DEFENSIVE AND SECONDARY METABOLISM IN PLANT-TISSUE CULTURES, WITH SPECIAL REFERENCE TO NICOTINAMIDE, GLUTATHIONE AND OXIDATIVE STRESS

The purpose of the presentation is to interconnect and illuminate cert ain parts of metabolism regarding stress signalling and defensive func tions, including secondary metabolism in intact plants and plant tissu e cultures. Increased cell/tissue levels of reactive oxygen species li ke H2O2, O-2 and . OH and the metabolism of glutathione, are linked to defensive/secondary metabolism and tissue differentiation. Special at tention is paid to nicotinamide. A hypothetical role of nicotinamide a nd its metabolites as stress signals is also put forward especially in connection with hypomethylation of DNA. A role of DNA hypomethylation , as a link between various types of stressors and the induction of pl ant defensive metabolism, is discussed. We suggest that nicotinamide o r nicotinamide based substances may be of value within biotechnology f or the production of valuable substances as well as for plant protecti on.