Stimulation of direct embryogenesis from mesophyll protoplasts of Medicago sativa.

Mesophyll protoplasts of Medicago sativa were exposed to low voltage electrical fields immediately following isolation. Several exposure times and voltages were utilized. At the lower doses, protoplast aggregation and subsequent embryogenesis were stimulated. A clone of 'Rangelander', which was directly-embryogenic (i.e. embryos were derived from single mesophyll protoplasts without an intervening callus phase), was induced to form embryos in all samples exposed to the lowest level electrical fields, while unexposed controls formed few or no embryos. A clone of 'Regen S', which was previously not directly-embryogenic, was induced to follow the 'Rangelander' pattern of development and to produce early globular embryos.