Effects of 1-methylcyclopropene on flower senescence and petal abscission in Dianthus caryophyllus L.

In carnations, senescence initially occurs by inrolling and wilting of petals due to reduced turgidity; this is associated with autocatalytic ethylene synthesis in petals. However, whether petal abscission occurs during flower senescence or is induced by petal wilting is unknown. Here, we investigated this process by determining differences in cellular morphology at the abscission zone and measuring petal turgidity and breakstrength during development in carnations. DcACS1 and DcACO1 played roles in autocatalytic ethylene production in carnations, and changes in these genes correlated with changes in ethylene biosynthesis. DcACS1 and DcACO1 transcripts were upregulated by treatment with ethylene and downregulated by treatment with 1-methylcyclopropene (1-MCP). Longitudinal sections of flowers at the initial fully opened stage showed anatomically distinct cell layers in the petal-receptacle boundaries, similar to the abscission zone in Arabidopsis, suggesting that petal abscission could occur during flower senescence in Dianthus caryophyllus. Petal breakstrength was relatively low in turgid petals, but increased with loss of turgidity. Moreover, 1-MCP effectively delayed the loss of petal turgidity, and differences in petal breakstrength were unclear after senescence was initiated in wild-type and ethylene-treated flowers. Thus, although petal breakstrength decreased following ethylene treatment, petals did not abscise, even after complete wilting of the flowers.