Dipping ‘Jonathan’ apples in CaCl2 solution prior to storage greatly reduced the development of internal breakdown (IB) and retarded flesh softening during 19 weeks at 2.2°C plus 1 week at 23°C. Infiltration of fruit with sorbitol produced IB symptoms, whereas glucose caused a dissimilar browning coloration and sucrose yielded no visible damage. Infused Ca inhibited IB symptoms and browning, retarded respiration, reduced the metabolism of endogenous substrates, and increased the oxidation of exogenous substrates. The results suggest Ca inhibits IB by enhancing the uptake and compartmentation of substrates, particularly sorbitol.

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The disorder known as Jonathan spot commonly observed on ‘Jonathan’ apples actually consists of 2 spot types which must be distinguished in order to define the affecting factors and to resolve the confusing and contradictory evidence in the literature. The spots which occur in the epidermal tissues without definite relation to lenticels are considered as Jonathan spot. Those which occur directly around the lenticels are defined as lenticel spots. Histologically, the epidermal tissues afflicted with Jonathan spot showed a significant radial compression of the collenchyma cells in the 4 to 7 subepidermal tiers; whereas, such modification was not always apparent in tissues affected with lenticel spot. For the latter, some degree of rupture of the epidermis and the 3 to 5 subepidermal collenchyma tiers was usually noted. Jonathan spot development was inhibited by high temperature (70°F). It was favored by delayed harvest, yet none was observed until the fruit was stored at low temperature for several months. Conversely, lenticel spot often was present at harvest time and its development was accelerated at high temperature and inhibited at low temperature. High relative humidity (90%) enhanced lenticel spot development, whereas, humidity level had no effect on Jonathan spot.

Apple (Pyrus malus L.) seedlings or rooted layers growing in nutrient solution in the greenhouse were used to determine the role of xylem and phloem in the accumulation of Ca in the leaves. 45calcium accumulation increased with increasing rates of transpiration as measured by water losses. Girdling experiments demonstrated that the phloem was the primary route of translocation. Young leaves accumulated more 45ca than old leaves even though the water losses for plants bearing only young leaves or only old leaves were similar. 45calcium accumulation in mature leaves was decreased when the shoot tips were removed. Apparently, in young apple trees Ca moves primarily in the phloem, but leaks into the xylem at increasing reates in the younger stem and near the growing apex.

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