TOTIPOTENCY OF PLANT CELLS

During the 1950s a number of attempts were made to demonstrate the totipotency of plant cells. The first evidence of the possibility that single cells of higher plants could be cultured in isolation was provided by Muir et al. (1954), who obtained sustained cell divisions in single cells of tobacco placed on a small square of filter paper resting on an actively growing callus, which served as a nurse tissue. Similar results were obtained by Bergmann (1959) who plated single cells and cell groups suspended in an agar medium. Further progress was made by Jones et al. (1960), who were able to culture single isolated cells in a conditioned medium in specially designed microculture chambers. Each of these studies highlighted the importance of the nurse tissue or the conditioned medium for the survival and growth of the isolated cells. Direct and unequivocal evidence of the totipotency of plant cells was finally provided by Vasil and Hildebrandt (1965, 1967), who regenerated flowering plants of tobacco from isolated single cells cultured in microchambers, without the aid of nurse cells or conditioned media. This fulfillment of Haberlandt’s (1902) prophecy, combined with the more recent success in the genetic transformation of plants (see below), continues to provide the theoretical and conceptual basis of plant biotechnology.
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