Pharmacognosy Lecture Notes - Bark

Vocabulary flashcards generated from Dr. Enasl A. Mohamed's lecture on bark, covering definitions and key concepts.

Bark

All tissues of the stem or root outside the vascular cambium.

Vascular Cambium

A layer of meristematic cells responsible for secondary growth in stems and roots.

Cork Cambium (Phellogen)

A meristematic layer that produces cork cells (phellem) to the outside and phelloderm to the inside.

Pith

The central core of the stem, composed of parenchyma cells.

Epidermis

The outermost layer of cells in a young stem.

Cortex

The tissue between the epidermis and the vascular cylinder in a young stem.

Phloem

The vascular tissue that transports sugars and other nutrients.

Xylem

The vascular tissue that transports water and minerals.

Cork (Phellem)

A protective tissue composed of dead cells, formed by the cork cambium.

Primary Cortex

The cortex derived from the ground meristem.

Primary Phloem

The phloem derived from the procambium.

Secondary Phloem

Phloem produced by the vascular cambium.

Primary Xylem

The xylem derived from the procambium.

Secondary Xylem

Xylem produced by the vascular cambium.

Phelloderm

A layer of parenchyma cells formed to the inside by the phellogen (cork cambium).

Flat Bark

Bark that is quite flat and very thick (e.g., Quillaia).

Curved Bark

Bark that is slightly concave on the inner side (e.g., Wild cherry).

Recurved Bark

Bark where the concave side is the outer one (e.g., Pomegranate).

Channeled Bark

Bark that is deeply concave on the inner side (e.g., Cassia).

Single Quill Bark

Bark where one edge covers the other (e.g., Cascara & Cinchona).

Double Quill Bark

Bark where both edges are curved inward (e.g., Frangula).

Compound Quill Bark

Bark where smaller quills are packed into bigger ones (Cinnamon).

Epiphytes

Plants that grow on other plants (e.g., Lichens, Liverwort, Mosses).

Lenticels

Breathing pores for exchange of gases in bark.

Cracks & Fissures

Breaks in the bark surface due to growth and lack of elasticity.

Wrinkles & Furrows

Surface features due to shrinking in the softer tissues of bark.

Smooth Bark

Bark with a smooth outer surface.

Striated (Inner Surface)

The inner surface has fine parallel longitudinal ridges (e.g., Cinnamon).

Coarse Striated (Inner Surface)

The inner surface has coarse parallel longitudinal ridges (e.g., Cascara).

Corrugated (Inner Surface)

The inner surface has transverse parallel wrinkles (e.g., Cascara).

Short Fracture

The fractured surface is smooth.

Granular Fracture

The fractured surface exhibits small rounded projections.

Splintery Fracture

Jagged projecting points are formed when the bark is broken.

Fibrous Fracture

Fine fibrous threads extend from the broken surface.

Lamillated Fracture

The fractured region breaks into tangentially arranged layers.

Rhytidoma

The outermost layer of bark, composed of dead or collapsed tissues.

Periderm

The secondary protective tissue that replaces the epidermis in older stems and roots, consisting of cork, cork cambium, and phelloderm.

Phellogen

Another name for cork cambium: the meristematic layer that produces cork and phelloderm.

Secondary Cortex

Another name for phelloderm: a layer of parenchyma cells formed to the inside by the phellogen.

Pericycle

A layer of cells in the vascular cylinder that can be parenchymatous or sclerenchymatous.

Bast

Another name for phloem, particularly the secondary phloem.

Cortex (Primary)

The tissue between the epidermis and the vascular cylinder; may contain sclereids, fibers, oil cells and mucilage cells.

Outer Bark

Includes rhytidoma, cork, cork cambium and secondary cortex (phelloderm).

Middle Bark

Includes Primary cortex and Pericycle.

Inner Bark

Includes Primary and Secondary phloem.

Stem Bark

Typically lighter in color on the outer surface compared to the inner surface and often hosts epiphytes.

Root Bark

Both the outer and inner surfaces usually have the same dark color and typically lacks epiphytes.

Sclereid Cells

A reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue.

Parenchyma cells

Thin-walled cells that make up the fundamental tissue of plants.

Collenchyma cells

Type of elongated plant cells that have thick cell walls that provide structural support.

Cambium

A layer of actively dividing cells between xylem and pholem tissues that is responsible for secondary growth of stems and roots.