA(3) in stimulating germination confirmed the classification of dormancy in Butia capitata as non-deep physiological dormancy.