Xylem ray parenchyma cells in woody plants adapt to freezing of apoplast water by deep supercooling. The mechanism of deep supercooling is proved not due to merely cell wall property that water in micro-capillaries within the cell walls are sufficiently small to keep supercooling by which inhibits ice seeding of protoplasts through the cell walls. The mechanism of supercooling, thus, may respond to intracellular factors, such as accumulation of any substances that facilitate supercooling. Our approach to identify these intracellular substances from xylem ray parenchyma cells of woody plants that exhibit deep supercooling was introduced in this review.
