Plant Tissue

PLANT TISSUES

 

  •     The study of the internal structure of plants is known as anatomy.
  •     Plants are composed of cells, which organize into tissues, and these tissues further form organs.
  •     Plant tissues are groups of cells with similar structures and functions. 
  •     Two broad categories of plant tissues are meristematic and permanent tissues. 
  •      Variations exist in the internal structures of different plant organs. 
  •      Adaptations to various environments are evident in plant internal structures. 
  •      In angiosperms, monocots and dicots exhibit anatomical differences.

         

Meristematic tissues     

  •     Meristematic tissues are regions of actively dividing cells responsible for plant growth. 

 Types:

1. Apical Meristem:

Found at the tips of stems and roots.

Responsible for primary growth in length.

 

2. Lateral Meristem:

Located in the lateral (side) regions of stems and roots.

Responsible for secondary growth in thickness.

 

3. Intercalary Meristem:

Occurs at the base of leaf blades and internodes (stem segments).

Facilitates regrowth after damage.

 

  •        Characteristics:

- Meristematic tissues are small, isodiametric (similar in all dimensions) cells.

- They show rapid cell division.

- Lack of differentiation (cells remain undifferentiated).

 

  •       Functions:

- Meristematic tissues help in primary growth in length.

- By these tissues formation of new leaves, stems, and roots occurs.

- They are responsible for wound healing and regeneration.

 

Permanent Tissues:

  •      Permanent tissues are composed of mature cells that have lost their ability to divide.

 

  •      Types:

- Simple Permanent Tissues: Consists of only one type of cell.

1. Parenchyma:

Parenchyma cells are thin-walled cells with large central vacuoles.

They are involved in photosynthesis, storage, and healing.

 

  

2. Collenchyma:

Cells with irregularly thickened cell walls.

Collenchyma provides support to growing plant parts.

 

 

3. Sclerenchyma:

Cells of sclerenchyma have heavily thickened walls.

They enhance mechanical support and rigidity.

 

 

- Complex Permanent Tissues: Combinations of different cell types.

1. Xylem: Conducts water and minerals from roots to leaves.

Components of xylem-

Tracheids:

- They are long, tapering cells with thick lignified walls.

- They are responsible for water transport.

 

Vessel Elements:

- They are wider, shorter cells with perforated end walls.

- They are efficient water-conducting elements.

  

Xylem Parenchyma:

- Xylem parenchyma are thin-walled, living cells.

- Functions in storage and lateral conduction of water.

- It plays a role in repairing damaged xylem.

 

Xylem Fibers:

- Xylem fibres are long, thick-walled cells with tapering ends.

- They Provide mechanical support and rigidity to the plant.

- They are mostly dead at maturity.

 

Xylem Sap:

- Xylem sap is composed of water and dissolved minerals (mainly ions).

- It moves from roots to leaves, providing hydration and nutrients.

 

 

2. Phloem: Transports nutrients (mainly sugars) throughout the plant.

Components of phloem-

Sieve Tubes:

- Sieve tubes are elongated cells arranged end to end.

- They have perforated sieve plates at their ends.

- They are responsible for transporting nutrients (mainly sugars) throughout the plant.

 

Companion Cells:

- Companion cells are found alongside sieve tubes.

- They assist in the loading and unloading of sugars into and out of sieve tubes.

- They are connected to sieve tubes via plasmodesmata.

 

Phloem Parenchyma:

- Phloem parenchyma are thin-walled living cells.

- Their function is in the storage and lateral transport of nutrients.

- They can differentiate into companion cells when needed.

 

Phloem Fibers:

- Phloem fibers provide mechanical support to the phloem.

- It is made up of thick-walled, elongated cells.

- They may be dead at maturity.

 

Phloem Sap:

- Phloem sap primarily consists of water, sugars (mainly sucrose), and other organic compounds.

- Moves from photosynthetic areas (source) to where it's needed (sink) in the plant.

 

 

 

  •      Transport Function:

- Xylem transports water and minerals from roots to aerial plant parts (upward movement).

- Phloem transports sugars and other organic molecules from source to sink (bidirectional movement).