In this longitudinal view,
you can see the structure of the compound perforation plate. The
vessels are relatively narrow at about 50 Ám. Perforation plates are considered
to be a safety feature, which will prevent air bubbles
(embolisms) from traveling freely up the xylem vessels
when water in the xylem cavitates under severe water deficit
conditions. Perforation plates trap the bubbles, which
may be resorbed when water stress conditions
no longer prevail.
Look up the
word embolism and find out how these are formed
in plants. How do these relate to tyloses?