ETHYLENE RESPONSE TO MECHANICAL STRESS PERTURBATION OF SALVIA SPLENDENS L. POTTED PLANTS

Mechanical treatment could be an efficient method to control growth of vegetable and ornamental species cultivated under greenhouse conditions. Mechanical growth control is able to induce a 20-50% reduction in the vegetative growth depending on the species, the type and intensity of stress applied. In any case, plant growth and morphogenesis are influenced by mechanical perturbation and common features among many different plant species are a decrease in elongation growth and an increase in radial expansion. Exogenous application of ethylene can result in morphological and physiological changes that resemble aspects of thigmomorphogenesis. Ethylene production occurs after mechanical stimulation of plants and many studies suggest that ethylene may have a role in radial expansion aspects of thigmomorphogenesis although it is unlikely to be the primary signalling molecule that controls all touch responses. The aim of the this work is to investigate the effects of mechanical perturbation caused by brushing potted plants of Salvia splendens L. cv. Flamex 2000. Attention was focused on the production of ethylene from different organs of the stressed plants and was monitored the time course of ethylene released as response to brushing treatments. The effects of the mechanical stress were compared to those induced by a common chemical agent usually applied to reduce transplant size. The results obtained showed that the dimension of Salvia splendens potted plants could be efficiently reduced following brushing treatments. Ethylene was released mainly in the apical shoots exposed to the mechanical perturbation but the production decreased after repeated treatments suggesting a mechanism of adaptation to the imposed stress conditions.