CELL-DIVISION AND EXPANSION IN THE CUCUMBER FRUIT

The contributions of different fruit parts to the growth of a partheno carpic cucumber fruit were analysed throughout fruit development. Grow th in length and circumference were measured along the fruit. Cell siz e was measured at several places in the pericarp of the fruit during i ts development and the contribution of cell division and expansion to the growth of the fruit was quantified. All parts along the fruit expa nded in length and thickness at approximately the same rate, except fo r 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. C ells expanded continuously throughout ovary and fruit development. Cel l division, however, was restricted to the first part of the growing p eriod. Cell size decreased from the peduncle end towards the blossom e nd of the fruit. Along the pericarp radius there was also a gradient i n cell size with the largest cells in the middle of the pericarp. Duri ng 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.