Bark, Wood And Galls

Lecture-6 By

Dr. Ahmed Metwaly

1. Definition. 2. Kinds. 3. Structure. 4. Quassia wood. 5. Guaiacum wood. 6. Sandal wood.

The wood is the portion of the trunk, stem, branches or roots of woody plants inside the vascular cambium.

Sap wood Heart wood It is a living wood. Lighter in colour

•It contains reserve food material, e.g. starch. * It may be formed of whole xylem or only its outer layers.

•Function: Conductive and support. e.g. Quassia wood

* It is a dead wood. Darker in colour * It is originally a sap wood in which the vessels axe blocked by Tyloses. * It forms the inner part of xylem or the whole xylem * Function: support.

e.g. Guaiacum wood.

Kinds of woods

The wood or xylem is formed of:

Fibres Tracheids Vessels Wood parenchyma Medullary rays

All the wood elements are lignified and acquire a deep red color with phloroglucin and HCl.

Wood

Fibres

* Each fibre is a single, non-living, elongated cell, and having

usually very long tapering ends, very thick, lignified, pitted

walls and a narrow lumen

Tracheids * Elongated cells having thick lignified walls.

* The walls are pitted with bordered pits.

* They serve for conduction of water.

Vessels * Are long tubes. (number of cells placed end to end).

* The vessels may be:

a) Annular (the thickening is in the form of separate rings).

b) Spiral (the thickening is spirally coiled around the vessel).

c) Reticulate (the thickening meet together forming a network).

d) Pitted (the thickening leaving very small pits).

e) Scalariform (the thickening occurs as a ladder).

Medullary

rays

* Are regular bands of radially elongated parenchyma. It may be;

a) Primary medullary rays (running from the pith to the

pericycle).

b) Secondary medullary rays (running between xylem and

When the vessel stops its function, the parenchyma around it grows inside the vessel through the pits, so the vessels become blocked. These inner growths are called tyloses e.g. Guaiacum wood.

Origin: Dried wood of the trunk branches of Picrasma excelsa (known as Jamaica quassia) and Quassia amara (known as Surinam quassia). Family Simarubaceae.

Shape Occurs in the form of chips and rarely as small cubes.

Color Yellowish-white to yellow.

Odor Odorless

Taste Intensely bitter taste.

the powder is characterized by the following elements : 1) Fragments of wide bordered pitted xylem vessels. 2) Fragments of wood fibers with thin walls and linear pits. 3) Fragments of rectangular and lignified wood parenchyma. 4) Fragments of calcium oxalate prisms (absent in Surinam quassia). 5) Fragments of madullary rays With underlying fibers. Some of the cell contain starch granules or prisms of Ca-ox.The cell are pitted.

Bitter principles (Picrasmin, Quassin and Neoquassin).

Alkaloids (cathine-6-one) Coumarins (scopoletin)

1) Parasiticide for head and body lice. 2) As enema to expel threadworms. 3) Insecticide against certain agricultural

insects.

Origin: The heart wood of Guaiacum officinale and Guaiacum sanctum. Family Zygophllaceae.

Resins 15–20%. Guaiaretic acid, dihydroguaiaretic acid and guaiacin.

Simple phenolics (guaiacol) Sesquiterpenes (guaiol)

useful in chronic gout Antirheumatic. Anti-inflammatory.

An alcoholic solution gives a deep blue colour on the addition of oxidizing agents such as ferric chloride.

This colour is destroyed by reducing agent.

Origin: It is obtained from Santalum album. Family Santalaceae Active Conistetuents: Volatile oil, the chief constituents of the oil is the alcohol Santalol. Uses: 1) A source of volatile oils. 2) The oil is a stimulant and disinfectant of the whole genitor- urinary tract.

Sandal wood Santalol

1. Definition. 2. Kinds. 3. Structure. 4. Quassia wood. 5. Guaiacum wood. 6. Sandal wood.