HABITUATION IN SUGAR-BEET PLANT-CELLS - PERMANENT STRESS OR ANTIOXIDANT ADAPTATIVE STRATEGY

Habituation is one of the four neoplastic diseases of plants and occur s spontaneously in plant cell cultures. To date, and even if an epigen etic origin has been previously postulated, the fundamental concept th at underlies this neoplastic state remains obscure. Recently, a perman ent stress hypothesis has been proposed, using habituated nonorganogen ic (HNO) sugarbeet cell line (Bera vulgaris L. altissima) as a model. According to this proposal, the low catalase and peroxidase activities were supposed to be responsible for H2O2 accumulation. A supposed lip oxygenase activation would generate LOO degrees radicals. OH degrees, produced by the Fenton reaction would he responsible for a lipoperoxid ation process, leading to malondialdehyde (MDA) accumulation. In this paper, the elements of this hypothesis have been examined using data p reviously obtained by several teams, and the permanent stress idea app ears less sustainable. Several properties of the habituated nonorganog enic sugarbeet- and some other habituated-cell lines have been describ ed. A more realistic concept emerging from this analysis is that habit uated cells exhibit efficient scavenging properties (antioxidant and a ntilipoperoxidant) against deleterious free radicals produced during c ell culture. This thesis is developed in this article.