Relationship of seasonal changes in endogenous plant hormones and alternate bearing of olive trees

Abstract

Changes in hormone concentrations in leaf, node, shoot tip, and fruit samples of three Turkish olive (Olea europaea L.) cultivars ('Gemlik', 'Memecik', and 'Tavsan Yuregi') were monitored at monthly intervals over two successive years of the alternate-bearing cycle. Concentrations of abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid-like substances (GA), and kinetin-like cytokinin were determined and their relationship to flower bud formation were examined during "on" and "off" years. Results showed significant differences in IAA, ABA, GA3-like, and kinetin-like cytokinins between "on" and "off" cropping years in various tissues of olive trees. Relative balances between GA 3-like and ABA concentrations of tissues appears to exhibit evidence of being a key regulator of floral development and alternate bearing.