Tissue definition: Group of similar cells with same structure & specific function forming a tissue.

Examples: skin cells → skin tissue; muscle cells → muscle tissue; leaf green cells → leaf tissue.


Kinds of Tissues

Plant Tissues – two basic types


(A) Meristematic tissue

  • Made of actively dividing cells.
  • Function: produce new cells for plant growth.
  • Found at growing points: tip of roots, stems, branches.
  • Causes length & thickness growth of stem.

Characteristics:

i. cells are small.

ii. cell‑walls are thin.

iii. nuclei are large & conspicuous.

iv. cells have almost no vacuoles.

v. cells divide to add new cells.


(B) Permanent tissue

  • Non‑dividing, specialised cells that remain same throughout life.
  • Form bulk of plant body.

Permanent tissue Divided into two main types:

a. Simple permanent tissue – provides support & protection.

b. Complex permanent tissue – conducts nutrients & water.Simple permanent tissues – two types

(i) Protective tissue

  • Cells with thick walls on surface of roots, stems & leaves.
  • Example: epidermis of leaves (secretes waxy waterproof layer).


(ii) Supporting tissue

Three categories: 

  1. Parenchyma - पैरेन्काइमा 
  2. Collenchyma - कॉलेन्काइमा 
  3. Sclerenchyma - स्क्लेरेन्काइमा
(1) Parenchyma
  • Characteristics: Spherical, thin‑walled living cells with large intercellular spaces.
  • Location: Found throughout the soft parts of the plant.
  • Function: Performs photosynthesis, respiration, food storage, and provides buoyancy in aquatic plants.

(2) Collenchyma
  • Characteristics: Elongated living cells with unevenly thickened cell walls at the edges; little intercellular space.
  • Location: Found in petioles, leaf veins, and young stems.
  • Function: Provides flexible mechanical support to plant parts.

(3) Sclerenchyma
  • Characteristics: Long, narrow, thick‑walled dead cells; intercellular spaces are absent.
  • Location: Found in mature parts like wood, bark, etc.
  • Function: Provides rigid mechanical and structural support to the plant.

Key differences:
  • Parenchyma has large intercellular spaces and living cells.
  • Collenchyma has uneven wall thickening and living cells.
  • Sclerenchyma consists of dead cells with uniformly thick walls and no intercellular spaces.