query about lignin

[hassam]

i have read many times that lignin strengthens the xylem wall by preventing it from collapsing......i want to ask what does this collapsing resfers to....is it bursting OUTWARDS or Collapsing INWARDS...and how do u figure out this

 

[XPFMember]

Assalamoalaikum!!

well it is actually collapsing inwards...quoting directly from Mary Jones:

The water in the xylem vessels, like the liquid in a sucked straw, is under tension. If u suck hard on a straw, its walls may collapse inwards as a result of the pressure differences u are creating. Xylem vessels have strong, lignified walls to stop them collapsing in this way.