PICKING MATURITY OF APPLES 6 



of fruit on the tree, the moisture supply, and climatic conditions, 

 as well as with degree of maturity. The sugar content of fruit from 

 heavily loaded trees will be below that of fruit from lightly loaded 

 trees under similar growing conditions and in a similar stage of 

 maturity. 3 The recent work of Caldwell 4 indicates that during 

 seasons of high sunlight the sugar content of apples will be higher 

 than in seasons of low sunlight. These changes in chemical com- 

 position due to variations in growing conditions are so great in 

 relation to those due to stage of maturity in apples that any picking 

 test based on chemical composition would prove unsatisfactory. 



CORKING OVER OF THE LENTICELS 



The lenticels or pores in the skin, which in the immature fruit 

 open more or less directly to the flesh tissue below, become filled 

 with cork cells and sealed over as the fruit approaches maturity on 

 the tree. This change is of much importance in retarding wilting 

 and the moisture loss from the fruit. The waxy coating on the sur- 

 face of the fruit also develops during the latter part of the growing 

 season. The development of the heavy wax coating and the sealing 

 of the lenticels result in the fruit which is well matured at picking 

 time being much more resistant to wilting in storage than that which 

 is picked in an immature condition. These changes, although im- 

 portant from the storage viewpoint, are not sufficiently discernible 

 to make them of much value in determining when the fruit should 

 be removed from the tree. 



CHANGE IN COLOR 



The change in color of apples as they mature on the tree is two- 

 fold. There is a direct development of the red color in blushed or 

 colored varieties, while in the unblushed portions of the immature 

 fruit the green color changes to a greenish yellow and finally to al- 

 most a full yellow color. The development of red color is a tre- 

 mendously important factor in determining when to pick apples for 

 commercial purposes, since high color is essential to the advan- 

 tageous marketing of many varieties. The development of red color 

 depends very largely, however, upon the exposure of individual 

 fruits to sunlight and upon the prevalence of bright, sunny days 

 during the ripening season. The sugar content of the fruit also 

 appears to be an important factor in color development. Conse- 

 quently, red color is not an accurate index to the actual condition of 

 maturity of the fruit, since fruit borne in the shade or on trees 

 producing a very heavy crop may be in the best picking condition 

 while showing relatively little red color. 



The disappearance of the green color in the unblushed portion of 

 apples is largely independent of light exposure and in many varieties 

 affords an excellent index of the time when the fruit is ready to re- 

 move from the tree. The methods of estimating this color change 

 and its relation to picking season in the different varieties are dis- 

 cussed in detail below. 



3 Haller, M. FL, and Magness, J. R. relation" of leaf area to size and chemical 

 composition of apples. Amei . Soc. Hort. Sci. Proc. 102."). 



4 Caldwell, J. S. effect of climatic conditions upon chemical composition of 

 apple juices. [Unpublished manuscript.] 



