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

Abstract

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 (GA3) 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.