Totipotence du péricycle des organes souterrains et aériens de Rorippa sylvestris. I. Rhizogenèse et caulogenèse à partir de racines sur plante intacte ou de fragments de racines cultivés in vitro

Abstract

Old and tuberized roots of Rorippa sylvestris (Brassicaceae) can form adventitious buds. Moreover, in vitro culture on Murashige and Skoog medium supplemented with sucrose can induce bud regeneration from nontuberized young root explants. An unusual stimulation of both lateral rhizogenesis and caulogenesis is obtained in the presence of auxin (indoleacetic acid), with optimal responses at 5 mg∙L−1. Kinetin inhibits rhizogenesis but strongly enhances caulogenesis, with optimal responses between 1 and 5 mg∙L−1. In all conditions (natural and experimental), lateral roots and buds arise from the pericycle layer or pericycle-derived tissues (outer layer of a several-layered pericycle, phellogen, and pericycle-derived callus). Thus, the pericycle of R. sylvestris roots, as well as the pericycle-derived cells, exhibits an original double potential for rhizogenesis and caulogenesis, especially in the close vicinity of the xylem poles. As the early steps of root and bud regeneration are similar, the possibility that the two kinds of meristems are undetermined and perhaps interchangeable is considered.