Pharmaceutical botany - Lighthouse Survival Blog

PLANT TISSUES
PLANT TISSUES
A tissue is an aggregation of cells of common source, structure
and function in intimate union.
According to structure the following tissues are found in various
forms of higher plants:
1. Meristem 8. Laticieerous tissue
2. Pasenchyme 9. Cribieorm or sieve tissue
3. Collenchyme 10. Woody fibre tissue
4. SCLERENCHYME II. HaRD BAST
5. Epidermis 12. Tracheary tissue
6. Endodermis 13. Medullary rays
7. Cork
A mass of tissue so united in the plant as to constitute a distinct
unit is called a tissue system. Three systems of tissues are commonly
distinguished in higher forms of plants:
The epidermal or tegumentary system
The fundamental system
The pibrovascular system
Meristem, frequently called embryonic tissue, is undifferentiated
tissue composed of cells in the state of rapid division.
Parenchyme or Fundamental Tissue is the soft ground tissue of
plants consisting of cells about equal in length, breadth and thickness
(isodiametric) with thin cellulose cell walls enclosing protoplasm and
a nucleus. Three important kinds of parenchyme, viz. : Chlorophyll
parenchyme, containing chloroplasts and found in green parts of plants;
reserve parenchyme occurring in seeds, and underground parts of
plants and containing starch, aleurone grains, fixed oils, etc. ; conducting
parenchyme found distributed in various parts of plants and serving for
the transferral of food.
Collenchyme consists of elongated prismatic cells whose walls are
of cellulose. The angles of the ceUs are thickened with a colloidal
substance. It is found beneath the epidermis of many plants, rarely
alongside the endodermis and forms the "ribs" of stems such as in
Burdock, Caraway, etc. Its function is that of support.
Sclerenchyme or "stony tissue" is made up of stone cells variously
shaped. These were formerly parenchyme cells whose walls became