ABSTRACT
The ability of plants to tolerate low temperatures is one of the key factors in their successful growth, productivity, survival, and geographical distribution. Crop plants, especially in temperate and subtropical regions, are adversely affected by low temperatures on a routine basis. Hence, there is a need to understand the nature and mechanism of tolerance to low temperatures in plants, and to develop plants with greater tolerance. As temperate perennial plants have to survive winters, they need to tolerate not only low temperatures but also the freezing of their tissue water. Freezing of plant tissue usually involves the presence of ice in the tissue and accompanying cell dehydration. Typically, plant tissues can tolerate extreme low temperatures by freezing extracellularly, that is, by allowing ice growth to occur only in intercellular spaces [1], which entails extreme cellular dehydration, particularly in plants that survive moderate to extreme low temperatures. Although typically herbaceous plants may not be very freezing tolerant, many woody species can survive extremely low temperatures, some even below –196
°
C.
