Studies on induced tracheary element differentiation in cultured tissues of tubers of the Jerusalem artichoke, Helianthus tuberosus.

A model system for the study of cell differentiation in plants is described. Tracheary elements differentiate from storage parenchyma cells in cultured explants of the Jerusalem artichoke, Helianthus tuberosus, in the presence of auxin and cytokinin. Differentiation occurs in G1 cells following three successive divisions of precursor cells; the onset of secondary wall deposition follows within 6--8 h of the final mitosis. Differentiation is inhibited by levels of FUdR, actinomycin-D, cycloheximide or gamma-irradiation sufficient to block mitosis. Inhibition was equally effective whether blocking treatments were applied at the beginning of the culture period or after one or two rounds of mitosis.