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Meristematic tissue

The document discusses meristematic tissue in plants, which consists of immature cells capable of division and is essential for growth at various plant regions such as the apex of roots and shoots. It classifies meristems based on origin, position, function, and plane of division, highlighting types like promeristem, primary meristem, and secondary meristem, as well as characteristics such as being living cells with thin walls. Several functions of specific meristems like protoderm, procambium, and ground meristem are also described.

Science◦
meristematic tissue DR. C. BEULAH JAYARANI M.SC., M.A, M.ED, M.PHIL (EDN), M.PHIL (ZOO), NET, PH.D (EDN) ASST. PROFESSOR, LOYOLA COLLEGE OF EDUCATION, CHENNAI - 34
Plant tissue  Group or mass of cells that are similar in origin, structure, function form a tissue.  Plants are made up of vegetative and reproductive part.  In general plant tissues are classified into two types namely. 1. Meristems 2. Permanent tissue 2
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meristematic tissue  The term “meristem” means ‘divisible’ or having cell division activity.  Meristematic tissues are a group of immature cells that are capable of division.  In plants meristem is found in three regions where growth can take place for example apex of stem, root, leaf etc.. 4
characteristics of meristematic tissue  They are made of living cells.  Cells are oval ,polygonal or round in shape.  They are thin walled with dense cytoplasm.  They undergo mitotic division.  They do not store food materials. 5
tyPes of meristem  1. Based on Origin and development  2. Based on position  3. Based on function  4. Based on plane of divisions 6
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1. origin and develoPment  Based on origin and development they are classified into three types: 1. Promeristem or primordial meristem 2. Primary meristem 3. Secondary meristem: 8
1. Promeristem or primordial meristem  In plants they occupy a small area at the tip of root and shoot.  They further divide to form primary meristem. 9
2. Primary meristem  They are present below the promeristem at the shoot and root apices.  These cells divide to form permanent tissues. 10
3. Secondary meristem:  It is derived from primary permanent tissues which have the capacity of division. 11
Based on Position Apical meristem: They are found at the apices of root and shoot and bring about increase in length. They include both promeristem and primary meristem. Intercalary meristem It lies between the region of permanent tissue and is part of primary meristem which is formed due to intermittent permanent tissues. Lateral meristem: these are arranged to the parallel sides of origin and normally divide radially to give secondary permanent tissues . 12
functions Protoderm: it is the outermost layer of the growing region which develop to form epidermis. Pro cambium: it is composed of narrow elongated cells that give rise to vascular tissue. Ground meristem: it is composed of large thick walled cell which develop to form hypodermis, cortex and pith. 13
Plane of division  The growth pattern and plane of division of meristematic tissue is important to govern the mode of growth.  Mass meristem  Rib or file meristem  Plate meristem 14
Rib or file meristem cell division occurs only on one plane. Mass meristem: In this plane cell division occurs in all planes resulting in increase of volume. It can be observed in meristems of cortex and pith Plate meristem: These cells divide in two planes resulting to an increase in the area of an organ. Eg: leaf formation. 15
REFERENCE “BIOLOGY READER”  Tamil Nadu text book  NCERT Books  Google Images 16