On the cause of cold death of plants

Summary

The death of plants as a result of exposures to temperatures low enough to bring about freezing of the water in the tissues, is caused by the formation of ice crystals in the protoplasm, which bring about a disturbance in the relations between the disperse phase and the dispersion medium, so that aggregations of particles of the former are induced. Such changes are usually irreversible so that, on thawing, the original colloidal system of the living protoplasm is not re-formed, and the protoplasm in consequence is no longer living. Evidence in support of this view is derived from actual observations on the freezing of living and non-living colloidal systems and on the effect of varying the rate of freezing on the structure of such systems. By very rapid freezing it is possible to obtain the original system again on thawing, in cases in which by slow freezing the original structure is lost, and by such treatment, cases are on record in which living plant and animal cells have remained alive after freezing and subsequent thawing. In cases of frost resistant plants, however, it is probable that water is bound to hydrophile colloids of the protoplasm and is non-freezable, so that the formation of ice crystals, and the consequences of their formation, to which the death of the cells is attributed, does not take place.