Biochemical Changes Associated with Natural and Gibberellin A3 Delayed Senescence in the Navel Orange Rind

Several factors associated with senescence of the rind of the Navel orange fruit and their response to GA were studied from the time of color change, green to orange, until the fruit passed the point of any commercial value. This period is typified by a doubling in the concentration of sugar, a decrease in glucose respiration, and increase in the ratio of K/Ca+Mg. No seasonal trend could be assigned to Oz uptake, protein N, total N, or P, Zn, Cu, B, or Na. GA treatment at the time of color change did not seem to affect these factors until the rind approached senescence. At this point, GA effects were observable in the form of higher rates of Oz uptake, higher rate of glucose respiration, a lag in sugar accumulation, a lower K/Ca+Mg ratio, and a higher level of P. These results were interpreted as indicating that GA maintained a more functional mitochondrial membrane and plasmalemma