FRUIT GROWTH AND CELL EVOLUTION IN 'WILLIAMS' PEARS

One of the most important quality parameters in pear fruit is its size, it is directly related to the number of cells formed in it. A logistic pattern, which describes, from 10 days after full bloom, the process of fruit growth was fitted in the pear cultivar ‘Williams’, however, the initial stage of growth, has not been addressed so far. The understanding of it is a way to improve the management of fertilizers, growth regulators, pruning, fruit thinning and size prediction. An experiment was established in a 20-year-old commercial orchard, on fruit trees of Pyrus communis L. ‘Williams’. Trees in full production and grafted on seedling rootstocks with homogeneous vigor, health, nutritional status, flowering and fruiting were selected to study fruit caliper, weight and cell size during the entire period of growth from fruit set to 120 days after full bloom. From petal fall, and every three days thereafter, 100 fruits were taken randomly from selected plants at a height of 1 to 1.8 m above the ground extracting the lateral fruit of the bouquet cluster. Ten fruits of the sample were weighed and immediately preserved in FAA solution (50% alcohol, formalin 25%, 20% distilled water and 5% acetic acid). The histological analysis was done making three cuts with a razor blade in the equatorial zone of each fruit. Each section was stained with toluidine blue and observed under an optical microscope with a digital camera. Two photographs were taken of each section and then analyzed with image j software. Data were analysed statistically using the R language. This study measured the evolution of fruit cells, presenting an initial area of 10.44 square microns and 201.1 square microns at the end of the evaluation. The pear fruit weight measurements described an exponential pattern from fruit set until harvest.