Biochemical Changes Associated With Natural and Gibberellin A3 Delayed Senescence in the Navel Orange Rind1

Abstract

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 membrane.The imminence of senescence in many plant organs is marked by the loss of green color and appearance of anthocyanins or carotenoids. This change is sufficiently dependable so that comparative measures of chlorophyll content are often used to plot the approach of senescence. The fruit of Citrus sinensis, cultivar, Navel orange approach senescence with the typical decrease in chlorophyll content, synthesis and accumulation of carotenoids, as well as softening and general weakening of the rind. Gibberellin A3 (GA), which has often been associated with the hastening of senescence (1, 2), appears to delay senescence in the rind of the Navel orange. GA-treated fruit exhibit a delayed chlorophyll loss (3), slower carotenoid accumulation (4), delayed softening of the rind, and diminished accumulation of rind exudate (5) . (This latter condition should not be confused with the exudate resulting from an aphid infestation.)To gain a better understanding of the changes accompanying senescence in the Navel orange rind and the probable manner in which GA acts in delay-

Gibberellic Acid Application Timing Affects Fruit Quality of Processing Oranges

“…Application dates that resulted in the highest peel hue angles (most green color) usually had the lowest juice Brix, whereas control fruit, which usually had the lowest peel hue angles, typically had the highest juice Brix. Peel hexose levels are inversely related to peel chlorophyll levels (Huff, 1984) and GA 3 increased navel orange peel respiration (Lewis et al, 1967). Perhaps GA 3 affects the peel vs. the pulp sink strength.…”

Acceleration and Delay of Ripening in Banana Fruit Tissue by Gibberellic Acid

“…In leaves, this retention is associated with retardation of senescence, which in turn is related to a maintenance of the activity of nucleic acid and protein synthesis. Furthermore, in the delay of senescence in the Navel orange rind caused by GA3 treatment, it has been suggested that this maintained synthesis keeps a more functional mitochondrial membrane (Lewis et al 1967). GA3 is known to induce the formation of some enzymes and the activation of others in seed tissues (Chrispeels and Varner 1967) and it is also known to increase auxin levels in other tissues (Kuraishi and Muir 1962;Valdovinos, Ernest, and Henry 1967).…”

“…In fruits in general, higher concentrations of GA3 are needed to produce an effect (Ooggins and Lewis 1962;Abdel-Kader, Morris, and Maxie 1966;Dostal and Leopold 1967;Lewis et al 1967) as compared with the amount required in other systems, such as the release of oc-amylase from barley endosperm, where a concentration as low as 1O-11 M is effective (Ooombe, Oohen, and Paleg 1967). GA3 is effective on ripening of banana fruit over a wide range of concentrations.…”

Biochemical bases and molecular regulation of pigmentation in the peel of Citrus fruit

“…The effect of gibberellic acid (GA) delaying peel degreening is known for several decades (Coggins et al, 1960;Lewis et al, 1967;Cooper and Henry, 1968). Pre-harvest treatment with GA before the onset of colour break is a common practice to delay colour changes and harvest date (García-Luís et al, 1992).…”