Fig. 4. (A) Longitudinal section stained with Safranin, Fast Green, and Orange G, of a cold-hardened oat crown frozen at –13°C and then allowed to recover for 10 d at 13°C in planting medium. This section is from the plant in Fig. 1D. (B) A large root with plugged phloem, but in this case with no plugging in the xylem. (C) Abnormal phloem in the central part of the crown core. Note the lack of nuclei and reddish color as compared with the control (Fig. 2D). (D) Plugged metaxylem and parenchyma with abnormal nuclei as compared with control (Fig. 2C). (E) Cross-section of a small root from a different section of the same plant with several xylem vessels plugged. Most of the phloem vessels in a ring outside the xylem also appear plugged. The unlabeled bar in each subpanel is 100 µm.