Morphogenetic regulation of seed germination in Orobanche aegyptiaca Pers.

Abstract

The seed of Orobanche aegyptiaca (Orobanchaceae) is very small and contains a subglobose embryo which has not differentiated into radicle, hypocotyl, cotyledons, and plumule. Seeds were aseptically cultured to study germination and the morphogenesis of the embryo. In response to the composition of the medium, the embryo displayed either a monopolar organization or a bipolar organization of the seedling. Medium supplemented either with coconut milk (20% v/v) or yeast extract (5000 ppm) resulted in a monopolar seedling development where the roots and shoot originated from the morphological radicular pole of the embryo. The bipolar pattern of seedling development occurred in response to auxin (0.1 ppm), cytokinin (0.5–10 ppm), gibberellin (1–30 ppm), and strigol (0.01 μg). In bipolar development, the shoot originated from the plumular pole and the roots from the radicular pole of the embryo.