Upon infection by Cladosporiumfulvum, tomato plants start to produce pathogenesis-related (PR)proteins. The PR proteins 1,3-13-glucanase, chitinase, and PR-lb accumulated near the stomata in the lower epidermis of C. fulvum-inoculated tomato leaves as could be determined by immunolocalization with polyclonal antibodies. However, no differences in accumulation of PR proteins between a compatible and an incompatible interaction were found. Results obtained from enzyme activity measurements of 1,3-13-glucanase and chitinase on similar leaf material as used for the immunolocalization did not fully reflect the immunolocalization data. The antibodies possibly detect only the extracellular but not the intracellular enzymes. The accumulation of PR proteins near the stomata might be part of a general defence response of plants against pathogens and potential pathogens.

Cell suspensions of Morinda citrifolia are able to produce large amounts of anthraquinones (AQ) when they are cultivated on a B5-medium containing 1 mg 1-1 naphtyl acetic acid (NAA); this production is inhibited by addition of 2,4-dichloro-phenoxyacetic acid (2,4-9). Also during cultivation on 1 mg 1-l 2,4-D AQ-production is absent.It appeared that in the presence of NAA a kind of 'AQ-production' program is switched on: cell division rate is low as well as metabolic activity, while endogenous sugar levels are high. The same properties develop in the presence of auxins like indolyl-acetic acid and p-chloro-phenylacetic acid. With 2,4-D and related auxins (like p-chloro-phenoxyacetic acid) AQ production is absent and emphasis is laid on a developmental program characterized by high cell division rates, high metabolic activity and low endogenous sugar contents. Independent of the type of auxin applied, the cells grow as a suspension consisting of finely dispersed cells. The 'AQ-producing differentiation program' cannot be maintained during a consecutive series of subculturings: with increasing AQcontents the viability of the cells and the cell division rate decrease.The possible mechanisms of regulation of AQ-production by auxins are discussed as well as the advantages of the use of the Morinda model system in the study of the relation between growth, primary and secondary metabolism.