Seed Number in Apples Can Affect Calcium 

 Accumulation and Keeping Quality 



William J. Bramlage, Sarah A. Weis, and Duane W. Greene 

 Department of Plant & Soil Sciences, University of Massachusetts 



Apple growers are well aware of the importance of 

 pollination and seed development for fruit set. How- 

 ever, the importance of seeds continues throughout 

 fruit development, affecting not just the fruit but also 

 the tree. During experiments designed to test other 

 questions, we have observed some of these relation- 

 ships between seed number and fruit quality, which we 

 shall describe briefly here. 



In a study of effects of growth regulators on Mcin- 

 tosh apples, we found that vdth increasing concentra- 

 tions of gibberellins A^^, and benzyladenine, an in- 

 creasing number of seedless fruit remained on the 

 trees and ripened. However, during and after storage 

 the amount of senescent breakdown that occurred 

 increased as growth regulator concentration that had 

 been applied to the fruit increased. When the fruit 

 were examined and analyzed, we found that the senes- 

 cent breakdown was mostly in seedless fruit, and that 

 the treatments were depressing fruit calcium concen- 

 tration at the same rate that they were increasing the 

 numbers of seedless fruit that matured. This result 

 suggested that calcium was much lower in seedless 

 fruit than in ones with seeds. 



In a later study of effects of growth regulators on 

 Delicious apples, we again noticed large differences in 



seed numbers among fruit, so samples from all of the 

 treatments were examined for size, seed number, and 

 mineral composition. The results are summarized in 

 Table 1. 



There was a significant linear relationship be- 

 tween seed number and fruit diameter: the more seeds 

 in the apple, the larger the apple. This relationship has 

 been seen before with a number of different kinds of 

 fruit, so one effect of abundant seed development ap- 

 pears to be larger fruit size. 



It is well known that increasing fruit size reduces 

 the amount of calcium in apples, yet as can be seen in 

 Table 1 there was a significant increase in fruit calcium 

 with increasing seed number. Thus, the extra calcium 

 drawn into the apple as a result of increased seed 

 number was greater than the dilution effect that the 

 increased size had on fruit calcium concentration. The 

 end result was larger fruit with more calcium in them. 

 In the case of magnesium, the data on Table 1 show that 

 it was reduced by seed number, but statistical analysis 

 showed that this reduction was merely the dilution 

 effect of larger fruit size. For potassium, seed number 

 had no effect. Therefore, the effect of seed number was 

 specific to calcium — increased seed number attracted 

 extra calcium into the fruit. 



Fruit Notes, Summer, 1989 



11 



