BOTANY Higher Secondary Second Year - Textbooks Online

2. PLANT ANATOMY
Plant anatomy (Ana = as under, tamnein = to cut) is the study of
internal structure and organization of plants, especially of their parts by
means of dissection and microscopic examination. The simple type of
plant body is unicellular. In such forms, the single cell performs all the
vital functions of life. It grows, prepares food, undergoes metabolism,
reproduces and completes its span of life. The progressive evolution in
plants has resulted in increasing complexity of structures. In higher plants,
root, stem, leaves and flowers carry out different functions. Due to these
divisions of labour, the cells of the plant are differentiated to form different
tissues.
2.1. Tissues and tissue systems
The study of internal structure of plants reveals many types of tissues.
Morphologically, a tissue is a group of cells, which are similar in origin,
form and function. Physiologically, a tissue is composed of dissimilar
cells that perform a common function, for example, phloem elements and
food conduction respectively. The cells form various kinds of tissues.
Two or more types of tissues form tissue systems. Different tissue systems
form the organs. Each tissue carries out a specific function. Tissues can
be classified into two types – Meristematic tissue and permanent tissue.
Meristematic tissue
A meristematic tissue (meristos = divisible) is a group of identical
cells that are in a continuous state of division. Some cells produced by
meristematic tissue stop dividing and acquire certain changes to become
permanent tissues of the plant. This change from meristematic to permanent
tissue is called differentiation. The remaining cells in the meristem retain
their meristematic activity. Meristematic cells are self-perpetuating.
Characteristics of meristematic cells
The meristematic cells may be round, oval, polygonal or rectangular
in shape. They are closely arranged without intercellular spaces. They
have dense cytoplasm with large nucleus. They have smaller vacuoles,
which are scattered throughout the cytoplasm. Their cell walls are thin,
elastic and made up of cellulose.
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