The physiological and molecular responses of carnation flowers to high temperature

Abstract

Abstract Carnation ( Dianthus caryophyllus cv. `White Sim') flowers were subjected to a heat treatment to investigate the physiological and molecular effects of high temperatures on flower senescence. Flowers were exposed to 44°C for 24 h in the dark. Control flowers were held at 23°C. In heat-treated flowers the ethylene climacteric occurred 120 h after treatment, a delay of 24 h when compared to control flowers. Maximum ethylene production was decreased from 44 to 31 nl g −1 h −1 in heat-treated flowers. Northern blot analysis of the ethylene biosynthetic genes ACC synthase and ACC oxidase indicated that the accumulation of these mRNAs is delayed by 24 h in heat-treated flowers. The accumulation of senescence-related (SR) genes followed a similar pattern. Further investigation revealed a decreased responsiveness to exogenous ethylene and a reduced capacity to produce ethylene in petals from heat-treated flowers. Northern blot analysis again revealed a delay in the accumulation of ACC synthase and ACC oxidase transcripts. SR gene expression induced by ethylene, however, was not affected by the heat treatment. The beneficial effects of high temperatures, a delay in ethylene production and reduced responsiveness to ethylene, may lead to horticultural application.