ROLE OF SHORT-CHAIN SATURATED FATTY-ACIDS IN THE CONTROL OF ETHYLENE SENSITIVITY IN SENESCING CARNATION FLOWERS

In cut carnations (Dianthus caryophyllus L. cv. Cally), petal senescen ce was associated with a climacteric pattern in ethylene production an d an increase in ethylene sensitivity during the preclimacteric stage. The increase in ethylene sensitivity was caused by short-chain satura ted fatty acids (C7 to C10) produced in the petals during the early st ages of senescence. Pollination or application of octanoic acid to the styles of unpollinated flowers resulted in a sudden increase in ethyl ene sensitivity and a marked acceleration of senescence. Treatment wit h silver thiosulfate (STS) resulted in a suppression of ethylene sensi tivity and a marked reduction in the levels of these fatty acids. Howe ver, even in STS-treated flowers pollination or treatment with octanoi c acid gave rise to a drastic increase in ethylene sensitivity. Exposu re of carnation flowers to 2,5-norbornadiene (NBD) vapours resulted in a dramatic suppression of ethylene sensitivity which was also overrid den by stylar application of octanoic acid. Exposure to NBD suppressed the increase in ethylene sensitivity caused by treatment with octanoi c acid. It appears that short-chain saturated fatty acids increased et hylene sensitivity by increasing the ability of the tissue to bind eth ylene.