Oxidative Turnover of Auxins in Relation to the Onset of Ripening in Bartlett Pear

Abstract

Pears (Pyrus communis var. Bartlett) kept in 100% O₂ showed an increase in the rate of softening, chlorophyll degradation, and ethylene evolution. The O₂ application could overcome, in part, the inhibition of ripening by 1 mm indoleacetic acid. Ripening of pears was also accelerated by the application of solutions containing indoleacetic acid-oxidation products, obtained by an overnight incubation of 0.1 and 1 mm indoleacetic acid with traces of H₂O₂ and horseradish peroxidase. Although both treatments stimulated ethylene evolution, the promotion of ripening could not be attributed to an indirect ethylene effect. Indoleacetic acid oxidation products obtained in vivo by high O₂ tensions or in vitro by enzymatic degradation may function in the promotion of fruit ripening and the synthesis of ethylene.