Effect of water stress on ethylene production and on membrane microviscosity in carnation flowers

Abstract Carnation flowers subjected to two 12-h stress periods separated by a 12-h recovery period were visually indistinguishable from non-stressed flowers for up to 60 h after the termination of stress. During this time-period, no differences were observed in water saturation deficit (WSD), ethylene (C 2 H 4 ) production or degree of depolarization for microsomal membranes ( p ). The only detectable effect of the stress periods was accelerated onset of senescence. After the onset of senescence, as determined visually by petal inrolling and fading of colour, there was a simultaneous increase in the three parameters (WSD, C 2 H 4 production and p ), suggesting that they are interrelated. In flowers subjected to continuous stress, the usual visual symptoms associated with senescence were not observed, but flower petals dried out and shrivelled. The WSD of the petals and p values reflecting degree of depolarization of microsomal membranes began to rise within 24 h of the start of stress. However, C 2 H 4 production did not increase until after 48 h, thus apparently ruling out a simple cause and effect relationship between WSD, p and C 2 H 4 production. Generally, the measurements of C 2 H 4 production in both petals and green tissue in response to stress confirmed reports suggesting that the accelerated onset of senescence in response to stress is not directly mediated by C 2 H 4 .