HORT 413 Tree Fruit Production

Fruit Development

Factors which influence fruit growth can be divided into 3 categories:

Genetic

Cultural

Environmental

Apple fruit growth is composed of 2 phases, cell division and cell expansion. As the name suggests, cell division is where the cells in the small fruitlet are dividing, so fruit growth during this phase is mainly by an increase in the number of cells in the fruit. The cell division phase lasts for approximately 30-40 days, and the growth rate depends to a large extent on temperature and crop load. Small differences in the rate of cell division can translate into large differences at harvest. After this period of cell division, fruit grow mainly by each cell expanding, and virtually no new cells are formed. The size of the fruit at harvest depends to a large extent on the number of cells in the fruit, so cell division is the critical stage for obtaining large fruit size. Therefore genetic, cultural and environmental factors which limit cell division, are also likely to reduce fruit size at harvest.Factors which encourage cell division are early thinning and warm temperatures during flowering and for 4-6 weeks following.

The growth of peach fruit is a little different to that of apples in that it follows a double sigmoid pattern. The apparent slowing of growth after an initial logarithmic phase is due to pit hardening.