Difference Between Meristematic Tissue and Permanent Tissue

Main Difference – Meristematic Tissue vs Permanent Tissue

Meristematic tissue and permanent tissue are two types of tissues found in plants. The growth of the plant body occurs in two steps; the new cells are produced first, and then these cells are expanded by absorbing water by the vacuole. The cell division only occurs in meristematic tissue but, the expansion can occur anywhere on the plant body. The cell differentiation produces permanent tissue. The main difference between meristematic tissue and permanent tissue is that meristematic tissue consists of young living cells that are capable of continuously dividing and are responsible for the plant growth while permanent tissue consists of specialized cells that have lost their ability to divide and function as protective, conductive, and supportive tissue.

This article looks at, 

1. What is Meristematic Tissue
      – Definition, Classification, Structure, Characteristics
2. What is Permanent Tissue
– Definition, Classification, Structure, Characteristics
3. What is the difference between Meristematic Tissue and Permanent Tissue

What is Meristematic Tissue

The meristematic tissue is a young, immature, undifferentiated cell mass that continuously divides throughout the lifetime of the plant. It can be found at the apex of the stem, leaf primordia, and root. The meristematic tissue is also found in vascular cambium. During cell division, the cells that are separated towards the apex, but remain in the meristem are called initial, and the cells that start expanding are called derivative. Thus, half of the dividing cells remain in the meristem and the rest gradually lose their power of division and become permanent tissue. Meristematic tissue is responsible for the growth and development of the plant body.

Classification of Meristematic Tissue

The meristematic tissue can be classified based on nature of divisions, position, origin, function and plane of division. Based on the position, the meristem can be divided into three types: apical meristem, intercalary meristem, and lateral meristem.

Apical Meristem

The apical meristem occurs at the apex of stem and roots, increasing the length of the plant. In the root, the meristem is situated behind the tip (sub-terminal) and in the shoot, it is terminal. The apical meristem of the root is shown in figure 1.

Figure 1: Root apical meristem
1 – Meristem, 2 – Columella, 3 – Lateral part of the tip, 4 – Dead cells, 5 – Elongation Zone

Intercalary Meristem

The intercalary meristem is the remaining apical meristem that lies between permanent tissues. It occurs at the base of node, internodes, leaf, sheathing leaf of monocots or stipule of dicots.

Lateral Meristem

The lateral meristem lies laterally in the stem and roots, and is involved in the secondary growth. Vascular cambium and cork cambium belongs to the lateral meristem. The cells in the vascular cambium are thin-walled and highly vacuolated. The cork cambium is originated during the differentiation of permanent tissue. It serves as the secondary lateral meristem.

What is Permanent Tissue

A plant tissue that has completed its growth and differentiation and is incapable of dividing is known as the permanent tissue. Cells in the permanent tissue are mature and consist of a defined size, shape, and function. The permanent tissue can be found in every part of the plant body. It is involved in photosynthesis, storing food, conducting nutrients and water, and support. 

Classification of Permanent Tissue

The permanent tissue can be divided into three types: simple, complex and special tissues.  

Simple Permanent Tissue

The simple permanent tissue consists of similar types of cells, performing similar functions. Parenchyma, collenchyma, and sclerenchyma are the three types of simple permanent tissues. Parenchyma is the most abundant tissue that is mostly isodiametric in shape. It is called potential meristematic tissue. It is also involved in photosynthesis. Parenchyma consists of living cells that are loosely packed. Hence, it serves as the basic packing tissue. Collenchyma provides flexibility and support. It is found in leaf stalks below the epidermis. Sclerenchyma makes the plant hard and stiff. It consists of dead cells with lignified, long and narrow cell walls.

Complex Permanent Tissue

The complex permanent tissue consists of several cell types, acting cooperatively as a functional unit that performs a common function. Xylem and phloem are the two types of complex permanent tissues. Plants which consist of xylem and phloem are called vascular plants. Xylem is the main water-conducting tissue of plants. It consists of four cell types: tracheids, vessels, xylem fibers, and xylem parenchyma. Phloem is the food-conducting tissue. It also consists of four cell types: phloem elements, companion cells, phloem fibers and phloem parenchyma. Both xylem and phloem have a supportive function in the plant. The simple and complex permanent epithelium are shown in figure 2.

Figure 2: Simple and complex permanent tissue

Special Permanent Tissue

The specialized permanent tissue consists of cells that are involved in the secretion or excretion of materials. It is also called secretory tissue. Glandular and laticiferous tissue are two types of secretory tissue. Cells in the glandular tissue consist of dense cytoplasm along with a prominent nucleus. They secrete enzymes. Laticiferous tissue produces white or yellow alkaloid called latex.  

Difference Between Meristematic and Permanent Tissue

Definition

Meristematic Tissue: The meristematic tissue is a young tissue that is capable of continuously dividing and is responsible for the growth of the plant.

Permanent Tissue: The permanent tissue is a specialized tissue that has lost its ability to divide and functions as protective, conductive, and supportive tissue.

Cell Differentiation

Meristematic Tissue: The meristematic tissue consists of undifferentiated cells.

