ISHS Acta Horticulturae 556: V International Congress on Hazelnut
NUT GROWTH AND DEVELOPMENT IN ‘BUTLER’ HAZELNUT |
| Authors: | A.P. Silva, A. Santos, E. Rosa |
| Keywords: | filbert, Corylus avellana L., ovary, ovules, embryo, reproduction, Portugal, light microscopy |
| Abstract:
Orchard management practices to optimize fruit set, development, and yield can be improved by knowledge of the reproductive process. In a trial where 11 hazelnut cultivars were evaluated in Northern Portugal, ‘Butler’ has been the most productive genotype with good eating characteristics. In this region, this cultivar is protandrous with female bloom occurring between mid-December and mid-March. ‘Butler’ was selected to study ovule, endosperm, and embryo development in hazelnuts. In 1996, ten clusters were harvested from 12-year-old trees, at weekly intervals, between the beginning of ovary development (March) until the end of April. Afterward, sample size was increased to twenty clusters and sampling intervals were decreased to 4 days, to better characterize the reproductive process. Samples were fixed in CRAF or Navashin’s fixative for 2 days and dehydrated in a series of increasing ethanol concentrations. Standard procedures for sectioning and staining techniques were used, and the specimens were observed under an optical microscope. Vascularization, obturator, chalaza and micropyle were identified 2 weeks after ovule appearance, between 15 April and 15 May. Ovule rotation occurred during this period. At the end of May, the ovule contained mature embryo sacs. Fertilization occurred around 10 July, about 5 months after pollination. The first stage of embryo development (globular embryo), occurred around 20 June, evolving to the heart-shaped stage 10 days later, and to the torpedo stage (cotyledons formed) by the end of July. The embryonic axis was clearly observed a few days later and continued elongating until nut maturity (20 August to 10 September). | |
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