ROOT REGENERATION FROM LEAF CUTTINGS OF LYCOPERSICON-ESCULENTUM MILL - APPLICATION OF LEAF PLASTOCHRON INDEX AND RESPONSES TO EXOGENOUS GIBBERELLIC-ACID

Application of the leaf plastochron index (LPI) allowed the consistent description of root regenerative capacity from tomato leaf cuttings. GA inhibited root regeneration regardless of LPI. This inhibition was alleviated by IAA or IBA [indolebutyric acid] if applied prior to, during or after GA treatment. However, ABA [abscisic acid] reversed rooting inhibition only if applied prior to or during GA treatment. The GA effect on rooting was correlated with an inhibition of localized starch accumulation within the basal petiole regions prior to and during initiation of the root primordia. GA had no significant effect on the amount or intercellular distribution of amylolytic activity within the petiole tissues during this period. It is hypothesized that the mode of GA action involves a localized inhibition of starch synthesis rather than increased hydrolysis which may, in turn, lead to inhibition of root regeneration in tomato leaf cuttings.