Articles
EFFECTS OF SOME GROWTH REGULATORS ON THE RIPENING AND STORAGE QUALITY OF APPLES AND PEARS
Thus the effects of ethephon and similar compounds in promoting ripening in apples can be interpreted as augmentation of ethylene concentrations in fruit tissues which synchronously advance most of the normal ripening processes and influence storage quality in the same way as delayed harvesting.
Aminoethoxyvinylglycine (AVG) appears to inhibit ripening by blocking ACC synthase activity and its effects can be overcome by treatment with exogenous ethylene.
Daminozide also delays the rate of ripening by suppression of ethylene synthesis and, where pre-harvest spray application of daminozide is supplemented by efficient ethylene removal, significant improvements in the quality of apples stored in controlled atmospheres may be achieved.
The increase in core flush (brown core) and breakdown which may occur in some varieties after treatment with daminozide can be largely overcome by reducing application rates and selecting appropriate storage conditions.
Cycocel (CCC) appears to have relatively little effect on fruit composition or ripening rate but Paclobutrazol promotes fruit calcium levels and, in some trials, has improved fruit firmness and increased acidity.
These effects are consistent with those of an anti-gibberellin treatment since GA sprays applied close to full bloom, can depress fruit calcium levels and lead to an increase in disorders during storage.
Tri-iodobenzoic acid has also been shown to depress fruit calcium levels and to lead, in some cases, to increased bitter pit.
Synthetic auxin sprays applied to prevent premature shedding before harvest time increase fruit red colour and may advance ripening in certain varieties.
Post-havest application of GA and IAA may have beneficial effects on the storage qualities of several varieties of apples and pears.
Injection of GA into the core of Jonathan apples reduces breakdown whereas abscisic acid tends to promote this disorder.
It is evident that application of growth regulators to harvested fruits may often produce very different effects in the stored crop to those observed when the same compound is applied to the fruiting tree.