Flower Development in Walnut: Altering the Flowering Pattern by Gibberellic Acid Application

Abstract

The pattern of walnut flowering varies depending on genetic and environmental factors. This research was carried out to study the patterns by which pistillate flowers develop as a result of applying gibberellic acid (GA3). To study the effect of gibberellin on flowering, we used a factorial test. Factor A was the diameter of the tree trunks, and three levels were considered (10 to 12 cm, 12 to 14 cm and 14 to 16 cm). Factor B was comprised of four levels of GA3 (0, 50,100 and 200 mg/lit). Different levels of GA3 were sprayed twice on the ‘Chandler’ cultivar, i.e. 2 and 4 weeks after flowering. Also, a new (without using a microtome or scanning electron microscopy) method was used to study the development of pistillate flower buds.  Different stages of development included induction, initiation and differentiation of the pistillate flower bud which were observed respectively in late May, early June, September and March. The results of GA3 application showed that GA3 treatment can alter the flowering pattern of walnut. GA3 application significantly increased the number of male flowers, total flowers, and male: female flower ratio per branch. The number of female flowers increased as the diameter of the tree trunk increased. The highest number of female flowers (62.3) was observed in trees with trunk diameters between 14-16 cm and when GA3 was applied at 100 mg/liter. Also, a linear regression model was used in order to find a relationship between GA3 levels and the diameter of the trunk with flowering pattern.