Page 3 - LN-ANATOMY OF FLOWERING PLANT

Classification Based on Functions
The meristems are also classified on the basis of their functions as
(a) Protoderm It is the outermost portion of the primary meristem found at the apex
of the stem and root. It develops into epidermis.
(b) Procambium It develops into primary vascular tissues. It forms the isolated
strands of elongated cells, very near to the central region.
(c) Ground Meristem It develops into the ground tissue. The cells are thin-walled,
living and isodiametric. In the later stages of growth, they become differentiated into
hypodermis, cortex, endodermis, pericycle, medullary rays and pith.
Classification Based on Origin
The meristems are grouped on the basis of origin as
(a) Primary Meristems These meristems are derived during the early embyonic
stages. They divide rapidly and differentiated into primary permanent tissues which
make the fundamental structure of the plant body. They are mainly found in the
growing apical regions of the root and shoot.
(b) Secondary Meristems These meristems appears in later stage of development in
the plant body. They lie lateral in position in both the stem and root. Some primary
permanent tissues acquire the power of division and become meristematic.
These tissues dedifferentiate and form secondary meristems. Some examples of
secondary meristems are cork cambium and interfascicular cambium. They allow
secondary growth in tissues.
II. Permanent Tissues
The meristematic cells gradually differentiate and become mature or permanent.
The permanent tissues actually composed of cells in which the growth has stopped.
Permanent tissues can be divided into two types
1. Simple Permanent Tissues
The permanent tissues having all cells similar in structure and function are called
simple tissues. These are groups of homogenous cells which perform the same
function.
i.Parenchyma
It is a living, simple permanent tissue composed of thin-walled cells. Parenchyma
(Para-beside; enchein – to pour) is also called primary tissue or ground tissue. It is
present in cortex, pith, palisade, mesophyll and some other parts of flower. It is
mostly produced by the ground tissue. The parenchyma terms the major component
within the organs.
The characteristic features of parenchyma are as follow
(a) The cells are thin-walled, less spherical and polyhedral in shape, these are
generally isodiametric.
(b) The cell wall composed of cellulose, hemicellulose and pectin.
(c) Cells have a large central vacuole, peripheral cytoplasm with a nucleus.
(d) The cells may be either closely packed or have small intercellular spaces.