ABSTRACT
Developing an understanding of cold hardiness in fruit trees is a complex issue due to the discovery that different tissues within the same plant respond in quite different ways to exposure to subzero temperatures. Although injury of fruit tree tissues due to exposure to freezing temperatures is not a pathological disease, the dead tissues that result from freeze injury often serve as a primary infection court for other fruit tree pathogens. Additionally, economic losses can occur as a direct result of severe winter temperatures and/or untimely spring frosts. Thus, it is commonly recognized that low temperatures are a major limiting factor in the production of deciduous fruit crops. Living xylem tissues of several temperate woody species, including species of temperate fruit trees, avoid low temperature stress by deep supercooling. Low-temperature scanning electron microscopy has also been utilized with great effectiveness to examine plant tissue while in a frozen state.
