Advance Plant Anatomy: Cork Cambium and Cork

Cork Cambium

• Phelogen: a type of secondary meristem, located laterally, composed of rectangular cells with more vacuoles, responsible for forming cork (outside) and secondary cortex (inside).
• Originates from:
  • Pericycle in roots
  • Hypodermis region in stems

Cork

• Phellem: a permanent tissue, composed of dead cells with thickened walls containing suberin, impermeable to water and gases, and provides thermal insulation.
• Functions: prevents water and gas exchange, and regulates temperature effects on inner tissues.

Phelloderm

• Composed of parenchymatic cells, differing from ordinary cortex cells in their regular strips and few layers (sometimes only one layer).
• Forms at a slower rate than phellem, with an average of 1-20 layers per season of growth.
• Originates from the first periderm, which is derived from the sub-epidermal layer.

Rhytidom

• Refers to all dead tissues outside the phelogen, formed when the phellogen grows into deeper layers.
• Also known as outer bark, composed of alternating layers of cork and tissue cut off by the cork.

Bark

• A term encompassing all tissues outside the vascular cambium of the axis, including primary and secondary phloem, cortex, periderm, and other tissues.
• Contains sclerenchymatic cells, phloem fibers, and sclerides.
• Can be divided into two types.
• The formation of periderm involves the development of multiple layers, including:
  • Epiderm: the outermost layer
  • Outer layer: located immediately inside the epidermis
  • Cortex: located inside the outer layer
  • First cork cell: located at the bottom of the cortex
  • Cork cambium: located below the first cork cell
  • Phelloderm: located underneath the cork cambium