Alnus nepalensis xylem structure

 

 

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?