Different Flower-Inducing Conditions Elicit Different Responses for Free Polyamine Levels in Olive (Olea europaea) Leaves

Abstract

In various plant species, polyamines have been implicated in regulating developmental phenomena as well as responses to environmental stimuli. The role of polyamines in regulating developmental phenomena in olive trees, such as flowering, is poorly understood, although seasonal changes and temperature effects on polyamine levels in olive trees have been reported. In this study, levels of free polyamines (putrescine, spermine, and spermidine) in the leaves of trees kept under non-inducing conditions were compared with polyamine levels in trees that were induced to flower under chilling and non-chilling conditions. Putrescine and spermine levels were much higher in leaves kept under inductive chilling conditions compared to control trees kept vegetative, but such increased levels of polyamines did not occur in trees that were induced to flower under non-chilling conditions. These results clearly differentiated between the effects of temperature versus the effect of developmental change on free polyamine levels in olive leaves. The results show that changes in free polyamine levels in leaves have little relevance to flowering in olives. Free polyamine levels within auxiliary buds increased when vegetative buds transformed into flowering buds and then declined when buds developed into flowers. Compared to floral buds, immature and mature fruits contained much smaller amounts of polyamines.