Cell division and expansion in the cucumber fruit

The contributions of different fruit parts to the growth of a parthenocarpic cucumber fruit were analysed throughout fruit development. Growth in length and circumference were measured along the fruit. Cell size was measured at several places in the pericarp of the fruit during its development and the contribution of cell division and expansion to the growth of the fruit was quantified. All parts along the fruit expanded in length and thickness at approximately the same rate, except for the fruit ends, where the growth rate slowed down sooner than in the middle part. The increase in thickness of the fruit was the result of a constant increase in thickness of placenta and pericarp throughout development of the fruit. No specific expansion zones were observed. Cells expanded continuously throughout ovary and fruit development. Cell division, however, was restricted to the first part of the growing period. Cell size decreased from the peduncle end towards the blossom end of the fruit. Along the pericarp radius there was also a gradient in cell size with the largest cells in the middle of the pericarp. During fruit development the zone with the largest cells shifted a little towards the epidermis. Although there were marked differences in cell size within a fruit, all cells continuously expanded and cell division ceased in the whole fruit at approximately the same time.