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A leaf scar is the area left behind when a leaf breaks free from a stem or a branch. When a leaf falls from a tree, the petiole softens and the leaf breaks free and falls. The petiole is the part of the leaf that connects it to the stem or branch of the plant. At the time the petiole breaks free, it severs all of the vessels through which food and water travel. After breaking free from the plant, the small area on the stem that is left open heals over and leaves a distinctive mark. This mark is easy to spot, as it is normally lighter than the stem. The mark is also speckled with dots which are located where the vessels used to be connected. These vessels are grouped together in clusters called bundle scars. Both the leaf scar and the bundle scars within are very useful for identifying plant species during the winter months.
When trying to identify a plant, the leaf scars and the bundle scars are examined closely, often with a magnifying glass. By looking at the size and shape of the leaf scar, a general idea of what type of leaf used to be there can be discerned. Plants with large leaf scars and many bundle scars normally had large leaves. A small leaf typically has less of a curvy scar and only a couple bundles. A curved leaf scar is characteristic in larger leaves because a curved petiole helps to support the weight of the leaf better than a flat one can. By using the scars, a botanist can determine the pattern of the leaves on the plant as well as their size and in some instances their shape. All of these characteristics are very important when trying to determine different plant species in the wintertime.
Although all leaf scars are the result of falling leaves, they can be many different shapes, sizes, and colors. The color of the scar depends on the color of the stem on which they are located. Green, brown, and red, are all common colors for one of these scars. There are also large and small scars and round and flat ones. Shapes can include oval, shamrock and crescent, among others. This depends on the shape and size of the leaf that made the scar. There also can be hairs along the scar that can help in identification as well.
@seHiro - Sounds great in theory, although really if I was trying to stay alive in the wilderness during the winter, staying warm would be higher on my priority list than identifying edible plants.
Does anybody know if leaf scars are helpful in diagnosing or identifying any plant diseases? i know some diseases cause plants' leaves to wither and fall off, and I would bet the leaf scars from leaves that withered before falling look different than the leaf scars from plants whose leaves fell off while still healthy and green.
For plants like roses, for example, could you identify if they had some kind of leaf blight by looking at the leaf scars, even if it was wintertime or they had been heavily pruned so you really couldn't examine any current leaves?
Very interesting subject for an article! I'm impressed that botanists can tell what size the plant's leaves are, how heavy they are and even what shape they are, all from the little scar mark the leaf leaves when it falls off.
Botany aside, wouldn't this be extremely helpful knowledge for anybody stuck in a survival situation out in the wilderness in the winter?
Survival manuals usually tell you to look at the leaves of plants to determine which ones are safe to eat, but if the plants had no leaves then I sure would want to know which leaf scars meant which lead types so that I could still locate the edible plants!
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