CODIT, Walls of Wall 1  - After being wounded, the tree responds in a dynamic way by plugging the vertical vascular system above and below the wound.  The conducting elements-vessels in angiosperms and tracheids in gymnosperms-are plugged in various ways: tyloses, gum deposits, pit asperations, etc.  The plugged elements complete the transverse top and bottom walls of the compartments.  Wall 1 is the weakest wall. Wall 2.  The last cells to form in each growth ring make up the tangential walls of the compartments.  These walls are CONTINUOUS around each growth ring-except where sheets of ray cells pass through. Wall 2 is the second weakest wall. Wall 3.  Sheets of ray cells make up the radial walls.  They are DISCONTINUOUS walls because they vary greatly in length, thickness, and height.  Walls 3 are the strongest walls in the tree at the time of wounding. Wall 4.  After a tree is wounded, the cambium begins to form a new protective wall.  The wall is both an anatomical and a chemical wall.  This wall separates the tissue present at the time of wounding from tissue that forms after. It is the strongest of the four walls.

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