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- Author or Editor: R. Fernandez-Escobar x
- Journal of the American Society for Horticultural Science x
Abstract
Experiments with heavily-flowering olive trees showed only one period of abscission of flowers and fruit in the 5-6 weeks following full bloom. This abscission of flowers and fruit is responsible for the small percentage of fruit retained to maturity. Most of the fruit drop was concomitant with initial fruit growth for all cultivars. There were no differences in the number of fruit per inflorescence among cultivars, but the percentage of inflorescences with fruit at harvest was related negatively to final fruit size for each cultivar. Thinning of perfect flowers within the inflorescence did not affect fruit set at the inflorescence level; thus, the inflorescence behaved as a unit of fruitfulness. Competition among fruits played a significant role in fruit set. Initial setting induced by pollination and fertilization is counteracted early by fruit abscission originated by competition among fruit. In light of this early abscission, the use of fruit set to indicate response to pollination in previous experiments is questioned.
A low-pressure injection method for introducing chemical formulations into trees is presented. The apparatus consists of a plastic injector and a tube providing a pressure of 60 to 80 kPa, which is below the injurious level for the xylem. The efficiency of the method was determined by injecting PTS, a marker of apoplastic flux dye solutions, and rubidium chloride into young trees, main scaffolds, or tree trunks. The depth of the hole drilled) and the number of injections necessary to distribute the solutions was also determined. The injected solutions moved mainly upward through the older rings of the xylem, suggesting that uptake is directly controlled by the transpiration rate. A single injection was enough to distribute solutions in scaffolds with a diameter of 8 cm, but two injections were necessary for 17-cm-diameter trunks. According to the results, the injection method was effective in introducing chemicals into olive (Olea europaea L.) trees. The method is easy to use, safe and economical and does not involve special equipment. Chemical name used: trisodium, 3-hydroxi-5,8,10-pyrenetrisulfonate (PTS).
GA3 scaffold injections applied between May and November to nonbearing olive (Olea europea L.) trees inhibited flowering the following year, increased shoot width when applied in May, June, and July, and increased inflorescence length when applied in November and February. Fruit removal and seed destruction were effective in improving the return bloom in `Manzanillo' olives when done before endocarp sclerification. Depending on-the year, endocarp sclerification takes place 7 to 8 weeks after full bloom (AFB), usually about 1 July. Fruit removal had no effect on flowering when done after this time. Scaffold injection of paclobutrazol applied to bearing trees between May and September did not affect flowering the following year. The results of our research supports the hypothesis that olive flower induction occurs around the time of endocarp sclerification. Chemical names used: gibberellic acid (GA3), (2RS,3RS)-1-(4-chlorophenyl)-4-dimethyl-2-1,2-4-triazol-1-yl) pentan-3-ol(paclobutrazol).