10 CIRCULAR 6 2 7, U. S. DEPARTMENT OF AGRICULTURE 



size of apples was increased by an increased supply of elaborated foods 

 (increased leaf area per fruit), the firmness of the fruit was increased 

 (30). Thus, whether size increases or decreases the firmness may de- 

 pend on the cause of the difference in size. 



Fruit Color 



Highly colored apples were firmer than poorly colored ones and the 

 blush side of apples or of pears was firmer than the unblushed side of 

 the fruit (5, 50, 61). The difference between the blushed and the 

 unblushed sides of the fruit makes it important to pressure-test the 

 fruit at two or three points. A sample to be tested should also be 

 representative of the color of the lot sampled. 



Rootstock 



Allen (3) found that Bartlett pears grown on Japanese rootstock 

 [Pyrus pyrifolia (Burm.) Nakai] were generally considerably firmer 

 than when grown on French stock [P. communis L.] and that Clairgeau 

 and Hardy pears (4) were firmer on quince than on French pear stock. 



APPLICATION OF PRESSURE TEST TO VARIOUS 



FRUITS 



Apples 



Attempts have been made to use the pressure test as an index of 

 maturity in apples. Magness et al. (46) found that the rate of soft- 

 ening may vary greatly under different growing conditions and that 

 frequently there was not enough softening previous to harvest for the 

 pressure test to be of value as an index of when to start picking the 

 variety. The actual pressure test at picking time was more uniform, 

 but it also varied too much to be a satisfactory index. They concluded 

 that the value of the pressure test as an index of maturity will be main- 

 ly to determine when certain varieties are becoming too soft on the 

 trees for satisfactory storage. Magness et al. (45) gave the approxi- 

 mate pressure-test range at which optimum maturity is most likely 

 to occur, and indicated the minimum test value below which certain 

 varieties may be too soft. These data are presented in column 2 of 

 table 2. Magness and Taylor (48) in an earlier publication indicated 

 the approximate range at which certain varieties are generally picked, 

 as shown in column 3 of table 2; this generally is a somewhat wider 

 range than the optimum given in column 2. Magness et al. (46) noted 

 that apples (particularly those requiring a long season of growth) 

 are generally softer at picking time when grown in a district having 

 a long than in one having a short growing season. They attribute 

 this difference partly to difference in maturity at time of picking. 

 Apples grown in sections with short growing seasons are likely to be 

 picked in the upper limits of the ranges given in table 2, columns 2 

 and 3, whereas those 4 grown in districts with long growing seasons are 

 likely to fall in the lower limits of the ranges. The lower limits for 

 varieties that are likely to become too soft before harvesting are also 

 indicated in column 2. 



