ABSCISSION OF FLOWER PEDUNCLES IN ROSE (ROSA X HYBRIDA) PLANTS AND EVOLUTION OF ETHYLENE

Ethylene evolution from decapitated rose (Rosa x bybrida cv. Nubia) pe duncles in planta and explants showed a climacteric pattern typical of abscising plant organs. The rate of ethylene evolution from non-decap itated explants was higher than that from decapitated ones and was the highest from separated flower buds. Local application of LAA at the s ite of bud removal postponed abscission of decapitated peduncles by 10 clays in comparison with decapitated peduncles without IAA. The inhib ition of abscission with IAA was accompanied by an earlier and higher rise in ethylene evolution and by yellowing of the peduncles; basal ap plication of STS (silver thiosulphate) postponed the abscission of dec apitated peduncles for a period longer than 6 weeks without any visibl e symptoms of senescence and was also associated with increased evolut ion of ethylene. Application of 1-aminocyclopropane-1-carboxylic acid (ACC) stimulated evolution of ethylene and promoted abscission of non- decapitated and decapitated peduncles, as well as of peduncles treated with IAA, but did not affect the STS-imposed inhibition of peduncle a bscission. An extremely high rise in ethylene was measured without aff ecting abscission when STS and IAA treatments were combined. The role of auxin in context of the concept of <<tissue sensitivity>> to ethyle ne is discussed. A possible existence of two separate ethylene systems , one involved in regulation of flower bud development and the second in regulation of flower bud and leaf absiccion, is discussed.