The effects of GA3 treatment on yield, carbohydrate, and endogenous hormone changes in Memecik olive cultivar

Abstract

In this experiment, 100 ppm gibberellic acid ($GA_3$ ) was applied to Memecik olive trees in the middle of June in the ‘on’ (bearing) year to research the effects on yield, reducing sugar amount, and endogenous hormones with the purpose of bearing fruit regularly. The yield was 19.33 kg/tree in control plants and 17.33 kg/tree in $GA_3$ -treated plants in the ‘on’ year. The yield was 7.17 kg/tree in $GA_3$ -treated plants and 4.00 kg/tree in control plants in the ‘off ’ year. While $GA_3$ treatment was not very effective on the decrease of fruit amount in the ‘on’ year, it increased fruit amount in the ‘off ’ year. Moreover, $GA_3$ treatment did not significantly affect total reducing sugar amount, but it affected endogenous hormones. Total reducing sugar amount was determined at the 4% level in both years (‘on’ and ‘off ’). Glucose content was determined to be higher than sucrose and fructose in all plant organs and during flower bud formation periods (induction, initiation, and differentiation). Furthermore, $GA_3$ treatment increased abscisic acid, $GA_3$ , indole-3-acetic acid, and zeatin levels during flower bud formation periods and in all plant organs (leaf, node, and fruit) in both years.