-2- 



BIGGER APPLES, LESS CALCIUM, MORE PROBLEMS 



William J. Bramlage 

 Department of Plant and Soil Sciences 



It has frequently been observed that large apples do not store as well as small 

 apples within a given variety. When storage problems occur, they tend to be much 

 more prevalent on the largest apples within a box. 



This relationship of storage disorders with fruit size is largely a reflection 

 of the fact that within a sample of fruit, calcium (Ca) concentrations are lower 

 within the larger fruit. For example, Dr. Mack Drake recently analyzed some 

 random samples of different sizes of packed Mcintosh apples. The results (Table 

 1) showed a marked reduction of fruit Ca as size increased. We have seen many 

 times that differences in Ca concentration of this magnitude can lead to quite 

 different amounts of breakdown, rot, bitter pit, and even scald on Mcintosh after 

 storage. 



Table 1. Calcium concentration in Mcintosh apples of different sizes, 1983. 



Box Fruit Average Ca concentration^ 



count circumference fruit weight (ppm dry wt.) 



(g) 



160 2.5 - 2.6 100 129 



140 2.7 - 2.8 122 119 



120 2.9 - 3.0 154 HI 



96 3.1 - 3.2 186 90 



^Ca concentration in outer cortex tissue on calyx half of the fruit. 



The relationship between fruit size and fruit Ca concentration in apples has 

 been studied extensively by Michael A. Perring at the East Mailing Research Station, 

 Kent, England. In bulk samples, he has found that the relationship is very dramatic 

 (Figure 1). The main reason for larger fruit having lower Ca concentrations is 

 that the amount of Ca transported by the tree into developing apples is very small, 

 and as apples enlarge their cells get larger and the concentration of Ca in them 

 becomes diluted by water and other cellular constituents. Large apples have larger 

 cells, hence their Ca is more diluted. 



Another reason for the fruit size: Ca relationship is that relatively large fruit 

 generally come from low-yielding trees, or areas of trees. With light cropping 

 more vegetation is produced, and what Ca is available in the tree is preferentially 



