EFFECT OF ASSIMILATE SUPPLY ON THE GROWTH OF INDIVIDUAL CUCUMBER FRUITS

The effects of assimilate supply on the growth of individual fruits du ring different stages of fruit development were analysed in cucumber ( Cucumis sativus L. cv. Corona). The assimilate supply was varied by ma intaining different numbers of fruits per plant or maintaining differe nt irradiances. The growth rate of a cucumber fruit strongly increased with increasing assimilate supply, but its growing period was not not iceably affected. At a low assimilate supply both cell number and cell size were reduced. Increasing the assimilate supply at different stag es of fruit development showed that the early development of a cucumbe r fruit was not crucial for setting its growth potential. A small numb er of cells, due to a low assimilate supply during early fruit develop ment, was to a great extent compensated by an increased expansion rate of individual cells. It is concluded that cell number is not an impor tant determinant of fruit size in cucumber, although fruit size is oft en positively correlated with cell number. In the early stages of frui t development the effect of irradiance on the fruit growth rate depend s on the presence of an earlier developed fruit because of dominance b etween fruits. In later stages of fruit development, a decrease in irr adiance reduced the growth rate of all fruits relatively to the same e xtent independent of age or presence of other fruits.