Histological and physiological studies on the cause of the Jonathan spot in apples. II

Nitrogen fertilization and harvest time in relation to the spot-development

Abstract

1. In this study, influences of nitrogen fertilization and harvest time on the development of Jonathan spots were investigated with the Jonathan apples stored at 0-3°C with 95% relative humidity from September 1956 to February 1957.
2. The fruits on which many spots developed, generally contained more nitrogen than those on which few spots occurred. This relation was also found in the result of fertilization experiment. In the plot with heavy N and without P, leaves and fleshes contained the most abundant nitrogen and fruits caused the spot most severely.
3. The fruits picked at early time of the harvest were apt to suffer from the spots. Even in the above mentioned plot of heavy N and non P, the spot never developed on the fruits which were picked as late as at the end of October.
4. The nitrogen content and its distribution in the tissues were determined as the fruit grew. When the seed development ceased and the fruit began to enlarge, nitrogen increased rapidly in the flesh, causing many cracks of the skin around the lenticels.