Permanent Tissues - Diagram, Types Notes Biology Class 9

Permanent tissues are a type of plant tissue that has completed its growth and differentiation. They remain in a specialized state throughout the plant's life. These tissues perform specific functions and are responsible for the overall structural growth and function of the plant. There are three main types of permanent tissues in plants: Parenchyma, Collenchyma, and Sclerenchyma.

Table of Content

• What is Permanent Tissue?
• Types of Permanet Tissue
• Simple Permanent Tissue
• Difference Between Parenchyma, Collenchyma, and Sclerenchyma
• Complex Permanent Tissue
• Secretory Tissues
• FAQs on Permanent Tissues

What is Permanent Tissue?

Plant tissues are groups of specialized cells that have similar structures and functions. They work together to perform specific roles within a plant. There are two main types of plant tissues: meristematic tissues and permanent tissues. Permanent tissues consist of mature, differentiated cells that have lost the ability to divide. These mature cells carry out specific functions that are necessary for the plant's growth, survival, adaptability, and functionality.

Types of Permanet Tissue

The permanent tissue are divided into Simple, Compex and Secretory Tissue.

• Simple Permanent Tissues
  • Parenchyma
  • Collenchyma
  • Sclerenchyma
• Complex Permanent Tissues
  • Xylem 
  • Phloem
• Secretory Tissues
  • Laticiferous Tissues
  • Glandular Tissues

Simple Permanent Tissue

These tissues consist of a single type of cell, mainly originating from the same source and having similar structure and functions. They are also called homogeneous tissues. Simple permanent tissue is classified into three types that is as follows:

Parenchyma 

Parenchyma cells have thin cell wall composed of hemicellulose or cellulose and a large central vacuole. These cells are involved in photosynthesis, gas exchange and nutrient storage.

Types of Parenchyma

The parenchyma is divided into two types as follows:

1. Chlorenchyma: It contains chlorophyll and helps in photosynthesis is known as chlorenchyma 
2. Aerenchyma: It contains air cavities and is present in aquatic plants is known as aerenchyma. It provides buoyancy to aquatic plants. They help in the formation of the anaerobic rhizosphere in anaerobic soil.

Collenchyma

These tissues consists of living and elongated cells which are irregularly thickened at the corners due to mechanical stress on plants. They provide flexibility and mechanical support to the plant. It helps various parts of plants to bend without breaking. They are found under the epidermis and in the vascular bundle of dicot leaf. They lack intercellular spaces. They produce new cells and help in the elongation of the stem. They are mostly found in monocot plants such as palm, coconut, etc. Collenchyma contains cellulose, hemicelluloses, and pectic materials. It may or may not contain a chloroplasts and perform photosynthesis and store food.

Types of Collenchyma

The collenchyma is divided into four types as follows:

1. Tangential Collenchyma: In this collenchyma cells are thickened at the tangential part of the cell wall and are arranged into lined-up rows.
2. Lacunar Collenchyma: In this collenchyma, they have space within the cells.
3. Angular Collenchyma: In this collenchyma, the intercellular contact points are thickened.
4. Annular Collenchyma: In this collenchyma, cell walls are thickened uniformly.

Sclerenchyma  

These tissues are made up of long and narrow dead cells and lack inter-cellular space. They have thick, lignified cell walls, thereby it provides strength and durability to plant structure. Sclerenchyma cells offer rigidity, structural support and protection. These are present in the stem, around the vascular bundle, in the veins of leaves, and in the hard covering of seeds and nuts.

Types of Sclerenchyma

The sclerenchyma is divided into two types as follows:

• Fiber: They have long cells which provide strength to the plant. They are often found in bundles or strands and present in the stem, the roots, and the vascular bundles of leaves. They are mainly found in clusters, clumps, or patches.
• Sclereids: They are present in different shapes and are found in tissue such as the periderm, cortex, pith, xylem, and phloem. They are present in various parts of the plants like in the outer covering of nuts and seeds. Example: The grainy texture of pears and guavas.

Difference Between Parenchyma, Collenchyma, and Sclerenchyma

The difference between parenchyma, collenchyma, and sclerenchyma is as follows:

Complex Permanent Tissue 

Complex permanent tissues are made up of different kind of specialized cells that work together to perform specific functions within a plant. It help in the transportation of food, water, and minerals throughout the plant.

Xylem

It is mostly made up of dead cells and is used to transport water and mineral from root to leaves and other parts of the plant. It consists of various cell types, including tracheids and vessel elements for water conduction, fibers for support, and xylem parenchyma cells for storage. Only, the Xylem parenchymas is made up of living cells and contains food. The tracheid and vessels are long, elongated, and hollow.

Phloem 

Phloem is composed of living cells and helps in the transportation of food from leaves to other parts of plants. It is made up of sieve tube elements, which are responsible for transporting nutrients, and companion cells that support sieve tube elements, phloem fiber, and phloem parenchyma. Only phloem fiber is made up of dead cells. They are also responsible for the transportation of proteins and mRNAs.

Secretory Tissues 

As the name indicates these tissues are related to the secretion of substances such as gums, raisins, latex, nectar, etc. The secretory tissues are of two types that are as follows:

• Laticiferous Tissues: They are long, elongated, thickened, and multi-nucleated cells and contains a yellowish substance called latex. When laticifers are damaged, they release latex, which can have protective, defensive, or healing functions for the plant. Its function range from deterring herbivores to healing wounds. They are spread over the parenchyma cells of plants. 
• Glandular Tissues: These tissues contain glands that secrete various essential products like essential oils, mucilage (in betel leaf), gum, resin, tannin, digestive enzymes, etc. Glandular tissues are commonly found in structures such as flower petals, leaves, and stems. The secretions they produce can serve various purposes, including attracting pollinators, deterring herbivores, or aiding in wound healing.