86 FUNDAMENTALS OF FRUIT PRODUCTION 



the tree with its reduced root system may suffer for lack of water and 

 drought injury ensue. It is a case of drought injury but in the last 

 analysis excess soil moisture at another season is the real determining 

 factor. It is likewise a paradox that some forms of watercore must be 

 regarded as due to drought. Though many cases are to be attributed to 

 other factors, Sorauer^^^ describes at least one form as associated with a 

 deficient soil moisture supply. In this form, water fills the intercellular 

 spaces and the affected tissues become hard and glassy. The outer 

 portion of the fruit is involved more directly than the tissues immediately 

 surrounding the core. The seeds remain white and do not ripen and the 

 affected fleshy tissues turn dark upon exposure to air more rapidly than 

 normal tissues. They have less dry matter, less ash and less acid. 

 Zurich Transparent, Gloria Mundi, White Astrachan and Virginia 

 Summer Rose are mentioned as varieties particularly susceptible to this 

 disease. 



The watercore more frequently occurring in the United States is 

 found in the core of the fruit and in the region of the main vascular 

 bundles, though it not infrequently extends to the surface or may be 

 limited even to the surface layers. This form of watercore is particularly 

 virulent in regions of intense sunlight and abundant soil moisture. 

 Tompkins King, Fall Pippin, Yellow Transparent, Early Harvest, 

 Rambo and Winesap are mentioned as particularly susceptible varieties. ^^ 



DISTURBANCES DUE TO MOISTURE DEFICIENCIES 



A deficiency in the water supply is likely to be accompanied by dis- 

 turbances in the conductive system and an excessive development of 

 stone cells and strengthening tissue. 



Defoliation. Premature Ripening of Wood. — Summer drought often 

 leads to premature ripening of the fruit, early leaf fall and premature 

 entrance into the winter rest period. Frequently the attacks of certain 

 fungi hasten these processes so that distinction between their influence 

 and that of drought is difficult ; nevertheless there can be no doubt that a 

 lack of available moisture has an important influence of this kind. These 

 effects of drought are manifest in various ways in the different fruits. 

 For instance, the leaves of the peach and cherry turn yellow and fall, 

 those of the grape turn yellow or red at the edges or between the veins 

 and those of the pear do not become yellow but appear brown or burned 

 in spots and remain clinging to the trees. ^^* When yellowing is due to 

 drought injury it is as a rule those parts of the leaf farthest removed from 

 the veins that yellow first. A somewhat unusual form of defoliation due 

 to a drought has been mentioned as a pectin disease."* It has been 

 observed on the grape and consists in the formation of an abscission layer 

 between the leaf blade and petiole, resulting in the premature falling of 

 the blade. The loss of leaves from drought robs the plant of essential 



