Bark

Bark is the collection of tissues outside a woody plant’s vascular cambium, covering its stems and roots. It includes living inner tissues and, in many species, dead outer tissues.

Vascular cambium: A cylindrical layer of dividing cells that produces secondary xylem inward and secondary phloem outward. It forms the boundary between bark and wood and produces bark’s inner conducting tissue.
Secondary growth: An increase in stem or root thickness produced by lateral meristems, especially vascular cambium and cork cambium. It drives the formation of new wood and successive protective bark tissues.
Cork oak: An evergreen oak native to the western Mediterranean whose bark yields commercial cork. Its renewable cork layer is harvested without felling the tree.
Wood: The secondary xylem that accumulates inside the vascular cambium of woody plants. Wood lies inward of the cambium, whereas bark comprises tissues outward of it.
Secondary phloem: The tissue produced outward by vascular cambium, transporting sugars and other organic compounds through woody plants. It is the innermost living part of bark in stems with secondary growth.
Phloem transport: The movement of sugars and other substances through phloem from sources to sinks in a plant. Living phloem beneath bark distributes products of photosynthesis to growing and storage tissues.
Quinine: An alkaloid used to treat malaria, historically obtained from the bark of Cinchona trees. Cinchona bark became a major source of this antimalarial medicine.
Epidermis (botany): The outermost primary tissue covering young plant organs before secondary growth replaces it. Unlike bark, the epidermis is a primary covering that generally gives way as woody organs thicken.
Cork cambium: A lateral meristem that produces protective cork cells toward the plant surface. It generates much of the dead outer covering in woody stems.
Suberin: A hydrophobic biopolymer deposited in plant cell walls, limiting water and gas movement. Suberin helps cork cells make bark resistant to water loss and infection.

Linked from 17 pages