Penetration of surface-applied 45Ca into apple fruitt

SummaryThe uptake of 45Ca applied to the skin of apple fruit was examined in the laboratory with regard to the practice of spraying with calcium solutions to prevent bitter pit.The speed of penetration of 45Ca from a drop on the fruit surface was found to be much higher under conditions of 50–80% relative humidity of the air than at saturation. Evaporation of the drop apparently strongly influenced the absorption of Ca into the apple. Penetration was faster in cv. Cox’s Orange Pippin than in James Grieve. The Ca which entered the fruit remained either in the skin or immediately beneath it.When 45Ca was applied more than once, the subsequent treatments, especially those applied at high relative humidity, were less effective. It is concluded that for practical purposes it would be advisable to spray repeatedly when the relative humidity is low.