CHAPTER VI 



PATHOLOGICAL CONDITIONS ASSOCIATED WITH 

 EXCESSES OR. DEFICIENCIES IN MOISTURE 



Not only is water a limiting factor to growth, but when there is a 

 deficiency or when it is present in excess well defined pathological condi- 

 tions may arise. Some of the most difficult disorders with which the 

 fruit grower has to deal are to be regarded as drought or as excess moisture 

 diseases. 



DISTURBANCES DUE TO MOISTURE EXCESSES 



Excessive moisture conditions are likely to be accompanied by a 

 disproportionate development of certain tissues usually parenchyma and 

 this is at the expense of conductive tissue. 



The Splitting of Fruit. — One of the most frequent troubles incident to 

 the presence of too much water at certain seasons of the year is a splitting 

 of the fruit. This is most likely to occur shortly before maturity when 

 rains follow a period of drought during which the fruit has been checked 

 in its growth. Apparently the checking of growth is accompanied by 

 changes in the fruit skin rendering it less elastic so that when growth 

 processes are accelerated following a rain it is unable to expand rapidly 

 enough to make provision for the developing tissues within. Heavy, 

 late irrigation following a long dry season has the same effect. The 

 stone fruits are particularly subject to this trouble and certain varieties 

 of apples, for example the Stayman Winesap, are likewise susceptible. 

 In the stone fruits, splitting is sometimes limited to the stone, the flesh 

 and skin remaining intact. Treatment of this trouble, as of most dis- 

 turbed conditions due to abnormal water relations, should be preventive 

 rather than remedial. Cultural practices should be directed toward 

 maintaining in the soil a moderate amount of available moisture so that 

 growth will not be checked, even though there may be an extended 

 period of dry weather. Splitting of flesh and of stones seldom occurs if 

 the tissues of the fruit are kept growing. It is suddenly renewed growth 

 following a check that causes the trouble. 



In the fig, splitting may accompany high atmospheric humidity during the 

 ripening period even though there be no rain or no sudden changes in water 

 content of the soil. However, they are much less likely to split under such con- 

 ditions than when rain accompanies a humid atmosphere so that the trees can 

 take up an increased amount of moisture. ^"^ Should dry, warm weather follow 

 the splitting of this fruit the fissures may close and partially heal over without 

 fermentation setting in. 



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