Plant Tissue System

PLANT TISSUE SYSTEM

  •     Tissues vary based on cell types and their locations within the plant body.
  •      Plant tissues are groups of specialized cells with specific functions.
  •      The plant body comprises three primary tissue systems, each with distinct roles. 

Three primary types of tissue systems:

1. Epidermal tissue system. 

2. Ground or fundamental tissue system. 

3. Vascular or conducting tissue system.

 Epidermal tissue system     

- The epidermal tissue system is the outermost covering of the plant body and plays a crucial role in protection and regulation.

 Components of the Epidermal Tissue System:

 1. Epidermal Cells:

- Epidermal cells are elongated, compactly arranged cells forming a continuous layer.

- Structure: Parenchymatous cells with small cytoplasm and a large vacuole.

- Function: Forms a protective barrier for the plant.

 2. Cuticle:

- A waxy thick layer on the outer surface of the epidermis.

- Prevents water loss through transpiration; absent in roots.

 3. Stomata:

- Found in the epidermis of leaves.

- Composed of two bean-shaped guard cells surrounding a stomatal pore.

- Regulate transpiration and gaseous exchange.

- Guard Cells: Possess chloroplasts and control stomatal opening and closing.

- Subsidiary Cells: Specialized in shape and size, surrounding the guard cells, forming the stomatal apparatus.

 

 

4. Trichomes:

- Root Hairs: Unicellular extensions of epidermal cells; aid in water and mineral absorption from the soil.

- Stem Hairs (Trichomes): Usually multicellular, can be branched, unbranched, soft, stiff, or even secretory.

- Function: Help prevent water loss through transpiration.

 

Ground tissue system

- Ground tissue is one of the primary tissue types in plants, encompassing all tissues except for the epidermis and vascular bundles.

- It plays a fundamental role in various plant functions. 

Components of Ground Tissue:

 1. Simple Tissues:

- Ground tissue consists mainly of simple tissues, which include:

a. Parenchyma:

  •     Thin-walled cells with living protoplasts.
  •      Involved in photosynthesis, storage of food, and wound repair.
  •     Typically found in the cortex, pericycle, pith, and medullary rays of primary stems and roots.

 

b. Collenchyma:

  •     Cells with irregularly thickened cell walls, often at the corners.
  •     Provides flexible structural support to growing plant parts.
  •     Present in regions requiring flexible support, such as young stems and petioles.

 

c. Sclerenchyma:

  •     Cells with heavily thickened, lignified walls.
  •     Imparts rigidity and mechanical strength to plant parts.
  •     Commonly found in mature parts of the plant, like stems, branches, and the outer covering of seeds.

 2. Mesophyll:

  •      In leaves, the ground tissue is specialized as mesophyll.
  •      Thin-walled cells containing chloroplasts for photosynthesis.
  •       Facilitates the photosynthetic process by capturing light energy.

 

Vascular tissue system

- The vascular system in plants comprises complex tissues responsible for the transport of water, nutrients, and food throughout the plant.

- It consists of two primary components: the xylem and the phloem, which collectively form vascular bundles.

 Vascular Bundles:

- Vascular bundles are structural units in the plant that contain both xylem and phloem tissues.

- They are found in various plant parts, including stems, leaves, and roots.

 Types of Vascular Bundles:

 1. Open Vascular Bundles:

- Found in dicotyledonous stems.

- Contains cambium tissue between phloem and xylem.

- Cambium enables the formation of secondary xylem and phloem, allowing for growth in thickness.

- Supports secondary growth, leading to increased stem girth.

 

 

2. Closed Vascular Bundles:

- Common in monocotyledonous plants.

- Lack of cambium tissue between phloem and xylem.

- Unable to form secondary tissues, limiting the growth in thickness.

- Restricted to primary growth, making them suitable for slender plant structures.

 

 

 

3. Radial Arrangement:

- Occurs in roots.

- Xylem and phloem are arranged alternately along different radii (rays) within the vascular bundle.

- Facilitates efficient water and nutrient uptake in roots.

 

 

4. Conjoint Vascular Bundles:

- Common in stems and leaves.

The xylem and phloem are jointly situated along the same radius within the vascular bundle.

The phloem is usually positioned on the outer side of the xylem.

- Supports both primary growth and lateral transport of nutrients in stems and leaves.