Morphogenic investigations on parasitic angiosperms. I. Cistanche tubulosa (Orobanchaceae)

Abstract

In Cistanche tubulosa (Orobanchaceae), a herbaceous obligate root parasite, the seed is tiny and contains a subglobose embryo that lacks differentiation into radicle, hypocotyl, cotyledons, and plumule. Seeds were axenically cultured to study germination and the morphogenesis of the embryo. Germination occurred only when coconut milk was supplied in the agar nutrient medium and was characterized by the activity of only the morphological radicular pole of the embryo, which formed a mass of tissue. Differentiation of the shoot bud occurred when this tissue was grown in the dark on a complex nutrient medium. The plumular pole of embryo did not contribute to the formation of the shoot bud, nor did the embryo attain bilateral symmetry and organ formation before germination.