CHANGES IN ELECTRIC RESISTANCE OF LIVING AND INJURED TISSUES OF APPLE SHOOTS DURING WINTER AND SPRING

Abstract

The study indicated the possibility of testing the winterhardiness of outdoor plants without injuring their tissues by freezing or drying. Varietal differences in the electric resistance of living shoots of certain apples were recorded throughout the winter season. These differences were of the same order of magnitude as their frost-hardiness rating, which was previously established by applying controlled freezing tests. The association between the electric resistance and the varietal ratings of hardiness became less apparent during the spring weather when the shoots resumed growing.During winter the electric resistance of detached shoots, or of shoots whose roots were frozen, was generally lower than the resistance of similar, normally grown shoots. With the advent of spring weather, the electric resistance of all abnormally grown shoots greatly increased due to desiccation injury, whereas the resistance of all living shoots decreased with their resumption of growth. These findings suggested a viability test during winter for outdoor plants. The differences in electric resistance indicated a method for differentiating between winter injury of outdoor plants resulting from injured shoots and/or from injured roots. The method also assisted in determining the probable time and cause of such injuries.