Page 1 - LN-ANATOMY OF FLOWERING PLANT

This chapter introduces the internal structure and functional organisation of higher
plants. The study of internal structure of plant is called anatomy.

1. Tissues and Tissue Systems

The plants have cells as their basic unit. Compared to animal cells, plant cells have a
cell wall consisting of a primary cell wall, secondary cell wall and middle lamella. To
make the plant structure, the cells with common function, joint together and form a
complex structure, called tissue.
Tissues
A tissue is a group of cells having a common origin and usually perform a common
function. A plant body is made up of different kinds of tissues. Generally, the cells of
a tissue share the same origin in the embryonic stage. The tissues help in body
function by allowing division of labour, e.g., In leaf, various cells commonly perform
the function of photosynthesis.
The plant tissues can be divided into two main types I. Meristematic tissues II.
Permanent tissues
I. Meristematic Tissues
The growth in plants is mainly restricted to specialised regions of active cell division
called meristems (Gk. Memtar—divided). A meristematic tissue is an
undifferentiated mass of cells, that is in a continuous state of division or retain their
power of division. These tissues divide to form new cells which differentiate to give
rise to permanent tissues.
Characteristics of Meristematic Tissue
The characteristics of meristematic tissue are listed below
(i) They are living and contain undifferentiated mass of rapidly dividing cells.
(ii) The shape of cells is spherical, polygonal or rectangular.
(iii) The cells are compactly arranged without intercellular spaces and are
interconnected by plasmodesmata.
(iv) Nucleus is large and present either in interphase or in divisional stages.
(v) Cell wall is thin with only a primary wall made up of cellulose. Secondary wall is
absent.
Classification of Meristematic Tissue
Meristem can be classified broadly based on three ways, i.e., position in the plant
body, functions and origin.
Classification Based on Position
Meristems can be divided into three types, based on their position in the plant body.
These are as given below
(a) Apical Meristems The meristems which occurs at the tips of root and shoot and
produce primary tissues are called apical meristems. The Root Apical Meristem
(RAM) occupies the tip of a root while, the Shoot Apical Meristem (SAM) occupies
the distinct most region of the stem axis.