leaf scar definition
From Wikipedia, the free encyclopedia. A leaf scar is the mark left by a leaf after it falls off the twig. It marks the site where the petiole attached to the stem. A leaf scar is found where a plant branches. The leaf scar on Ailanthus altissima. Leaf scars are formed naturally at the end of the growing season for deciduous plants when a layer of cells called the absciss layer forms between the petiole and stem. The absciss layer acts as a point of cleavage and the leaf breaks off leaving a cleanly shaped scar.