A mathematical model for the growth kinetics and synthesis of phenolics inoregano (Origanum vulgare) shoot cultures inoculated with Pseudomonas species

Elicitation with Pseudomonas sp. reduced hyperhydricity in clonally propaga ted shoot cultures of oregano under in vitro conditions and over many subcu ltures without re-inoculation. This was characterized by changes in the gro wth kinetics, total chlorophyll, total phenolics and moisture content. Tota l chlorophyll in the inoculant-containing shoot cultures was higher than th e control throughout the growth cycle of all subcultures. Moisture content (wb) of the inoculated shoot cultures was 8% lower than the control. The pa ttern of total phenolics synthesis in the inoculated shoot cultures showing characteristics of a periodic response and significant differences when co mpared to control was observed. A Leudking-Piret's logistic model was used to study the growth kinetics of the control and inoculated shoot cultures t o describe quantitatively the differences in the growth kinetics. There was a fourfold reduction in the biomass by fresh weight and a twofold reductio n by dry weight due to inoculation. The specific growth rate remained uncha nged, but the length of the growth cycle was reduced by 6 days for the inoc ulated shoot cultures. It appeared that the growth reduction was linked to the stress-related response mediated by the elicitation from Pseudomonas sp . to stimulate the synthesis of secondary metabolites. In spite of the grow th reduction, the inoculated shoot cultures, however, had similar numbers o f shoot node explants for subsequent propagation and all the shoot node exp lants were unhyperhydrated. (C) 1999 Elsevier Science Ltd. All rights reser ved.