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

Abstract

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.

Cellular and molecular changes associated with competence acquisition during passion fruit somatic embryogenesis: ultrastructural characterization and analysis of SERK gene expression

“…Since the first reports of SE in the umbellifers Oenanthe aquatica and carrot by Harry Waris in 1957 (Krikorian and Simola 1999) and by Steward et al (1958), respectively, this regeneration pathway has become a model system for studying the physiological, biochemical, cellular and molecular mechanisms involved in the transition of somatic cells to the embryogenic state for many species (Elhiti and Stasolla 2011;Fehér et al 2003;Fehér 2015). Continuing the studies of P. edulis zygotic embryo-derived SE that were performed by Paim- Pinto et al (2011), Rosa et al (2015) and Rocha et al (2015), here we provide additional information based on an ultrastructural description of the events involved in embryogenic competence acquisition during the early stages of somatic embryo development.…”

Embryo production through somatic embryogenesis can be used to study cell differentiation in plants

“…The first reports to address somatic embryogenesis came in the late 50's, in cultures of D. carota (Steward et al 1958;Reinert 1959) and Oenanthe aquatica (Waris 1957;Krikorian and Simola 1999). Since then somatic embryos have been obtained in many other plant species (Ammirato 1983;Williams and Maheswaran 1986) even though the carrot has been the most widely used model, mainly due to its feasibility, fast response and high yields.…”

Historical Insights into Some Contemporary Problems in Somatic Embryogenesis

“…"Neomorph" was originally applied by Waris in 1957 to refer to experimentally-induced morphological offtypes from cells sloughed off seedlings grown for prolonged periods in liquid culture containing nonphysiological levels of various amino acids (see Waris, 1962;Krikorian and Simola, 1999). Neomorphosis was defined as a "fundamental morphological change, without any irreversible change of the genome .... " I adopted the term neomorph in an attempt to codify in vitro-generated embryonal forms of daylily that seemed terminally aberrant and unable to yield plantlets directly (Krikorian and Kann, 1981;Smith and Krikorian, 1991).…”