Free endogenous growth regulators in Pistachio (Pistacia vera L.)

This research was carried out in order to observe seasonal changes of internal plant growth regulators in pistachio. This research was conducted during three years at a commercial pistachio orchard located in Firat valley in Nizip, Gaziantep. 'Kirmizi' pistachio cultivar trees grafted on Pistacia vera L. were used as plant material. Changes in auxin (IAA), cytokinin (Zeatin), gibberellin (GA(3)) and abscisic acid (ABA) were observed in leaves in May, July and September of the first (heavy cropping year - 'on'-year) and second (subsequent light cropping year 'off'-year) years. Besides, yield and flower bud abscission rate were observed during three years to determine the relationships among the level of plant growth regulator, yield and flower bud abscission. It was observed that the IAA, zeatin and ABA levels in the leaf were high in the first year, and was low in the second year. The annual GA3 levels were lower in the 'on' year and higher in the alternate bearing, 'off' year. The correlation analysis between the hormones and fruit bud abscission rates showed that increase in the ABA levels caused also increase in fruit bud abscission at all months in the first year.