抄録
Freezing process of plants is an old issue but mechanisms remain unsolved. To address this problem, we utilized digital infra-red thermography that allows 2-D differential thermal analysis. We observed freezing events in wintering blueberry stems to characterize the initiation and spread of freezing to help understand ice nucleation in stem tissues. Differential imaging clearly visualized where the first freezing events occurred and how they spread in the stems. The results maybe summarized as follows: 1) freezing pattern was different from one experiment to another even when the same stem was repeatedly used 2) in many cases, freezing was initiated from multiple sites 3) freezing was sometimes arrested or slow-downed at stem nodes. These things allow us to speculate that the ice nucleation activity should occur throughout the stems. To test this hypothesis, we determined ice nucleation activity (INA) of blueberry stems and comprising tissues using a test tube method. The results showed that stems had a high INA, especially in the bark tissues. Further precise localization of the activity is now under investigation. The high INA allow spontaneous swift freezing of the stems.
