Growth stresses during fruit development in Cox’s Orange Pippin apples

Abstract

Summary Early in the season young Cox’s Orange Pippin fruits were free from mechanical stress, but stress developed rapidly when the larger fruits on the tree had grown to about 15 mm diameter. Elastic strain reached a maximum in summer when fruit diameter was about 25 mm (around mid-June) in both 1974 and 1975, despite very different weather conditions. During the rest of the growing season, elastic strain seemed to depend on the conditions of that particular year, especially on rainfall. Transverse cuts in the fruit surface gaped more than longitudinal cuts until mid-July, indicating that elastic strain was greater in the longitudinal direction—also the direction of greatest growth—but later in the season longitudinal cuts gaped more than transverse ones. Small fruits were more strained than large ones throughout the season.