8 CIRCULAR 6 2 7. U. S. DEPARTMENT OF AGRICULTURE 



TURGIDITY AND MOISTURE CONTENT OF FRUIT 



Murneek (52) has observed that pears held at room temperature 

 for 30 hours tested higher than those held for 6 hours. A similar in- 

 crease in firmness of apples is indicated by results published by 

 Magness et al. (46). Hartman (32) attributed this increase in firm- 

 ness to loss of turgidity, as pears held at high relative humidities 

 softened whereas those held at low humidities became firmer. He 

 further observed an increased firmness of pears on the tree under 

 drought conditions. Morris (50) observed a considerable increase 

 in the pressure test of apples in storage, and he attributed it to wilting. 

 That the increase in firmness after harvest may be due in part to some 

 factor other than turgidity seems likely, since such increases have been 

 observed in fruit held at high humidities. In studying the firmness of 

 fruit as it matures on the tree, these results emphasize the importance 

 of making tests promptly after harvest. They suggest also the 

 desirability of picking fruit for testing in the early morning when it is 

 most likely to be turgid. 



The moisture content of fruit as well as turgidity may influence its 

 firmness. Haller et al. (28) reported an indirect relation between the 

 moisture content of strawberry varieties and their resistance to flat- 

 tening. An increased soil-moisture content has been found to result 

 in an increase in moisture content and reduction in firmness of straw- 

 berries by Kimbrough (38), of apples by Haller and Harding (26). and 

 of pears by Ryall and Aldrich (57). The firmness of the fruit might 

 also be influenced by climatic or other cultural conditions that would 

 affect the moisture content of the fruit. Thus, Magness, Diehl. and 

 Allen (44) found that Bartlett pears grown in California under high 

 temperatures and at low humidity, which would tend to produce fruit 

 of low moisture content, were distinctly firmer than those grown 

 under coastal influences where lower temperatures and higher humid- 

 ities prevailed. Similar results with Gravenstein apples have been 

 obtained by Allen (6). 



Blake et al. (11) observed that rapidly growing peaches on trees 

 with a high-nitrogen growth status were softer previous to the shipping- 

 ripe stage than peaches from trees having a high-carbohydrate growth 

 status. Although there was very little difference, peaches of the high- 

 nitrogen growth status averaged slightly less in percentage of dry 

 matter. 



Fertilization 



Somewhat conflicting results have been obtained relative to the 

 effect of nitrogen fertilization on the firmness of apples. Magness and 

 Overley (47) reported no difference in firmness or rate of softening in 

 storage between apples from nitrated and nonnitrated plots when 

 fruits of the same size and color were used from each treatment. 

 Overley and Overholser (54), however, reporting on the same project, 

 found the apples from the nitrated plots slightly softer when samples 

 representative of the fruit produced by the different treatments were 

 compared. Knowlton and Hoffman (39), finding the apples from 

 nitrated plots significantly softer in most instances but with no 

 differences in other instances, considered the differences obtained of 

 no practical importance. Verner (61) reported that apples from 



