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Tissue

Anatomy Of Flowering Plants of Class 11

  • A group of cells having similar origin, structure and function is called tissue. Tissues are really formed in response to a basic division of labour. The term tissue was coined by N. Grew (1682).
  • Based on the capacity to divide, the plant tissues have been classified into two fundamental types, meristematic and permanent.
  • A simple tissue consists of only one type of cells e.g., meristem, parenchyma, etc. while a complex tissue has two or more types of cells e.g., xylem and phloem.

MERISTEMATIC TISSUE

Meristematic tissue, commonly called meristem (Gk. meristos: divisible) is composed of cells which possess the power of cell division. The term 'meristem' was introduced by C. Nageli (1858) for a group of continuously dividing cells.

characteristics of meristems

  • Cells of meristems are living and are at active divisional stage.
  • The cells are usually small and isodiametric. The cells of cambium are, however, elongated.
  • The cells are compactly arranged without any intercellular spaces.
  • The cell wall is thin and made up of cellulose.
  • Cytoplasm is dense, granular with a central, large and prominent nucleus.
  • Vacuoles are either very small or absent. The cells of cambium are, however, vacuolated.
  • Metabolic activity is high, so is the rate of respiration.
  • Cytoplasm has all the cell organelles, but instead of plastids there are proplastids  (elaioplasts)
  • Ribosomes are abundant, ER is simple.

classification of meristems

  • Meristems have been classified on the basis of origin, position, function and plane of cell division.

Basis

Types

Origin

Promeristem, Primary meristem and Secondary meristem

Position

Apical meristem, Lateral meristem and Intercalary meristem

Function

Protoderm, Procambium and Ground or Fundamental meristem

Plane of cell division

Rib meristem, Plate meristem and Mass meristem

 

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