Determination of endogenous hormones, sugars and mineral nutrition levels during the induction, initiation and differentiation stage and their effects on flower formation in olive
Salih Ulger1,*, Sahriye Sonmez2, Mustafa Karkacier3, Nisa Ertoy1, Ozgur Akdesir1 and Mehmet Aksu3
1Department of Horticulture, 2Department of Soil Science, and 3Department of Food Engineering, Faculty of Agriculture, Akdeniz University, Antalya, Turkey; *Author for correspondence (e-mail: email@example.com)
Received 27 November 2002; accepted in revised form 11 September 2003
Key words: ABA, Ca, Cu, Fe, Fructose, GA3, GA4, Glucose, IAA, K, Mg, Mn, N, Olea europaea, Olive, P, Sucrose,Zeatin, Zn
Abstract Olive (Olea europaea L.) is one of the most important crop plants grown in the Mediterranean region. Varying levels of hormones, sugars and mineral nutrient are thought to influence flower bud formation. The objective of this study was to evaluate the changes in endogenous sugar, mineral nutrition and hormone levels in leaf, node and fruit samples of ‘Memecik’ olive during theinduction, initiation and differentiation periods in on (bearing) and off (non-bearing) years. Leaf, node and fruit samples of mature 15-year-old Memecik olive were used. The samples were taken during the induction, initiation and differentiation periods of olive in on (2000) and off (2001) years. Sugar (glucose, fructose and sucrose), mineral nutrient (N, P, K, Ca, Mg, Fe, Zn, Mn and Cu) andhormone [abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA3, GA4) and zeatin (Z)] levels were determined in on and off years. Hormone and sugar levels were measured by gas chromatography and high-performance liquid chromatography. The K, Ca, Mg, Fe, Mn, Zn and Cu levels were quantified by an atomic absorption spectrophotometry. Nitrogen was determined by the Kjeldahl procedure, andP by a spectrophotometric method. The differences in any of the sugar concentrations, with the exception of fructose, were not significant in on and off years. Hormone levels, however, were significantly different in on and off years. Glucose had the highest concentrations in both years, followed by sucrose and fructose, respectively. The highest macro and micro element concentrations were foundto be Ca and Fe, respectively. Thus, the results suggest that carbohydrates and mineral nutrients may not have a direct effect to induce flower initiation. However, high GA3 level exhibited an inhibitory effect on floral formation during the induction and initiation periods. On the other hand, the high concentrations of GA4, ABA and certain cytokinin levels may have a positive effect on flowerformation in olive during the induction and initiation periods. Abbreviations: AAS – atomic absorption spectrophotometry; ABA – abscisic acid; Ca – calcium; Cu – copper; Fe – iron; FID – flame ionization detector; GAs (GA3, GA4) – gibberellic acid; GC – gas chromatography; HPLC – high performance liquid chromatography; IAA – indole-3-acetic acid; K – potassium; Mg – magnesium; Mn – manganese; N –nitrogen; P – phosphorus; RI – refractive index detector; TLC – thin layer chromatography; TS – total sugars; Z – zeatin; Zn – zinc
90 Introduction Olive (Olea europaea L.) is native to the Mediterranean basin where about 97% of the world’s olive fruit are produced. Unlike deciduous fruits with a short induction-to-initiation cycle, induction in olive may take up to 8 months, starting as early asJuly until about 6 weeks after full bloom, later in February. Although floral initiation occurs in November, the process of developing of visible flower parts does not start until March. Differentiation takes place in late February and bloom in May when the formation of each flower part occurs in the inflorescence (Martin et al. 1994). In apple (Malus communis L.), flower induction occurs early...