Permanent Tissue: The permanent tissue consists of both differentiated and non-differentiated cells.

Cell Division

Meristematic Tissue: The meristematic tissue divides rapidly.

Permanent Tissue: The differentiated cells in the permanent tissue have lost their ability to divide.

Complexity

Meristematic Tissue: The meristematic tissue is a simple tissue that consists of a single type of cells.

Permanent Tissue: The meristematic tissue is a combination of simple and complex tissue where the complex tissue consists of more than one type of cells.

Living/Non-living Cells

Meristematic Tissue: The meristematic tissue consists of all living cells.

Permanent Tissue: The permanent tissue consists of a combination of living (parenchyma and collenchyma) and non-living (sclerenchyma) cells.

Nucleus and Cytoplasm

Meristematic Tissue: Cells in the meristematic tissue always consist of a dense cytoplasm as well as a prominent nucleus.

Permanent Tissue: Non-living cells in the permanent tissue do not have a cytoplasm and nucleus.

Cells

Meristematic Tissue: Cells in the meristematic tissue are small and isodiametric in shape with a large lumen.

Permanent Tissue: Cells in the permanent tissue are large and varying in shape with very wide or very narrow lumen.

Intercellular Spaces

Meristematic Tissue: Cells in the meristematic tissue do not consist of intercellular spaces.

Permanent Tissue: Parenchyma is loosely packed and sclerenchyma is compactly packed.

Vacuoles

Meristematic Tissue: Cells in the meristematic tissue do not have vacuoles.

Permanent Tissue: Living cells in the permanent tissue consist of vacuoles and dead cells of that are devoid of protoplasm.

Metabolism of Cells

Meristematic Tissue: Cells in the meristematic tissue shows high rates of metabolism.

Permanent Tissue: Cells in the permanent tissue shows very less or no metabolism.

Cell Wall

Meristematic Tissue: Cell wall of the meristematic tissue is very thin and cellulosic.

Permanent Tissue: Cell wall of the permanent tissue is cellulosic (parenchyma and collenchyma) or lignified (sclerenchyma).

Secondary Cell Wall Thickening

Meristematic Tissue: The meristematic tissue does not undergo secondary cell wall thickening. Therefore, the lignified, secondary cell wall is completely absent in the meristematic tissue.

Permanent Tissue: Some cells of the permanent tissue undergoes secondary cell wall thickening. Therefore, a lignified secondary cell wall is present in sclerenchyma cells.

Pits

Meristematic Tissue: Cells in the meristematic tissue consist of primary pit fields.

Permanent Tissue: Cells in the permanent tissue consist of many advanced types of pits.

Ergastic Substances and Inclusions

Meristematic Tissue: Ergastic substances and inclusions are absent in the meristematic tissue.

Permanent Tissue: Ergastic substances and inclusions are present in the permanent tissue.

Food Reservation

Meristematic Tissue: The meristematic tissue does not contain reserved food.

Permanent Tissue: Some cells of the permanent tissue reserve food in the form of starch.

Correspondence

Meristematic Tissue: The meristematic tissue is a simple tissue that is restricted to certain parts of the body such as root and shoot apex.

Permanent Tissue: The permanent tissue is derived from the meristematic tissue. This tissue can be found throughout the plant body. Xylem, phloem, and mesophyll are the examples of the permanent tissue.

Function

Meristematic Tissue: The meristematic tissue is involved in the plant growth.

Permanent Tissue: The permanent tissue is involved in photosynthesis, conduction, and providing mechanical support.

Types

Meristematic Tissue: The apical meristem, intercalary meristem, and lateral meristem are the basic types of the meristematic tissue.

Permanent Tissue: Parenchyma, collenchyma, sclerenchyma, xylem, phloem, and secretory tissues are the types of permanent tissue.

Conclusion

Meristematic tissue and permanent tissue are two types of plant tissues. The main difference between meristematic tissue and permanent tissue is in their cellular organization and functions. Meristematic tissue occurs in growing parts of the plant like the apex of the stem and roots. It is responsible for the increasing length of the plant body parts. The intercalary meristem and lateral meristem are the other two types of meristematic tissue. Lateral meristem is involved in the secondary growth of the plant. The meristematic tissue consists of actively dividing cells. The central cells of the meristematic tissue are expanded and gradually differentiated into permanent tissues. Parenchyma, collenchyma, and sclerenchyma are simple permanent tissues. The complex permanent tissues are xylem and phloem.

Reference:
1. “Meristematic Tissues.” Sciencetopia. N.p., n.d. Web. 25 May 2017. <https://www.sciencetopia.net/biology/botany/meristematic-tissues>.
2. “Permanent Tissues in Plants.” Plant Science 4 U. N.p., n.d. Web. 25 May 2017. <http://www.plantscience4u.com/2014/04/permanent-tissues-in-plants_24.html#.WSara-uGPIU>.

Image Courtesy:
1. “Root-tip-tag” By SuperManu – Own work, based on File:Root tip.JPG by Clematis (CC BY-SA 2.5) via Commons Wikimedia
2. “Plant cell types” By Kelvinsong – Own work (CC BY-SA 3.0) via Commons Wikimedia