WINTER INJURY 



297 



under whitewash and under tar is due apparently to the respective heat 

 absorptive powers of white and black colors, as their minimum early 

 morning temperatures were practically the same. 



INJURIES DUE TO SUDDEN COLD 



Though some types of injury already discussed as associated with 

 immaturity of tissue might be considered to belong in the category of 

 injuries due to sudden cold, they may be classed more correctly as due to 

 untimely cold. Here, too, probably belongs the type known as winter 

 suriscald which is discussed under late winter injuries but the present 

 section is limited in its application to injuries occasioned by a sudden 

 change from moderate cold to intense cold. 



General Effects. — Chandler^^ has been quoted earlier as reporting 

 greater injury to plant tissue attendant upon sudden lowering of 

 temperature. His statement, however, should be reproduced here : " The 

 rate of temperature fall is very important indeed, especially in case of 

 winter buds. In fact, apple buds can be frozen in a chamber surrounded 

 by salt and ice rapidly enough so that practically all of them will be killed 

 at a temperature of 0°F., or slightly below, while it is well known that 

 they may go through a temperature of 20 to 30°F. below zero with but 

 slight injury where the temperature fall is not so rapid. . . . the 

 killing temperature of rapidly frozen twigs was 4.5° higher than those of 

 the more slowly frozen twigs and even then the buds of the rapidly 

 frozen twigs killed the worst." Table 36, chosen from several reported 

 by Chandler, shows the difference vividly. 



Table 36. 



-Effect of Slow and Rapid Temperature Fall on Cherry Fruit 



BUDS'« 



However, it should be remembered that Chandler found also a rapid 

 fall to — 12°C. more injurious than a rapid fall from — 12°C. to the 

 killing temperature. This is shown strikingly in Table 37, adapted from 

 a table by Chandler. 



No data bearing on this matter drawn from field observations are 

 available. Fortunately, as Chandler states, ''In this investigation it 

 was not possible to cause the temperature to fall more slowly than the 

 most rapid fall to be observed naturally in the climate of this station 



