Figure 3.

Antifreeze activity as shown by representative ice crystals grown in apoplastic extracts from all treatments described in Table I: A, NA20; B, CA5; C, NA18; D, NA18 INF; E, NA2; F, NA2 INF; G, CA2; and H, CA2 INF. Protein concentrations in all samples were adjusted to 1 mg mL⁻¹ to ensure that the lack of antifreeze activity was not due to the low protein concentration. Ice crystal morphologies observed in protein solutions indicate differences in antifreeze activity: circular or rounded hexagonal discs (A, C, and D) indicate no antifreeze activity, whereas hexagons, hexagonal columns (E), and bipyramids (B, F, G, and H) represent low, moderate, and high antifreeze activity, respectively. In ice crystals A, C, and D, the c-axis is perpendicular to the plane of the photograph. In ice crystals B and E to H, the c-axis is parallel to the plane of the photograph. Magnification bar = 20 μm.