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Fig. 3. (A) Longitudinal section stained with Safranin, Fast Green, and Orange G, of a cold-hardened oat crown that had been frozen at –11°C and then allowed to recover for 3 d at 13°C in planting medium. This section is from the plant in Fig. 1C. (B) Normal nuclei showing the somewhat grainy purple-blue color of the chromatin, and adjacent cells that contain abnormally condensed chromatin that stained a dark red color and lacked any clear internal definition. With a few exceptions, abnormal nuclei were primarily found in cells on the outside of stem bases. Inset: a closer view of two adjacent cells, one with a normal nucleus and the other with an abnormal one. (C) Phloem with abnormal nuclei and metaxylem beginning to plug with dark red material. Note tearing in the wall of the metaxylem vessel. (D) Tearing of tissue within the crown core. The unlabeled bar in each subpanel is 100 µm.
