Relation between primary and secondary metabolism in plant cell suspensions

Abstract

Cell suspensions ofMorinda 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-d). Also during cultivation on 1 mg 1^-1 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 AQ-contents 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 theMorinda model system in the study of the relation between growth, primary and secondary metabolism.