Senescence in cut carnation flowers: Temporal and physiological relationships among water status, ethylene, abscisic acid and membrane permeability

Abstract

Changes in water status, membrane permeability, ethylene production and levels of abscisic acid (ABA) were measured during senescence of cut carnation flowers (Dianthus caryophyllus L. cv. White Sim) in order to clarify the temporal sequence of physiological events during this post‐harvest period. Ethylene production and ABA content of the petal tissue rose essentially in parallel during natural senescence and after treatment of young flowers with exogenous ethylene, indicating that their syntheses are not widely separated in time. However, solute leakage, reflecting membrane deterioration, was apparent well before the natural rise in ethylene and ABA had begun. In addition, there were marked changes in water status of the tissue, including losses in water potential (ψw), and turgor (ψp), that preceded the rise in ABA and ethylene. As senescence progressed, ψw continued to decline, but ψp returned to normal levels. These temporal relationships were less well resolved when senescence of young flowers was induced by treatment with ethylene, presumably because the time‐scale had been shortened. Thus changes in membrane permeability and an associated water stress in petal tissue appear to be earlier symptoms of flower senescence than the rises in ABA or ethylene. These observations support the contention that the climacteric‐like rise in ethylene production is not the initial or primary event of senescence and that the rise in ABA titre may simply be a response to changes in water status.