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Involvement of Hydrogen Peroxide in the Regulation of Senescence in Pear ¹

^a Department of Botany and Department of Horticulture and Forestry, Rutgers University, New Brunswick, New Jersey 08903

Endogenous peroxide levels in pear fruit (Pyrus communis) were measured using a titanium assay method, and were found to increase during senescence in both Bartlett and Bosc varieties. Application of glycolic acid or xanthine, serving as substrates for the formation of H₂O₂, increased the peroxide content of the tissue and accelerated the onset of ripening, as measured by increased softening and ethylene evolution. Application of ethylene also induced increased peroxide levels. Ripening processes were similarly promoted when peroxides were conserved by inhibiting the activity of catalase with hydroxylamine or potassium cyanide. By comparison, the inhibition of glycolate oxidase with alphahydroxy-2-pyridinemethanesulfonic acid decreased the peroxide content of the tissue and delayed the onset of ripening. These results indicate that the onset of ripening correlates with the peroxide content of fruit tissues as occurring under normal conditions or as influenced by the treatments. Hydrogen peroxide may be involved in oxidative processes required in the initiation and the promotion of ripening.

¹ This study was supported, in part, by Hatch funds and by a Rutgers University Research Council Grant. Paper of the Journal Series, New Jersey Agricultural Experiment Station, Cook College, Rutgers-The State University, New Brunswick, N. J. 08903.