Flower bud morphogenesis and effects of exogenous GA3 application on development of flower components in two Iranian commercial apricots

Morphogenesis of flower buds of two commercial apricot cvs. ‘Noori’ (early blooming) and ‘Shahroodi’ (late blooming) were studied in Karaj climatic condition. The effect of foliar application of gibberellin (GA3, 250 mgL-1) on flower bud development of two cultivars was also studied. GA3 was applied at three times during autumn (first week of October, third week of October and second week of November). Scanning electron microscope was used to study flower bud development. Based on results, the first stage of flower bud development in both cultivars showed the same growth pattern. Growth of floral parts was continued until the beginning of dormancy period. Stamens were developed, but no pollen grains were formed during the autumn. At this stage, pistil developed and ovarian cavity was observed in both cultivars in mid-November but no ovules were observed. Both cultivars were different in second and third stages of flower bud development. Final stage of flower bud development was earlier in ‘Noori’ in compare to ‘Shahroodi’. The results showed that all three times of foliar applications of GA3, were delayed final stage of flower bud development and the longest delay was with exogenous application of GA3 in mid-November. The results suggested that the application of GA3 at autumn increased GA3 levels at dormancy stage, thus the flowering was delayed that is a way to avoid to exposure to late spring frosts. So, the differences between both early and late blooming cultivars can relate to the content of gibberellin within flower buds during dormancy stage.