The growth of apricot fruit. I. Morphological changes during development and the effects of various tree factors

Abstract

A study has been made of growth in the fruit of apricot, Prunus armeniaca L. cv. Moorpark, in Adelaide, S.A. Morphological changes in the seed and mesocarp from anthesis to maturity are described. Significant positive correlations have been shown between the diameter of fruit at early pit-hardening, and that at the end of pit-hardening and at maturity. Large fruit at pit-hardening were also shown to ripen earlier. Other factors such as leaf/fruit ratio, fruit or leaf number per branch, branch diameter, and amount of light received by branches could not be correlated with fruit growth or final size. Differences were found in the rate of fruit growth during the first 3 or 4 weeks after anthesis between seasons, and also between fruit from early and late flowers. These differences were positively correlated with air temperature during this period; a constant number of "degree-days" above 5°C had accumulated when the fruit had grown to 2.3 cm in diameter. Fruit were shown to vary in volume and in the number and volume of mesocarp cells, both within and between trees. Volume differences in fruit within a tree were mainly due to differences in cell number, but between trees the contribution of cell volume was relatively more important.