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Class 9, Science, Chapter-6, Lecture-1, Plant Tissue(Notes)

TISSUE:

A group of cells having a common origin, similar or related structure which work together to perform a common function is called tissue.

DIFFERENCES BETWEEN:

Plant Tissue

Animal Tissue

Most of the plant tissues are dead.

Most of the animal tissues are living.

Require less energy for maintenance.

Require more energy for maintenance.

Can be classified into meristematic (dividing) and permanent (non-dividing) tissues.

Cannot be classified on the basis of cell division. Growth is uniform.

Meristematic tissues grow throughout life.

Do not grow after reaching maturity.

Have simple organisation.

Have complex organisation

Are adapted to sedentary existence (stationary).

Are adapted to active locomotion (high mobility).

Meristematic Tissues

The plant tissues consisting of immature living cells that are capable of dividing and forming new cells are called Meristematic Tissues.

Three Types (based on location)

  1. Apical Meristem - 
    Location - at the tip of stems and roots
    Role - growth in length
  2. Intercalary Meristem -
    Location - at the base of leaves, base of internodes, below the nodes.
    Role - growth of leaves, straightening of branches.
  3. Lateral Meristem -
    Location - at the sides of stems and roots
    Role - growth in the girth (radius) of stem and root.

Characteristics:

  1. Cells are spherical or polygonal in shape
  2. Thin and elastic cell wall
  3. Dense cytoplasm in the cells.
  4. Large nucleus in the cells.
  5. Vacuoles are absent in the cells.
  6. Consists of living cells.

Permanent Tissues

The plant tissues consisting of mature living or dead cells having permanent shape, size and function that are incapable of dividing and forming new cells are called Permanent Tissues.

Two Types (based on types of cells)

  1. Simple Permanent Tissue–
    The permanent tissues in plants which consist of one type of cells, all performing the same function are called the Simple Permanent Tissues. 
    Examples: Parenchyma, Collenchyma, Sclerenchyma, Protective tissue (epidermis and cork) 
  2. Complex Permanent Tissue–
    The permanent tissues in plants which consist of more than one type of cells co-ordinating to perform a common function are called the Complex Permanent Tissues.
    Examples: Xylem, Phloem

Characteristics:

  1. Cells have permanent shape and size.
  2. Irregular cell wall
  3. Vacuoles are present in the cells.
  4. Consists of both living cells and dead cells.

Differentiation:

The process of maturing of cells to take a permanent shape, size and functions is called differentiation.

 Differences Between:

Meristematic Tissue

Permanent Tissue

The cells are small and undifferentiated.

The cells are large and differentiated.

Intercellular spaces are absent.

Intercellular spaces are often present.

Vacuoles are absent.

Large central vacuole occurs in living permanent cells.

Nucleus is large and prominent.

Nucleus is less conspicuous.

Cell wall is thin.

Cell wall is thin or thick.

The cells undergo regular divisions.

The cells do not normally divide.

Meristematic tissue is a simple tissue.

It can be simple, complex or special.

Cell organelles are simple.

Cell organelles are well developed in living tissue.

The cells are living.

The cells may be living or dead.

It takes part in growth.

It provides protection, support, conduction etc.