Natural and post-harvest ethylene-induced pigment changes in the rind of Satsuma mandarin (Citrus unshiu Marc.) fruits respond differently to the exogenous application of growth regulators.
Both gibberellin A3 and the synthetic cytokinins N6-benzyladenine and kinetin opposed the ethylene-induced chlorophyll destruction, while the loss of chlorophyll during natural maturation was retarded by the gibberellin but not by the cytokinins.
This different behaviour suggests that ethylene may not be playing a central role in the endogenous control of ripening.
Carotenoid accumulation during natural maturation is apparently controlled through a different mechanism than chlorophyll loss since it is reduced both by the cytokinins and gibberellin A3.
Kinetin and gibberellin A3 increased to a similar extent the accumulation of reducing sugars and free amino acids, and reduced that of non-reducing sugars in the peel during natural maturation.
Their differential effect on chlorophyll loss may not be explained through their effects on sugar accumulation.