Bark
/bɑrk/
Definition
Bark is the protective outer covering of woody stems, trunks, and roots in trees and shrubs. In botanical use, it includes all tissues outside the vascular cambium, the growth layer that produces new wood and inner bark. Depending on the source, this may include the inner bark, or phloem, which moves sugars, and the outer bark, made of older, dead protective tissue. It differs from wood, which forms inside the cambium.
Function in Plants
- Defense against injury: Bark helps shield stems and trunks from physical damage, drying, and many insects or disease-causing organisms that would otherwise reach living tissues more easily.
- Transport and storage links: Its inner layers include phloem, the tissue that moves sugars from leaves to other parts of the plant. Some species also store food reserves and other compounds there.
- Clues to plant identity: Color, texture, peeling patterns, and lenticels, small pores for gas exchange, can help distinguish trees and shrubs, especially in winter when leaves are absent.
- Care-sensitive tissue: Damage from string trimmers, staking ties, sunscald, or gnawing can interrupt phloem flow. When injury circles the stem, the plant may decline because sugars can no longer move past the wound.
Related Terms
Cambium
Cambium is a thin layer of actively dividing cells in vascular plants, found between xylem and phloem in stems, roots…
Cortex
Cortex refers to the layer of mostly ground tissue found between the epidermis, the outer protective layer, and the…
Epidermis
Epidermis is the outermost layer of cells covering young leaves, stems, roots, flowers, fruits, and seeds. It is a…
Phloem
Phloem is the plant vascular tissue that transports sugars and other organic nutrients made during photosynthesis from…
Xylem
Xylem is the plant vascular tissue that carries water and dissolved minerals from the roots to stems and leaves. It…
Vascular tissue
Vascular tissue is the plant transport system, made of xylem and phloem. Xylem carries water and dissolved minerals…
Trunk
Trunk refers to the main woody stem of a tree, palm, or other tree-like plant. It forms the central upright axis…
Woody plant
Woody plant refers to a plant that produces persistent woody stems or trunks through secondary growth, the thickening…