Experiment 2: Does embolism spreading also depend on the conduit
size?
The percentage of cumulative embolised xylem area in leaves with
cut-open minor veins and intact leaves was plotted against time for the
six species studied (Figure S5). For leaves with several artificial cuts
in the 3rd or 4th order veins, no
immediate embolism formation was detected after the cutting, except for
the vessels that were cut open. In all six species, however, we observed
embolism events in minor veins adjacent to the cuts during the first
hours of desiccation (Figure 3, Figure S3). These embolism events in
minor veins, with relatively narrow and short vessels, occurred prior to
embolism formation in the wide and long vessels of major veins. Since
the amount of embolised pixels near the cuts had a local effect only and
was relatively small compared to the total amount of embolised pixels
that could be detected in the entire leaf area, there was no large
overall difference in embolism spreading between intact and cut leaves.
Therefore, the embolism spreading patterns did not differ when the
percentage of embolised pixels of the entire scanned leaf area was
plotted against time. After the artificially induced embolism events
near the cuts, embolism spreading occurred in the major veins, and then
spread to the minor veins in both intact and cut leaves (Figure 3).