Plant Tissues

Plant tissues may be categorised into two fundamental types based on their ability to divide:

Meristematic Tissue

Meristematic tissues are those in which cells continually divide, giving rise to new cells. These tissues are necessary for plant growth. Plants grow only in locations with meristematic tissues, such as the root and shoot tip. Additionally, it is referred to as growing tissue. This tissue’s cells are very active, with a thick cytoplasm, thin cellulose walls, and conspicuous nuclei. They are free of vacuoles.

Meristem produces new cells that first like those meristem cells. Once they grow and become differentiated as components of other tissues, their characteristics alter.

Meristematic tissue is categorised according to the areas in which it is found.

• Apical Meristem : These are found at the tips of developing stems and roots. As a result, they help in the growth of stems and roots. It functions as a pro-meristem, with actively dividing cells that give rise to other meristems.

• intercalary Meristem : These are found near the base of twigs’ leaves and internodes (on each side of the node). It helps in the longitudinal growth of plants (elongation).

• Lateral Meristem (Cambium) : On the lateral sides of stems and roots, they are found. It increases to the girth of the stem and root.

Permanent Tissue

This tissue is generated from meristematic tissue cells that have lost their capacity to divide and develop a stable shape, size, and function via a process called differentiation.

The meristematic tissues tend to do so as a consequence of differentiation.

The many forms of permanent tissues include the following:

Simple Permanent Tissue

It is composed completely of a single kind of cell, i.e. the cells that compose these tissues are structurally and functionally identical.

Additional classifications for simple permanent tissue include:

Parenchyma

The basic packing tissue is made of a few layers of cells. They are found in the cortex and pith of stems, as well as in the mesophyll of leaves and roots.

• Characteristics

1. 1. 1. These are unspecialized living cells with a thin cell wall.
      2. Typically, cells are loosely packed with significant gaps between them (intercellular spaces).

Functions

1. 1. Ir serves as a food store tissue; 
   2. This tissue supports plants; 
   3. In certain circumstances, when the parenchyma cell includes chlorophyll, it performs photosynthesis. This form of parenchyma tissue is referred to as chlorenchyma. 
   4. Large air spaces are found in parenchyma cells of aquatic plants to provide buoyancy to planes, which aids in their flotation. Aerenchyma is a form of parenchyma tissue.
   5. Additionally, the parenchyma of stems and roots retains nutrients and water.

Collenchyma

These tissues are often found under the epidermis of leaves and in leaf midribs.

Characteristics

1. 1. 1. Cells are alive, elongated, and irregularly thickened at the corners owing to pectin deposition.
      2. They have a small amount of intercellular space.

Functions

1. 1. It gives mechanical support and elasticity (flexibility) to plants. 
   2. It also enables simple bending of different plant components (leaf and stem) without breaking.

Sclerenchyma

Some of this tissue is found in stems, surrounding vascular bundles, in leaf veins, and in the hard coverings of seeds and nuts.

Characteristics

1. 1. 1. Sclerenchymatous tissue cells are dead.
      2. The cells seem to be long and narrow.
      3. Cell walls become thicker as a result of lignin deposition, which acts as a cement and hardens them.
      4. Due to the thick walls of the cells, there is no internal space.

Functions

1. 1. It is recognised as the primary mechanical tissue that contributes to the plane’s hardness and stiffness; for example, the husk of the coconut is composed of sclerenchymatous tissue.
   2. It envelops seeds and nuts in a protective sheath. It provides the plant body with stiffness, flexibility, and suppleness.

Protective -Tissues

      (a)  Epidermis

      (b) Cork

Complex Permanent Tissue

It is formed of many cell types that have a similar origin. Regardless of their appearance, all cells work together to fulfill a common function.

The following are examples of complex permanent tissue:

• Phloem 
• Xylem 

Both are conducting tissues that form a vascular bundle. This is a characteristic of complex plants. le enables them to survive in a terrestrial environment.

Xylem

It is in charge of the movement of water and minerals from the roots to the rest of the plant. The xylem cells have thick walls, and many of the chem cells are dead. Xylem is composed of a variety of different elements, which are as follows:

• Tracheids : 

• • • These are non-living, long, tapering tubular structures that convey water and minerals upward.

• Vessels 

• • • Long, tube-like structures generated by a row of cells laid end to end. 
    • These are also dead cells with lignified walls.
    • Additionally, they assist in the conduction of water.

• Xylem parenchyma 

• • • These are the only living xylem cells with thin celJ walls. 
    • They store food and assist in water’s sideways conduction.

• Xylem fibres 

• • They are elongated dead cells with tapering Xylem parenchyma ends and thick cell walls. 
  • They are xylem-associated fibres that help in the xylem’s function.

• Phloem

It is responsible for transporting food from the leaves to other areas of the plant.

It is capable of material movement in both directions. Except for phloem fibres, all phloem cells are alive.

Phloem is composed of four basic types of elements:

Sieve tubes

• • • These are tubular cells with perforated walls and a thin cytoplasmic layer.

Companion cells

• • • These are small elongated cells with perforated walls and active cytoplasm. They assist in the transfer of food via sieve tubes.

Phloem fibres

• • • They are thick-walled sclerenchyma cells that provide the tissue its mechanical strength.

Phloem parenchyma

• • They are thin-walled cells that help in the storage of food and its slow lateral conduction.