INHIBITION OF PETUNIA FLOWER SENESCENCE BY 2,2'-BIPYRIDYL

Chelating agents were applied to Petunia flowers to test for the invol vement of apoplastic metal ions in ethylene-induced senescence. Compou nds varying in charge and polarity were applied directly to the coroll a prior to a 24-h treatment with 1 mu l 1(-1) ethylene. Charged and po lar chelators (EDTA and EGTA) were inactive. The only compound which i nhibited senescence was 2,2'-bipyridyl and there was evidence of cellu lar uptake of this compound. Fe2+ and Zn2+ did not reverse the inhibit ion of senescence by bipyridyl. Cu2+ as low as 0.1 mM reversed the eff ect of bipyridyl but senescence was independent of ethylene treatment. Bipyridyl caused a rapid shift in flower color from red to blue, but untreated flowers became more blue than bipyridyl-treated during 9 day s. CO2 and ethylene production were stimulated by ethylene but inhibit ed by bipyridyl applied before or after a 24-h ethylene treatment. Con tinuous ethylene treatment did not reverse the delay of senescence by bipyridyl.