Totipotency, somatic embryogenesis, and Harry Waris (1893–1973)

F. C. Steward and Jakob Reinert in the late 1950s, independently and with different degrees of scientific exactness, demonstrated that somatic cells of cultivated carrot can produce embryo-like structures in aseptic culture. Growth substances in the nutrient medium were viewed as central to the process. The now classic papers of Steward and Reinert have found a special and enduring place in the literature of plant development. But Harry Waris also deserves credit for his observation that vegetative cells sloughed off from aseptically germinated seedlings reared in liquid nutrient medium can produce 'embryos'. In his studies, seedlings of Oenanthe aquatica (Umbelliferae) were maintained in culture for protracted periods under nutrient conditions designed to foster imbalance in protein metabolism, but without exogenous growth hormones. Seedlings placed in media with high concentrations of glycine grew normally for 3–4 months; after this a "period of morbidity" occurred, followed by production of new plants from the root tips. These new plants, later called "neomorphs", in turn reproduced by colorless outgrowths of leaf epidermis. Such outgrowths, and "nodules" formed in a callus produced by the original seedlings, passed through stages described as "nodule", "fusiform", and a stage with two or more "lobes". Transfer of the neomorphs to a medium lacking glycine resulted in the development of normal plants. We show that Waris was among the first, if not the first, to observe and recognize somatic embryo production in aseptic culture, and indeed to call them "embryos". We also discuss his investigations in the context of understanding development at the cellular level, then and now.