Simple Permanent tissue in Plant, Types, Structure and function

 

• A simple Permanent tissue is homogenous tissue which is made up of only one type of cells that are common in origin.

• These are of three type- Parenchyma, collenchyma and sclerenchyma.

Parenchyma -

• It is a simple Permanent tissue and made up of isodiametric cells. The term parenchyma was coined by N.Grew.

• It is most abundant and most primtive tissue of plant body . It is present in epidermis, cortex, endodermis , pericycle , xylem and phloem etc.

• A parenchyma cell has a central large vacuole, peripheral cytoplasm, prominent nucleus and thin cell wall.

Read about the Meristmatic tissue in Plant 

• Cell wall is made up of cellulose and pectose.

• Adjacent cell wall is connected by the plasmodesmata or cytoplasmic bridge. Inter cellular spaces are formed through the splitting of cells.

• Storage, slow conduction, providing turgidity to soft part of plants and photosynthesis etc are common function of parenchyma.

Collenchyma -

• The term collenchyma are coined by schleiden . Its wall is thick due to pectocellulosic .

• The cell wall is made up of cellulose and hemi cellulose.

• Their cells contain large central vacuole and peripheral cytoplasm. Chloroplast may present in most of the cases.

• Collenchyma are present in region of plant that undergone enlargement.

• Basically they provide mechanical strength to soft organ including young stem therefore it is called living mechanical tissue.

• In old parts of plants, their cells are harder and undergo sclerification due to deposition of lignin.

• The function of collenchyma are as follows

• It act as mechanical tissue to young stem , leaves and flower.

Read about the Complex permanent tissue : Xylem

• It also provide elasticity and support to growing organs.

• They also perform photosynthesis in some cases and may store food in small quantities.

Sclerenchyma-

• It is simple permanent tissue and made up of dead cells with narrow lumen.

• Mettinius coined the term sclrenchyma.

• Their cell wall is made up of cellulose and lignin.

• Their cells at young stage has protoplasm but at maturity, it degenerate with the exception of some plants.

• Sclerenchyma is of two types : fiber and sclereids. 

• Fibers are often divided into two groups : xylary and extra xylary.

• Fibers are found inside the xylem, phloem, around vascular bundles in monocot, pericycle, hypodermis, petiole and leaves.

• The fibers are well adapted to tolerate the  forces of compression, pull, bending. 

• Sclereids are thick walled short isodiametric, polyhedral or cylindrical which occur in single  or in groups for providing stiffness and protection in various parts of the plant.

• They have pit canals and lumen is usually narrow.

• These Sclereids can be seen in grit of Apple and Pear.

• Stony endocarp in  drupe fruit  is largely made up of sclereids.

• The Seed Coat of legume also contains sclereids.

• Sclerenchyma fiber provides mechanical strength to various plant parts.

• The fiber specially tolerates stress,  bending and compression and pull.

• It provides for elastic stretching and compression.

• It prevents the collapse of the soft plant organ under the condition of temporary wilting.

• Sclerenchyma fibers are commercially obtained from a number of plants like  flax  jute Hemp. 

👌👌Remember : cotton fibers are not sclerenchyma. 

• Splitting and coiling of valves  during dehiscence  of some fruit is due to specific orientation of sclerenchyma fibers.