June 3, 1918 Density of Cell Sap and Winter Hardiness in Grain 505 



The results show beyond doubt the effect of turgidity on the freezing 

 point of the extracted sap, the difference between wilted and turgid 

 leaves being decidedly greater than was observed between different kinds 

 of grain. 



Further evidence is furnished by experiments conducted during the 

 winter of 191 5-1 6 in which wilted and turgid plants were exposed for 

 different periods to freezing temperatures. L,ots of 15 plants each were 

 treated in four different ways before exposure to cold as follows: (i) 

 Exposed to air for 30 minutes, (2) kept in air-tight cans for 30 minutes, 

 (3) roots in water for 10 minutes, and (4) entire plant submerged in 

 water for 10 minutes. All plants were then placed in a chamber sur- 

 rounded with salt and ice in which the temperature was from —2.0° to 

 — 3.0° C. Portions of each lot were removed at intervals of 10, 20, and 

 30 minutes and placed with their roots in water to test their ability to 

 recover. The results are shown in Table XIII. 



Table XIII. — Relation of turgidity to cold resistance 



In all cases the plants which were submerged in water or whose roots 

 were in water were killed or injured decidedly more than those which 

 were exposed to the air previous to freezing. 



In another experiment conducted in a similar manner the plants were 

 exposed to the air at greenhouse temperature for different periods of 

 time and then exposed to a temperature of —6.5° C. for about 10 min- 

 utes. One set was exposed to the air for 2.5 hours, another for 1.5 hours, 

 another for i hour, and another for 30 minutes before freezing. Plants 

 which had not been exposed to the air and others that had been exposed 

 to the air for 2.5 hours but which had not been frozen were included as 

 controls. All which had been wilted for 1.5 hours or longer survived 

 with no apparent injury, while all turgid plants and those wilted for i 

 hour or less were entirely killed. The appearance of typical plants from 

 each lot after treatment is shown in Plate 53. 



SUMMARY 



To summarize briefly, there appears to be no relation between the 

 cryoscopic value of the extracted sap of winter rye, wheat, emmer, 

 barley, and oats grown in the field with normal conditions and their 



