MadSci Network: Botany

Re: Why do needles leave scars when they fall off the tree?

Date: Wed May 8 19:17:30 2002
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1020863896.Bt

The leaf scar occurs because the stem has to heal over the area where the leaf 
was attached to prevent disease entry and water and nutrient loss. It is 
especially important to seal off the vascular connections (xylem and phloem) 
that carried water and dissolved substances into and out of the leaf. The 
orderly process of leaf death or senescence ends with the dropping or 
abscission of the leaf. An abscission zone forms before the leaf drops.

Leaf scars are often useful for identifying deciduous trees and shrubs when 
they are leafless.

A person who loses a limb or finger would also have a scar where the wound 
healed over.


Plant Stem Growth

Leaf Abscission

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