Effects of spermine on ethylene biosynthesis in cut carnation (Dianthus caryophyllus L) flowers during senescence

To investigate the relationship between polyamine and ethylene during senescence of cut carnation (Dianthus caryophyllus L.) flowers, we studied the effects of spermine on ethylene biosynthesis. Spermine delayed the senescence of cut carnation flowers and reduced ethylene production, endogenous 1-aminocyclopropane-1-carboxylic acid (ACC) content, and the activities and transcript amounts of ACC synthase and ACC oxidase in petals. Methylglyoxal bis-(guanylhydrazone) (MGBG), an inhibitor of polyamine biosynthesis, elevated ethylene production, increased activities and amounts of transcripts for ACC synthase and ACC oxidase, and shifted the climacteric pattern of ethylene production ahead by 1 day. However, endogenous ACC content was not increased in the petals of MGBG-treated flowers because of the high activity of ACC oxidase. Spermine also inhibited MGBG-induced ethylene production by decreasing the activities and amounts of transcripts for ACC synthase and ACC oxidase. The accumulation of transcripts for ACC synthase and ACC oxidase in MGBG-treat ed and in climacteric control petals was correlated with the increase of these enzyme activities. By comparing ethylene production with the changes of endogenous polyamine levels from control and MGBG- or spermine-treated petals during the entire incubation period, it was suggested that endogenous polyamines possibly suppress ethylene production.