In this study, we examined freezing behavior of birch xylem ray parenchyma cells. In fresh samples, summer cells exhibited supercooling to around -15℃ and winter cells exhibited it to around -50℃. In samples where the plasma membranes were destructed by freeze-thawing, summer cells still exhibited supercooling to around -10℃ and winter cells exhibited it to around -30℃, showing that cell walls are responsible, at least partially, for supercooling and that cold acclimation alters the property of supercooling ability of the cell walls. As one of possible causes of the cell wall changes, we examined effects of cell wall-bounding proteins. The result showed that extraction of proteins from cell walls altered the freezing behavior of xylem ray parenchyma cells.