Figure 9.

Leaf areas that were used in the different experiments. A, In experiment 1, the red area (1 × 1.7 cm) was imaged using a microscope for embolism detection and the yellow area (2 × 3 cm) was used for gas exchange. Note that measurements of gas exchange and xylem cavitation were carried out on separate leaves attached to the same plant. B, In experiment 2, the green area was imaged using a scanner (the entire area shown). To evaluate the amount of embolism in leaves that were not followed during dehydration, we selected 12 points (red squares) located on second order veins. Gray values of small polygons (∼150 pixels; 30 × 500 µm²) from the center of the vein were measured before and after flushing the leaf with water at 150 kPa.