Effect of chilling and gibberellic acid on growth potential of excised embryos of Ruellia humilis.

Dormancy in intact seeds of Ruellia humilis is broken by chilling or by treatment with gibberellic acid (GA3). Embryos are nondormant and will grow when the seed coat is removed completely. Embryos from chilled or GA3-treated seeds have more growth potential than embryos from nontreated seeds. Dormancy is ascribed to the mechanical restriction of the embryo by the seed coat. Chilling and treatment with GA3 break dormancy by increasing the expansive force of the embryo; thus, chilled or GA3-treated embryos exert enough expansive force to break through the seed coat, whereas nontreated embryos do not.