CHANGES IN APPLES APPROACHING PICKING 
MATURITY 
INCREASE IN SIZE 
Previous studies (12, 14) have shown that as long as apples hold on 
the tree growth in size continues. The rate of increase depends on 
the availability to the fruit of elaborated foods and moisture. Spray 
or other injury to the leaves, low temperatures, water shortage, senil- 
ity of the leaves, and any other factors that decrease the photosyn- 
thetic activity of the leaves reduce the growth rate of the fruit. 
Fruits of summer varieties such as Yellow Transparent and Williams 
are growing rapidly as they approach maturity and may increase as 
much as 2 percent per day in volume during the harvest period. 
Fruits of early-fall varieties such as Jonathan and Grimes Golden 
normally average about 1-percent increase per day during the harvest 
period whereas those of late varieties such as Winesap that mature 
during the cool weather may not increase more than 0.5 percent per 
day. Under conditions favorable to growth, delaying the picking 
of the crop will result in larger fruit and an appreciable increase in 
crop volume. From 0.5 to 1 percent of the fruit must drop daily 
before the total tonnage will be materially reduced below that from 
an earlier picking. 
CHANGE IN SEED COLOR 
The browning of the seeds in apples as they approach picking ma- 
turity has often been suggested as an index of the best time for picking 
the fruit. The seeds of winter apples, however, usually become brown 
a considerable period prior to the optimum picking date. The time of 
the coloring of the seeds varies so greatly with variety and season that 
this change is of little value in determining when to pick the fruit. 
It may be stated, however, that winter apples are practically never 
ready to pick before the seeds have reached a full brown color. 
CHANGES IN CHEMICAL COMPOSITION 
There are a number of changes in the chemical composition of apples 
as they approach picking maturity, but the extent of these changes is 
not great and the rate of change is not rapid. In general, as the fruit 
matures on the tree the astringent substances, including tannin, tend 
to decrease, the acidity decreases, and the sugar content increases. 
Many studies have been made to develop chemical tests for picking 
maturity, similar to the sugar and acid tests used on citrus fruits and 
grapes. Because of the wide variations in the chemical composition 
of apples caused by factors other than ripening, however, a chemical 
test for time of picking appears to be of little practical value. The 
percentage of sugar varies with the quantity of fruit on the tree, the 
moisture supply, and the climatic conditions, as well as with the degree » 
of maturity. The sugar content of fruit from heavily loaded trees 
is below that of fruit from lightly loaded ones under similar growing 
conditions and in a similar stage of maturity (70). The work of 
Caldwell (3) indicates that the sugar content of apples is higher in 
seasons of high sunlight than in those of low sunlight. The changes 
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