The application of 50 mg l1 of GA3 significantly reduced
flowering in ‘Springlady’ peach compared to controls when
applied during the flowering induction period. The magnitude
of the response depended on the date of treatment, ranging from
40 to 50%, for treatments carried out 85–100 days after anthesis
(DAA), to 20% for treatments applied 120–130 DAA (Fig. 1).
This inhibitory effect was always higher in the proximal shoot
segment, followed by the middle segment and by the distal
segment, the latter being not significantly different from that of
control trees for all spraying dates (Fig. 2). The effect also
depended on the concentration applied. The higher the GA3
concentration applied, the lower the percentage of shoots that
presented flowers in their proximal and middle segments, both
in peach cv. ‘Springlady’ and nectarine cv. ‘Zincal 5’ (Fig. 3).
Regarding the effect of date of treatment, no significant
differences with untreated trees were found for the distal
segments due to treatment either in peach or nectarine.
Gibberellic acid sprays during the period of highest
sensitivity (85–100 DAA), showed a significant concentration
effect on flower inhibition (Table 1). In peach cv.‘Springlady’
and nectarine cv. ‘Zincal 5’, 25 mg l1 GA3 spraying with
pressurized handgun significantly reduced the number of
flowers per metre of shoot length. The effect became saturated
at 50 mg l1 for peach, whereas for nectarine the effect
increased up to 100 mg l1 GA3. Applications with turbosprayer
evolved similarly to pressurized handgun, but the effect