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