The purpose of the present study was to determine the participation of ethylene in the abscission process of the fruits of three species of Opuntia, and their relationship with the production of CO2 during the growth and maturation of the fruit. The concentration of ethylene CO2, pH and titulable acidity in four phases of maturation (initial: M1; intermediate: M2; maximum: M3; and final: M4) of the fruits of O. matudae, O. oligacantha and O. amyclaea was measured. The greatest concentration of ethylene and of CO2 in O. amyclaea was obtained in the M3 phase, coinciding with full maturity and the maximum dropping of fruit which suggests that the production of these gases is related to the abscission process of the fruit. With O. matudae and O. oligacantha the greatest concentration of ethylene was found in the M1 phase, indicating that this might be functioning as a developmental and maturation trigger for the fruit, but not sufficiently to stimulate abscission in them. The maximum production of CO2 in these two species occurred in the maximum maturation phase (M3), and could be related the coloration change and to the transformation of acids into sugar in the fruit.

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