In vitro Seed Germination and Haustorium Formation of a Parasitic Medicinal Plant: Cistanche tubulosa (Schenk) R. Wight

In vitro seed germination and haustorium formation of Cistanche tubulosa (Schenk) R. Wight without the host allowed for study of morphology to guide high-production cultivation. Stratified seeds were soaked for 36 h with GA₃ (1 000 mg·L⁻¹) before they were sown on 1/2 MS medium solidified with agar supplemented with 500 mg·L⁻¹ yeast extract, 250 mg·L⁻¹ NaCl and 100 mg·L⁻¹ mannitol, pH 5.83 (SEM). Seeds began to germinate after two weeks. Radicles elongated out of the micropylar end of the soft endopleura-formed germ-tube-like organ and then elongated gradually. Seventeen days later, elementary haustoria began to develop and several haustorial hairs were differentiated from thick ribbon epidermis, which formed fossae among the apices of elementary haustoria. Papillae were scattered on winkles of epidermis and in fossae. When they elongated to 4 mm, the germ-tube-like organs ceased development. Haustorial hairs and papillae play important roles in adhering to host roots and piercing to the cortex and finally develop as endophytes for parasitic connection between parasites and hosts.