Loss of Adenosine Triphosphate Synthesis Caused by Freezing and Its Relationship to Frost Hardiness Problems.

A great number of organismiis can wvithstan(d temperatures below the freezing point of water. Many plants are even resistant against severe frosts especially during the winter months. In the late spring, during summer and in the early fall, however, they may be killed by moderate frosts. In order to gain resistance they must undergo a hardening process; in spring this resistance is lost by dehardening. Although both phases, hardening and dehardening, have been studied intensively, little is actually known of the mechanisni of frost resistance. The common drawback of the few theories available capable of explaining the action of frost on the plant cell and the mode of protection of the protoplasnm (2, 15, 17, 18, 24, 34) is that they lack convincing experimlental evidence. In order to test the hypothesis, that cell death due to freezing is cause(d by the denaturation of proteins we studied the response of a number of enzymes and enzyme systems to freezing. As has already been pointed out in a previous paper (35) individual enzymes were not inactivated to any appreciable extent by freezing either in vitro or in vivo. Only the enzyme systems of electron transport in photosynthesis proved to be frost sensitive. These investigations have been extendled. In this communication experimental results are presented which throw light on the primary action of frost on the cell and the manner in which protection may be achieved.