Leaf scar

20150228Ailanthus altissima1

Leaf scar is a mark left on a stem after a leaf falls. It is an important feature in the identification of deciduous trees and shrubs during the dormant season. The leaf scar is formed as the plant seals off the vascular tissues that connected the leaf to the stem, preventing the loss of water and entry of pathogens.

Formation

The formation of a leaf scar begins with the process of abscission, where a specialized layer of cells, known as the abscission zone, forms at the base of the leaf petiole. This layer gradually breaks down, causing the leaf to detach from the stem. After the leaf falls, the plant forms a protective layer over the exposed area, resulting in a leaf scar.

Characteristics

Leaf scars vary in shape, size, and appearance depending on the species of the plant. They can be oval, round, or crescent-shaped and may have distinctive patterns of vascular bundle scars, which are the remnants of the vascular tissues that once connected the leaf to the stem. These patterns can be used to identify the species of the plant.

Identification

In dendrology, the study of trees, leaf scars are a key feature used to identify deciduous trees and shrubs during the winter months when leaves are absent. By examining the shape, size, and pattern of the leaf scars, along with other features such as buds and bark, dendrologists can accurately identify tree species.

Related Structures

• Bud scale scar: A mark left on a stem after a bud scale falls off.
• Lenticel: Small, corky pores on the stem that allow gas exchange.
• Node: The part of a plant stem where leaves and buds are attached.

Related Pages

• Abscission
• Dendrology
• Vascular bundle
• Bud scale scar
• Lenticel
• Node (botany)