Freezing Injury of Seed Corn 
PROBABLE CAUSE OF DEATH FROM FREEZING 
HISTORICAL REVIEW 
There is no doubt but that plant tissues, under certain con- 
ditions, die as a result of freezing, but just what freezing does 
to the vital part of such tissues to bring about death is not 
fully understood. The theories which have been advanced to 
explain death by freezing seem to lack sufficient evidence to 
prove their correctness. Wide differences of opinion are held 
by various investigators regarding the direct cause of death. At 
the present time, therefore, any explanation of the phenomenon 
of death by freezing must be considered as an expression of the 
probable cause and not as a definite statement of what actually 
happens. The theories which have been advanced to explain the 
cause of death from freezing may be grouped as follows: (1) 
crushing of plant tissues, or rupturing of cell structures, (2) 
too rapid thawing, (3) desiccation of the protoplasm, (4) 
physical and chemical disorganization of the protoplasm and 
other cell contents. 
CRUSHING OF PLANT TISSUES OR RUPTURING OF CELL STRUCTURES 
As stated by Salmon (1917), the early observers of ice for- 
mation within plant tissues, knowing nothing of the cellular 
structure of plants, attributed death from freezing to rending 
or crushing of the tissues. 
In 1737 Du Hamel and Buffon proposed that death resulted 
from a rupturing of the cell walls due to the expansion which 
accompanies ice formation. The same opinion was held by 
Geopert (1830) who discovered ice within the cells and also 
outside the cells in the intercellular spaces. Sachs (1860) found 
that ice was sometimes formed within the cells, and Muller - 
Thurgau (1886) concludes that ice is formed within the cells 
only in case of very large size, or very rapid freezing. 
Supercooling followed by ice formation, and very rapid 
cooling are more injurious to plant tissues than slow cooling, 
according to Mez (1905). Neither supercooling nor rapid cool- 
ing give the water in the cells time to escape and ice is, there- 
fore, formed within the cells. In each of the above cases where 
ice was formed within the cells, whether it was the result of 
slow or rapid cooling, or whether the tissues had been super- 
cooled, the investigators seemed to think that the increase in 
volume probably worked some injury to the cell walls. 
Plant tissues containing a large percentage of water, such 
as turgid leaves, and young, growing twigs are especially sub- 
