A SIMPLIFIED MEDIUM FOR INVITRO TRACHEARY ELEMENT DIFFERENTIATION IN MESOPHYLL SUSPENSION-CULTURES FROM ZINNIA-ELEGANS L

A simplified medium has been developed for the differentiation of tracheary elements in suspension cultures of mesophyll cells of Zinnia elegans L. All inorganic salts contained in media used previously were retained in the simplified medium, but most were reduced in concentration. The only organic supplements required for optimum differentiation were thiamine and nicotinic acid, in addition to the plant growth regulators N6-benzylaminopurine and alpha-naphthyleneacetic acid, and sucrose as a carbon source. Mannitol, an osmoticum, was necessary for rapid, synchronous differentiation. This simplified medium is particularly suitable for studies of the role of Ca2+ in tracheary element differentiation due to the elimination of myo-inositol, an intermediate in the phosphatidyl inositol signal transduction pathway and reduction in the concentrations of Mg2+ and Mn2+, which block calcium channels. It is also possible to eliminate EDTA from the medium, enabling studies using specific calcium chelators. Additional culture variables for the optimization of differentiation are discussed.