The physiology and biochemistry of polyamines in plants

Abstract

Our entry into the polyamine field was accidental. As plant physiologists interested in the regeneration of entire plants from isolated single cells and protoplasts, we had turned our attention to the two most important groups of food plants, the cereals and the legumes (1, 2). When we began this work about a decade ago, there had been no successful protoplast regeneration of any plants in these groups, although numerous researchers had been successful with various members of the Solanaceae (tobacco, petunia, potato, tomato), as well as a few species in other families (3). Today, several of the Leguminosae have been successfully regen erated from protoplasts (4-6), but only one report of cereal regeneration from protoplasts, in pearl millet, exists in the literature (7). Why should cereal leaf protoplasts behave so diflerently from protoplasts of other species? We had been working with oat, and our attention was drawn to a report that the rapid senescence of detached leaves of this plant could be delayed substantially by the application of arginine (8). It is well known to plant physiologists that leaves detached from the plant initiate a rapid and massive hydrolysis of proteins and nucleic acids, then senesce, yellow, and die. These events can be delayed, and sometimes prevented, by cytokinins, exemplified by N-isopentenyl adenosine or zeatin (9). We had, of course, applied cytokinins to our isolated oat leaf protoplasts, but without positive